January 7, 2014
News Review From Harvard Medical School -- Mediterranean Diet May Cut Diabetes Risk
Eating a Mediterranean-style diet may reduce the risk of diabetes, a new study suggests. The study included more than 3,500 older adults who were at high risk of heart disease. They were randomly divided into 3 groups. Two groups followed a Mediterranean-style diet. This type of diet is high in fruits, vegetables, fish, nuts, olive oil, beans and legumes. It is low in red meat and dairy. One Mediterranean-diet group added extra olive oil to the diet. The other group added extra mixed nuts. The third group followed a high-carbohydrate, low-fat diet. In the next 4 years, people on the Mediterranean-style diet were less likely to develop diabetes than those in the high-carb, low-fat group. Risk was 40% lower for the extra-oil group and 18% lower for the mixed-nuts group. The journal Annals of Internal Medicine published the study online. People in this study were not instructed to increase exercise or cut calories. But those steps might have lowered risk further, the journal's editor suggested to HealthDay News. Other research has shown that weight loss and exercise can reduce the risk of diabetes. HealthDay wrote about the study January 6.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
During the last half of the 20th century, "fat is bad" was the theme of American advice on eating. A high-carb, low-fat diet was promoted as the best way to avoid heart disease. Now we realize that this was totally misguided.
A high-carb, low-fat diet does not lead to better health. In fact, it might have been one of the major factors leading to the high rate of obesity and diabetes we see today.
This report adds more evidence about how diet composition affects your risk of developing type 2 diabetes. The researchers used information gathered from a study started in October 2003. The study enrolled older adults who had a higher than average risk of heart disease. It compared the effects of 3 different diets:
- A Mediterranean-style diet, supplemented with 3 to 4 tablespoons of extra-virgin olive oil daily
- A Mediterranean-style diet, supplemented with 30 grams (1 ounce) of mixed nuts daily
- A high-carb, low-fat diet with reduced intake of all types of fats
People were not told to restrict total calories, attempt weight loss or exercise more. When the groups were compared at the end of the study in December 2010, they had very similar average calorie intake, body weight and exercise time.
People who were assigned to the Mediterranean-style diet plus olive oil were 40% less likely to develop diabetes than those in the high-carb, low-fat group. The ones who ate a Mediterranean-style diet with extra mixed nuts also had a lower diabetes risk, but it was not as significant.
What Changes Can I Make Now?
There is no specific Mediterranean diet. These are the main components of a Mediterranean style of eating:
- Four or more servings of vegetables a day. A serving is ½ cup of raw or cooked vegetables, 1 cup of raw leafy greens or ½ cup of vegetable juice.
- Four or more servings of fruit a day. A serving is ½ cup of fresh, frozen or canned fruit; ¼ cup of dried fruit; one medium-sized piece of fruit; or ½ cup of fruit juice.
- At least 3 to 4 tablespoons of olive oil a day.
- One handful (about 1½ ounces) of nuts, 3 or more times per week.
- Three or more servings of legumes (beans, peas and lentils) per week. A serving is ½ cup.
- Six or more servings of whole grains a day. A serving is 1 cup of dry breakfast cereal; ½ cup of cooked cereal, brown rice or whole-grain pasta; or one slice of whole-grain or multi-grain bread.
- Three or more servings of fish (especially fatty fish) a week. A serving is 4 ounces.
- One serving of yogurt or cheese a day.
- If you enjoy alcohol, limit yourself to 1 (for women) or 2 (for men) drinks a day. One drink is 5 ounces of wine, 12 ounces of beer or 1½ ounces of liquor.
- Soda and sugary drinks
- Sweets, pastries and commercial bakery goods
- Red and processed meats (eat white meats instead)
- Margarines and most tub spreads
Other studies have suggested some people can lose more weight with a Mediterranean-style diet than with a low-fat diet at equal calorie counts. That did not occur in this particular study, however.
What Can I Expect Looking to the Future?
The takeaway from this study should not be just to eat a Mediterranean-style diet and forget about exercise and weight maintenance. Staying physically active and getting regular exercise still matter. And if you need to lose weight, cutting calories matters, too.