We all know exercise is beneficial to our health. Then why is it that ultramarathon runners may generate so many free radicals during a race that they can damage the DNA of a significant percentage of their cells? Researchers have looked at the exercise-induced increase in free radical production as a paradox: why would an apparently healthy act—exercise—lead to detrimental effects through damage to various molecules and tissues? This arises out of somewhat of a misunderstanding: exercise in and of itself is not necessarily the healthy act—it’s the recovery after exercise that is so healthy, the whole “that-which-doesn’t-kill-us-makes-us-stronger” notion. For example, exercise training has been shown to enhance antioxidant defenses by increasing the activities of our antioxidant enzymes. So, during the race ultra-marathoners may be taking hits to their DNA, but a week later they can experience great benefits, as shown in my video, Enhanced Athletic Recovery Without Undermining Adaptation.
In a recent study, researchers from Oregon State University looked at the level of DNA damage in athletes. Six days after a race, athletes didn’t just go back to the baseline level of DNA damage, but had significantly less, presumably because they had revved up their antioxidant defenses. So, maybe exercise-induced oxidative damage is beneficial, similar to vaccination. By freaking out the body a little, we might induce a response that’s favorable in the long run.
This concept, that low levels of a damaging entity can up-regulate protective mechanisms, is known as hormesis. For example, herbicides kill plants, but in tiny doses may actually boost plant growth, presumably by stressing the plant into rallying its resources to successfully fight back.
Wait a second, though. Could eating anti-inflammatory and anti-oxidant rich plant foods undermine this adaptation response? We know that berries may reduce inflammatory muscle damage (See Reducing Muscle Soreness with Berries), and greens may reduce free radical DNA damage (See Preventing Exercise Induced Oxidative Stress with Watercress). Dark chocolate and tomato juice appear to have similar effects. How it works is that flavonoid phytonutrients in fruits, vegetables, and beans seem to inhibit the activity of xanthine oxidase, considered the main contributor of free radicals during exercise. And the carbs in plant foods may also decrease stress hormone levels.
So in 1999, a theoretical concern was raised. Maybe all that free radical stress from exercise is a good thing, and increased consumption of some antioxidant nutrients might interfere with these necessary adaptive processes. If we decrease free radical tissue damage, maybe we won’t get that increase in activity of those antioxidant enzymes.
A group of researchers who performed a study on tart cherry juice and recovery following a marathon responded to this antioxidant concern by suggesting that, although it is likely that muscle damage, inflammation, and oxidative stress are important factors in the adaptation process, minimizing these factors may improve recovery so we can train more and perform better. So, there are theories on both sides, but what happens when we actually put it to the test?
While antioxidant or anti-inflammatory supplements may prevent these adaptive events, researchers found that blackcurrant extract – although packed with antioxidant and anti-inflammatory properties – actually boosted the health benefits of regular exercise.
If we take antioxidant pills—vitamin C and vitamin E supplements— we can also reduce the stress levels induced by exercise, but in doing so we block that boost in antioxidant enzyme activity caused by exercise. Now maybe we don’t need that boost if we don’t have as much damage, but vitamin C supplements seem to impair physical performance in the first place. With plant foods, though, we appear to get the best of both worlds.
For example, lemon verbena, an antioxidant-rich herbal tea, protects against oxidative damage and decreases the signs of muscular damage and inflammation, without blocking the cellular adaptation to exercise. In a recent study, researchers showed that lemon verbena does not affect the increase of the antioxidant enzyme response promoted by exercise. On the contrary: antioxidant enzyme activity was even higher in the lemon verbena group.
Welcome to my collection of health articles. Most of them contain little nuggets of health wisdom that we can easily apply to our daily lives. As you can gather, I've been consuming all sorts of supplements over the years, most of them from iherb. They deliver on time (DHL), and prices are good. If you're a first-time buyer, use my code 'pot089' to enjoy up to $10 off.
Thursday, 11 September 2014
Low carb better than low fat for heart disease reduction
A low-carbohydrate diet may be better than a low-fat diet for losing weight and reducing risks for cardiovascular disease (CVD), according to an article published in the September 2 issue of Annals of Internal Medicine.
Lydia A. Bazzano, MD, PhD, MPH, from the Department of Epidemiology at Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana, and colleagues conducted a randomized trial involving 148 adults who did not have diabetes or CVD.
The researchers randomly assigned 75 participants to the low-carbohydrate group and 73 to the low-fat group, with 59 (79%) low-carbohydrate participants and 60 (82%) low-fat participants completing the 1-year study. The groups were well matched, with a median age of 47.8 years in the low-fat group and 45.8 years in the low-carbohydrate group and baseline body mass indexes of 35.6 and 35.2 kg/m2. The groups were predominately female (89% and 88%, respectively) but were racially mixed, with approximately equal numbers of blacks (36 and 40, respectively) and whites (33 and 34, respectively) in each group.
At 1 year, the researchers found that the low-carbohydrate group had a significantly greater reduction in body weight (mean difference, −3.5 kg; 95% confidence interval [CI], −5.6 to −1.4 kg;P = .002), significantly greater proportional reductions in fat mass (mean difference, −1.5%; 95% CI, −2.6% to −0.4%; P = .011), and significantly greater relative increase in lean mass (mean difference, 1.7%; 95% CI, 0.6% - 2.8%; P = .003).
Total and low-density lipoprotein cholesterol levels and plasma glucose levels did not change significantly in either group, nor did blood pressure levels significantly decrease in either group.
However, the low-carbohydrate participants showed significantly greater decreases in C-reactive protein levels (mean difference, −15.2 nmol/L; P = .024); estimated 10-year risk for coronary heart disease, based on the Framingham risk score (mean difference, −1.4%; P < .001); ratio of total to high-density lipoprotein cholesterol (mean difference, −0.44; P = .002); and serum triglyceride levels (mean difference, −0.16 mmol/L;P = .038).
