Alzheimer's is the sixth leading cause of death in the United States, and experts predict that the number of people with the disease could triple by 2050. The most important risk factors, they say, seem to be linked to diet, especially the consumption of sugar, high-fat dairy, and meat that characterize a Western diet.

A new review appears to back up the theory, including studies which show that Alzheimer's rates in Japan rose from 1 percent in 1985 to 7 percent in 2008, reflecting a transition from the traditional Japanese diet to a Western diet.

In addition to reviewing earlier studies, the new study investigated the prevalence of Alzheimer's disease in 10 countries (Brazil, Chile, Cuba, Egypt, India, Mongolia, Nigeria, Republic of Korea, Sri Lanka, and the United States) along with dietary information from 5, 10, and 15 years previously.

Researchers found that the increase of meat or animal products (minus milk) in the diet had the highest correlations with the prevalence of Alzheimer's disease.

Residents of the United States seem to be at particular risk, according to the findings, with every American having about a 4 percent chance of developing Alzheimer's disease, likely due in part to their diets, which tend to include a lot of meat.

"Reducing meat consumption could significantly reduce the risk of Alzheimer's disease as well as of several cancers, diabetes mellitus type 2, stroke, and, likely, chronic kidney disease," said study author William B. Grant.

"Mounting evidence from ecological and observational studies, as well as studies of mechanisms, indicates that the Western dietary pattern — especially the large amount of meat in that diet — is strongly associated with risk of developing Alzheimer's disease and several other chronic diseases.

"Although the traditional Mediterranean diet is associated with about half the risk for Alzheimer's disease of the Western diet, the traditional diets of countries such as India, Japan, and Nigeria, with very low meat consumption, are associated with an additional 50 percent reduction in risk of Alzheimer's disease," Grant said.

The review was published in the Journal of the American College of Nutrition.

Another study released earlier this month found that healthy diet, regular physical activity, and a normal body weight can reduce the buildup of proteins in the brain associated with Alzheimer's disease.

The study, which was published in the American Journal of Geriatric Psychiatry, found that each one of several lifestyle factors — a healthy body mass index (BMI), physical activity, and a Mediterranean diet — were linked to lower levels of plaques and tangles on the brain scans. The Mediterranean diet is rich in fruits, vegetables, legumes, cereals and fish, and low in meat and dairy.