FOLLOWING NUTRITIONAL RECOMMENDATIONS PROTECTS COGNITIVE PERFORMANCE
Kesse-Guyot E, Amieva H, Castetbon K, Henegar A, Ferry M, Jeandel C, Hercberg S, Galan P; and the SU.VI.MAX 2 Research Group. Adherence to nutritional recommendations and subsequent cognitive performance: findings from the prospective Supplementation with Antioxidant Vitamins and Minerals 2 (SU.VI.MAX 2) study. Am J Clin Nutr. 2011;93:200–210.
Considerable research indicates that, when considering age-related cognitive decline, primary prevention is key. Observational studies link intake of a number of nutritional components, including fatty fish, antioxidant nutrients, and B vitamins, with reduced risk for cognitive decline and Alzheimer's disease. While each type of nutrient has been studied extensively for its role in brain function, the human diet is complex, and it is agreed that the diet as a whole contributes synergistic effects on brain structure and on cognitive performance. A better understanding of the predictive value of the overall diet on cognitive outcomes is consequently needed. Some research shows that adherence to a Mediterranean-style diet is associated with better cognitive outcomes over time. While the Mediterranean-style diet is touted for its health benefits, most nations have existing health guidelines that promote high intake of fruits, vegetables, and whole grains and limited intake of saturated fats. The current report by Kesse-Guyot et al. describes the degree to which adherence to French national nutritional guidelines over time affects cognitive function in older individuals.
Participants in the analysis (N = 2135) represent a subset of individuals enrolled in the Supplementation with Antioxidant Vitamins and Minerals (SU.VI.MAX; 1994–2002) and SU.VI.MAX 2 (2007–2009). During the first year of enrollment in SU.VI.MAX (1994–1996), participants completed 24-hour food recalls every 2 months to yield a total of six records/year. Food intake and physical activity scores (PNNS-GS) were determined using the French National Nutrition and Health Program Guidelines, with a higher score indicating greater compliance with national guidelines (max. score = 15). Cognitive assessments were conducted approximately 13 years later at the beginning of SU.VI.MAX 2 (2007–2009). The cognitive test battery included measures of verbal fluency, cued-recall, mental flexibility, and working memory. Mean age at baseline was approximately 52 years, with a mean PNNS-GS of 7.6 for men and 8.1 for women.
Verbal memory scores were positively associated with increasing PNNS-GS. Better verbal memory was seen in individuals who consumed at least five servings of fruits and vegetables per day in comparison to low-level consumers of fruits and vegetables. Additionally, better verbal memory was associated with lower consumption of meat, seafood, and eggs (0–1 portion/day), and breads, cereals, legumes, and potatoes (1–3 portions/day) in comparison to those who exceeded recommended intake levels. These prospective data suggest that adherence to nutritional guidelines in adulthood confers positive effects on verbal memory performance in later years, a cognitive domain that appears particularly vulnerable in age-related decline. The authors argue that public health nutritional programs can play an important role in the prevention of age-related cognitive impairments.
RECENT TRENDS IN DIETARY SUPPLEMENT USE IN THE UNITED STATES
Bailey RL, Gahche JJ, Lentino CV, Dwyer JT, Engel JS, Thomas PR, Betz JM, Sempos CT, and Picciano MF. Dietary supplement use in the United States, 2003–2006. J Nutr. 2011;141:261–266.
Dietary supplement use continues to be popular in the United States. Individuals typically ingest multivitamins and single-nutrient supplements as a perceived means of promoting self-health and as “insurance” against perceived nutrient deficiencies in the diet. The National Health and Nutrition Examination Survey (NHANES) has monitored the use of dietary supplements since NHANES I (1971–1974). In the 1970s, 28% of adult men and 38% of adult women used supplements. In NHANES III (1988–1994), use of supplements increased to 35% of all males and to 43% of all females over the age of 2 months, and use continues to rise. The analysis reported currently by Bailey et al. describes supplement use among the US population using NHANES data from 2003 to 2006. Data from the NHANES are nationally representative of noninstitutionalized civilian residents of the United States.
Dietary supplement use was estimated in individuals ≥1 year of age (n = 18,758), with the exclusion of pregnant women. Participants were stratified into daily recommended intake age groupings and further categorized by body mass index (BMI), race, and education. Dietary supplement use was assessed using the Dietary Supplement Questionnaire, which solicits information on the use of vitamins, minerals, herbals, and other supplements over the previous 30 days. Detailed information was collected about supplement type, dose, and frequency and duration of consumption. Supplement use was categorized into four major classes: multivitamin-multimineral, botanicals, and amino acids.