Counseling and Education
Study participants in both groups met with dietitians in weekly individual counseling sessions for the first 4 weeks and then in small groups biweekly for the next 5 months. They met monthly the last 6 months.
Staff members provided equal instructions to both groups in terms of dietary fiber and types of fats. Researchers collected 24-hour dietary recall data at baseline and at 3, 6, and 12 months.
"[T]his 12-month randomized, parallel-group trial showed that a low-carbohydrate diet resulted in greater weight loss and reduction in cardiovascular risk factors than a low-fat diet among obese black and white adults," the researchers conclude.
"Our findings suggest that people who want to lose weight and have risk factors for heart disease could consider a low-carbohydrate diet as an option to both lose weight and improve those risk factors," said coauthor Tian Hu, MD, a doctoral research fellow at Tulane.
Benefits Seen Across Ethnic Groups
The researchers write that their findings are consistent with the findings of other studies as to body weight. "In addition, our findings suggest that the loss of fat mass accounts for most of the reduction in body weight on a low-carbohydrate diet, which is consistent with other study findings," they note.
"Our study has a couple of important differences compared to others. Some previous studies had included only diabetics, or mostly participants with metabolic syndrome or cardiovascular disease. Participants in our study were generally healthy. They might have hypertension or dyslipidemia, but they did not have any clinical cardiovascular disease, kidney disease, or diabetes," said Dr. Hu.
"The diversity of the study group is also an important contribution. Previous studies included mostly white participants or did not test a typical low-carbohydrate diet," he added. "When we evaluated the effects of both diets in African-American and Caucasian participants separately, the results were similar."
What happens after the study is still to be determined. "We could only examine results over the 1-year period of the study. But it's very likely that adherence to the diet may have [an] impact on CVD risk reduction," Dr. Hu noted.
Balance Counts
"I thought [the study] was very well thought out. I'm glad that dieticians and nutrition education were used and the participants had good follow-up," said Kasia Ciaston, MS, RD, LDN, a clinical dietitian at Loyola University Medical Center in Maywood, Illinois.
"My big concern is studying low-carb or low-fat diet, especially with cardiovascular risk, is particularly due to the history of these types of diets," she continued. "For the last 50 to 60 years, fat has been created as the enemy, which caused a significant increase in carbohydrate intake and incidence of diabetes and blood sugar–related disease. I feel that it would be a similar mistake to point the finger of blame at carbohydrates and make another macronutrient the bad guy," she said.
"Although I do agree that decreasing carbohydrate intake from processed foods can have wonderful health benefits, I think the real message to get across here is that getting that right balance in your diet is what really helps to create health benefits, versus cutting out a certain macronutrient," she added.
For the low-carbohydrate participants in this study, "their intake of protein also increased dramatically, which can also create health effects over time. They're also eating a stable amount of fiber in their diet. All of these other factors that aren't necessarily focused on are playing a part in that balance," she said.
"I hope that what clinicians get out of this study is that nutrition is a huge impact factor on decreasing future risks and that [nutrition information] would make a much bigger impact if [patients] weren't just hearing it from me, but if they were hearing it also from their physician and each member of their healthcare team," she added.
Lydia A. Bazzano, MD, PhD, MPH, from the Department of Epidemiology at Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana, and colleagues conducted a randomized trial involving 148 adults who did not have diabetes or CVD.
The researchers randomly assigned 75 participants to the low-carbohydrate group and 73 to the low-fat group, with 59 (79%) low-carbohydrate participants and 60 (82%) low-fat participants completing the 1-year study. The groups were well matched, with a median age of 47.8 years in the low-fat group and 45.8 years in the low-carbohydrate group and baseline body mass indexes of 35.6 and 35.2 kg/m2. The groups were predominately female (89% and 88%, respectively) but were racially mixed, with approximately equal numbers of blacks (36 and 40, respectively) and whites (33 and 34, respectively) in each group.
At 1 year, the researchers found that the low-carbohydrate group had a significantly greater reduction in body weight (mean difference, −3.5 kg; 95% confidence interval [CI], −5.6 to −1.4 kg;P = .002), significantly greater proportional reductions in fat mass (mean difference, −1.5%; 95% CI, −2.6% to −0.4%; P = .011), and significantly greater relative increase in lean mass (mean difference, 1.7%; 95% CI, 0.6% - 2.8%; P = .003).
Total and low-density lipoprotein cholesterol levels and plasma glucose levels did not change significantly in either group, nor did blood pressure levels significantly decrease in either group.
However, the low-carbohydrate participants showed significantly greater decreases in C-reactive protein levels (mean difference, −15.2 nmol/L; P = .024); estimated 10-year risk for coronary heart disease, based on the Framingham risk score (mean difference, −1.4%; P < .001); ratio of total to high-density lipoprotein cholesterol (mean difference, −0.44; P = .002); and serum triglyceride levels (mean difference, −0.16 mmol/L;P = .038).
Counseling and Education
Study participants in both groups met with dietitians in weekly individual counseling sessions for the first 4 weeks and then in small groups biweekly for the next 5 months. They met monthly the last 6 months.
Staff members provided equal instructions to both groups in terms of dietary fiber and types of fats. Researchers collected 24-hour dietary recall data at baseline and at 3, 6, and 12 months.
"[T]his 12-month randomized, parallel-group trial showed that a low-carbohydrate diet resulted in greater weight loss and reduction in cardiovascular risk factors than a low-fat diet among obese black and white adults," the researchers conclude.
"Our findings suggest that people who want to lose weight and have risk factors for heart disease could consider a low-carbohydrate diet as an option to both lose weight and improve those risk factors," said coauthor Tian Hu, MD, a doctoral research fellow at Tulane.
