Understanding omega-3 polyunsaturated Fatty acids.

Understanding omega-3 polyunsaturated Fatty acids.

Calder PC, Yaqoob P.

Institute of Human Nutrition School of Medicine, Southampton General Hospital, Southampton, UK. pcc@soton.ac.uk.

Current intakes of very long-chain omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are low in most individuals living in Western countries. A good natural source of these fatty acids is seafood, especially oily fish. Fish oil capsules contain these fatty acids also. Very long-chain omega-3 fatty acids are readily incorporated from capsules into transport (blood lipids), functional (cell and tissue), and storage (adipose) pools. This incorporation is dose-dependent and follows a kinetic pattern that is characteristic for each pool. At sufficient levels of incorporation, EPA and DHA influence the physical nature of cell membranes and membrane protein-mediated responses, lipid-mediator generation, cell signaling, and gene expression in many different cell types. Through these mechanisms, EPA and DHA influence cell and tissue physiology and the way cells and tissues respond to external signals. In most cases the effects seen are compatible with improvements in disease biomarker profiles or health-related outcomes. As a result, very long-chain omega-3 fatty acids play a role in achieving optimal health and in protection against disease. Long-chain omega-3 fatty acids not only protect against cardiovascular morbidity but also against mortality. In some conditions, for example rheumatoid arthritis, they may be beneficial as therapeutic agents. On the basis of the recognized health improvements brought about by long-chain omega-3 fatty acids, recommendations have been made to increase their intake. The plant omega-3 fatty acid, alpha-linolenic acid (ALA), can be converted to EPA, but conversion to DHA appears to be poor in humans. Effects of ALA on human health-related outcomes appear to be due to conversion to EPA, and since this is limited, moderately increased consumption of ALA may be of little benefit in improving health outcomes compared with increased intake of preformed EPA + DHA.

Use of multivitamin supplements in relation to allergic disease in 8-y-old children

Use of multivitamin supplements in relation to allergic disease in 8-y-old children
[Dietary supplements]
from American Journal of Clinical Nutrition current issue by Marmsjo, K., Rosenlund, H., Kull, I., Hakansson, N., Wickman, M., Pershagen, G., Bergstrom, A.

Background: Multivitamins are frequently consumed by children, but it is unclear whether this affects the risk of allergic disease.

Objective: We sought to study the association between multivitamin supplementation and allergic disease in 8-y-old children.

Design: Data were obtained from a Swedish birth cohort study. Information on lifestyle factors, including use of vitamin supplements, environmental exposures, and symptoms and diagnoses of allergic diseases, was obtained by parental questionnaires. In addition, allergen-specific IgE concentrations of food and airborne allergens were measured in blood samples collected at age 8 y. A total of 2423 children were included in the study. The association between use of vitamin supplements and the selected health outcomes was analyzed with logistic regression.

Results: Overall, no strong and consistent associations were observed between current multivitamin use and asthma, allergic rhinitis, eczema, or atopic sensitization at age 8 y. However, children who reported that they started taking multivitamins before or at age 4 y had a decreased risk of sensitization to food allergens (odds ratio: 0.61; 95% CI: 0.39, 0.97) and tendencies toward inverse associations with allergic rhinitis. In contrast, there was no consistent association among children who started to use multivitamins at or after age 5 y.

Conclusion: Our results show no association between current use of multivitamins and risk of allergic disease but suggest that supplementation with multivitamins during the first years of life may reduce the risk of allergic disease at school age.

Dietary protein and bone health: a systematic review and meta-analysis

Dietary protein and bone health: a systematic review and meta-analysis [Bone metabolism]
from American Journal of Clinical Nutrition current issue by Darling, A. L, Millward, D J., Torgerson, D. J, Hewitt, C. E, Lanham-New, S. A

Background: There has been a resurgence of interest in the controversial relation between dietary protein and bone health.

Objective: This article reports on the first systematic review and meta-analysis of the relation between protein and bone health in healthy human adults.

Design: The MEDLINE (January 1966 to September 2007) and EMBASE (1974 to July 2008) databases were electronically searched for all relevant studies of healthy adults; studies of calcium excretion or calcium balance were excluded.

