by Craig Weatherby
Omega-3s from fish oil have been clinically tested in people with type 2 diabetes... but not to the extent that the positive results of animal, cell, and preliminary clinical studies would warrant.
Thanks to a lack of funding to test non-patentable solutions - as opposed to profitable drugs - we lack sufficient clinical evidence about foods and supplements that might reduce the risk or severity of common lifestyle diseases such as diabetes.
The outcomes of the few preliminary clinical trials conducted to date suggest that fish-borne omega-3 fats can lower blood markers for cardiovascular disease (CVD) risk quite considerably… though they’ve not been shown to lower blood sugar levels significantly (Nield L et al. 2008; Hartweg J et al. 2008).
But in a new clinical study from Iran, diabetics who took daily supplements of omega-3 fatty acids for just two months showed lower blood levels of markers for blood sugar.
And, for the first time in a clinical trial, fish oil reduced blood levels of a long-suspected promoter of cardiovascular disease risk: an amino acid called homocysteine.
Blood-sugar and heart-risk markers lowered
Participants who took daily fish oil supplements showed lower levels of a key blood marker called hemoglobin A1c (HbA1c), levels of which are used to follow changes in diabetics’ glucose levels over time.
Of the two major findings of the trial, the drop in HbA1c levels may be the most significant, because it goes to the heart of the problem in diabetes: chronically high blood sugar levels that lead to cardiovascular and nerve damage.
People taking fish oil also enjoyed 22 percent lower levels of the amino acid homocysteine, compared to a drop of only one percent in the placebo group.
Until now, only certain B vitamins (B12, B6, and folate) have been shown to lower blood homocysteine levels.
Most—but not all—studies have linked high blood levels of homocysteine to increased risks of heart disease and stroke.
A good deal of evidence suggests that lowering levels of homocysteine in the blood may cut the risk of cardiovascular disease, although some studies fail to find statistically significant links between lower homocysteine levels and a drop in the risk of developing CVD.
Details of the Tehran diabetes trial: Design and outcomes
Researchers from Iran’s Tehran University of Medical Sciences recruited 81 type-2 diabetics to take part in a randomized, double-blind, placebo-controlled clinical trial (Pooya S et al. 2009).
The volunteers were randomly assigned to take either 3 grams of omega-3 fish oil daily, which provided 2,376mg of EPA and DHA (the two most beneficial omega-3s)… or to take placebo capsules containing 2.1 grams of sunflower oil (high in omega-6 fatty acids, with virtually no omega-3s).
In addition to cutting their levels of homocysteine by 22 percent, the fish oil group’s main blood marker for sugar (glucose) levels dropped by 0.75 percent in the omega-3 group, but increased in the placebo group by 0.26 percent.
Blood tests showed no changes in certain other markers for vascular disease risk: fasting blood sugar, MDA, CRP, total cholesterol, and LDL-cholesterol levels.
However, prior trials in diabetics have consistently found that omega-3s exert beneficial effects on blood levels of key markers for cardiovascular disease… namely, triglycerides, VLDL cholesterol, non-HDL cholesterol, platelet aggregation, antioxidant enzymes, and oxidized cholesterol (Axelrod L et al. 1994; Kesavulu MM et al. 2002; Nield L et al. 2008; Hatrweg J et al. 2008).
Fatty fish and fish oil may or may not help prevent or ameliorate diabetes… the jury remains out.
But given the accumulating evidence, it seems smart to ensure adequate omega-3 intake as part of a good, nutrient-dense “green” diet.
- Axelrod L, Camuso J, Williams E, Kleinman K, Briones E, Schoenfeld D. Effects of a small quantity of omega-3 fatty acids on cardiovascular risk factors in NIDDM. A randomized, prospective, double-blind, controlled study. Diabetes Care. 1994 Jan;17(1):37-44.
- Hartweg J, Perera R, Montori V, Dinneen S, Neil HA, Farmer A. Omega-3 polyunsaturated fatty acids (PUFA) for type 2 diabetes mellitus. Cochrane Database Syst Rev. 2008 Jan 23;(1):CD003205. Review.
- Kesavulu MM, Kameswararao B, Apparao Ch, Kumar EG, Harinarayan CV. Effect of omega-3 fatty acids on lipid peroxidation and antioxidant enzyme status in type 2 diabetic patients. Diabetes Metab. 2002 Feb;28(1):20-6.
- Nield L, Summerbell CD, Hooper L, Whittaker V, Moore H. Dietary advice for the prevention of type 2 diabetes mellitus in adults. Cochrane Database Syst Rev. 2008 Jul 16;(3):CD005102. Review.
- Pooya S, Jalali MD, Jazayery AD, Saedisomeolia A, Eshraghian MR, Toorang F. The efficacy of omega-3 fatty acid supplementation on plasma homocysteine and malondialdehyde levels of type 2 diabetic patients.Nutr Metab Cardiovasc Dis. 2009 Jun 18. [Epub ahead of print]