Benefits Seen Across Ethnic Groups
The researchers write that their findings are consistent with the findings of other studies as to body weight. "In addition, our findings suggest that the loss of fat mass accounts for most of the reduction in body weight on a low-carbohydrate diet, which is consistent with other study findings," they note.
"Our study has a couple of important differences compared to others. Some previous studies had included only diabetics, or mostly participants with metabolic syndrome or cardiovascular disease. Participants in our study were generally healthy. They might have hypertension or dyslipidemia, but they did not have any clinical cardiovascular disease, kidney disease, or diabetes," said Dr. Hu.
"The diversity of the study group is also an important contribution. Previous studies included mostly white participants or did not test a typical low-carbohydrate diet," he added. "When we evaluated the effects of both diets in African-American and Caucasian participants separately, the results were similar."
What happens after the study is still to be determined. "We could only examine results over the 1-year period of the study. But it's very likely that adherence to the diet may have [an] impact on CVD risk reduction," Dr. Hu noted.
Balance Counts
"I thought [the study] was very well thought out. I'm glad that dieticians and nutrition education were used and the participants had good follow-up," said Kasia Ciaston, MS, RD, LDN, a clinical dietitian at Loyola University Medical Center in Maywood, Illinois.
"My big concern is studying low-carb or low-fat diet, especially with cardiovascular risk, is particularly due to the history of these types of diets," she continued. "For the last 50 to 60 years, fat has been created as the enemy, which caused a significant increase in carbohydrate intake and incidence of diabetes and blood sugar–related disease. I feel that it would be a similar mistake to point the finger of blame at carbohydrates and make another macronutrient the bad guy," she said.
"Although I do agree that decreasing carbohydrate intake from processed foods can have wonderful health benefits, I think the real message to get across here is that getting that right balance in your diet is what really helps to create health benefits, versus cutting out a certain macronutrient," she added.
For the low-carbohydrate participants in this study, "their intake of protein also increased dramatically, which can also create health effects over time. They're also eating a stable amount of fiber in their diet. All of these other factors that aren't necessarily focused on are playing a part in that balance," she said.
"I hope that what clinicians get out of this study is that nutrition is a huge impact factor on decreasing future risks and that [nutrition information] would make a much bigger impact if [patients] weren't just hearing it from me, but if they were hearing it also from their physician and each member of their healthcare team," she added.
Pilots, Crew Have Double the Rate of Melanoma
As in the mythical story of Icarus, human beings in the modern world who fly too close to the sun have a price to pay, new research suggests.
Airline pilots and cabin crews have twice the incidence of melanoma as the general population, according to the largest meta-analysis to date on the subject.
The standardized incidence ratio of melanoma for any flight-based occupation was 2.21 (P < .001).
Furthermore, melanoma was more deadly in these professionals, who had a disease-related mortality rate 42% greater than that of more regularly earthbound beings.
Specifically, the standardized mortality ratio for any flight-based occupation was 1.42 (P = .02).
"Further research on the mechanisms [of harm] and optimal occupational protection is needed," conclude the researchers, led by Martina Sanlorenzo, MD, a research fellow in the Department of Dermatology at the University of California, San Francisco.
They suspect that the increase in melanoma risk seen in airline pilots and cabin crews comes from exposure to ultraviolet (UV) light, which becomes more intense the higher a plane flies. "At 9000 meters [30,000 feet], where most commercial aircraft fly, the UV level is approximately twice that of the ground," the researchers report.
Remarkably, UV light exposure is "not a well-recognized occupational risk factor" for flight crews, they note. In contrast, ionizing radiation is a well-known risk, and levels in airline crews are regularly monitored.
This study provides no details on the clinical aspects of the melanomas.
"It would be interesting to see the anatomic distribution of skin cancers in the crew, because only hands and face should be exposed to UV passing through the windows," said Steven Wang, MD, director of dermatologic surgery and dermatology at the Memorial Sloan Kettering Cancer Center in Basking Ridge, New Jersey, who was not involved in the study.
Frequent flier passengers are probably not at an increased risk, he said in an email to Medscape Medical News. But for the worried, pulling down the window shade and sitting in an aisle seat are protective strategies, added Dr. Wang, who is the author ofBeating Melanoma: A 5-Step Survival Guide.
The meta-analysis examined 19 studies (15 with data on pilots; 4 with data on cabin crews). Data from the studies, which involved more than 266,000 participants, were collected from 1943 to 2008 in more than 11 countries.
The researchers conducted separate analyses for pilots and for cabin crews (which include flight attendants).
They found that pilots were at greater risk for melanoma than the cabin crew.
In fact, pilots and crews would have more than double the annual number of new melanomas per year, which is 21.3 per 100,000 individuals in the general population.
Pilots as a group were also at greater risk for mortality, and had a higher mortality ratio than cabin crews (1.83 vs 0.90).
UVA Radiation and Glass Might Be the Problems
The researchers discuss the technicalities of the types of UV radiation and windshields.
They cite measurements of UV radiation that passes through the windshields of a variety of aircraft — large (e.g., Boeing737 and Airbus A320) and small (e.g., Cessna 182) — from a 2007 report by the US Federal Aviation Administration.
The transmission of UVB is less than 1% for both plastic and glass windshields.
However, UVA is a different story, especially in airplanes with glass windows. "While plastic materials blocked almost all UVA radiation, 54% of it came through glass," Dr. Sanlorenzo and colleagues report.
Airline pilots and cabin crews have twice the incidence of melanoma as the general population, according to the largest meta-analysis to date on the subject.
The standardized incidence ratio of melanoma for any flight-based occupation was 2.21 (P < .001).
Furthermore, melanoma was more deadly in these professionals, who had a disease-related mortality rate 42% greater than that of more regularly earthbound beings.
Specifically, the standardized mortality ratio for any flight-based occupation was 1.42 (P = .02).