Results: In cross-sectional surveys, all pooled r values for the relation between protein intake and bone mineral density (BMD) or bone mineral content at the main clinically relevant sites were significant and positive; protein intake explained 1–2% of BMD. A meta-analysis of randomized placebo-controlled trials indicated a significant positive influence of all protein supplementation on lumbar spine BMD but showed no association with relative risk of hip fractures. No significant effects were identified for soy protein or milk basic protein on lumbar spine BMD.

Conclusions: A small positive effect of protein supplementation on lumbar spine BMD in randomized placebo-controlled trials supports the positive association between protein intake and bone health found in cross-sectional surveys. However, these results were not supported by cohort study findings for hip fracture risk. Any effects found were small and had 95% CIs that were close to zero. Therefore, there is a small benefit of protein on bone health, but the benefit may not necessarily translate into reduced fracture risk in the long term.

Dietary fat intake and subsequent weight change in adults: results from the European Prospective Investigation into Cancer and Nutrition cohorts

Dietary fat intake and subsequent weight change in adults: results from the European Prospective Investigation into Cancer and Nutrition cohorts
[Nutritional epidemiology and public health]

from American Journal of Clinical Nutrition current issue by Forouhi, N. G, Sharp, S. J, Du, H., van der A, D. L, Halkjaer, J., Schulze, M. B, Tjonneland, A., Overvad, K., Jakobsen, M. U., Boeing, H., Buijsse, B., Palli, D., Masala, G., Feskens, E. J., Sorensen, T. I., Wareham, N. J

Background: It is unclear from the inconsistent epidemiologic evidence whether dietary fat intake is associated with future weight change.

Objective: The objective was to assess the association between the amount and type of dietary fat and subsequent weight change (follow-up weight minus baseline weight divided by duration of follow-up).

Design: We analyzed data from 89,432 men and women from 6 cohorts of the EPIC (European Prospective Investigation into Cancer and Nutrition) study. Using country-specific food-frequency questionnaires, we examined the association between baseline fat intake (amount and type of total, saturated, polyunsaturated, and monounsaturated fats) and annual weight change by using the residual, nutrient density, and energy-partition methods. We used random-effects meta-analyses to obtain pooled estimates across centers.

Results: Mean total fat intake as a percentage of energy intake ranged between 31.5% and 36.5% across the 6 cohorts (58% women; mean ± SD age: 53.2 ± 8.6 y). The mean (±SD) annual weight change was 109 ± 817 g/y in men and 119 ± 823 g/y in women. In pooled analyses adjusted for anthropometric, dietary, and lifestyle factors and follow-up period, no significant association was observed between fat intake (amount or type) and weight change. The difference in mean annual weight change was 0.90 g/y (95% CI: –0.54, 2.34 g/y) for men and –1.30 g/y (95% CI: –3.70, 1.11 g/y) for women per 1 g/d energy-adjusted fat intake (residual method).

Conclusions: We found no significant association between the amount or type of dietary fat and subsequent weight change in this large prospective study. These findings do not support the use of low-fat diets to prevent weight gain.

Green tea consumption is associated with depressive symptoms in the elderly

Green tea consumption is associated with depressive symptoms in the elderly
[Nutritional epidemiology and public health]

from American Journal of Clinical Nutrition current issue by Niu, K., Hozawa, A., Kuriyama, S., Ebihara, S., Guo, H., Nakaya, N., Ohmori-Matsuda, K., Takahashi, H., Masamune, Y., Asada, M., Sasaki, S., Arai, H., Awata, S., Nagatomi, R., Tsuji, I.

Background: Green tea is reported to have various beneficial effects (eg, anti–stress response and antiinflammatory effects) on human health. Although these functions might be associated with the development and progression of depressive symptoms, no studies have investigated the relation between green tea consumption and depressive symptoms in a community-dwelling population.

Objective: The aim of this study was to investigate the relations between green tea consumption and depressive symptoms in elderly Japanese subjects who widely consumed green tea.

Design: We conducted a cross-sectional study in 1058 community-dwelling elderly Japanese individuals aged ≥70 y. Green tea consumption was assessed by using a self-administered questionnaire, and depressive symptoms were evaluated by using the 30-item Geriatric Depression Scale with 2 cutoffs: 11 (mild and severe depressive symptoms) and 14 (severe depressive symptoms). If a participant was consuming antidepressants, he or she was considered to have depressive symptoms.

