Sometimes there are clues when a food passes its prime: lettuce wilts, bananas turn brown. Other foods will look and smell OK long after their health punch has dramatically declined. “Certain nutrients are unstable when exposed to oxygen (from the air), heat (from cooking) and light,” says Carol Johnston, Ph.D., R.D., chair of the Department of Nutrition at Arizona State University. Keep track of how long you store the following nutrient-rich foods.
A 2009 study in the Journal of Food Science showed that catechins (antioxidants linked with a reduced risk of some cancers) in green tea decreased markedly over time. After six months, catechin levels were 32 percent lower. Make the most of the antioxidants by storing tea in a sealed container in a dark, cool place.
One cup of OJ can offer a full day’s dose of vitamin C. But, “OJ that has been opened loses all antioxidant benefit after just one week,” says Johnston. To get the most vitamin C, buy frozen concentrate and drink within a few days. Frozen concentrate is exposed to less light and air.
Extra-virgin olive oil contains more than 45 heart-healthy antioxidants, but after six months of storage their potency decreases by about 40 percent, according to researchers at the University of Foggia in Italy. Why? Oxygen bubbles in the bottle destroy the antioxidants.
Researchers at the University of Illinois found the antioxidant power of clover and buckwheat honey decreased by 30 to 50 percent after six months. Consider buying buckwheat—it generally has more antioxidants to start with.