One study looked at the organic compounds that are found in green tea leaves. These are known technically as catechins and are thought to have the capacity to fight off viruses and bacteria, and might even be able to limit cancer cell activity.
Since this type of tea doesn't spoil and stays on shelves for long periods, a team from the Western Regional Research Center of the U.S. Department of Agriculture looked to see if the catechins remained stable during long term storage in our cupboards, in restaurants, in warehouses and on store shelves.
The teas, eight different brands sold in the U.S., Japan and Korea, were kept in their original packages, stored in dark rooms that were heated to 68º F for one of five different lengths of time; one week, one month, two months, four months or six months.
At the end of each storage period, the teas were ground into powder, mixed with boiling water, cooled and then analyzed. There was some drop off in catechin content with even short-term storage, but there appeared to be a progressive decrease in the amount of antioxidants over time. By the end of six months of storage the concentrations had gone down by an average of 32%. While even the authors admit this work is preliminary, they hope that it will get people thinking about the storage and potency of antioxidants.
Another group of researchers from the University of Foggia in Italy evaluated a few varieties of olive oil that had been produced within a day of the olives being taken from the fields in the Apulia region of Italy. This team was strict about the oil being "extra-virgin" ensuring that the processing was limited solely to washing, decanting, filtration and high-speed mixing. The resulting oil is known to be rich in a specific blend of fatty acids and phenolic compounds that act as the antioxidants.
Making this oil part of your diet has long been thought helpful for cutting the risk of heart disease, stroke and even some types of cancer. Once Antonella Baiano and her team analyzed the oils during both production and packaging, they found that antioxidant activity remained unchanged during the initial 3 months of storage. But, by the 6-month mark, most of the oils had lost about 40% of their antioxidant properties.
This flies in the face of the idea that keeping something sealed and stored safely will be enough to preserve the nutritional value. Apparently antioxidants are pretty fragile. Also important to know is that when you choose plant foods, the nutritional value is better the fresher the food.
"The whole general concept driven by both of these studies 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," observed registered dietitian Connie Diekman, director of nutrition at Washington University in St. Louis who was not involved in either of the studies.
She also suggests choosing tinted containers instead of clear ones in the hopes that they provide some protection to the antioxidants from the sun. Another storage recommendation comes from the Italian researchers; they make a specific note that the extra virgin olive oil should be stored in small glass bottles in a dark place at a temperature that ranges between 68º-77º F.
While more work is being done, give some thought to the freshness of the antioxidant rich foods that you buy. Larger quantities, while appealing to our super-store sensibilities, might not be a good value if you end up eating less nutritionally complete foods.
Kirsten_Whittaker
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