WHOLE GRAIN INTAKE AND ABDOMINAL ADIPOSITY IN OLDER ADULTS
McKeown NM, Yoshida M, Shea MK, Jacques PF, Lichtenstein AH, Rogers G, Booth SL, and Saltzman E. Whole-grain intake and cereal fiber are associated with lower abdominal adiposity in older adults. J Nutr. 2009;139:1950–1955.
Obesity across all age groups continues to be a public health concern. The health risks associated with obesity are generally increased with abdominal obesity, which is defined as an accumulation of adipose tissue around the viscera. Diets high in fiber may be protective against the development of obesity, type 2 diabetes, and cardiovascular disease. Foods rich in soluble fiber, mainly fruits and vegetables, may modulate insulin secretion and delay gastric emptying. Foods high in insoluble fiber, such as cereal grains, may modulate the release of gut hormones involved in the regulation of food intake. Intake of unrefined cereal grains in particular is associated with lower body mass index and central adiposity in middle-aged individuals. In the present study, McKeown et al. examined the relationship between whole- and refined-grain intake and measures of body fat distribution in older free-living adults.
Participants in this study (N = 434; 257 women) represent a subset of individuals originally enrolled in a trial examining the effect of vitamin K supplementation on bone turnover and bone loss. Dietary intakes were determined using semiquantitative food-frequency questionnaires. Questionnaires were administered prior to measurement of body composition. Body composition measurements included BMI, weight, height, percent body fat, and abdominal adiposity. Participants had a mean dietary fiber intake of ∼18.6 g/d. The major dietary sources of whole grains were dark bread, hot and cold breakfast cereal, and brown rice. Participants with higher grain intakes tended to be female, to also take multivitamin supplements, and to not smoke. Individuals with higher intakes of refined grains tended to be male and to be more active. Whole-grain intake was associated with lower fat intake and higher carbohydrate intake. When examined across quartiles of intake, whole-grain intake was dose-dependently associated with lower percentages of total fat mass and abdominal fat. No associations were seen between body composition and total fiber intake or fiber intake from fruits or vegetables. The present findings of this cross-sectional analysis suggest that whole-grain intake may have a positive effect on body fat distribution in older individuals.
NO EFFECT OF MODERATE-DOSE FISH OIL ON MOOD OR CARDIOVASCULAR DISEASE RISK FACTORS IN STROKE PATIENTS
Poppitt SD, Howe CA, Lithander FE, Silvers KM, Lin RB, Croft J, Ratnasabapathy Y, Gibson RA, and Anderson CS. Effects of moderate-dose omega-3 fish oil on cardiovascular risk factors and mood after ischemic stroke. A randomized, controlled trial. Stroke. 2009;doi:10.1161/strokeaha.109.555136
Epidemiological data suggest a modest protective role of dietary fish oil or fish-oil supplements in the prevention of ischemic stroke and in the reduction of cardiovascular disease. Some evidence suggests that intake of omega-3 fatty acids may also be protective against depression, although the findings are not consistent. In ischemic stroke, as opposed to hemorrhagic stroke, atherosclerosis is a common pre-existing risk factor. To some degree, therefore, the positive effects of omega-3 fatty acids on the incidence of ischemic stroke may be related to overall improvement in cardiovascular health. In patients recovering from ischemic stroke, reductions in cardiovascular risk factors can be beneficial in the prevention of subsequent strokes. In patients with ischemic stroke, impairments in overall quality of life and stroke-related depression are common, and interventions are needed to improve patient outcome. Poppitt et al. report on a 12-week randomized, controlled trial designed to determine the efficacy of omega-3 fatty acid supplementation on patient outcome following ischemic stroke.
One hundred and two participants were randomized into either fish oil (3 g/d) or placebo conditions. All participants had confirmed stroke in the past, but not sooner than 3 months prior to enrollment into the trial. Supplements consisted of fish oil containing ∼1.2 g total omega-3 fatty acids (0.7 g docosahexaenoic acid; 0.3 g eicosapentaenoic acid); placebo capsules contained a combination of palm and soy oils. Primary outcome measures included total cholesterol, triglycerides, inflammatory markers, quality-of-life scores and general mood scores. Daily supplementation with fish oil capsules for 12 weeks did not alter serum lipids, inflammatory markers, or hemostatic markers. The authors note that, in particular, there was no decrease in triglycerides in the present trial following fish oil supplementation, which is not consistent with a recent review showing at least a 15% decrease in triglycerides following fish oil supplementation. Quality-of-life scores and mood scores were similarly unaffected by fish oil supplementation. The authors offer several arguments for the lack of efficacy of fish oil in the present trial. While a moderate dose of fish oil, similar to the one used here, may be sufficient to exert cardioprotective effects, it may be insufficient in individuals with ischemic stroke. Additionally, an administration period of 12 weeks may be too short a timeframe to see positive effects from a modest dose of fish oil. Although not addressed by the authors, all of the patients had a history of stroke not more recent than 3 months prior to entering the trial. It is possible that in individuals with ischemic stroke any intervention, particularly for mood and quality of life, needs to be in closer proximity to the ischemic event. The present trial does not show any positive effect of short-term, moderate-dose, fish-oil supplementation in patients who have had ischemic stroke.
