Omega 3 fatty acids for prevention and treatment of cardiovascular disease.

BACKGROUND: It has been suggested that omega 3 (W3, n-3 or omega-3) fats from oily fish and plants are beneficial to health. OBJECTIVES: To assess whether dietary or supplemental omega 3 fatty acids alter total mortality, cardiovascular events or cancers using both RCT and cohort studies. SEARCH STRATEGY: Five databases including CENTRAL, MEDLINE and EMBASE were searched to February 2002. No language restrictions were applied. Bibliographies were checked and authors contacted. SELECTION CRITERIA: RCTs were included where omega 3 intake or advice was randomly allocated and unconfounded, and study duration was at least six months. Cohorts were included where a cohort was followed up for at least six months and omega 3 intake estimated. DATA COLLECTION AND ANALYSIS: Studies were assessed for inclusion, data extracted and quality assessed independently in duplicate. Random effects meta-analysis was performed separately for RCT and cohort data. MAIN RESULTS: Forty eight randomised controlled trials (36,913 participants) and 41 cohort analyses were included. Pooled trial results did not show a reduction in the risk of total mortality or combined cardiovascular events in those taking additional omega 3 fats (with significant statistical heterogeneity). Sensitivity analysis, retaining only studies at low risk of bias, reduced heterogeneity and again suggested no significant effect of omega 3 fats. Restricting analysis to trials increasing fish-based omega 3 fats, or those increasing short chain omega 3s, did not suggest significant effects on mortality or cardiovascular events in either group. Subgroup analysis by dietary advice or supplementation, baseline risk of CVD or omega 3 dose suggested no clear effects of these factors on primary outcomes. Neither RCTs nor cohorts suggested increased relative risk of cancers with higher omega 3 intake but estimates were imprecise so a clinically important effect could not be excluded. REVIEWERS' CONCLUSIONS: It is not clear that dietary or supplemental omega 3 fats alter total mortality, combined cardiovascular events or cancers in people with, or at high risk of, cardiovascular disease or in the general population. There is no evidence we should advise people to stop taking rich sources of omega 3 fats, but further high quality trials are needed to confirm suggestions of a protective effect of omega 3 fats on cardiovascular health. There is no clear evidence that omega 3 fats differ in effectiveness according to fish or plant sources, dietary or supplemental sources, dose or presence of placebo.

The effect of zinc and vitamin A supplementation on immune response in an older population.

OBJECTIVE: To determine if either supplemental vitamin A, zinc, or both increases cell-mediated immune response in an older population. DESIGN: A double-blind, randomized, controlled trial of supplementation with vitamin A and zinc. SETTING: Casa Di Riposo Roma III, a public home for older people in Rome, Italy. SUBJECTS: The health and nutritional status of 178 residents were evaluated. One hundred thirty-six residents agreed to participate in the trial and were randomized into four treatment groups, and 118 of these residents completed the trial. INTERVENTION: The four treatments consisted of: (1) Vitamin A (800 micrograms retinol palmitate); (2) Zinc (25 mg as zinc sulfate); (3) Vitamin A and Zinc (800 micrograms retinol palmitate and 25 mg as zinc sulfate); (4) Placebo capsules containing starch. MAIN OUTCOME MEASUREMENTS: Immune tests-counts of leucocytes, lymphocytes, T-cell subsets, and lymphocyte proliferative response to mitogens-were measured before and after supplementation. RESULTS: Zinc increased the number of CD4 + DR + T-cells (P = .016) and cytotoxic T-lymphocytes (P = .005). Subjects treated with vitamin A experienced a reduction in the number of CD3 + T-cells (P = .012) and CD4 + T-cells (P = .012). CONCLUSIONS: These data indicate that zinc supplementation improved cell-mediated immune response, whereas vitamin A had a deleterious effect in this older population. Further research is needed to clarify the clinical significance of these findings.

Zinc supplementation and plasma lipid peroxides in an elderly population.

OBJECTIVE: To determine the effect of vitamin A, zinc or both on plasma lipid peroxides in a healthy elderly population. DESIGN: Double-blind randomized controlled trial supplementation of vitamin A and zinc. SETTING: Public home for elderly people, in Rome, Italy. SUBJECTS: A total of 178 residents of a Public home for elderly people were evaluated regarding health and nutritional status. 136 gave a written consensus to participate in the trial and were randomized in four groups of treatment. 118 elderly completed the trial. INTERVENTIONS: Three months supplementation of the following treatments: (1) vitamin A (800 micrograms retinol palmitate); (2) zinc (25 mg zinc as sulphate); (3) vitamin A and zinc (800 micrograms retinol palmitate and 25 mg zinc as sulphate); (4) placebo (starch containing capsules). MAIN OUTCOME MEASURES: Plasma lipid peroxides (TBA-RS) were measured before and after supplementation. RESULTS: Zinc supplementation was associated with a decrease in plasma lipid peroxides (beta = -0.19; 95% confidence levels: -0.37, -0.002; p-value = 0.05) after adjusting for sex, smoking habits, baseline plasma lipid peroxides and vitamin A plasma levels. CONCLUSIONS: Zinc supplementation decreased plasma lipid peroxides while vitamin A had no effect in this elderly population. Adequate zinc intake or supplementation could play an important role in the prevention and/ or modulation of diseases in the elderly people.