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 interferes 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.

    如果你喜欢牛奶巧克力胜过黑巧克力，你最好还是改变一下。黑巧克力能够提高血液中抗氧化剂的含量，有助于预防心脏病，而白巧克力则不能。

    研究人员发现吃牛奶巧克力或加奶的黑巧克力时，增加的抗氧化剂含量就少得多。现在还不清楚确切的原因，有可能是牛奶妨碍人体吸收巧克力所含的抗氧化成分。

    科学杂志《自然》刊登了这项研究结果。该研究在12个健康的志愿者中进行。他们在不同的时期内分别吃了100克黑巧克力，100克加奶的黑巧克力和200克牛奶巧克力。

    罗马国家食品与营养研究学会的毛罗·塞拉菲尼和他的助手说，受试者吃了黑巧克力一小时后，血液分析显示抗氧化成分的含量显著升高，包括表儿茶酸的含量。表儿茶酸是一种常见的食物类黄酮。

    相反，吃了牛奶巧克力或加奶的黑巧克力过后抗氧化剂的水平变化并不大。此外，血液吸收的表儿茶酸也比光吃黑巧克力低得多。

    研究人员说他们的结论增加了其他食品会削弱人体中类黄酮抗氧化活性的可能性。

    他们还补充说：“因此，在设计研究评估富含类黄酮的食物、抗氧化活性和变性疾病之间联系时，有必要将饮食习惯考虑进去。”