National Heart Foundation Recommends Fish Oil

Monday 29th December 2008 9:20am

The following is an extract from a National Heart Foundation position statement - “Fish, fish oils, n-3 polyunsaturated fatty acids and cardiovascular health”.

Position statement

Fish, fish oils, n-3 polyunsaturated fatty acids and cardiovascular health

This position statement was developed to provide recommendations to the general population and health professionals on the consumption of fish, fish oils and n-3 polyunsaturated fatty acids for cardiovascular health.

In addition, this statement provides cautions on the consumption of fish with high and medium methyl mercury content.

The Heart Foundation advocates for change within the food industry and from governments.

Recommendations

The Heart Foundation makes the following recommendations with respect to fish, fish oils and omega-3 polyunsaturated fatty acids (n-3 PUFA) to improve the cardiovascular health of all Australians.

These recommendations are based on the evidence presented in the Heart Foundation’s review of evidence Fish, fish oils, n-3 polyunsaturated fatty acids and cardiovascular health, as well as in our healthy eating guidelines.

To view Heart Foundation guidelines and position statements, and a full reference list for this position statement, see www.heartfoundation.org.au/Professional_Information/Lifestyle_Risk/Nutrition.

Fish that live in cold water are rich in n-3 PUFA—particularly docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA). Alpha-linolenic acid (ALA) is a plant-based n-3 PUFA that has many health benefits but does not benefit cardiovascular health as well as marine n-3 PUFA.

To lower their risk of coronary heart disease (CHD), all Australians should:

  1. Consume about 500 mg per day of combined DHA and EPA through a combination of the following: two or three serves (150 g serve) of oily fish per week, fish oil capsules or liquid, food and drinks enriched with marine n-3 PUFA.
  2. Consume at least 2 g per day of ALA.
  3. Follow government advice on fish consumption regarding local safety issues.
  4. Discuss healthy eating and concerns about nutrition with an Accredited Practising Dietician or a doctor.

Health professionals should advise adult Australians with documented CHD to:

  1. Consume about 1000 mg per day of combined DHA and EPA through a combination of the following: two or three serves (150 g serve) of oily fi sh per week, fish oil capsules or liquid, food and drinks enriched with marine n-3 PUFA.
  2. Consume at least 2 g per day of ALA.
  3. Follow government advice on fish consumption regarding local safety issues.
  4. Discuss healthy eating and concerns about nutrition with an Accredited Practising Dietitian or a doctor.

Health professionals should advise adult Australians with elevated triglycerides (TG) to take fish oil capsules or liquid and marine n-3 PUFA enriched foods and drink as first-line therapy by:

Australian recommendations

The average n-3 PUFA intake of Australians has been estimated at 246 mg/day comprising and 100 mg/day from EPA, DPA and DHA respectively.39 Seafood is by far the richest source of n-3 PUFA in the diet.

The NHMRC has recently published Nutrient Reference Values, which include recommendations for intake of ALA, DHA, EPA and DPA for the first time. Adequate intake values were set as follows:

An upper limit for children, adolescents and adults was set at 3000 mg/day for DHA, EPA and DPA. No upper limit was set for ALA because there is no known level at which adverse effects occur.

To prevent chronic disease, dietary intakes for DHA, EPA and DPA have been set at the current 90th centile in the population, values that are known to be safe and to provide potential benefit. The suggested dietary target to reduce chronic disease is 610 mg/day for men and 430 mg/day for women.

Mechanisms of action

Fish and fish oils are thought to decrease the risk of CHD through several possible mechanisms, including:

Fatty acids, particularly marine n-3 PUFA, are incorporated into cell membranes, and increasing the amount of PUFA in the membrane increases its fluidity and deformability. There is a dose-response relationship between intake of marine n-3 PUFA and reduction in blood TG level. The higher the baseline TG level, the greater the response. In individuals with extremely high TG levels, n-3 PUFA supplementation may lower TG level by 50%.

Intake of marine n-3 PUFA is positively correlated with HDL levels. Animal and in vitro studies show that intake of marine n-3 PUFA increases the number of receptors for, and turnover of, HDL. Marine n-3 PUFA significantly decreases chylomicron levels and size, which improves their clearance. Supplementation does not appear to alter the levels of total cholesterol or low-density lipoprotein (LDL) if the TG level is not high.

Marine n-3 PUFA modulates the activities of several enzymes involved in carbohydrate and lipid metabolism. These changes lead to decreased TG synthesis and increased mitochondrial beta-oxidation, with a subsequent decrease in the formation of very LDL cholesterol.

Marine n-3 PUFA have an additive effect when combined with lipid-lowering medication such as statins. Combined treatment decreases TG level, increases HDL level, and redistributes LDL particle size to a less dense (less atherogenic) form beyond the response to statin only. Marine n-3 PUFA supplementation inhibits nuclear transcription factor kB, a key transcription factor in cytokine gene expression, cellular adhesion and inflammation. Supplementation decreases cytokine and nitric oxide production by macrophages, and release of inflammatory markers and cytokines in response to mitogenic and inflammatory stimuli.

Elevated plasma leptin level is independently associated with CVD risk. Marine n-3 PUFA supplementation inhibits leptin gene expression in an animal model, and a diet rich in fish and marine n-3 PUFA is associated with low plasma leptin level independent of body fat content.65 Marine n-3 PUFA has a mild anti-platelet effect but does not affect bleeding time.

Terminology

ALA Alpha-linolenic acid, n-3 fatty acid with 18-carbon chain, C18:3n-3

CHD Coronary heart disease

CVD Cardiovascular disease

DHA Docosahexaenoic acid, n-3 fatty acid with 22-carbon chain, C22:6n-3

DPA Docosapentaenoic acid, n-3 fatty acid with 22-carbon chain, C22:5n-3

EPA Eicosapentaenoic acid, n-3 fatty acid with 20-carbon chain, C20:5n-3 Fish oil Oil derived from fi sh rich in EPA and DHA

HDL High-density lipoprotein cholesterol

LDL Low-density lipoprotein cholesterol Marine n-3 PUFA Combination of EPA, DHA and DPA n-3 PUFA Omega-3 polyunsaturated fatty acid

PCB Polychlorinated biphenyl

TG Triglycerides

Source - National Heart Foundation of Australia