Is it true that the polyphenols in blueberries block fat storage and that dairy interferes with polyphenols?
I recently read in Woman's World magazine that "A recent Texas Woman's University study suggests that eating a half a cup of blueberries daily reduces the amount of fat your body stores from food by an incredible 27% and the more you eat, the more gets zapped! The berries are loaded with polyphenols that block the formation of new fat cells, as well as trigger the breakdown of existing fat cells, explains lead study author Shiwani Moghe, M.S. Avoid eating blueberries with milk or yogurt - proteins in dairy can block the polyphenols from being absorbed by the body."
I always eat blueberries with yogurt. Is there credence to these claims about polyphenols blasting fat and that dairy can block them from being absorbed by the body? Do dairy products negate any of the other healthful benefits of any/all berries?
Dr. Gourmet Says...
This is another one of the sensational items reported in the media as if it were a fact. They are knitting together a number of research studies in order to draw conclusions that have simply not been shown to be true in humans. The study you cite was performed in test tubes with cloned mice cells. It is an interesting finding, but at this time not much more than good dinner table conversation.
Likewise, there is no evidence that consuming fruit high in polyphenols and other antioxidants, in combination with yogurt or with other dairy products, has a significant effect on your health (other than the known positive effects of antioxidants). This is another place where people leap to conclusions that, while based on interesting research, don't have known clinical significance in humans.
Researchers in Germany looked at the effect black tea had on circulation by using ultrasound measurements of the arteries in the arm after consumption of tea. There appeared to be improved blood flow with black tea, but with the addition of milk to the tea, the effect was not as strong. They also showed that when the milk was added to the tea it seemed to bind up some of the antioxidants in the tea.
All of this is interesting, but it is not anywhere near enough information to make a clinical judgement or for me to make any sort of recommendation regarding change in behavior. People often do this, however, drawing the wild sort of claims that you have mentioned.
Does the effect of milk on tea actually have long term benefits or drawbacks? We don't know the answer to this question any more than we know the effect of dairy on blueberries. One study was on tea in humans two hours after consumption and the other in the test tube. Study A is true (but may or may not mean anything) and Study B is true (but may or may not mean anything). Study A has absolutely no relationship to Study B and you certainly can't draw any conclusions from the two together.
Eat your yogurt. Have your fruit with it. Enjoy - and it's great that you are eating such healthy foods.
Thanks for writing,
Timothy S. Harlan, M.D.