11 July 2009

Antioxidants - Comparing Apples to Oranges

Which will keep the doctor way? The orange contains about 10 times more vitamin C, which is an essential antioxidant for many complex roles in the human body (1). On the other hand, the apple contains quercetin, which has been shown to have a higher antioxidant capacity than vitamin C, thus, potentially offering better protect against free radicals (2;3). Clearly these antioxidants are not equal.

Free radicals are atoms or molecules that have one or more unpaired electrons. These are mainly result of the mitochondria leaking electrons that bind to oxygen; however, there are a variety of other free radicals from exposure to smog, ozone, drugs, and drugs (1).

Because “oxidative stress” is thought to be associated with many diseases including cancer, antioxidant nutrients are frequently evaluated for ability to neutralize free radicals, particularly the oxygen-centered radicals: superoxide, hydroxyl and peroxyl radicals (1).

While antioxidants help decrease neutralize free radicals, they themselves become free radicals although—in some cases such as vitamin E, C, ubiquinol and glutathione—regeneration pathways in the body often help them function over again (1). The regeneration process is key for optimal defense against oxidative stress and so is receiving enough of different kind of antioxidants (1).

As science continues to discover more and more, high-antioxidant foods continue to grown in the marketplace. Walk down the isle of any health food store and you’re sure to spot the latest and greatest—pomegranate, blueberry, acai berry, green tea. What makes one food greater than another?

These compete by antioxidant capacity including measures of oxygen radical absorption Capacity (ORAC) (4;5). Each ORAC unit indicates greater antioxidant protection—the higher the score, the more “super” the food (5). Another test more relevant biologically is cellular antioxidant activity (CAA), performed on cell cultures, which has found quercetin, pomegranate and berries clear favorites for decreasing oxidative stress (6). Antioxidant capacity can also be helpful to determine one fruit with another of the same fruit. For example, organically grown fruit and vegetables often have a higher ORAC score indicating greater content of fruit (7).

Should consumers rely strictly on ORAC or CAA tests for making food choices? The answer is, no. While single antioxidants may have unique functions that may link them to reduced risk of disease, such as vitamin C and heart disease (1), quercetin and liver cancer (8), no single antioxidant or antioxidant complex has appeared yet to decreases oxidative stress enough overall to reduce risk of all diseases (1).

As discussed above, however, antioxidants often work with each other synergistically in the body. Thus, for superior nutrition, adopt the “color code”: five to nine servings daily of fruits and vegetables of different colors provides the reds, red-purples, oranges, yellows, and greens for your body daily and is in line the National Cancer Institute and American Institute (9). Until more is known about antioxidants, the color code offers the the best guideline for health and prevention of disease (1).

Reference List

1. Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. Belmont, CA: Thomson Wadsworth, 2009.
2. Wolfe KL, Liu RH. Cellular antioxidant activity (CAA) assay for assessing antioxidants, foods, and dietary supplements. J Agric Food Chem 2007;55:8896-907.
3. Kim DO, Lee KW, Lee HJ, Lee CY. Vitamin C equivalent antioxidant capacity (VCEAC) of phenolic phytochemicals. J Agric Food Chem 2002;50:3713-7.
4. Kohri S, Fujii H, Oowada S et al. An oxygen radical absorbance capacity-like assay that directly quantifies the antioxidant's scavenging capacity against AAPH-derived free radicals. Anal Biochem 2009;386:167-71.
5. Cao G, Alessio HM, Cutler RG. Oxygen-radical absorbance capacity assay for antioxidants. Free Radic Biol Med 1993;14:303-11.
6. Wolfe KL, Kang X, He X, Dong M, Zhang Q, Liu RH. Cellular antioxidant activity of common fruits. J Agric Food Chem 2008;56:8418-26.
7. Di RL, Di PD, Bigioni M et al. Is antioxidant plasma status in humans a consequence of the antioxidant food content influence? Eur Rev Med Pharmacol Sci 2007;11:185-92.
8. Seufi AM, Ibrahim SS, Elmaghraby TK, Hafez EE. Preventive effect of the flavonoid, quercetin, on hepatic cancer in rats via oxidant/antioxidant activity: molecular and histological evidences. J Exp Clin Cancer Res 2009;28:80.
9. Heber D, Bowerman S. Applying science to changing dietary patterns. J Nutr 2001;131:3078S-81S.

No comments: