EGG CONSUMPTION AND CARDIOVASCULAR DISEASE: PHYSICIANS’ HEALTH STUDY
Djoussé L, Gaziano JM. Egg consumption in relation to cardiovascular disease and mortality: the Physicians’ Health Study. Am J Clin Nutr. 2008;87:964–969.
Elevated levels of low-density lipoprotein (LDL) cholesterol is a major risk factor for developing coronary artery disease (CAD). Dietary guidelines reflect this association by recommending an upper limit on dietary cholesterol intake of <300 mg/d. Eggs contribute ∼200 mg cholesterol each to the diet, making them prime targets for reducing dietary cholesterol. However, in addition to cholesterol, eggs contribute nutrients such as B vitamins and folate, which are beneficial in CAD. Some research shows elevated risk of CAD with consumption of >2–6 eggs/week. Conversely, other studies do not support these observations. Recent recommendations for egg consumption indicate that eggs are not a significant health concern in healthy individuals. Djoussé and Gaziano report on a subset of data from the Physicians’ Health Study (PHS) that examines the interaction between egg consumption and CAD risk and mortality.
Male physicians (n = 21,327; mean age at randomization 53.7 ± 9.5 y) were enrolled into the PHS in 1981. Egg intakes were determined using an abbreviated food frequency questionnaire given every 2 years for 10 years, and the main outcome was evidence of CAD or mortality within 20 years of enrollment. Outcome events were judged by the Endpoint Committee of the PHS. Frequent egg consumption was associated with older age, higher BMI, greater vegetable intake, and lower breakfast cereal intake; it was also noted among smokers and current drinkers. When adjustments were made for confounding variables, intake of ≥7 eggs/week was associated with ∼23% greater risk of death, but egg consumption was not associated with incident myocardial infarction or stroke. The relationship between high egg intake and mortality was strongest for diabetics compared with non-diabetics. The authors conclude that while infrequent egg consumption (<6 eggs/week) is not associated with CAD risk and mortality, more frequent consumption (≥7 eggs/week) is positively associated with mortality, particularly in older diabetic males.
Comment: While the article described above has received considerable media attention, Dr. Eckel lists some cautions in interpreting the findings. First, dietary cholesterol is less consistently a risk factor for cardiovascular disease than are dietary saturated fat and trans fatty acid. Second, lifestyle differences associated with high and low egg consumers are also predictive of cardiovascular disease. Additionally, the abbreviated food frequency questionnaires that were used gave a narrower index of dietary quality and did not capture whole grain intake, fatty fish intake, or saturated fat intake, all of which are significant predictors of cardiovascular health.
Eckel RH. Egg consumption in relation to cardiovascular disease and mortality: the story gets more complex. Am J Clin Nutr. 2008;87:799–780.
SHORT SLEEP DURATION IN INFANCY A RISK FACTOR FOR LATER OVERWEIGHT
Taveras EM, Rifas-Shiman SL, Oken E, Gunderson EP, Gillman MW. Short sleep duration in infancy and risk of childhood overweight. Arch Pediatr Adolesc Med. 2008;162:305–311.
Several studies have established lack of sleep, or lack of good-quality sleep, as a risk factor for developing overweight in adulthood. Poor sleep is linked with reduced levels of leptin and increased levels of ghrelin, the combination of which may increase appetite and subsequently influence weight gain. Childhood obesity is increasingly of concern, and the etiology of childhood overweight may be more complex than increased television viewing or increased snack consumption. Taveras et al. examined the effects of short sleep duration in infancy on overweight later in life, with a follow-up at 3 years.
Participants included 915 children in Massachusetts in the Project Viva cohort. Mothers reported the number of hours the children slept at ages 6 months, 1 year, and 2 years. Body composition was measured at age 3 years using BMIs, skinfold thicknesses, and overweight for age at 3 years. Covariates included ethnicity, socioeconomic status, and television viewing. Sleep duration of less than 12 hours/night in infancy was associated with higher levels of overweight and adiposity at age 3. This effect was more pronounced in children watching more than 2 hours of television a day. The authors suggest that improved sleep hygiene may be an important component in the prevention of childhood obesity.
CENTRAL OBESITY AND DEMENTIA RISK
Whitmer RA, Gustafson DR, Barrett-Connor E, Haan MN, Gunderson EP, Yaffe K. Central obesity and increased risk of dementia more than three decades later. Neurol. 2008; 0: 01.wnl.0000306313.89165.efv1.
Central obesity, fat distributed around the abdomen, is widely recognized as a risk factor for developing type 2 diabetes, cardiovascular disease, and mortality. The metabolic activity of visceral fat is thought to contribute to insulin resistance and adipocytokine production. Total body obesity is linked with impairments in brain function and neurodegeneration. However, it is not known if visceral adiposity plays an important and selective role in the development of cognitive impairment as it does for the development of diabetes and cardiovascular disease. Whitmer et al. examined the association between peripheral obesity, central obesity, and total body obesity in middle age on the development of dementia in later life.
Participants were members of the Kaiser Permanente Medical Care Program in Northern California. Periodic Multiphasic Health Checkups were conducted on 6,583 members starting between 1964 and 1973 when participants were between 40 and 45 years old. Measurements at the time included BMI data, thigh circumference, sagittal abdominal diameter (SAD), and detailed clinical measures such as total serum cholesterol and blood glucose. Dementia status was determined using medical records between 1994 and 2006, when participants were between 73 and 87 years old; categories included dementia, Alzheimer's disease, vascular dementia, and dementia not otherwise specified. An increased risk for the development of dementia was found across quintiles of SAD, with the biggest increase noted for the highest quintile. There was no association between thigh circumference and risk for dementia. In comparing individuals with a normal BMI and a low SAD and a normal BMI and a high SAD, those with a high SAD were more likely to develop dementia than those with a low SAD. Obese individuals with a high SAD were at greatest risk for developing dementia. Overweight or obesity without central obesity was also a significant risk factor for developing dementia.
The present data suggest that visceral adiposity is a risk factor for dementia, whereas peripheral adiposity (as measured by thigh circumference) is not. Importantly, this relationship is evident in individuals with BMIs in the normal range, indicating that body mass alone is not the sole determinant in the interaction between adiposity and the development of dementia.
DARK CHOCOLATE CONSUMPTION AND CARDIOVASCULAR RISK FACTORS IN HYPERCHOLESTEROLEMIA
Allen RR, Carson LA, Kwik-Uribe C, Evans EM, Erdman JW. Daily consumption of a dark chocolate containing flavanols and added sterol esters affects cardiovascular risk factors in a normotensive population with elevated cholesterol. J Nutr. 2008;138:725–731.
Hypercholesterolemia is associated with the development of cardiovascular disease (CVD). To some degree, hypercholesterolemia can be modified with dietary changes, but reductions in total cholesterol have been modest. Diets rich in plant sterols (PS) and flavonoids are associated with lower cholesterol levels and reduced risk of CVD. Foods rich in flavanols, such as chocolate, are currently receiving special attention as potential nutritional interventions for medical conditions. The study by Allen et al. compared the effects of a sterol-enriched dark chocolate bar (CocoaVia PS+, Mars Inc.) on serum cholesterol to that of placebo (CocoaVia PS-, Mars Inc.) in a crossover, double-blind procedure.
Normotensive participants with total serum cholesterol concentrations of 5.20–7.28 mmol/L were randomized into one of two groups receiving either a PS-enriched bar or a placebo bar and were instructed to consume two bars/day in combination with an American Heart Association diet for 4 weeks. Participants were then switched to receive the other bar for 4 weeks; thus, all participants received both bars in a counterbalanced fashion. Cholesterol and other CVD markers were measured at baseline, 4 weeks, and 8 weeks. Four weeks of consumption of the PS-enriched bar was associated with reductions in total and LDL cholesterol and reductions in systolic blood pressure.
The authors propose that regular intake of chocolate containing PS and cocoa flavonoids would be beneficial in lowering cholesterol in hypercholesterolemic individuals and may promote cardiovascular health in this population. It should be noted that the placebo bars (CocoaVia) without PS were not effective in reducing cholesterol. While dark chocolate, which is rich in flavanols, may have some health benefits, the addition of PS provided the cholesterol-reducing benefit. Plant sterols are readily found in cereals, fruits, and vegetables, which are less calorically dense sources of these compounds.
OMEGA-3 FATTY ACIDS IN RELAPSE PREVENTION FOR CROHN'S DISEASE
Feagan BG, Sandborn WJ, Mittmann U, et al. Omega-3 free fatty acids for the maintenance of remission in Crohn disease: the EPIC randomized controlled trials. JAMA. 2008;299:1690–1697.
Crohn's disease is one of several inflammatory bowel disorders that are associated with nutritional deficiency, anemia, pain, and weight loss. Drug therapies to maintain remission of disease symptoms include immunosuppressive agents that have moderate efficacy but are also associated with increased risk of infection. Alternative therapies are actively being sought for remission maintenance. Omega-3 fatty acids have anti-inflammatory properties, and supplements are generally well tolerated. Their use as a novel therapy in remission maintenance was investigated in the Epanova Program in Crohn's Studies (EPIC)-1 and EPIC-2.
In both studies, 730 participants were randomized into either the omega-3 fatty acid condition (Epanova: 4 g/d; n = 377) or placebo (n = 376) and were followed for up to 58 weeks. Epanova is under development as a novel clinical intervention for both cardiovascular disease and Crohn's disease, with a proprietary formula consisting of 50–60% eicosapentanoic acid and 15–25% docosahexanoic acid. During the active arm of the study, no other treatments for Crohn's disease were allowed. The primary outcome measure was relapse of symptoms, defined either as an increase of a Crohn's Disease Activity Index (CDAI) to ≥150 points and an increase of more than 70 points from the baseline assessment, or as initiation of other treatment for Crohn's disease symptoms.
There were no differences in quality of life or changes in CDAI scores as a consequence of omega-3 fatty acid supplementation. Rates of relapse in the omega-3 group were approximately 38% in comparison to approximately 39% in the placebo group. The results from EPIC-1 and EPIC-2 suggest there is no beneficial effect of omega-3 fatty acids in the rate of relapse of Crohn's disease symptoms. The authors suggest that individuals seeking agents to prevent relapse should investigate established therapies.
DIET QUALITY AND ACADEMIC PERFORMANCE
Florence MD, Asbridge M, Veugelers PJ. Diet quality and academic performance. J School Health. 2008;78: 209–215.
The interaction between nutritional status and cognitive performance has been evaluated extensively in both children and adults, with research indicating that intake of specific micro- or macronutrients are associated with better overall mental ability. Recently, research has focused on the importance of single meals, such as breakfast, on short-term cognitive outcomes in young people. However, overall diet quality is likely to have long-term consequences on learning and mental development in young people. Florence et al. report on findings from the Children's Lifestyle and School-performance Study (CLASS) in Nova Scotia, Canada.
In the study, 4,589 fifth-grade students were given a modified version of the Harvard Youth/Adolescent Food Frequency Questionnaire (YAQ) appropriate for the region, and height and weight were determined for each student. Academic performance was determined approximately 6 months later, when students were in the sixth grade, using the Elementary Literary Assessment. Using this method, academic performance is limited to reading comprehension and writing ability and is dichotomized into pass/fail scores. Data were analyzed using multilevel logistic regression between indicators of diet quality and academic performance. Analyses included covariates such as socioeconomic status, parental education, and rural versus urban residence. Overall diet quality was positively associated with academic performance. Students with higher levels of fruit and vegetable intakes were less likely to fail the assessment.
The researchers report that variety and adequacy in the diet rather than balance and moderation were most strongly associated with performance. When adjusted for demographic and socioeconomic variables, higher diet quality remained a significant predictor of academic performance. The present findings highlight the importance of high-quality, varied diets in school-aged children.