Results: The prevalence of mild and severe and severe depressive symptoms was 34.1% and 20.2%, respectively. After adjustment for confounding factors, the odds ratios (95% CI) for mild and severe depressive symptoms when higher green tea consumption was compared with green tea consumption of ≤1 cup/d were as follows: 2–3 cups green tea/d (0.96; 95% CI: 0.66, 1.42) and ≥4 cups green tea/d (0.56; 95% CI: 0.39, 0.81) (P for trend: 0.001). Similar relations were also observed in the case of severe depressive symptoms.

Conclusion: A more frequent consumption of green tea was associated with a lower prevalence of depressive symptoms in the community-dwelling older population.

Effect of a dietary intervention and n-3 fatty acid supplementation on measures of serum lipid and insulin sensitivity in persons with HIV

Effect of a dietary intervention and n-3 fatty acid supplementation on measures of serum lipid and insulin sensitivity in persons with HIV [AIDS and other wasting syndromes]

from American Journal of Clinical Nutrition current issue by Woods, M. N, Wanke, C. A, Ling, P.-R., Hendricks, K. M, Tang, A. M, Knox, T. A, Andersson, C. E, Dong, K. R, Skinner, S. C, Bistrian, B. R

Background: Elevated serum triglyceride and low HDL-cholesterol concentrations have been reported in persons with HIV.

Objective: The effect of a dietary intervention plus n–3 (–3) fatty acid supplementation on serum triglycerides and markers of insulin sensitivity was investigated.

Design: Fifty-four persons with HIV and elevated serum triglycerides (>150 mg/dL) and/or abnormal Quantitative Insulin Sensitivity Check Index values (<0.35 but >0.30) were recruited for a dietary intervention in which total fat, type of fat, fiber, and glycemic load were controlled along with supplementation with n–3 fatty acids to achieve an intake of 6 g/d. The subjects were randomly assigned to an intervention or control group, and serum lipids, markers of insulin sensitivity, and serum phospholipid fatty acids were measured in both groups at baseline, 3 wk, and 13 wk.

Results: Triglycerides in the intervention group decreased from a median of 180 mg/dL (interquartile range: 141, 396) to 114 mg/dL (interquartile range: 84, 169) from baseline to 3 wk, whereas they remained stable in the control group (P = 0.003). Serum phospholipid fatty acids indicated a decrease in de novo lipogenesis and a decrease in arachidonic acid (% nmol; P ≤ 0.001) in the intervention group. At 3 wk, the insulin area under the curve decreased but not significantly.

Conclusions: Diet and n–3 fatty acid supplementation dramatically reduced serum triglycerides, decreased arachidonic acid in the phospholipids fraction, and appeared to decrease the de novo lipogenesis associated with the metabolic syndrome in the intervention group.

Short-term sleep loss decreases physical activity under free-living conditions but does not increase food intake under time-deprived laboratory conditions in healthy men

Short-term sleep loss decreases physical activity under free-living conditions but does not increase food intake under time-deprived laboratory conditions in healthy men [Obesity and eating disorders]

from American Journal of Clinical Nutrition current issue by Schmid, S. M, Hallschmid, M., Jauch-Chara, K., Wilms, B., Benedict, C., Lehnert, H., Born, J., Schultes, B.

Background: Short sleep duration is correlated with an increased risk of developing obesity and cardiovascular disease, but the mechanisms behind this relation are largely unknown.

Objective: We aimed to test the hypothesis that acute sleep loss decreases physical activity while increasing food intake, thereby shifting 2 crucial behavioral components of energy homeostasis toward weight gain.

Design: In 15 healthy, normal-weight men, spontaneous physical activity was registered by accelerometry during the entire experiment, and food intake as well as relevant hormones were assessed during a 15-h daytime period after 2 nights of regular sleep (bed time: 2245–0700) and after 2 nights of restricted sleep (bed time: 0245–0700). Experiments were performed in a crossover design.

Results: Sleep restriction significantly decreased physical activity during the daytime spent under free-living conditions after the first night of sleep manipulation (P = 0.008). Also, intensities of physical activity were shifted toward lower levels, with less time spent with intense activities (P = 0.046). Total energy intake, feelings of hunger, and appetite as well as ghrelin and leptin concentrations during day 2 remained unaffected by acute sleep restriction.

