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United States Department of Agriculture

Agricultural Research Service

If A Little Is Good, A Lot Must Be Great??
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John Finley

We have all heard the logic, perhaps even used it ourselves - if a little of something is good, then a lot more should be great. This logic pervades our culture and one of the places it is most entrenched is in our concepts of nutrition. We hear that a nutrient is important, and soon we are bombarded with advertisements urging us to buy "supplements" and "nutritional additives" containing the nutrient. The inference is always the same: Nutrient "X" helps your body fight cancer, so if you consume copious amounts of "X" everyday, you will ward off the dreaded disease. But is this true? Common sense casts doubt on this logic - if you put 10 gallons of gas in your Yugo and it runs well, does it run like a Ferrari if you put in 100 gallons? No, if you attempt to put in 100 gallons, 90 go down the storm drain, and you still have a Yugo.

You may have heard a taped message in which an "expert" explains the function of mineral nutrients and claims that if only we consumed more minerals we would fight off almost all of the diseases and health problems that now kill us, and we just might live to be 200! So, with the availability of cheap nutritional supplements, the choice is clear. Save $40 a month and prepare for cancer, heart attacks and bone loss, or buy supplements and enjoy 110 extra years of bingo. Put like that, who wouldn’t choose the bingo?

Most nutritionists agree that too little of a nutrient may be harmful. But if you are not deficient (analogous to your Yugo being out of gas), does consumption of excess nutrient benefit you? That is, if you add gas after the "Full" line, can you make your Yugo run like a Ferrari? Or does your body send the excess nutrients, and the money to purchase them, down the sewer? Usually, the sewer wins. An example comes from research on a nutrient called beta-carotene.

Increased fruit and vegetable consumption is associated with decreased risk of cancer, and many scientists believed beta-carotene in the fruits and vegetables was the magic anti-cancer ingredient. So beta-carotene sales soared, and many people warded off dreaded cancers by popping a beta-carotene pill. But did they? A controlled study with Finnish smokers found that beta-carotene supplementation actually slightly increased the risk of lung cancer!

However, some say that a nutrient called selenium (Se) contradicts our argument. The Recommended Dietary Allowance (RDA) for Se is 70 micrograms (mcg)/day for adult men, but recent studies at the Grand Forks Human Nutrition Research Center found that consumption of up to three times (or 210 mcg) the RDA for Se resulted in less anxiety, depression and confusion and a more energetic feeling. A more dramatic example is from a study that gave 1,312 volunteers in the Southeastern U.S. a placebo or 200 mcg of supplemental Se daily for ten years. Selenium did not protect against skin cancer, but lung, colorectal and prostate cancer was reduced an astounding 42%!

So does this mean that we should all rush out and start taking Se supplements? Definitely not! First, Se is very toxic, and only a narrow margin separates safe and adequate intakes and toxic intakes; people in the U.S. have died from toxicity but not deficiency. The above studies were carefully controlled to prevent Se toxicity. Moreover, these are preliminary results for small groups in specific areas, and the same results may not be obtained with different subjects or in different areas. But they do raise the possibility that the current RDA for Se may be too low, and more research needs to be conducted. So, in the case of Se, maybe our Yugo didn’t run better when overfilled - maybe the gas gauge just wasn’t calibrated correctly.

These examples show that nutritional supplementation is complex, and there are no magic elixirs. The best advice is from the American Dietetic Association which states: "... the best nutritional strategy ... is to obtain adequate nutrients from a wide variety of foods....supplementation is appropriate when...scientific evidence shows safety and effectiveness."

So, regardless of what the spokespeople for nutritional supplements tell you, popping a supplement once a day won’t give your Yugo an overhead cam drive, and probably won’t prolong your life. For that, eat more fruits and vegetables, exercise more, and go to Cancun on the money you saved.

Last Modified: 4/4/2007
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