"Further research on the mechanisms [of harm] and optimal occupational protection is needed," conclude the researchers, led by Martina Sanlorenzo, MD, a research fellow in the Department of Dermatology at the University of California, San Francisco.
They suspect that the increase in melanoma risk seen in airline pilots and cabin crews comes from exposure to ultraviolet (UV) light, which becomes more intense the higher a plane flies. "At 9000 meters [30,000 feet], where most commercial aircraft fly, the UV level is approximately twice that of the ground," the researchers report.
Remarkably, UV light exposure is "not a well-recognized occupational risk factor" for flight crews, they note. In contrast, ionizing radiation is a well-known risk, and levels in airline crews are regularly monitored.
This study provides no details on the clinical aspects of the melanomas.
"It would be interesting to see the anatomic distribution of skin cancers in the crew, because only hands and face should be exposed to UV passing through the windows," said Steven Wang, MD, director of dermatologic surgery and dermatology at the Memorial Sloan Kettering Cancer Center in Basking Ridge, New Jersey, who was not involved in the study.
Frequent flier passengers are probably not at an increased risk, he said in an email to Medscape Medical News. But for the worried, pulling down the window shade and sitting in an aisle seat are protective strategies, added Dr. Wang, who is the author ofBeating Melanoma: A 5-Step Survival Guide.
The meta-analysis examined 19 studies (15 with data on pilots; 4 with data on cabin crews). Data from the studies, which involved more than 266,000 participants, were collected from 1943 to 2008 in more than 11 countries.
The researchers conducted separate analyses for pilots and for cabin crews (which include flight attendants).
They found that pilots were at greater risk for melanoma than the cabin crew.
In fact, pilots and crews would have more than double the annual number of new melanomas per year, which is 21.3 per 100,000 individuals in the general population.
Pilots as a group were also at greater risk for mortality, and had a higher mortality ratio than cabin crews (1.83 vs 0.90).
UVA Radiation and Glass Might Be the Problems
The researchers discuss the technicalities of the types of UV radiation and windshields.
They cite measurements of UV radiation that passes through the windshields of a variety of aircraft — large (e.g., Boeing737 and Airbus A320) and small (e.g., Cessna 182) — from a 2007 report by the US Federal Aviation Administration.
The transmission of UVB is less than 1% for both plastic and glass windshields.
However, UVA is a different story, especially in airplanes with glass windows. "While plastic materials blocked almost all UVA radiation, 54% of it came through glass," Dr. Sanlorenzo and colleagues report.
Reducing sedentary time protects DNA
Less time spent sitting may lengthen telomeres and protect DNA from age-related damage, a new study shows. However, the researchers found no significant association in telomere length with increased exercise in this small randomized trial.
"We're excited about this study," said lead author Mai-Lis Hellenius, MD, PhD, a professor of cardiovascular disease prevention in the Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden. "Long telomeres are linked to a longer, healthier life."
Per Sjögren, PhD, from the Unit of Clinical Nutrition and Metabolism, Department of Public Health and Caring Sciences, Uppsala University, Sweden, and colleagues published the study online September 3 in the British Journal of Sports Medicine.
Telomeres are sections of DNA that protect the ends of chromosomes from damage during cell division. Telomeres tend to shorten with age, and previous research has linked shorter telomeres with shorter life spans and increased risk for some types of cancer and cardiovascular disease.
"Our DNA will be damaged during a lifetime," Dr. Hellenius said. "It's damaged by bad diets, smoking, infections, and so on. Our capability to copy and produce new DNA and new cells is so important."
Previous research has shown that people who exercise more tend to have longer telomeres.
In the current study, Dr. Sjögren and colleagues analyzed the length of telomeres a subset of people who had participated in a randomized exercise trial. The original study included 101 predominantly sedentary and overweight people adults aged 68 years at baseline. The investigators randomly assigned half of the participants to an exercise program and the other half to their regular behavior.
They asked the participants to keep a 7-day diary and to wear a pedometer to measure the number of steps taken every day. They also asked them to fill out a questionnaire tallying up the amount of time spent sitting down each day.
As the researchers reported previously, the time spent exercising, as well as the number of steps taken daily, increased significantly in the group assigned the exercise program, whereas the amount of time spent seated fell in both groups ( Br J Sports Med. 2011;45:158). Various risk factors for heart disease and stroke also improved in both groups, particularly those on the exercise program, who lost more weight than their counterparts left to their own devices.
In the current subset analysis, the researchers examined telomere length from blood samples drawn at baseline and after the 6-month intervention in 49 randomly chosen participants. They found that the number of daily steps taken was not associated with changes in telomere length.
An increase in moderate-intensity physical activity correlated to a shortening in telomere length in both groups, but this finding was not statistically significant. However, a reduction in the amount of time spent sitting in the exercise group was associated with telomere lengthening in blood cells.
"We hypothesise that a reduction in sitting hours is of greater importance than an increase in exercise time for elderly risk individuals," the researchers conclude.
Dr. Hellenius acknowledged that the study was a small one and needed to be replicated before drawing conclusions from it. However, she notes, other research has also shown that people who spend more time sitting have shorter lives, regardless of whether they also exercise regularly.
"So I think you can say to our patients yes, it's important to break up sedentary time and take a break for 1 or 2 minutes every 30 minutes," said Dr. Hellenius.
"We're excited about this study," said lead author Mai-Lis Hellenius, MD, PhD, a professor of cardiovascular disease prevention in the Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden. "Long telomeres are linked to a longer, healthier life."
Per Sjögren, PhD, from the Unit of Clinical Nutrition and Metabolism, Department of Public Health and Caring Sciences, Uppsala University, Sweden, and colleagues published the study online September 3 in the British Journal of Sports Medicine.
Telomeres are sections of DNA that protect the ends of chromosomes from damage during cell division. Telomeres tend to shorten with age, and previous research has linked shorter telomeres with shorter life spans and increased risk for some types of cancer and cardiovascular disease.
