Vitamins are nutrients that help your body to function correctly in myriad ways. You can find vitamins in nearly all of the foods you eat, particularly fruits, vegetables, grains, dairy and meats. As many as 68 percent of all adult Americans also take some type of vitamin supplement. However, vitamins in supplements and food can degrade over time or after undergoing cooking processes. Knowing if the vitamins you consume lack potency can help you determine if your intake of a particular vitamin is sufficient.
Water-Soluble Vitamins
Water-soluble vitamins are nutrients that dissolve in water, such as vitamin C and the B vitamins. Your body naturally excretes water-soluble vitamins in your urine, requiring you to consume them daily for replacement. A 2007 research review appearing in "Journal of the Science of Food and Agriculture" points out that vitamin C loss in fruits can be substantial after harvest, with potency decreasing by as much as 50 percent in the first 48 hours. Some water-soluble vitamins are more stable over time, such as riboflavin, but degradation still takes place. Potency of these vitamins may decrease significantly during cooking, particularly at high heat or in water for a long period of time.
Fat-Soluble Vitamins
Fat-soluble vitamins, such as A, E and K, are vitamins that your body can store in fat tissue. Their potency tends to degrade less than water-soluble vitamins during fresh storage and preservative processes like canning or freezing. However, research into the decline of the potency of fat-soluble vitamins in foods is scarce and contradictory. For example, the "Journal of the Science of Food and Agriculture" study points out vitamin E potency may increase slightly with initial heating and then decrease with continued heating, while vitamin A potency has been shown to increase in cooked broccoli and decrease in cooked carrots.
Supplement Potency
If you have approval from your doctor to take a vitamin supplement, be aware that the supplement can lose potency over time just like fresh foods. North Dakota State University nutrition specialist Julie Garden-Robinson suggests only consuming vitamin supplements with an expiration date, and always storing them in a cool, dry place to maximize potency. Some vitamins, such as vitamin A, may be sensitive to oxidation. Limiting a supplement's exposure to light and fresh air can reduce potential degradation.
FDA Regulation
The U.S. Food and Drug Administration oversees the safety of all dietary supplements and makes it a priority to investigate and remove any supplements that pose a danger to public health. However, the FDA does not have the resources to check the potency of vitamins and other supplements. Manufacturers are responsible for truthfully reporting the content and potency of their vitamins. As a consumer, you must carefully do your research to ensure you are purchasing high-quality vitamin supplements.
References
- "Journal of the Science of Food and Agriculture"; Nutritional Comparison of Fresh, Frozen and Canned Fruits and Vegetables, Part 1; Joy C.Rickman, et al.; March 2007
- "Journal of the Science of Food and Agriculture"; Nutritional Comparison of Fresh, Frozen and Canned Fruits and Vegetables, Part 2; Joy C.Rickman, et al.; March 2007
- Linus Pauling Institute; Vitamin A; Jane Higdon, Ph.D.; December 2003
- Colorado State University; Food vs. Pills; J. Anderson and J. Roach; May 2010
- North Dakota State University; Q&A About Dietary Supplements; Julie Garden-Robinson; September 1997
- U.S. Food and Drug Administration; Overview of Dietary Supplements; October 2009
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