Vegan Diets Short on Omega-3 and Vitamin B12 May Increase Cardiovascular Risk

According to a new review, vegetarian and vegan diets may require additional omega-3 and vitamin B12 supplementation to reduce factors that increase heart disease risk.

A new review in the Journal of Agricultural and Food Chemistry indicates that many vegetarians, especially vegans, may unknowingly be at risk for certain cardiovascular health problems due to inadequate intakes of omega-3 fatty acids and vitamin B12.

The review stated that although meat eaters are known to have a significantly higher combination of cardiovascular risk factors than vegetarians, people following strict vegetarian and vegan diets are not invulnerable to risk. These diets tend to lack several key nutrients, including iron, zinc, vitamin B12, and omega-3 fatty acids.

Meat eaters are known to have a significantly higher incidence of certain cardiovascular risk factors compared with vegetarians, including increased BMI and waist-to-hip ratio, and higher blood pressure, plasma total cholesterol, and triglycerides. However, after reviewing 30 years of studies on vegetarianism, vegetarians and vegans typically have lower concentrations of serum vitamin B12 and omega-3 polyunsaturated fatty acid levels in tissue membrane phospholipids when compared to meat eaters.

Risks associated with low vitamin B12 and omega-3 status include an increase in blood clotting (platelet aggregation) due to increased levels of homocysteine, and decreased levels of ‘good’ HDL-cholesterol. Low HDL cholesterol and high homocysteine levels may be linked to an increase in cardiovascular and stroke risk.

The authors suggest that vegetarians, especially vegans, could benefit from increased dietary intake of omega-3 fatty acids to improve the balance and ratio of omega-3s to omega-6s. They can also benefit from increased vitamin B12 intake, including use of supplements containing vitamin B12 if necessary. Increasing dietary or supplemental omega-3 and vitamin B12 may reduce clotting tendencies that increase vegetarian and vegans’ otherwise low risk of cardiovascular disease.

Duo Li. Chemistry behind Vegetarianism. 2011. J Agric Food Chem 59(3):777–84.

During Pregnancy, Low–Glycemic Diets Improve Health Outcomes in Obese Women & Their Infants

A new study shows that a low-glycemic load diet in overweight and obese pregnant women results in longer pregnancy duration, greater infant head circumference, and improved maternal cardiovascular risk factors.
Read more about this research below.

Excess body weight is known to complicate pregnancies, but the optimal diet during pregnancy is currently unknown. New research published in the American Journal of Clinical Nutrition aimed to examine the effects of a low–glycemic load (low-GL) diet in overweight and obese pregnant women.

Researchers randomly assigned 46 overweight or obese pregnant women to receive a low-GL or a low-fat diet. The women received carbohydrate-rich foods, fats, and snack foods through home delivery or study visits. Birth weight, infant body measurements, gestational duration, maternal weight gain, and maternal metabolic parameters were measured.

No significant differences in birth weight or measures of infant body fat were seen between the two groups. However, in the low-GL compared with the low-fat group, gestational duration was significantly longer and fewer deliveries occurred at less than 38.0 weeks (13% versus 48%). Adjusted head circumference was greater in the low-GL versus the low-fat group. Women in the low-GL group had smaller increases in triglycerides and total cholesterol and a greater decrease in C-reactive protein (a marker of inflammation).
In this study, a low-GL diet correlated with longer pregnancy duration, greater infant head circumference, and improved maternal cardiovascular risk factors. Researchers suggest that large-scale studies may be useful in determining whether a low-GL diet may be beneficial in the prevention of prematurity and other unfavorable maternal and infant outcomes.

Rhodes ET, et al. Effects of a low–glycemic load diet in overweight and obese pregnant women: a pilot randomized controlled trial. 2010. Am J Clin Nutr 92(6):1306-15.

Low Vitamin D Levels Linked to Prediabetes and Prehypertension

A recently published study showed that adults with low vitamin D levels had more than double the risk of prehypertension and prediabetes than adults with higher vitamin D levels.

Prediabetes and prehypertension have been associated with low vitamin D levels. In a recent issue of the journal Diabetes Care, scientists report a correlation between reduced vitamin D levels and prediabetes and prehypertension in adults. Both prediabetes and prehypertension are estimated to exist in at least one-fourth of disease-free adults. 