Conclusions: In contrast to our expectation, short-term sleep loss neither increased food intake nor affected concentrations of the hunger-regulating hormones leptin and ghrelin. However, the observed decrease in daytime physical activity may point to another potentially important behavioral mechanism for the health-impairing influence of sleep loss.

Increased food energy supply is more than sufficient to explain the US epidemic of obesity

Increased food energy supply is more than sufficient to explain the US epidemic of obesity

from American Journal of Clinical Nutrition current issue by Swinburn, B., Sacks, G., Ravussin, E.

Background: The major drivers of the obesity epidemic are much debated and have considerable policy importance for the population-wide prevention of obesity.

Objective: The objective was to determine the relative contributions of increased energy intake and reduced physical activity to the US obesity epidemic.

Design: We predicted the changes in weight from the changes in estimated energy intakes in US children and adults between the 1970s and 2000s. The increased US food energy supply (adjusted for wastage and assumed to be proportional to energy intake) was apportioned to children and adults and inserted into equations that relate energy intake to body weight derived from doubly labeled water studies. The weight increases predicted from the equations were compared with weight increases measured in representative US surveys over the same period.

Results: For children, the measured weight gain was 4.0 kg, and the predicted weight gain for the increased energy intake was identical at 4.0 kg. For adults, the measured weight gain was 8.6 kg, whereas the predicted weight gain was somewhat higher (10.8 kg).

Conclusions: Increased energy intake appears to be more than sufficient to explain weight gain in the US population. A reversal of the increase in energy intake of 2000 kJ/d (500 kcal/d) for adults and of 1500 kJ/d (350 kcal/d) for children would be needed for a reversal to the mean body weights of the 1970s. Alternatively, large compensatory increases in physical activity (eg, 110–150 min of walking/d), or a combination of both, would achieve the same outcome. Population approaches to reducing obesity should emphasize a reduction in the drivers of increased energy intake.

Green tea, black tea, and epigallocatechin modify body composition, improve glucose tolerance, and differentially alter metabolic gene expression in rats fed a high-fat diet

Green tea, black tea, and epigallocatechin modify body composition, improve glucose tolerance, and differentially alter metabolic gene expression in rats fed a high-fat diet

from Nutrition Research
by Nora Chen, Rebecca Bezzina, Edward Hinch, Paul A. Lewandowski, David Cameron-Smith, Michael L. Mathai, Markandeya Jois, Andrew J. Sinclair, Denovan P. Begg, John D. Wark, Harrison S. Weisinger, Richard S. Weisinger

Abstract: The mechanisms of how tea and epigallocatechin-3-gallate (EGCG) lower body fat are not completely understood. This study investigated long-term administration of green tea (GT), black tea (BT), or isolated EGCG (1 mg/kg per day) on body composition, glucose tolerance, and gene expression related to energy metabolism and lipid homeostasis; it was hypothesized that all treatments would improve the indicators of metabolic syndrome. Rats were fed a 15% fat diet for 6 months from 4 weeks of age and were supplied GT, BT, EGCG, or water. GT and BT reduced body fat, whereas GT and EGCG increased lean mass. At 16 weeks GT, BT, and EGCG improved glucose tolerance. In the liver, GT and BT increased the expression of genes involved in fatty acid synthesis (SREBP-1c, FAS, MCD, ACC) and oxidation (PPAR-α, CPT-1, ACO); however, EGCG had no effect. In perirenal fat, genes that mediate adipocyte differentiation were suppressed by GT (Pref-1, C/EBP-β, and PPAR-γ) and BT (C/EBP-β), while decreasing LPL, HSL, and UCP-2 expression; EGCG increased expression of UCP-2 and PPAR-γ genes. Liver triacylglycerol content was unchanged. The results suggest that GT and BT suppressed adipocyte differentiation and fatty acid uptake into adipose tissue, while increasing fat synthesis and oxidation by the liver, without inducing hepatic fat accumulation. In contrast, EGCG increased markers of thermogenesis and differentiation in adipose tissue, while having no effect on liver or muscle tissues at this dose. These results show novel and separate mechanisms by which tea and EGCG may improve glucose tolerance and support a role for these compounds in obesity prevention.