3 New Articles on Omega-3

7/15/2002

1. Essential fatty acids in visual and brain development.

Essential fatty acids are structural components of all tissues and are indispensable for cell membrane synthesis; the brain, retina and other neural tissues are particularly rich in long-chain polyunsaturated fatty acids (LC-PUFA). These fatty acids serve as specific precursors for eicosanoids, which regulate numerous cell and organ functions. Recent human studies support the essential nature of n-3 fatty acids in addition to the well-established role of n-6 essential fatty acids in humans, particularly in early life. The main findings are that light sensitivity of retinal rod photoreceptors is significantly reduced in newborns with n-3 fatty acid deficiency, and that docosahexaenoic acid (DHA) significantly enhances visual acuity maturation and cognitive functions. DHA is a conditionally essential nutrient for adequate neurodevelopment in humans. Comprehensive clinical studies have shown that dietary supplementation with marine oil or single-cell oil sources of LC-PUFA results in increased blood levels of DHA and arachidonic acid, as well as an associated improvement in visual function in formula-fed infants matching that of human breast-fed infants. The effect is mediated not only by the known effects on membrane effect is mediated not only by the known effects on membrane biophysical properties, neurotransmitter content, and the corresponding electrophysiological correlates but also by a modulating gene expression of the developing retina and brain. Intracellular fatty acids or their metabolites regulate transcriptional activation of gene expression during adipocyte differentiation and retinal and nervous system development. Regulation of gene expression by LC-PUFA occurs at the transcriptional level and may be ediated by nuclear transcription factors activated by fatty acids. These nuclear receptors are part of the family of steroid hormone receptors. DHA also has significant effects on photoreceptor membranes and neurotransmitters involved in the signal transduction process; rhodopsin activation, rod and cone development, neuronal dendritic connectivity, and functional maturation of the central nervous system.

By Uauy R; Hoffman D R; Peirano P; Birch D G; Birch E E
Institute of Nutrition and Food Technology (INTA), University of Chile, Santiago, Chile. uauy@uchile.cl
Lipids; 36 (9) p885-95
United States
Sep 2001
Clinical Trial; Journal Article; Meta-Analysis; Randomized Controlled
Trial; Review; Review, Tutorial

2. Polyunsaturated fatty acids. Is there a role in postmenopausal osteoporosis prevention?

OBJECTIVE: To review the effect of a diet supplemented with polyunsaturated fatty acids (PUFA) on prevention or treatment of osteoporosis.
METHODS: MEDLINE (1966-April 2001), Allied Complementary Medicine (1985-2001), Cochrane Library and Database of Systematic Reviews (1st Quarter 2001) was searched. Five reviews and no systematic reviews were found on this topic in the Cochrane Library. Eleven relevant in-vivo studies were identified on the effect of these compounds on bone. Eight were animal studies and three were randomized control trials (RCT) in human.
RESULTS: There are two classes of PUFA designated as n-3 and n-6 with alpha-linolenic acid (ALA). These two different types of PUFA differently influence prostaglandin formation and hence modulate bone metabolism differently. These are several in vitro and animal data suggesting that diet with a low n-6/n-3 ratio may have beneficial effects on bone mineral density. Only three, short-term, small studies have been performed in human so far. Two studies, one performed with bone markers and one with bone density showed a positive effect of PUFA on bone. While a third study showed no effect.

CONCLUSIONS: Preliminary, data have suggested that a diet with a low n-6/n-3 ratio may have beneficial effects on bone mineral density. Further studies are, however, required to fully assess the dose and type of PUFA to be used for optimum bone effects. This may be useful particularly for the prevention of disease in the elderly, since a diet rich in n-3 PUFA has been shown to have additional benefit on the cardiovascular, central nervous system and joints.

By Albertazzi Paola; Coupland Keith
Centre for Metabolic Bone Disease, H. S Brocklehurst Building, Hull
Royal Infirmary, 220-236 Anlaby Road, HU3 2RW, Hull, UK
Maturitas; 42 (1) p13-22
Ireland
May 20 2002

3. Fish consumption and self-reported physical and mental health status.

OBJECTIVE: The aim of this study was to assess whether self-reported mental health status, measured using the SF-36 questionnaire, was associated with fish consumption, assessed using a food-frequency questionnaire.

DESIGN: The cross-national data were collected in the 1996/97 New Zealand Health Survey and 1997 Nutrition Survey, which were conducted using the same sampling frame. Survey respondents were categorised into those who consumed no fish of any kind and those who consumed some kind of fish, at any frequency. Data were adjusted for age, household income, eating patterns, alcohol use and smoking. Other demographic variables and potential confounding nutrients were included in the preliminary analyses but were not found to have a significant relationship with fish consumption.

SUBJECTS: Data from a nationally representative sample of 4644 New Zealand adults aged 15 years and over were used in this analysis.

RESULTS: Fish consumption was significantly associated with higher self-reported mental health status, even after adjustment for possible confounders. Differences between the mean scores for fish eaters and those who never eat fish were 8.2 for the Mental Health scale and 7.5 for the Mental Component score. Conversely, the association between fish consumption and physical functioning was in the opposite direction.

CONCLUSIONS: This is the first cross-sectional survey to demonstrate a significant relationship between fish intake and higher self-reported mental health status, therefore offering indirect support for the hypothesis that
omega-3 polyunsaturated fatty acids may act as mood stabilisers.

By Silvers Karen M; Silvers Karen M; Scott Kate M
Private Bag 11600, Palmerston North, New Zealand:, Wellington School of Medicine, New Zealand.
Public health nutrition; 5 (3) p427-32
England
Jun 2002

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