Omega-3 fats are a hot topic for health professionals and consumers alike. Why the resurgence of interest? It is partly due to more studies being published, which strengthen the science links between long chain omega-3 fats and health. Long chain omega-3 fats include; docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA). They have been associated with a long list of health benefits including:
Cardiovascular health
Most studies support the recommendation that regular consumption of fatty fish, such as tuna and mackerel, is good for heart health. 1
This is mainly through improved cardiovascular function and a beneficial effect on blood cholesterol levels.
Brain development and function
The brain and nervous system contain a lot of DHA, known to be important for optimal vision and communication between brain cells. It is thought that critical times for obtaining dietary DHA are; during pregnancy and breastfeeding, in infancy and in older age (when eyesight and brain function can start to decline). 1
Mental health
Long chain omega-3 fats may help improve symptoms of behavioral disorders (such as ADHD), depression, bipolar disorder and age-related dementia, though the evidence is limited at this stage. 1
Full-term pregnancy
Eating fish once a week in early stages of pregnancy may help guard against pre-term delivery.
Inflammatory disease
There is evidence that fish oils can modulate immune responses, improving symptoms of inflammatory diseases, such as rheumatoid arthritis, asthma, cystic fibrosis and inflammatory bowel disease. Of these, rheumatoid arthritis is the only condition that shows good evidence of a potential benefit from DHA and EPA, though it
is required in higher doses than could be achieved by diet alone. 1
This means a combination of regular fish consumption and fish oil supplements may give the best benefit.
Colorectal cancer
A recent Japanese study indicated that regular consumption of fish and fish products seems to protect against colorectal cancer. 3 More research is required to better establish this.
Adequate intake (AI) and upper limit (UL) recommendations for long chain omega-3 fats in New Zealand and Australia were published last year.
The UL recommendation for all ages is 3,000 mg per day. There is no lower recommended limit, as the human body can make its own long chain omega-3 fatty acids from shorter chain omega-fats. Evidence for the health benefits is mainly from consumption of long chain omega-3 fats, either from fish or supplement sources.
The AI levels for children aged 1-13 years range from 40-70mg per day and the AI levels for teenagers and adults over 14 years range from 85 – 160mg per day. There is no AI or UL set for infants under the age of one year.
Shorter chain omega-3 fats occur naturally in a variety of plant sources (including canola oil, olive oil, seeds and nuts). However, the only naturally occurring long-chain omega-3 fats in the diet are from marine sources such as fish (especially oily fish like tuna), crustaceans and shellfish.
References
1. Ruxton CHS, Reed SC, Simpson MJA, Millington KJ. The health benefits of omega-3 polyunsaturated fatty acids: a review of the evidence. J Hum Nut Dietet, 2007; 20: 275-85.
2. Olsen SF, Secher NJ. Low consumption of seafood in early pregnancy as a risk factor for preterm delivery: prospective cohort study. BMJ, 2002; 324: 447.
3. Kimura Y, Kono S, Toyomura K, et al. Meat, fish and fat intake in relation to subsite-specific risk of colorectal cancer: The Fukuoka Colorectal Cancer Study. Cancer Sci, 2007; 98: 590-7.
4. Department of Health and Ageing, National Health and Medical Research Council and Ministry of Health. Nutrient Reference Values for Australia and New Zealand, May 2006.
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