In The News: March 2012

The results of a meta-analysis published in a recent issue of the American Journal of Clinical Nutrition add evidence to preliminary findings concerning a protective effect for soy against the development of lung cancer.*

Yong-Bing Xiang of Shanghai Jiaotong University School of Medicine and colleagues selected eight case-control and three prospective cohort studies for their review, which included 8,436 cases of lung cancer. The analysis uncovered a 23% reduction in lung cancer risk in association with high versus low soy consumption. When the analysis was limited to five studies of high quality, a 30% reduction was revealed. In analyses of specific groups, significant protective effects were observed for women, people who have never smoked, and Asian populations. For studies that documented intake of soy isoflavones, an approximate 27% reduction in lung cancer risk was associated with high intake.

Editor’s Note: While unfermented soy foods were associated with a protective effect, fermented foods such as miso were not.

A report published in Cancer Epidemiology, Biomarkers & Prevention* revealed a connection between coffee drinking and protection against the development of endometrial cancer.

The Harvard team analyzed data from 67,470 participants in the Nurses’ Health Study who were aged 34 to 59 in 1980. Dietary questionnaires completed at seven time points between 1980 and 2002 provided information on the type and frequency of coffee consumption. Biennial questionnaires ascertained endometrial cancer diagnoses during the preceding two years. Six hundred seventy-two endometrial cancer cases were documented over the 26-year follow-up period.

A declining risk of the disease was observed in association with increasing consumption of coffee. Following adjusted analysis of the data, a 25% lower risk of endometrial cancer remained in association with the intake of four or more cups of coffee per day in comparison with women who consumed less than one cup.

Editor’s Note: Youjin Je and colleagues note that the chlorogenic acid contained in coffee has strong antioxidant properties that help prevent oxidative DNA damage and improve insulin resistance.

In an article in Cancer Epidemiology, Biomarkers & Prevention, Brian M. Wolpin and his colleagues report an association between higher circulating levels of vitamin D and a lower risk of pancreatic cancer among participants in five large prospective studies.*

The study included 451 subjects diagnosed with pancreatic cancer matched with two to three cancer-free controls, selected from participants in the Health Professionals Follow-Up Study, the Nurses’ Health Study, the Physicians’ Health Study, the Women’s Health Initiative-Observational Study, and the Women’s Health Study. Follow-up periods ranged from 14.1 to 25.3 years. Plasma samples collected upon enrollment were analyzed for 25-hydroxyvitamin D.

A decreasing risk of pancreatic cancer was associated with rising levels of vitamin D. When participants whose vitamin D level was among the top one-fifth of subjects were compared with those in the lowest fifth, a 33% reduction in pancreatic cancer risk was observed.

Editor’s Note: In contrast with findings suggested by an earlier study, no increased risk was observed among men and women whose vitamin D levels were 40 ng/mL or greater.

An analysis of a clinical trial published in Diabetes Care reveals a reduction in the risk of ventricular arrhythmia-related events and fatal myocardial infarction among diabetics who received low doses of the omega-3 fatty acids EPA, DHA, and ALA.*

Participants were randomized to receive margarine that provided 223 mg EPA and 149 mg DHA per day, 1.9 grams ALA per day, both EPA/DHA and ALA, or no additional omega-3 fatty acids for 40 months. The subjects were followed for clinical events, including fatal coronary heart disease (defined as mortality from heart attack), and fatal and nonfatal ventricular arrhythmia-related events.

An 84% lower risk of ventricular arrhythmia-related events and a 72% lower risk of combined ventricular arrhythmia-related events and fatal coronary events were observed in participants who received both EPA/DHA and ALA compared to those who consumed unenhanced margarine.

Editor’s Note: The subjects included men and women with a history of heart attack within the decade prior to enrollment in the Alpha Omega Trial, which sought to determine the effects of EPA, DHA, and ALA on fatal coronary heart disease and ventricular-arrhythmia related events. While a benefit for omega-3 was not confirmed in this population, the current analysis sought to determine the effects in a subgroup of 1,014 diabetic patients, aged 60 to 80 years.

Researchers from Sweden report that consuming a diet that is rich in antioxidants is associated with a lower risk of stroke in women.*

The team evaluated data from 5,680 women with a history of heart disease and 31,035 women with no history of the disease. Questionnaire responses were analyzed for total antioxidant capacity (TAC), a measure of the free radical-reducing capacity of all dietary antioxidants. Disease-free subjects were followed for 11 years and those with a disease history for 9.6 years.

For women with no history of disease whose diets were rated among the top fifth of participants in TAC, there was a 17% lower risk of stroke in comparison with those whose TAC was among the lowest fifth. Although having a TAC level that was among the highest fourth of those with a history of the disease was not associated with a significant reduction in the risk of total stroke, women in this group experienced 46% lower risk of hemorrhagic stroke.

Editor’s Note: Fruit, vegetables, whole grains, and tea were strong contributors to TAC levels.

In the Journal of Clinical Endocrinology & Metabolism, Micah Olson, MD, and colleagues report that children suffering from obesity and insulin resistance (both associated with diabetes) are more likely to have reduced serum levels of vitamin D, in comparison with non-overweight children.*

The current study evaluated serum 25-hydroxyvitamin D levels, fasting glucose and insulin levels, insulin resistance, and other factors in 411 obese and 87 non-overweight children between the ages of six and 16 residing in North Texas. While 68% of non-overweight participants had insufficient vitamin D levels and 22% had deficient levels, among obese children, the incidence of insufficiency and deficiency rose to 92% and 50%. A significant relationship was observed between increased insulin resistance and lower vitamin D levels in the obese group.