"Our DNA will be damaged during a lifetime," Dr. Hellenius said. "It's damaged by bad diets, smoking, infections, and so on. Our capability to copy and produce new DNA and new cells is so important."
Previous research has shown that people who exercise more tend to have longer telomeres.
In the current study, Dr. Sjögren and colleagues analyzed the length of telomeres a subset of people who had participated in a randomized exercise trial. The original study included 101 predominantly sedentary and overweight people adults aged 68 years at baseline. The investigators randomly assigned half of the participants to an exercise program and the other half to their regular behavior.
They asked the participants to keep a 7-day diary and to wear a pedometer to measure the number of steps taken every day. They also asked them to fill out a questionnaire tallying up the amount of time spent sitting down each day.
As the researchers reported previously, the time spent exercising, as well as the number of steps taken daily, increased significantly in the group assigned the exercise program, whereas the amount of time spent seated fell in both groups ( Br J Sports Med. 2011;45:158). Various risk factors for heart disease and stroke also improved in both groups, particularly those on the exercise program, who lost more weight than their counterparts left to their own devices.
In the current subset analysis, the researchers examined telomere length from blood samples drawn at baseline and after the 6-month intervention in 49 randomly chosen participants. They found that the number of daily steps taken was not associated with changes in telomere length.
An increase in moderate-intensity physical activity correlated to a shortening in telomere length in both groups, but this finding was not statistically significant. However, a reduction in the amount of time spent sitting in the exercise group was associated with telomere lengthening in blood cells.
"We hypothesise that a reduction in sitting hours is of greater importance than an increase in exercise time for elderly risk individuals," the researchers conclude.
Dr. Hellenius acknowledged that the study was a small one and needed to be replicated before drawing conclusions from it. However, she notes, other research has also shown that people who spend more time sitting have shorter lives, regardless of whether they also exercise regularly.
"So I think you can say to our patients yes, it's important to break up sedentary time and take a break for 1 or 2 minutes every 30 minutes," said Dr. Hellenius.
Hotter breath linked to lung cancer
MUNICH, Germany — A preliminary study of exhaled breath suggests that temperatures higher than 34°C may be a strong indicator of the presence of lung cancer. In a sample of 82 patients who presented with clinical suspicion of lung cancer, 96% of patients had the disease.
"Airway inflammation and angiogenesis play a key role in the pathogenesis of lung cancer," Giulia Scioscia, MD, a fellow in pulmonary medicine at Hospital Clínic i Provincial de Barcelona, said at a news conference here at the European Respiratory Society (ERS) International Congress 2014. "Exhaled breath temperature has been proven to be an indicator of airway inflammation and increased vascularity. The aim of our research is to determine possible correlations of exhaled breath with progression, metastasis or other clinical outcomes of patients with cancers."
The researchers aimed to find breath temperature values that correlate with lung cancer. They analyzed 82 consecutive participants with a radiologic suspicion of lung cancer using the X-Halo (Delmedica Investments) breath thermometer. Lung cancer was later diagnosed in 40 people. A total of 42 did not have lung cancer and served as controls. All patients underwent standard diagnostic and staging procedures.
The team compared breath temperatures in patients with lung cancer and controls in various categories, including by sex, age, smoking habit, and the presence or absence of chronic obstructive pulmonary disease. In each category, people with cancer had statistically significantly higher breath temperatures than controls.
The researchers then used a receiver operating characteristic curve to determine an ideal temperature threshold for signaling lung cancer. That analysis showed that values above 34°C would be a good cutoff. Most — 96% — who had breath temperatures in that range were found to have lung cancer.
Pilot Study
The researchers stressed that this was a pilot study. "It's not sensitive enough," coauthor Giovanna Elisiana Carpagnano, MD, from the University of Foggia in Italy, said at the news conference. However, Dr. Carpagnano added that it could eventually become part of a screening panel. The researchers plan to explore the test in patients with other inflammatory conditions to get a better idea of its performance.
"I think the data are quite interesting," chair of the ERS lung cancer group Fernando Gamarra, MD, from Klinikum St. Elisabeth Straubing in Germany said. It's also novel. "I'm not aware that anybody has done it before," he added. Dr. Gamarra said he thinks that the researchers will have to account for other factors that could affect breath temperature, such as whether the person is currently smoking, the velocity with which a person exhales, or overall size. Large people may have higher breath temperatures, he pointed out.
It also remains to be seen if the approach could work consistently in early-stage cancers, which is the population that would most benefit from screening. The current study drew from patients already presenting at a hospital, and so they tended to have more advanced disease, although the researchers did note higher temperatures even in early cancers. "I would like to see a study in a limited group, say just in patients with stage 1 or 2," Dr. Gamarra said.
"Airway inflammation and angiogenesis play a key role in the pathogenesis of lung cancer," Giulia Scioscia, MD, a fellow in pulmonary medicine at Hospital Clínic i Provincial de Barcelona, said at a news conference here at the European Respiratory Society (ERS) International Congress 2014. "Exhaled breath temperature has been proven to be an indicator of airway inflammation and increased vascularity. The aim of our research is to determine possible correlations of exhaled breath with progression, metastasis or other clinical outcomes of patients with cancers."
The researchers aimed to find breath temperature values that correlate with lung cancer. They analyzed 82 consecutive participants with a radiologic suspicion of lung cancer using the X-Halo (Delmedica Investments) breath thermometer. Lung cancer was later diagnosed in 40 people. A total of 42 did not have lung cancer and served as controls. All patients underwent standard diagnostic and staging procedures.
The team compared breath temperatures in patients with lung cancer and controls in various categories, including by sex, age, smoking habit, and the presence or absence of chronic obstructive pulmonary disease. In each category, people with cancer had statistically significantly higher breath temperatures than controls.
