There is considerable evidence showing the protective effect of dietary omega-3 fatty acids in the prevention of heart disease, especially in high-risk populations. Fish oils, which are high in fatty acids, improve high cholesterol, triglyceride levels, blood vessel and platelet function and lower blood pressure.
People with type 2 diabetes have an increased risk of cardiovascular disease, hypertension, high cholesterol, and insulin resistance. Therefore, an increased intake of omega-3 fatty acids may be of particular benefit for diabetics.
However, some recent trials suggest that fish oil could actually worsen diabetic control. In one study, the use of purified EPA and DHA (fatty acids found in fish oil) by diabetic patients was evaluated.
Participants took high doses (4 grams per day for a six-week period) of EPA, DHA or olive oil in addition to their regular diets. It was found that, compared with the olive oil, the EPA and DHA increased the blood sugar in diabetics. Interestingly, the insulin levels were not increased.
The researchers speculate that the EPA causes the liver to break it down and actually increase its production of glucose in the process.
American Journal of Clinical Nutrition, November 2002 Vol. 76, No. 5, 1007-1015
My dad is 75 years old and has had type 2 diabetes for nearly 15 years. His diabetes has typically been well controlled with a low-carb diet and two hours of exercise a day.
I recommended fish oil for him as it typically is beneficial for diabetes.
Shortly after he started the fish oil, his blood sugar started rising uncontrollably, even up to 300. Of course, I thought he was cheating, but he hadn't gained any weight and was quite adamant that he was being faithful with his grain restriction.
My dad is not as obsessive as I am, and he still has a few grains occasionally, despite having diabetes.
However, when I read this study I realized instantly what had happened:
The Reverse Effect.
Omega-3 fish oil is terrific for most of us, but if we get too much it actually worsens our health. This is obviously what happened in my dad.
I believe most diabetics will do just fine with typical dose of fish or cod liver oil of 1 to 2 teaspoons per day. However, if you are diabetic you will want to monitor your sugar levels very carefully when you use fish oil, especially at doses higher than two teaspoons per day. You may need to lower the dose if your blood sugar rises.
As an aside, I also checked my dad's ferritin level and was shocked to find that he had hemochromatosis. His level was 450, and he was seriously iron overloaded. It is likely that the high iron levels further impaired the beta cells in his pancreas, impairing his ability to even make insulin.