Omega-3 Fatty Acids Improve Insulin Sensitivity

| September 12, 2013

There now seems to be little doubt that eating fish is good for us and particularly good for those of us who have diabetes. As I pointed out in The Real Diabetes Truth on 6 March 2012 and 3 April 2012, population studies have previously linked high fish consumption, and the omega-3 fatty acids found especially in oily fish, with a lower risk of developing type 2 diabetes.

Showing an association, as these studies have done, doesn’t actually prove cause and effect. Nor does it imply that eating fish or taking omega-3 fatty acids can reverse the effects of diabetes once it has been diagnosed. So I was very interested to see the results of two new clinical trials, published this summer, which seem to furnish the necessary proof that omega-3 fats really can make a difference for people who already have diabetes or metabolic syndrome.

The first, published in July, was a double-blind clinical trial carried out in Iran, in which overweight people with type 2 diabetes were given either 2000 mg of EPA (eicosapentaenoic acid, one of the two omega-3 fatty acids present in fish oil) or a corn oil placebo, daily for twelve weeks. Blood analysis showed that levels of plasma glucose, insulin and glycosylated haemoglobin (HbA1c, a marker of long term glucose control) all fell in the patients taking EPA, while they rose in the control group.

Then, in August, a second 12-week study was published by researchers in Mexico. This one compared the effects of omega-3 fatty acids (1800 mg a day) with the standard diabetes drug metformin (500 mg a day), in obese and insulin-resistant children and adolescents. By the end of the study, those taking the omega-3 supplements showed significant reductions in their glucose, insulin and triglyceride (blood fat) levels, as well as reductions in insulin resistance and body mass index. Metformin, on the other hand, had only a negligible effect on insulin levels and no effect on triglycerides, but was associated with increases in HDL (‘good’) cholesterol and decreases in LDL (‘bad’) cholesterol.

The results of this second study show that omega-3 fatty acids could be a more effective treatment for pre-diabetic teenagers than standard medication. But were these findings trumpeted in the health pages of national newspapers? No, I had to dig to find them among academic abstracts, where hard-pressed GPs rarely have time to search. So expect to get a blank look if you ask your doctor whether fish oil might be a better option for you than drugs!

Omega-3 fatty acids appear to improve insulin sensitivity in several ways. They increase the fluidity of the membranes surrounding muscle cells, so letting glucose enter the cells more easily; they also positively affect genes associated with insulin resistance. In addition, omega-3 fatty acids reduce the chronic inflammation that can be a root cause of type 2 diabetes (see The Real Diabetes Truth of 25 September 2012).

How to get your omega-3 fatty acids

• Cold-pressed fish oils and krill oil (from tiny marine crustaceans) are the best sources of omega-3 fatty acids for most people and contain both EPA and DHA (docosahexaenoic acid). Aim to get around 2000 mg of total omega-3 fatty acids a day.

• Linseed (flaxseed) oil and ground linseeds also contain high levels of the omega-3 fatty acid alpha-linolenic acid (LNA) and are suitable for vegetarians and vegans. Walnuts and rapeseed oil are other good sources. However, LNA needs to be converted to DHA in the body and some people do this better than others.

• Mackerel, salmon and herring provide plenty of omega-3 fats if bought fresh and cooked gently in the oven until just done (don’t overcook). Eat at least two portions of these oily fish a week. White fish also contain fair amounts of omega-3 fatty acids.

• Canned tuna is NOT a great source of omega-3. Canned salmon is a better option.

• Spinach, broccoli and cauliflower can also add to your daily intake of omega-3 fatty acids. As with fish, don’t overcook them.

Women who are pregnant or breastfeeding need to get plenty of omega-3 fatty acids. Breast milk is the growing baby’s best source of these essential nutrients. Exactly when and how babies should be introduced to solid foods has long been a subject of debate, but new evidence shows that the timing of this weaning process may determine a child’s risk of developing type 1 diabetes. That important finding will be the subject of my next blog post.

Wishing you the best of health,

Martin Hum
PhD DHD Nutritionist
for Real Diabetes Truth

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1. Sarbolouki S, Javanbakht MH, Derakhshanian H, Hosseinzadeh P, Zareei M, Hashemi SB, Dorosty AR, Eshraghian MR, Djalali M. Eicosapentaenoic acid improves insulin sensitivity and blood sugar in overweight type 2 diabetes mellitus patients: a double-blind randomised clinical trial. Singapore Med J. 2013; 54(7):387-390.

2. Juárez-López C, Klünder-Klünder M, Madrigal-Azcárate A, Flores-Huerta S. Omega-3 polyunsaturated fatty acids reduce insulin resistance and triglycerides in obese children and adolescents. Pediatr Diabetes. 2013; 14(5):377-383.

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