Karen Collins, MS, RD, CDN American Institute for Cancer Research
Weekly column for the week of November 28, 2005
Q: Do B vitamin supplements help people who are nervous or low on energy?
A: Claims on the labels of supplements are frequently misleading. Companies are allowed to make claims about how a product can affect body parts and functions, but these claims don't always mean what consumers suppose. For instance, vitamins B-12 and B-1 (thiamin) are important for healthy nerve cells. These cells send messages between different body parts and the brain, allowing us to feel, see and move. However, more of these vitamins will probably not make anyone less nervous. Likewise, several of the B vitamins are necessary for metabolic processes that convert the food we eat into energy. It is possible that people whose diets are low in B vitamins might feel less fatigued if they consume more of these vitamins. But once their needs are met, more vitamins will not give them more energy. If you are low on energy, you need to address the underlying problem to resolve your energy shortage. A lack of sleep, too strict dieting, a diet low in several nutrients, a sedentary lifestyle, too much work, or too much stress could be the real problem.
Q: Should I diet or exercise to get rid of the flab around my waist?
A: "Flab" that is due to sagging, untoned muscles means you must exercise to strengthen the muscles in that area. Various kinds of crunches (the improved version of sit-ups) condition these abdominal muscles. Excess body fat around the waist or anywhere else, however, will not be fixed with toning exercises. Extra body fat means that you've been eating more calories than you burn up. You can tackle this problem by cutting back on your calorie consumption or boosting your activity level through exercises like walking and cycling. For most people, doing a little of each is the most successful strategy. An easy way to consume fewer calories is to look for places in your usual habits where you can replace a high-calorie drink with water, or eat a smaller portion of a high-calorie food. In general, many people find that they need to lower their calorie intake and exercise more to tone abdominal muscles to get rid of a flabby waistline.
Q: Why do DV and RDA guidelines both exist?
A: Both Daily Values (DVs) and Recommended Dietary Allowances (RDAs) can help steer you to healthy eating, each in a different way. The DV figures on labels allow you to compare products and see whether a food is high or low in various nutrients. If you want to find out what is the amount of a nutrient you should set as a personal target, however, RDAs are a better choice. The current RDAs can be found at www.iom.edu/Object.File/Master/21/372/0.pdf. One of the reasons RDAs are better to use as targets is that they are based on more recent scientific analyses than the DVs. For example, 60 milligrams (mg) of vitamin C meets 100 percent of the DV for this nutrient, but recent studies prompted the RDA for this vitamin to rise to 75 to 90 mg for adults. As a result of other recent studies, the DV recommendation falls below the RDA for potassium and calcium, too, for some or all adults. But if you reach 100 percent of the DV for most B vitamins (thiamin, riboflavin, niacin, B-6 and B-12), iron and zinc, you've gone beyond the current RDA goal. Another difference between these two guidelines is the ranges given for RDAs. Several RDAs are set for each nutrient to reflect differences in a person's age and gender. For example, women over the age of 50 and all adult men don't need to aim for 100 percent of the DV for iron. This amount is more than double the RDA for these groups.
Reprinted with permission from the American Institute for Cancer Research
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