Researchers analyzed data from 898 men and 813 women who participated in the National Health and Nutrition Examination Survey (NHANES), 2001-2006. Blood pressure measurements were obtained during examinations conducted upon enrollment, and blood samples were evaluated for glucose, serum 25-hydroxyvitamin D and other factors.


Prediabetes was defined as having a fasting serum glucose of between 100 and 125 milligrams per deciliter, and prehypertension was defined as systolic blood pressure of 120 to 139 mmHg and/or diastolic blood pressure between 80 and 89 mmHg. Prediabetes was 33 percent higher among those with vitamin D levels of 76.3 nmol/l (30.5 ng/ml) or less compared to those with higher levels. Prehypertension was evident in 61 percent of those with the lower vitamin D levels. Participants with undiagnosed diabetes and untreated hypertension had even lower vitamin D levels on average. Serum vitamin D levels tended to decline with increasing age and body mass.

When the risk of having both conditions was considered, those with low vitamin D levels had 2.4 times the risk of that experienced by subjects with higher vitamin D levels.  

It is reasonable that among those with prediabetes or prehypertension, vitamin D supplementation resulting in increased serum vitamin D levels may help reverse subtle changes in fasting serum glucose and resting blood pressure that may lead to more advanced disease states. 

Alok K. Gupta, MD, Meghan M. Brashear, MPH and William D. Johnson, PHD. Prediabetes and Prehypertension in Healthy Adults Are Associated With Low Vitamin D Levels. Diabetes Care March 2011 vol. 34 no. 3 658-660.

Glycemic Load is a Better Predictor of Glycemic Response Than Carbohydrate Content Alone

A new study provides evidence that the glycemic load of a meal is a better predictor of blood glucose and insulin response that simply accounting for total carbohydrates.

The glycemic load (GL) is a ranking system for carbohydrate content in food portions based on their glycemic index (GI) and the portion size. Glycemic load for a single serving of a food can be calculated as the quantity (in grams) of its carbohydrate content, multiplied by its GI, and divided by 100. While GL is increasingly used in nutritional research, its ability to predict postprandial (after meal) blood glucose and insulin response for a wide range of foods or mixed meals has been unclear.   

In a recent issue of the American Journal of Clinical Nutrition, researchers sought to assess the degree of correlation between calculated GL and observed glucose and insulin responses in healthy subjects consuming calorically identical portions of single foods and mixed meals.

In study 1, healthy subjects consumed 240 calorie portions of 121 single foods in 10 food categories. In study 2, healthy subjects consumed 480 calorie servings of 13 mixed meals. Foods and meals varied widely in macronutrient content, fiber, and GL. Blood glucose and insulin responses were measured and compared to a reference food (= 100).

Among the single foods, GL was a more powerful predictor of postprandial glucose and insulin response than was the available carbohydrate content itself. Similarly, for mixed meals, GL was also the strongest predictor of postprandial glucose and insulin responses. Carbohydrate content alone was predictive of the glucose and insulin responses to single foods, but not to mixed meals.

The results of this study are the first to provide large-scale evidence of the superiority of using dietary GL over carbohydrate content alone to estimate postprandial glucose and insulin response in healthy individuals.   

Jiansong Bao et al. Prediction of postprandial glycemia and insulinemia in lean, young, healthy adults: glycemic load compared with carbohydrate content alone. Am J Clin Nutr May 2011 vol. 93 no. 5 984-996.

Energy Expenditure is Reduced by Sleep Deprivation – A Possible Link to Obesity

A new study shows that total sleep deprivation reduces energy expenditure and may partly explain the connection between poor sleep and an increased risk of obesity.

Observational and epidemiologic evidence has shown that chronic deficits in sleep are related to an increased risk of obesity, but the mechanisms behind this relation have not been fully explained.   

In a recent study published in the American Journal of Clinical Nutrition researchers examined the effect of a single night of total sleep deprivation on food intake and morning energy expenditure.

Using a balanced crossover design, scientists examined 14 healthy, normal-weight males on 2 occasions during a regular 24 hour sleep-wake cycle (including 8 hours of nocturnal sleep) and a 24 hour period of continuous wakefulness. On the morning after regular sleep and total sleep deprivation, resting and postprandial (after meal) energy expenditures were analyzed.  Food intake in both groups was assessed again in the late afternoon after the subjects were given a free-choice food intake from a large buffet. Circulating concentrations of ghrelin, leptin, norepinephrine, cortisol, thyreotropin, glucose, and insulin were repeatedly measured over the entire 24 hour session.

