People who ate a diet similar to that proposed by Harvard researchers reduced their risk of chronic diseases such as heart disease and cancer, according to new findings.

Men whose diets paralleled the new guidelines reduced their risk of chronic disease by 20%, while in women the reduction was 11%.

Marji McCullough, ScD, RD, formerly with the Harvard School of Public Health and now an epidemiology researcher at the American Cancer Society (ACS), co-authored the study, which appears in the December issue of the American Journal of Clinical Nutrition (Vol. 76).

Most Americans are familiar with the US Department of Agriculture (USDA) dietary guidelines and the accompanying food pyramid, which stress a diet low in fat and high in carbohydrates. It also emphasizes eating more fruits and vegetables, and consuming moderate amounts of dairy products and foods from the "meat" (meat, chicken, fish, beans) group.

Harvard researchers developed an alternative to these guidelines, which takes into account some of the differences within these food groups. It emphasizes white meat (chicken and fish) over red meat, whole grains over refined grains, unsaturated fats over saturated fats, and accounts for multivitamin use and moderate alcohol intake.

McCullough and colleagues looked at how well the diets of 100,000 men and women taking part in two large, long-term health studies matched the new guidelines. The study participants had previously filled out food frequency questionnaires every two years for about a decade.

In previous reports, the researchers looked at this same group to determine how following the USDA guidelines affected chronic disease risk. They translated questionnaire answers into a score using the Healthy Eating Index (HEI).

The researchers found those who followed the USDA guidelines most closely had a "modest" reduction in risk for chronic diseases — 11% lower among men and 3% lower among women. They also found risk of cancer was not significantly affected.

In the present study, the researchers looked at the same group of people and measured how similar their diets were to the Harvard guidelines, using the Alternative Healthy Eating Index (AHEI).

Men whose diets were most similar to the alternative guidelines — those with the highest AHEI scores — had a 20% reduced risk of chronic disease overall, and a 39% reduced risk of cardiovascular disease (CVD) — heart attacks, strokes, etc. — compared to those with the lowest AHEI scores.

Among women, the risk reduction was 11% overall, and 28% for cardiovascular disease.

However, the risk of cancer was not significantly reduced in either group.

"The new diet pattern gave credit for eating more fruits and vegetables, fiber from grains, fish, or chicken versus red meat, and from consuming alternate protein sources like nuts and soy products," said McCullough. "Benefits came from consuming polyunsaturated fats such as liquid vegetable oils rather than saturated fats from butter or lard.

"Another plus was consuming lower amounts of trans fatty acids such as vegetable shortening, taking a multivitamin pill regularly, and drinking moderate amounts of alcohol," she said. However, even those not consuming alcohol had a strongly reduced risk, McCullough said.

"All components of the [AHEI] diet score we tested were thought to reduce heart disease risk, but only half were thought to reduce cancer," said McCullough. "Therefore, it was not surprising that the pattern was more predictive of cardiovascular disease risk than cancer risk."

The types of cancer that occurred during the study may have affected the results as well. Prostate cancer was most common among men, and breast cancer most common among women. Few dietary factors in adult life are thought to be stongly related to these cancers.

Other factors also may have influenced the results, McCullough added. "For certain cancers, diet earlier in life is thought to play a larger role," she said. "This study measured diets in adults only."

Although we know diet is important in cancer risk reduction, further research is needed to clarify the associations between dietary patterns and overall cancer risk reduction, McCullough concluded.