Fruits are rich in fibre, antioxidants, and phytochemicals.
Increasing fruit consumption has been recommended for the primary prevention of many chronic diseases, including type 2 diabetes.
However, epidemiologic studies have generated somewhat mixed results regarding the link with risk of type 2 diabetes.
The inconsistency among these studies may be explained by differences in types of fruits consumed in different study populations as well as difference in participants’ characteristics, study design, and assessment methods. Furthermore, the greater variety, but not quantity, of fruits consumed was associated with a lower risk of type 2 diabetes.
Fruits have highly variable contents of fibre, antioxidants, other nutrients, and phytochemicals that jointly may influence the risk.
Researchers at the Harvard School of Public Health (HSPH) thus embarked on a study involving 10 individual fruits: grapes or raisins; peaches, plums, or apricots; prunes; bananas; cantaloupe; apples or pears; oranges; grapefruit; strawberries; and blueberries.
The researchers examined data gathered between 1984 and 2008 from 187,382 participants in three long-running studies (Nurses’ Health Study, Nurses’ Health Study II, and Health Professionals Follow-Up Study). Participants who reported a diagnosis of diabetes, cardiovascular disease, or cancer at enrollment were excluded. Results showed that 12,198 participants (6.5%) developed diabetes during the study period.
The researchers looked at overall fruit consumption, as well as consumption of individual fruits.
Blueberries, Grapes, and Apples
People who ate at least two servings each week of certain whole fruits — particularly blueberries, grapes, and apples — reduced their risk for type 2 diabetes by as much as 23 percent in comparison to those who ate less than one serving per month.
Conversely, those who consumed one or more servings of fruit juice each day increased their risk of developing type 2 diabetes by as much as 21 percent.
The researchers found that swapping three servings of juice per week for whole fruits would result in a 7 percent reduction in diabetes risk.
The researchers theorize that the beneficial effects of certain individual fruits could be the result of a particular component. Previous studies have linked anthocyanins found in berries and grapes to lowered heart attack risk, for example. But more research is necessary to determine which components in the more beneficial fruits influence diabetes risk.
The above story is based on the Harvard Gazette of August 29, 2013
The study appeared online in the Aug. 29 issue of the British Medical Journal:
Muraki I, Imamura F, Manson JE, Hu FB, Willett WC, van Dam RM, Sun Q. Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies. BMJ 2013;347:f5001
Click HERE for the full text.
So, should you skip the juice?
The study did not any distinction between freshly expressed juice and packet juice with or without added sugar.
However, the high glycaemic index (a measure of how rapidly carbohydrates in a food boost blood sugar) of fruit juice — which passes through the digestive system more rapidly than fiber-rich fruit — may explain the positive link between juice consumption and increased diabetes risk.
For more about diabetes, try the Malaysian Diabetes Association.