In comparison with normal sleep, resting energy expenditure was reduced by 5% and postprandial expenditure by 20% in the sleep deprived subjects.  Nocturnal wakefulness increased morning plasma ghrelin concentrations (a hormone that stimulates hunger), and nocturnal and daytime circulating concentrations of thyreotropin, cortisol, and norepinephrine) as well as morning postprandial plasma glucose concentrations. Changes in food intakes were variable, and no differences between wake and sleep conditions were detected.   

These research findings show that one night of sleep deprivation significantly reduces energy expenditure in the short-term, which suggests that sleep contributes to the regulation of daytime energy expenditure in humans.  

Christian Benedict et al. Acute sleep deprivation reduces energy expenditure in healthy men Am J Clin Nutr June 2011 vol. 93 no. 6 1229-1236.

Magnesium Reduces Risk of Sudden Cardiac Death in Women

A recent study involving a large group of women studied over 26 years found that those with the highest magnesium intake (and corresponding plasma levels) had a 41% lower risk of sudden cardiac death.

Magnesium has beneficial cardiovascular properties in cellular and experimental models, but its relation to sudden cardiac death (SCD) risk in humans is unclear.

In a recent study published in the American Journal of Clinical Nutrition, researchers examined the association between magnesium, as measured in diet and plasma, and risk of SCD. The association for magnesium intake was examined prospectively in 88,375 women who were free of disease in 1980 and part of the Nurses’ Health Study. Information on magnesium intake, other nutrients, and lifestyle factors was updated every 2–4 years through questionnaires. In this group of women, there were 505 cases of sudden or arrhythmic death documented over 26 years of follow-up.

After adjustment for confounders and potential intermediaries, the relative risk of SCD was significantly lower in women in the highest quartile of both dietary intake and plasma levels of magnesium (when compared to those in the lowest quartile). The inverse relation with SCD was stronger for plasma magnesium than dietary intake of magnesium, with each 0.25 mg/dL (one standard deviation) increment in plasma magnesium associated with a 41% lower risk of SCD.

In this study group of women, higher plasma concentrations and dietary intakes of magnesium were associated with lower risks of SCD. The researchers stated that if the observation is causal, interventions aimed at increasing dietary or plasma magnesium might lower the risk of sudden cardiac death.

Chiuve SE, et al. Plasma and dietary magnesium and risk of sudden cardiac death in women. 2011. Am J Clin Nutr 93(2):253-260.

Higher Dietary Fiber Intake Reduces Risk of Death in Older Adults

In the largest diet and health study ever conducted, dietary fiber intake was associated with a reduced risk of overall death, including death caused specifically by cardiovascular, infectious, and respiratory diseases.

Previous research on dietary fiber has shown beneficial effects in lowering the risk of cardiovascular disease, diabetes, and some cancers. Less is known about the effect of dietary fiber on overall mortality and specific causes of death.

In a recent study published in the Archives of Internal Medicine, researchers analyzed dietary fiber intake in relation to total mortality and death from specific causes in the NIH (National Institutes of Health)-AARP Diet and Health Study. The study included over 500,000 men and women ages 50-71 who answered questionnaires with specific diet and lifestyle questions. Diet was assessed using a food-frequency questionnaire at baseline, then again after an average of 9 years of follow-up.

Researchers identified 20,126 deaths in men and 11,330 deaths in women during the study period. Cause of death was identified using the National Death Index Plus.

Dietary fiber intake was associated with a 22% reduction in risk of total death in both men and women. Dietary fiber intake also lowered the risk of death from cardiovascular, infectious, and respiratory diseases by 24% to 56% in men and by 34% to 59% in women. In men, there was an inverse association between dietary fiber intake and cancer death. Dietary fiber from grains was most closely related to a reduction in the risk of overall mortality and cause-specific death in both men and women.

Dietary fiber may reduce the risk of death from cardiovascular, infectious, and respiratory diseases. Ensuring adequate fiber intake by eating a fiber-rich diet appears to provide significant health benefits.

Park Y, Subar AF, Hollenbeck A, Schatzkin A. Dietary Fiber Intake and Mortality in the NIH-AARP Diet and Health Study. 2011. Arch Intern Med, published online 14-Feb-2011. doi:10.1001/archinternmed.2011.18 http://archinte.ama-assn.org/cgi/content/abstract/archinternmed.2011.18v1