December 21/London/Press Association Mediapoint -- A natural substance found in dairy foods could help prevent diabetes, according to research.

The trans-palmitoleic acid compound occurs in the dairy fat of milk, cheese, yogurt and butter but cannot be made by the body.

Now researchers at the Harvard School of Public Health in the U.S. have found the compound could help combat type 2 diabetes, which affects more than 2.3 million Britons. Up to half a million more people in the U.K. also have the condition but do not know it.

The latest research, published in the Annals of Internal Medicine, involved more than 3,700 people. They were followed for 20 years by researchers looking at the risks of developing cardiovascular disease as people get older.

Measurements included blood glucose and insulin levels, and levels of fatty acids (including trans-palmitoleic acid) in the blood.

The results showed that higher levels of trans-palmitoleic acid were associated with healthier levels of blood cholesterol, insulin levels and insulin sensitivity, even when other factors were taken into account.

Overall, people with the highest levels of trans-palmitoleic acid had about a 60% reduced risk of developing type 2 diabetes, compared to those with the lowest levels.

The authors called for further studies, but lead author, associate professor Dariush Mozaffarian, said, "The magnitude of this association is striking."

He added, "This represents an almost three-fold difference in risk of developing diabetes among individuals with the highest blood levels of this fatty acid."

The study also appears to confirm previous research showing that a diet rich in dairy foods is linked to lower risk of type 2 diabetes and related metabolic abnormalities.

Mozaffarian said, "There has been no clear biologic explanation for the lower risk of diabetes seen with higher dairy consumption in prior studies. This is the first time that the relationship of trans-palmitoleic acid with diabetes risk has been evaluated.

"We wonder whether this naturally occurring trans fatty acid in dairy fats may partly mimic the normal biologic role of its cis counterpart, cis-palmitoleic acid, a fatty acid that is produced in the body.

"In animal experiments, cis-palmitoleic acid protects against diabetes."

Professor Gokhan Hotamisligil, senior author on the study, said this latest research had strong findings.

"This is an extremely strong protective effect, stronger than other things we know can be beneficial against diabetes.

"The next step is to move forward with an intervention trial to see if there is therapeutic value in people."

Deepa Khatri, clinical advisor at Diabetes U.K, said, "People should not take the findings of this research as a reason to exceed the recommended portion amounts of dairy food in order to prevent their risk of developing type 2 diabetes.

"Milk and dairy foods can be high in fat, which if eaten in excess can contribute to weight gain. So it's advisable to choose lower-fat dairy foods instead.

"More research is needed to see whether these trans-palmitoleic acids can play a useful role in preventing type 2 diabetes.

"In the meantime, however, Diabetes U.K. advises that all people, with or without diabetes, should have a healthy balanced diet, low in fat, salt and sugar with plenty of fruit and vegetables.

"This is based on robust, nutritional research and it is not recommended for people to increase their intake of any one food type in order to prevent their risk of developing type 2 diabetes."

From the January 10, 2011, Prepared Foods E-dition