The researchers then used a receiver operating characteristic curve to determine an ideal temperature threshold for signaling lung cancer. That analysis showed that values above 34°C would be a good cutoff. Most — 96% — who had breath temperatures in that range were found to have lung cancer.
Pilot Study
The researchers stressed that this was a pilot study. "It's not sensitive enough," coauthor Giovanna Elisiana Carpagnano, MD, from the University of Foggia in Italy, said at the news conference. However, Dr. Carpagnano added that it could eventually become part of a screening panel. The researchers plan to explore the test in patients with other inflammatory conditions to get a better idea of its performance.
"I think the data are quite interesting," chair of the ERS lung cancer group Fernando Gamarra, MD, from Klinikum St. Elisabeth Straubing in Germany said. It's also novel. "I'm not aware that anybody has done it before," he added. Dr. Gamarra said he thinks that the researchers will have to account for other factors that could affect breath temperature, such as whether the person is currently smoking, the velocity with which a person exhales, or overall size. Large people may have higher breath temperatures, he pointed out.
It also remains to be seen if the approach could work consistently in early-stage cancers, which is the population that would most benefit from screening. The current study drew from patients already presenting at a hospital, and so they tended to have more advanced disease, although the researchers did note higher temperatures even in early cancers. "I would like to see a study in a limited group, say just in patients with stage 1 or 2," Dr. Gamarra said.
Prediabetes Increases Cancer Risk
Prediabetes — even at lower levels of impaired fasting glucose (IFG) as defined by the American Diabetes Association (ADA) — is associated with a significant increase in cancer risk that is independent of the effects of obesity, according to the results of a large new meta-analysis.
Yuli Huang, MD, PhD, from First People's Hospital of Shunde, Foshan, China, and colleagues found that prediabetes was associated with a 15% increased risk for cancer overall, based on data derived from 16 prospective cohort studies, with differing risks depending on the type of cancer. The risk was particularly increased for liver cancer and stomach or colorectal cancer.
"Epidemiological studies have shown that diabetes increases the incidence of cancer and mortality from it, but we thought that maybe not only diabetes but prediabetes may be associated with an elevated cancer risk," Dr. Huang said.
"And considering the high prevalence of prediabetes as well as the robust and significant association between prediabetes and cancer we demonstrated in our study, a successful lifestyle intervention could have a major public-health impact on cancer prevention," he added.
"This information is important to health professionals and those engaged in the prevention of cancer," Dr. Huang and colleagues stress.
The study was published online September 8 in Diabetologia.
Screen for Prediabetes Using ADA Criteria for Cancer Prevention
A total of 891,426 participants from the 16 studies, 4 of which were from Asia, 11 from the United States and Europe, and 1 from Africa, were included in the meta-analysis. Prediabetes included individuals with impaired glucose tolerance (IGT), IFG, or a combination of the 2.
Over 10 years ago, the ADA lowered its definition of prediabetes to that of a fasting plasma glucose concentration ranging from 5.6 to 6.9 mmol/L, but other organizations have maintained their definition at a higher level, as a fasting plasma glucose concentration between 6.1 and 6.9 mmol/L.
The risks of site-specific cancer among individuals with prediabetes was highest for liver cancer (relative risk [RR], 2.01), followed by colorectal and stomach cancer (RR, 1.55 for both), endometrial cancer (RR, 1.60), and breast as well as pancreatic cancer (RR, 1.19 for both).
But prediabetes was not associated with cancer of the bronchus, lung, prostate, ovary, kidney, or bladder.
The risks were increased even when a lower fasting plasma glucose value of 5.6 to 6.9 mmol/L was used, as well as in participants with IGT — "an interesting finding," investigators note, "and one that reaffirms the importance of screening for prediabetes using the ADA criteria with a view to cancer prevention."
As the authors point out, obesity — in itself a key risk factor for diabetes — has also been linked to cancer.
To rule out obesity as a potential confounder, the authors did a sensitivity analysis that included only studies that adjusted for body mass index (BMI).
After controlling for BMI, "we found that...the presence of prediabetes remained associated with an increased risk of cancer by 22%," they state. "So we believe that the increased risk of cancer in individuals with prediabetes is independent of obesity."
"Our study indicates that, on the basis of a snapshot blood glucose measurement, prediabetes is associated with an increased risk of cancer," they state.
Need for Trials of Metformin to Prevent Cancer
Speculating on the reasons for the association between prediabetes and increased cancer risk, Dr. Huang and colleagues suggest that chronic hyperglycemia and resulting states, including chronic oxidative stress and the accumulation of advanced glycated end products, may serve as carcinogens.
Alternatively, increased insulin resistance characteristic of prediabetes increases insulin secretion, and increased insulin levels may promote the growth of cancer cells.
Certain genetic mutations may also predispose individuals with prediabetes to an elevated cancer risk, they suggest.
As the authors point out, it is noteworthy that metformin is associated with an approximately 30% reduction in the lifetime risk of cancer in diabetic patients.
"Considering the protective anticancer properties of metformin in patients with diabetes, as well as its ability to delay progress to diabetes in patients with prediabetes, we feel studies are urgently needed to explore the effects of metformin on cancer risk in people with prediabetes, and [if shown to be protective], metformin might be recommended in select high-risk individuals, especially those with IGT or a combination of IGT and IFG," they conclude.
Yuli Huang, MD, PhD, from First People's Hospital of Shunde, Foshan, China, and colleagues found that prediabetes was associated with a 15% increased risk for cancer overall, based on data derived from 16 prospective cohort studies, with differing risks depending on the type of cancer. The risk was particularly increased for liver cancer and stomach or colorectal cancer.
"Epidemiological studies have shown that diabetes increases the incidence of cancer and mortality from it, but we thought that maybe not only diabetes but prediabetes may be associated with an elevated cancer risk," Dr. Huang said.
