Effect of Vitamins on Blood Pressure in People With Type 2 Diabetes

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Farvid MS, Jalali M, Siassi F, et al.: The impact of vitamins and/or mineral supplementation on blood pressure in type 2 diabetes. J Am Coll Nutr 23:272-279, 2004.

What is the problem, and what is known about it so far?

People with type 2 diabetes are twice as likely to get hypertension (high blood pressure) than people without diabetes. It is even more important to control high blood pressure in people with type 2 diabetes because they are already at an increased risk of circulatory (blood flow) problems (like swelling) of the eye's retina.

Although most people with high blood pressure can be treated with medications, there has been recent interest in also using vitamins and minerals to help lower blood pressure. In particular, magnesium, zinc, and vitamins C and E have shown promise.

The researchers wanted to find out if providing vitamins and minerals in different combinations had an effect on high blood pressure in people with diabetes.

Who was studied?

A total of 76 people who had had type 2 diabetes for more than 1 year, were aged 30 to 69, and who had normal or slightly high blood pressure were included in the study.

How was the study done?

The researchers interviewed all participants individually. They collected information on eating habits, body mass index (BMI, a measure of weight in relation to height), medical history, smoking, and any medications or vitamins and minerals the participants were taking.

Then, the researchers divided the study members into four groups: those receiving only zinc sulfate and magnesium oxide; those receiving only vitamin C and vitamin E; those receiving all the supplements the first two groups received; and those receiving a placebo (a "fake" pill).

What did the researchers find?

The researchers found that the third group -- the one receiving zinc sulfate, magnesium oxide, and vitamins C and E -- had the greatest reduction of blood pressure after 3 months. None of the other groups showed a significant lowering of blood pressure.

What were the limitations of the study?

One limitation of this study was that the researchers took each participant's blood pressure readings themselves. There could be differences in blood pressure readings if an automatic blood pressure cuff were used. Also, the patients studied here had normal or slightly high blood pressure; the same study should be repeated for people with type 2 diabetes and higher blood pressure.

What are the implications of the study?

The study showed that for people with type 2 diabetes, a combination of several vitamins and minerals can help lower blood pressure.