The ultimate goal of cholesterol-lowering therapies is a reduced risk of heart disease—the number one killer of adults in the United States. Statin drugs, such as simvastatin (Zocor), have proven highly effective in reducing cholesterol levels. But research has shown that some dietary regimens are as effective as statin drugs at reducing heart disease risk and that these diets can even work more quickly than the drugs.

A recent study in the J ournal of the American Medical Association suggests that in combination, simvastatin and a modified Mediterranean diet have independent and additive effects on cholesterol levels. In addition, the diet helps offset simvastatin's negative effects on insulin resistance—an unwanted side effect that increases your risk of diabetes.

About the study

Researchers in Finland enrolled 120 men aged 35 to 64 with untreated high cholesterol into this study from August 1997 to June 1998. All the men had fasting cholesterol levels between 232 mg/dL (6.0 mmol/L) and 309 mg/dL (8.0 mmol/L) and triglyceride levels of no more than 266 mg/dL (3.0 mmol/L). Men were excluded from the study if they had diabetes, coronary artery disease, cardiovascular disease, claudication, body mass index (BMI) higher than 32, or high blood pressure treated with medication.

At the start of the study, baseline measurements of blood pressure, weight, and blood levels of cholesterol, antioxidants, glucose, and insulin were collected. Information about dietary habits was collected via a 7-day food record and a questionnaire was used to assess the frequency of physical exercise.

Sixty men were assigned to follow a modified Mediterranean diet that was low in saturated fats and high in monounsaturated and polyunsaturated fats, cereal, fruits, berries, and vegetables. The other 60 men continued to eat their usual diets. Throughout the study, men on the Mediterranean-type diet attended a total of 8 sessions with a nutritionist who monitored their dietary habits and provided nutrition advice.

Within the Mediterranean-type diet group, 30 men were assigned to take simvastatin and 30 to take a placebo (inactive pill) for 12 weeks. Likewise, within the regular diet group, 30 men were assigned to take simvastatin and 30 to take a placebo. At 12 weeks, baseline measurements were repeated in both groups. At this time, the men taking the placebo were switched to simvastatin and vice versa, for another 12-week period. At the end of the 24 weeks, baseline measurements were repeated. This allowed researchers to test the effects of the simvastatin between the two groups and in each individual participant.

At the end of the study, researchers compared simvastatin's effects on blood levels of cholesterol, antioxidants, glucose, and insulin with the special diet's effects on these measures.

The findings

The special diet and simvastatin each had independent effects on cholesterol, antioxidants, glucose, and insulin levels; these effects were additive, as well. For example, the special diet alone lowered LDL (bad) cholesterol levels by 11%, simvastatin alone lowered LDL levels by 30%, and together they lowered LDL levels by 41%.

Simvastatin also did other good things that the diet did not: it increased HDL (good) cholesterol levels and it lowered triglyceride levels. However, simvastatin increased insulin in the blood and insulin resistance (both risk factors for diabetes) and reduced levels of certain antioxidants (a risk factor for heart disease). The diet, however, reduced insulin levels and insulin resistance, thereby offsetting the increase caused by simvastatin. And the combination of the diet with simvastatin did not reduce antioxidant levels.

There are several limitations to this study, however. First, the participants were all Finnish men, so these findings may not apply to women and people of other ethnic and racial groups. In addition, only the drug simvastatin was used in this study, so it is unclear whether these results apply to other statin drugs. Second, because the treatment period was fairly short, further studies are needed to test the effectiveness of the diet and simvastatin over a longer time period. Long-term studies are also needed to assess whether the combined treatment actually provides protection against heart disease. Third, although the short study period increased the chances that the men would follow the special diet and take their assigned medications, there is no way to know if they really did. Fourth, the men in this study had nutrition counseling sessions, which may have increased their adherence to the diet. The results may be different for people who try this diet without access to such counseling.

How does this affect you?

These findings suggest that statin drugs alone may not be the answer for cholesterol problems.

Specifically, a diet low in saturated fats and high in monounsaturated and polyunsaturated fats, cereal, fruits, berries, and vegetables may play an important role in reducing your risk for heart disease by offsetting the antioxidant decline and insulin resistance associated with simvastatin. Insulin resistance can increase your risk of type 2 diabetes, which itself is a major risk factor for heart disease. The researchers don't propose that drugs like simvastatin increase your chance of getting diabetes, but the results do show that with the good effects may come some bad ones.

If you have high cholesterol and you take a statin drug, do you need to eat the Mediterranean-type diet, too? Why not? Although this study simply suggests that the Mediterranean-type diet helps lower cholesterol, it's also likely to reduce your risk of diabetes, heart disease, stroke, and certain cancers.