"And considering the high prevalence of prediabetes as well as the robust and significant association between prediabetes and cancer we demonstrated in our study, a successful lifestyle intervention could have a major public-health impact on cancer prevention," he added.
"This information is important to health professionals and those engaged in the prevention of cancer," Dr. Huang and colleagues stress.
The study was published online September 8 in Diabetologia.
Screen for Prediabetes Using ADA Criteria for Cancer Prevention
A total of 891,426 participants from the 16 studies, 4 of which were from Asia, 11 from the United States and Europe, and 1 from Africa, were included in the meta-analysis. Prediabetes included individuals with impaired glucose tolerance (IGT), IFG, or a combination of the 2.
Over 10 years ago, the ADA lowered its definition of prediabetes to that of a fasting plasma glucose concentration ranging from 5.6 to 6.9 mmol/L, but other organizations have maintained their definition at a higher level, as a fasting plasma glucose concentration between 6.1 and 6.9 mmol/L.
The risks of site-specific cancer among individuals with prediabetes was highest for liver cancer (relative risk [RR], 2.01), followed by colorectal and stomach cancer (RR, 1.55 for both), endometrial cancer (RR, 1.60), and breast as well as pancreatic cancer (RR, 1.19 for both).
But prediabetes was not associated with cancer of the bronchus, lung, prostate, ovary, kidney, or bladder.
The risks were increased even when a lower fasting plasma glucose value of 5.6 to 6.9 mmol/L was used, as well as in participants with IGT — "an interesting finding," investigators note, "and one that reaffirms the importance of screening for prediabetes using the ADA criteria with a view to cancer prevention."
As the authors point out, obesity — in itself a key risk factor for diabetes — has also been linked to cancer.
To rule out obesity as a potential confounder, the authors did a sensitivity analysis that included only studies that adjusted for body mass index (BMI).
After controlling for BMI, "we found that...the presence of prediabetes remained associated with an increased risk of cancer by 22%," they state. "So we believe that the increased risk of cancer in individuals with prediabetes is independent of obesity."
"Our study indicates that, on the basis of a snapshot blood glucose measurement, prediabetes is associated with an increased risk of cancer," they state.
Need for Trials of Metformin to Prevent Cancer
Speculating on the reasons for the association between prediabetes and increased cancer risk, Dr. Huang and colleagues suggest that chronic hyperglycemia and resulting states, including chronic oxidative stress and the accumulation of advanced glycated end products, may serve as carcinogens.
Alternatively, increased insulin resistance characteristic of prediabetes increases insulin secretion, and increased insulin levels may promote the growth of cancer cells.
Certain genetic mutations may also predispose individuals with prediabetes to an elevated cancer risk, they suggest.
As the authors point out, it is noteworthy that metformin is associated with an approximately 30% reduction in the lifetime risk of cancer in diabetic patients.
"Considering the protective anticancer properties of metformin in patients with diabetes, as well as its ability to delay progress to diabetes in patients with prediabetes, we feel studies are urgently needed to explore the effects of metformin on cancer risk in people with prediabetes, and [if shown to be protective], metformin might be recommended in select high-risk individuals, especially those with IGT or a combination of IGT and IFG," they conclude.
Wednesday, 12 March 2014
How Selenium, Vitamin E Increase Prostate Cancer Risk
New data from the much publicized Selenium and Vitamin E Cancer Prevention Trial (SELECT), which sought to determine whether these supplements could protect against the development of prostate cancer, confirm that both antioxidants can be risky business for men.
As previously reported, men receive no preventive benefit from either selenium or vitamin E supplements; in fact, for certain men, these supplements actually increased the risk for prostate cancer.
The new study, published online February 22 in the Journal of the National Cancer Institute, explored which men who take these supplements are most at risk for prostate cancer, and why.
However, the ongoing public health message from the trial remains the same, said a trial investigator.
"Men using these supplements should stop, period. Neither selenium nor vitamin E supplementation confer any known [health] benefits — only risks," said lead author Alan Kristal, DrPH, from the Fred Hutchinson Cancer Research Center in Seattle, in a press statement.
"Many people think that dietary supplements are helpful or at the least innocuous. This is not true," he added.
The cohort of 4856 men was culled from SELECT, the larger phase 3 placebo-controlled trial in which more than 35,000 men were randomized to high-dose vitamin E (400 IU/day) and/or selenium (200 µg/day) supplements.
SELECT began in 2001 and was expected to run for 12 years, but it was stopped early, in 2008, after participants had been on the supplements for an average of 5 years. The results demonstrated that there was no protective effect from selenium and suggested that vitamin E increased prostate cancer risk.
Although the use of the supplements stopped, the study actually continued. After 2 years of follow-up, the men who took vitamin E had a statistically significant 17% increased risk for prostate cancer, as previously reported.
Notably, the rate of prostate cancer detection was higher in the groups that received either supplement alone or a combination of the 2 than in the placebo group (but the difference was significant only in the vitamin E group).
Selenium is a nonmetallic trace element found in plant in foods such as rice, wheat, and Brazil nuts, and in seafood and meat. In a previous large skin cancer prevention trial, it was associated with a reduced risk for prostate cancer. According to the National Cancer Institute, it is an antioxidant that might help control cell damage that can lead to cancer.
Vitamin E is found in a wide range of foods, especially vegetables, vegetable oils, nuts, and egg yolks. Like selenium, vitamin E is considered an antioxidant.
Key: Increased Risk Depends on Baseline Selenium
In this new case–cohort study, 1739 men diagnosed with prostate cancer during SELECT were compared with 3117 men who were not.
Dr. Kristal and colleagues found that baseline selenium status alone, in the absence of supplementation, was not associated with prostate cancer risk.
However, they also found that the effects of the supplements differed substantially between men with low levels at baseline and those with high levels.
