If you favor those milk chocolate bon-bons over the dark variety, you might be better off switching. Eating dark chocolate -- but not milk chocolate -- raises levels of antioxidant in the blood, which could help protect against heart disease.

Researchers found that the rise in antioxidant levels is much lower when milk chocolate is eaten or when dark chocolate is eaten along with milk. Although the exact reason is unclear, it may be that milk interferes¹ with the absorption of antioxidants from chocolate.

The findings, reported in scientific journal Nature, come from a study of 12 healthy volunteers who, on different days, ate 100 grams of dark chocolate alone, 100 grams of dark chocolate with milk, or 200 grams of milk chocolate.

Blood analysis one-hour after dark chocolate was eaten showed a significant rise in antioxidant levels, including levels of epicatechin, a well-known dietary flavonoid, report Dr. Mauro Serafini, from the National Institute for Food and Nutrition Research in Rome, and associates.

In contrast, not much change in antioxidant levels was seen after eating of milk chocolate or dark chocolate with milk. Moreover, epicatechin absorption into the bloodstream was much lower than when dark chocolate was eaten alone.

The researchers say their findings highlight the possibility that other items in the diet could reduce the antioxidant activity of flavonoids in the body.

"There is therefore a need to take into account dietary habits when designing studies to assess the association between flavonoid-rich foods, antioxidant activity and degenerative disease," they add.