During the 2003–2006 NHANES, 44% of males and 53% of females over the age of 1 year used dietary supplements. Use of supplements increased as a function of age and as a function of education level. Use of any type of supplement was highest for participants over the age of 71 years (71%). Multivitamin-multimineral supplements were the most commonly used (33% of reported use), and use was higher in individuals over the age of 51 years. When stratified across BMI, obese individuals were less likely to use supplements relative to overweight or normal-weight people. When comparing across race, non-Hispanic white people reported higher supplement use than non-Hispanic blacks or Mexican-Americans. The most commonly consumed vitamin supplements included vitamin B6, B12, C, A, and E; the most commonly consumed mineral supplements included iron, selenium, chromium, zinc, and magnesium. Dietary supplement use has increased some 10 percentage points since NHANES III (1988–1994), and 2 percentage points from NHANES 1999–2000. With approximately one-half of the US population using at least one form of dietary supplement, and 10% using more than five dietary supplements, the authors argue it is important to correctly determine nutrient intakes from all sources to correctly determine nutrient over- or underexposure.
CALORIC RESTRICTION AND BIOMARKERS OF OXIDATIVE STRESS
Meydani M, Das S, Band M, Epstein S, and Roberts S. The effect of caloric restriction and glycemic load on measures of oxidative stress and antioxidants in humans: results from the CALERIE trial of human caloric restriction. J Nutr Health Aging. 2011; DOI: 10.1007/s12603-011-0002-z
In recent years, long-term caloric restriction has garnered considerable interest as a potential tool in modifying pathology associated with aging. It is theorized that oxidative stress negatively impacts health and longevity over time, and that reducing oxidative stress would reduce the rate of aging. In animal studies, chronic moderate caloric restriction reduces oxidative stress, enhances the antioxidant defense system, and increases life span. Caloric restriction in animals reduces oxidative damage to DNA, brain and muscle proteins, and the immune system. Reductions in oxidative stress may be moderated by increases in antioxidant enzymes, including superoxide dismutase, catalase, and glutathione peroxidase, produced by caloric restriction. Information on the effect of long-term caloric restriction in normal-weight humans is more limited. To better understand these observations, the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) study was designed to assess the practicality and effect of prolonged caloric restriction on aging in humans. Meydani et al. report on the relationship between body weight, adiposity, and markers of oxidative stress in a subset of the CALERIE cohort.
Healthy men and women from the greater Boston area between the ages of 24 and 42 years and with body mass index scores between 25 and 29.9 kg/m2 were enrolled into the trial (N = 46). Baseline assessments of typical energy requirements were measured prior to caloric restriction. Participants were randomly assigned to either 10% (n = 12) or 30% (n = 34) caloric restriction for 6 months. Within each level of caloric restriction, participants were randomized into either a high-glycemic-load diet or a low-glycemic-load diet. High-glycemic-load diets consisted of 60% carbohydrate, 20% protein, 20% fat, and 15 g fiber/1,000 kcal. Low-glycemic-load diets consisted of 40% carbohydrate, 30% protein, 30% fat, and 15 g fiber/1,000 kcal. Diets contained levels of macronutrients and micronutrients consistent with current dietary guidelines. All food was provided to the participants, and compliance was ascertained using participants' reports of leftover food or additional food consumed. Individual and group sessions with a study dietician were employed to maximize adherence to the study protocols. Primary outcome measures included changes in body weight and changes in urinary concentrations of biomarkers for oxidative stress and defense, including glutathione peroxidase, catalase, 8-epi-PGF2α, superoxide dismutase, protein carbonyl, and 8-OHdG.
Over 6 months, participant compliance with the caloric restriction protocol was good, and the body weight of participants in both restriction conditions decreased. Changes in body weight were not different between caloric restriction conditions or between glycemic load conditions. Glutathione peroxidase (oxidative defense) increased over the study period and protein carbonyl (oxidative stress) decreased. Six-month caloric restriction was not associated with changes in catalase, 8-epi-PGF2α, superoxide dismutase, or 8-OHdG. There was a trend, however, for a decrease in 8-epi-PGF2α, suggesting a trend for decreased lipid peroxidation. Decreases in body mass index, percent body fat, or total fat were not associated with changes in markers of oxidative stress/defense. In humans, 6-month caloric restriction is associated with changes in some biomarkers indicative of oxidative stress and antioxidant defense.