Specifically, selenium supplementation increased the risk for prostate cancer in men who already had high selenium levels at baseline.
Before SELECT even began, there was evidence that selenium supplementation would not benefit men who already had an adequate intake of the nutrient.
For this reason, at baseline, the investigators measured the concentration of selenium in the toenails of participants. The plan was to test whether supplementation would benefit only the subset of men with low selenium levels at baseline, they explain.
Instead, they found that men with high selenium levels at baseline who took selenium supplements increased their risk for high-grade cancer by 91% (P = .007). In other words, the levels of selenium in these men became toxic.
The investigators also report that vitamin E increased prostate cancer risk in men, but only in those with low selenium levels at baseline.
Specifically, in the men with low levels of selenium randomized to receive vitamin E alone, the total risk for prostate cancer increased by 63% (P = .02) and the risk for high-grade cancer increased by 111% (P = .01).
This might explain why, in the 2008 SELECT results, only the men randomized to receive vitamin E alone, not those who received both vitamin E and selenium, had an increased risk for prostate cancer.
There is some evidence from basic science to support the idea of a meaningful dynamic. "An interaction between vitamin E and selenium has long been hypothesized because of their activities in preventing lipid peroxidation," Dr. Kristal and colleagues write.
Selenium, whether from dietary sources or supplements, might protect men from the harmful effects of vitamin E, they suggest. So selenium, at low levels, is not necessarily harmful to men.
Nevertheless, these new results are consistent with the medical literature on supplements and cancer, the investigators report. The message is that nothing good is gained in healthy people.
The literature "suggests that effects of supplementation are dependent upon the nutrient status of the target population, such that supplementation of populations with adequate nutrient status, leading to supraphysiological exposure, has either no effect or increases cancer risk," they write.
As previously reported, men receive no preventive benefit from either selenium or vitamin E supplements; in fact, for certain men, these supplements actually increased the risk for prostate cancer.
The new study, published online February 22 in the Journal of the National Cancer Institute, explored which men who take these supplements are most at risk for prostate cancer, and why.
However, the ongoing public health message from the trial remains the same, said a trial investigator.
"Men using these supplements should stop, period. Neither selenium nor vitamin E supplementation confer any known [health] benefits — only risks," said lead author Alan Kristal, DrPH, from the Fred Hutchinson Cancer Research Center in Seattle, in a press statement.
"Many people think that dietary supplements are helpful or at the least innocuous. This is not true," he added.
The cohort of 4856 men was culled from SELECT, the larger phase 3 placebo-controlled trial in which more than 35,000 men were randomized to high-dose vitamin E (400 IU/day) and/or selenium (200 µg/day) supplements.
SELECT began in 2001 and was expected to run for 12 years, but it was stopped early, in 2008, after participants had been on the supplements for an average of 5 years. The results demonstrated that there was no protective effect from selenium and suggested that vitamin E increased prostate cancer risk.
Although the use of the supplements stopped, the study actually continued. After 2 years of follow-up, the men who took vitamin E had a statistically significant 17% increased risk for prostate cancer, as previously reported.
Notably, the rate of prostate cancer detection was higher in the groups that received either supplement alone or a combination of the 2 than in the placebo group (but the difference was significant only in the vitamin E group).
Selenium is a nonmetallic trace element found in plant in foods such as rice, wheat, and Brazil nuts, and in seafood and meat. In a previous large skin cancer prevention trial, it was associated with a reduced risk for prostate cancer. According to the National Cancer Institute, it is an antioxidant that might help control cell damage that can lead to cancer.
Vitamin E is found in a wide range of foods, especially vegetables, vegetable oils, nuts, and egg yolks. Like selenium, vitamin E is considered an antioxidant.
Key: Increased Risk Depends on Baseline Selenium
In this new case–cohort study, 1739 men diagnosed with prostate cancer during SELECT were compared with 3117 men who were not.
Dr. Kristal and colleagues found that baseline selenium status alone, in the absence of supplementation, was not associated with prostate cancer risk.
However, they also found that the effects of the supplements differed substantially between men with low levels at baseline and those with high levels.
Specifically, selenium supplementation increased the risk for prostate cancer in men who already had high selenium levels at baseline.
Before SELECT even began, there was evidence that selenium supplementation would not benefit men who already had an adequate intake of the nutrient.
For this reason, at baseline, the investigators measured the concentration of selenium in the toenails of participants. The plan was to test whether supplementation would benefit only the subset of men with low selenium levels at baseline, they explain.
Instead, they found that men with high selenium levels at baseline who took selenium supplements increased their risk for high-grade cancer by 91% (P = .007). In other words, the levels of selenium in these men became toxic.
The investigators also report that vitamin E increased prostate cancer risk in men, but only in those with low selenium levels at baseline.
Specifically, in the men with low levels of selenium randomized to receive vitamin E alone, the total risk for prostate cancer increased by 63% (P = .02) and the risk for high-grade cancer increased by 111% (P = .01).
This might explain why, in the 2008 SELECT results, only the men randomized to receive vitamin E alone, not those who received both vitamin E and selenium, had an increased risk for prostate cancer.
There is some evidence from basic science to support the idea of a meaningful dynamic. "An interaction between vitamin E and selenium has long been hypothesized because of their activities in preventing lipid peroxidation," Dr. Kristal and colleagues write.
Selenium, whether from dietary sources or supplements, might protect men from the harmful effects of vitamin E, they suggest. So selenium, at low levels, is not necessarily harmful to men.
Nevertheless, these new results are consistent with the medical literature on supplements and cancer, the investigators report. The message is that nothing good is gained in healthy people.
The literature "suggests that effects of supplementation are dependent upon the nutrient status of the target population, such that supplementation of populations with adequate nutrient status, leading to supraphysiological exposure, has either no effect or increases cancer risk," they write.
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