LOW B-VITAMIN STATUS AND ALTERED BONE STRUCTURE IN OLDER ADULTS
Holstein JH, Herrmann M, Splett C, Herrmann W, Garcia P, Histing T, Graeber S, Ong MF, Kurz K, Siebel T, Menger MD, and Pohlemann T. Low serum folate and vitamin B-6 are associated with an altered cancellous bone structure in humans. Am J Clin Nutr. 2009;doi:ajcn.2009.28116v1-ajcn.28116
Epidemiological data link low B-vitamin status and high homocysteine with increased incidence of osteoporosis and bone fracture. Additionally, high levels of homocysteine and low levels of B vitamins are associated with increased bone resorption. However, in vivo studies do not show a clear relationship between B-vitamin deficiency and bone health, and human data on B-vitamin status and bone mineral density and bone structure lack consistency. In the present paper, Holstein et al. examine the relationship between serum levels of homocysteine, vitamin B12, vitamin B6, and folate and morphology of bone.
Fasting blood samples and femoral heads were obtained from 94 men and women (52–83 years) who underwent hip arthroplasty due to osteoarthritis. Exclusion criteria included prior hip trauma, vitamin D or calcium insufficiency, thyroid disease, and use of hormone therapy. Serum concentrations were determined for homocysteine, vitamins B6 and B12, folate, osteocalcin, and the bone resorption marker tartrate-resistant acid phosphatase (TRAP). Bones were analyzed using dual x-ray absorptiometry, biomechanical testing, and histomorphometry. Osteocalcin levels were positively associated with B-vitamin levels. Bone mineral density did not vary according to B-vitamin status. Cancellous bone structure, however, was impaired in those with low folate status, and it was altered to a lesser degree in those individuals with low vitamin B6 status. A limitation to interpreting the present data is that all serum measurements and bone collection were done in older individuals with osteoarthritis, and the findings may have limited applicability to non-arthritic individuals. Additionally, as older individuals are at risk for B-vitamin deficiency, observations on the relationship with B-vitamin status and bone structure in younger people are needed.
CARBOHYDRATE-INDUCED GHRELIN RELEASE IN OBESE ADOLESCENT GIRLS
Misra M, Tsai PM, Mendes N, Miller KK, and Klibanski A. Increased carbohydrate induced ghrelin secretion in obese vs. normal-weight adolescent girls. Obesity. 2009;17:1689–1695.
Obesity is associated with a number of metabolic changes, some of which can lead to insulin resistance and diabetes, and some of which may predispose an individual to overeat and become resistant to weight reduction. Several neuropeptides, including ghrelin and peptide YY (PYY), work in concert to regulate appetite, satiety, and food intake. Ghrelin, an orexigenic hormone, peaks before a meal and may be important for initiation of food intake. In adults, ghrelin secretion decreases after ingestion of fat and carbohydrate, but the pattern of ghrelin secretion is less well understood in younger individuals. PYY, an anorexigenic hormone, increases post-meal and may be important in satiety. It has been proposed that deficiency of PYY is involved in the development of obesity though decreased cues to cease eating. Like ghrelin, secretion of PYY may vary according to the macronutrient content of a meal, although the current research in this area is limited. In the present study reported by Misra et al., post-meal changes in secretion of ghrelin and PYY were measured in obese and normal-weight adolescent girls.
Twenty-six girls (13 obese; 13 normal weight) between the ages of 12 and 18 years were given each of three test meals for breakfast. Test meals varied in both food type and macronutrient composition, i.e., high-fat, high-protein, and high-carbohydrate. All participants received all meals in a randomized manner. Primary outcome measures included secretion of ghrelin and PYY, self-reported satiety, and total food intake at a subsequent meal. Biochemical measures were determined prior to eating breakfast and at 20-min intervals following breakfast for a total sampling time of 5 h 15 min. Fasting ghrelin levels were lower in the obese participants relative to normal-weight girls. Following ingestion of the high-carbohydrate breakfast, ghrelin increased to a greater degree in the obese girls relative to the normal-weight girls, and remained elevated over the entire sampling period. Fasting PYY levels did not differ between obese and normal-weight girls. Following ingestion of a high-fat breakfast, PYY release was lower in the obese girls relative to the normal-weight girls. Self-reported satiety was lower in obese relative to non-obese girls, and the obese girls ate significantly more food at lunch following the high-fat and high-carbohydrate test breakfasts. In the present study, there were changes in orexigenic and anorexigenic hormones in obese girls relative to normal-weight girls following intake of high-fat or high-carbohydrate test meals. The subsequent decreased satiety ratings and increased food intake at lunch indicate that, in adolescent girls, changes in hormonal milieu related to obesity may contribute to a pattern of increased hunger and increased food intake.