“Although our study cannot prove causation, it does suggest that low vitamin D levels may play a role in the development of type 2 diabetes,” Dr. Olson stated.

Editor’s Note: In their discussion of the findings, the authors note that, “The difference in mean 25-hydroxyvitamin D levels between obese and non-overweight subjects was 18.5 nmol/L. Obese children would need to consume an extra 600 to 1,200 IU (the equivalent of six to twelve 8-ounce cups of milk) of vitamin D daily to make up the difference in mean 25-hydroxyvitamin D levels seen in our study. Thus, poor dietary habits alone cannot explain the low 25-hydroxyvitamin D levels seen in obese children.”

A doctoral thesis by Morten Georg Jensen of the University of Copenhagen in Denmark concludes that alginate, a viscous fiber derived from brown seaweed, can improve weight loss when regularly consumed by overweight adults.*

“Over a three-year period, we have studied the effect of taking different alginate doses,” Jensen reports. “We are able to demonstrate that the healthy subjects who took alginates felt less hungry and ate less than the subjects not drinking fiber drinks with alginates.”

The thesis describes a twelve week study in which 96 overweight men and women received a drink that contained alginate or a placebo daily in combination with a reduced-calorie diet. Participants who received the seaweed fiber lost nearly 4 pounds more on average than those who received the placebo, which was primarily due to a decrease in body fat percentage.

Editor’s Note: Dr. Jensen commented that, “A probable explanation of the weight loss is that the alginates form a gel in the stomach which strengthens the gastrointestinal satiety signals to the brain because the gel takes up space in the stomach. The overweight subjects thus ate less than usual.”

The results of a pilot study published in the Southern Medical Journal suggest a benefit for soy in men whose prostate cancer failed to respond to radiation or surgery.*

Monika Joshi, MD, and her colleagues at Pennsylvania State University enrolled 10 men with treatment-resistant prostate cancer that had not metastasized, and assigned them to three servings of soy per day for two years, during which PSA levels were monitored. After 24 months, half of the men showed a response to soy with temporary or permanently declining PSA levels or stable PSA levels. The researchers remark that soy may reduce PSA via a reduction in the expression of the androgen receptor and other mechanisms.

Editor’s Note: The success of prostate cancer therapy is evaluated by measuring a protein known as serum prostate-specific antigen (PSA). A rise in PSA following radiation or surgery for prostate cancer indicates treatment failure. An option for these patients is androgen deprivation therapy, which reduces testosterone (a hormone that may increase the growth of prostate cancer); however, the treatment has significant side effects and is not effective for all who use it.

The American Journal of Clinical Nutrition published an analysis of a randomized, controlled trial which found that supplementation with folic acid and vitamin B12 improved immediate and delayed memory in older men and women.*

The current study analyzed data from a trial of 900 participants with psychological distress who received 400 micrograms folic acid plus 100 micrograms vitamin B12, or a placebo for two years. The original trial was designed to analyze the effect of the supplements and other factors on depressive symptoms. Cognitive function was assessed at the beginning of the study and at 12 and 24 months.

While orientation, attention, verbal memory, and processing speed remained unchanged, greater improvements from baseline in immediate and delayed recall scores were observed among those who received vitamin B12 and folic acid, compared with the placebo group.

Editor’s Note: Plasma homocysteine, an amino acid that, when elevated, is associated with a greater risk of cardiovascular events, increased by an average of 22.45% among those who received the placebo and by 8.33% among those who received the two B vitamins. Having a high homocysteine level at the beginning of the study was associated with reduced cognitive performance at 24 months, as was higher depression scores.

Reporting in Nature Communications, researchers from Georgia Health Sciences University unveil new findings concerning the ability of alpha-tocopherol (vitamin E) to maintain and repair the cell membrane: a permeable barrier surrounding the cell that separates its contents from its environment while allowing the transport of necessary substances.*

“Considerable evidence, dating from early studies, shows that muscle health is dependent on an adequate supply of dietary vitamin E,” the authors write. “Why vitamin E, at the cellular and molecular level, is crucial to muscle health has remained an unanswered question.”

In the current research, Dr. McNeil and colleagues demonstrated that treatment of cultured muscle cells with alpha-tocopherol results in increased membrane repair to injured cells. Further experimentation confirmed the involvement of vitamin E’s antioxidant function in its repair-promoting benefit, as well as its ability to insert itself into the cell membrane due to its lipid solubility.

The results of a meta-analysis published in the American Journal of Clinical Nutrition reaffirm an increased risk of all-cause mortality over follow-up periods ranging from 1.3 to 24 years in association with reduced serum levels of vitamin D.*

Sara Gandini and her associates selected 14 prospective cohort studies in which serum vitamin D levels were determined for a total of 62,548 men and women. Over the studies’ varying follow-up periods, 5,562 deaths occurred.

When the studies were analyzed according to highest versus lowest vitamin D levels, a 29% lower average risk of dying was observed for those whose levels were highest. A separate, nonlinear analysis of 11 studies, which utilized approximately 11 ng/mL 25-hydroxyvitamin D as the reference range, found reductions of 14%, 23%, and 31% in association with increases of 5, 10, and 20 ng/mL above this level.