Antioxidant foods loose potency over time

Antioxidants and antioxidant rich foods like blueberries, grapes and green tea have become very popular. Their popularity is due to the potential health benefits associated with the antioxidant nutrients found in these foods. However, two new studies show those health benefits can decrease if the products are stored for too long a time.

These studies focused specifically on how well antioxidant activity holds up in commercially available green tea bags and olive oil when stored unopened and unexposed to light or moisture. In each case, the research revealed that siginficiant drops in antioxidant activity occur within the first six months.

One study focused on the antioxidant compounds found in green tea leaves that are known as catechins. When consumed in tea, these antioxidant compounds are thought to have a bacterial and virus-fighting capacity, as well as the ability to inhibit cancer cell activity. The researchers examined the stability of catechins during long-term storage in homes, restaurants, commercial warehouses, and/or stores. The researchers found that at the end of six months, the catechin levels in the teas had decreased by 32%.

The other study looked at the durability of antioxidants found in extra-virgin olive oil. In this study, the researchers found that antioxidant activity remained unchanged throughout the first three months of storage. However, by the six-month mark, most of the oils had lost about 40 percent of their antioxidant properties.

Although these studies are preliminary and more research is needed to establish product shelf-life with regards to antioxidant content of commercial products, the bottom line is that if we want to maximize the nutritional value of the foods we eat, we really should buy only what we can use in a short period of time. This is true whether we're talking about the actual food -- for example, olives -- or whether it is the olive oil derived from the food.

Here are a few tips to maximize the nutritional value of your purchases:

• Ask the question: 'Can I use it within a reasonable period of time?' From a nutritional standpoint, buying in bulk may not be a real dollar savings, when you look at the loss of nutritional value that will occur over time.
• Choose products that are packaged in tinted containers over clear ones. This helps to protect antioxidant, vitamins and minerals from exposure to the sun.
• Store products, especially oils in a dark setting at room temperatures ranging from 68 degrees to 77 degrees Fahrenheit.
• Buy fruits and vegetables that are locally grown or buy foods that are frozen, canned or packaged immediately - i.e. fresh frozen.

For more on antioxidants, visit the U.S. National Library of Medicine.