A. Judith C. Thalheimer, RD, LDN, managing editor of Tufts Health & Nutrition Letter, answers: “Some studies have found that dairy products may reduce antioxidant capacity of other foods and beverages, but a number of studies have not found this effect, and some studies even show a positive impact.
“Antioxidants prevent oxidation, a common chemical reaction that can lead to the production of cell-damaging free radicals. The theory is that the protein casein in dairy products can bind with antioxidants in other foods and beverages, blocking absorption or reducing effectiveness of the antioxidants. It is important to keep in mind that even in studies where antioxidant capacity was found to be reduced it was not eliminated. For example, if the antioxidant capacity of a food is reduced by 20 percent, 80 percent of the beneficial effect remains, so this food is still a healthy choice. Additionally, there are no studies that have examined whether consuming dairy with high-antioxidant foods is actually associated with any negative effects on health. Never fear: a nice yogurt-berry parfait and a coffee or tea with a splash of milk is a nutritious, tasty breakfast choice—just watch the added sugars!”