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Clearing Up Common Nutrition Myths

Jan 09, 2012

Written by Janet Walberg Rankin, Ph.D., FACSM

Who hasn’t been confused by conflicting reports about what to eat? Let’s take a look at recent scientific evidence to clear up five very common nutrition myths.

Myth 1: Calcium will guarantee strong bones.
Most adults should consume between 1000-1300 mg of calcium per day in order to promote good health, including bone health. However, even this level of calcium intake should not be considered an insurance policy against bone loss. Exercise, hormones and vitamin D are major contributors to bone health. Some believe that most people don’t need to worry about vitamin D because our skin naturally produces it after sun exposure. However, recent research broke this myth wide open.

Growing evidence of the importance of vitamin D led some scientists to propose that we triple the previously recommended 400 IU (international unit) daily amount of vitamin D. Experts at the Institute of Medicine (IOM) recently took on this volatile topic to develop a consensus. In Dec. 2010, the IOM report on vitamin D and calcium bumped the recommended vitamin D intake to 600 IU per day for children and adults and up to 800 IU per day for those over 71 years. Oversupplementing, defined as an intake greater than 4000 IU, can damage kidneys and contribute to kidney stones, so experts caution against consuming too much calcium.

Myth 2: Low-carb diets are the best for weight loss.
Several large-scale studies have compared popular weight loss diets head-to-head, and none of the diets emerged as the clear winner. This may be partly due to the fact that although people adhere carefully to the restrictions initially, they digress toward old eating habits over time. The boring conclusion is that the people who adhere most closely to the diet recommendations are most successful in their weight loss, regardless of which diet they follow.

When health factors other than weight loss are measured, most studies report the greatest reduction in blood triglycerides for low-carb diets and the greatest reduction in blood cholesterol levels for low-fat diets. Although my professional opinion holds to a low-fat diet rich in fruits, vegetables and whole grains as the best for weight loss, I would consider agreeing to a low-carb diet for someone who prefers this, as long as they agree to careful monitoring of their micronutrient intake and blood cholesterol levels.

Myth 3: Water is just as good as a sports drink for athletes.
This myth needs clarification. Although water is a good hydrator for most people under most conditions, athletes are anything but typical. Highly competitive athletes may experience significant reduction of glycogen stores and dehydration during an intense, prolonged competition or workout. Sports drinks provide carbohydrate as well as the electrolytes and fluid that replenish critical energy reserves and delay fatigue. I believe if exercise is less than an hour, or of only moderate intensity, water is sufficient. High-intensity, longer performance may be improved by regular consumption of a sports drink.

Myth 4: I eat only 1,200 calories per day, but I can’t lose weight.
Few people are good at estimating portion sizes of their food. This can cause them to underestimate their true calorie intake. For example, a USDA study found that the average baked potato is 2.5 times the defined serving size. So, using the food table calories for one potato may substantially underestimate actual intake. Alternatively, maybe you only ate 1,200 calories one day, but you splurged the next with 2,500 calories. It is difficult to accurately determine how many calories you should consume each day to lose weight (it’s best to consult a dietitian), but you can get a rough estimate of your daily goal by multiplying your weight in kilograms by 35 and subtracting 500-600 calories.

Myth 5: Avoid coffee.
This is my personal favorite myth, as I am rarely seen first thing in the morning without my coffee. Recent research does not vilify coffee; rather, it finds health benefits in consuming this brew. Coffee consumption has been associated in some research studies with lower risk of diabetes, stroke and Parkinson’s disease. In fact, one recent study of more than 86,000 nurses reported that the risk of dying was 26 percent lower among those who drank four to five cups of coffee per day compared to those who abstained. People with heart or sleep problems, or women who are pregnant, should consult their doctor first, but most of us can drink our morning coffee without worry.

So, why do we get conflicting messages about nutrition? Scientists are a naturally skeptical bunch who continually question “truths” to be sure they are correct. One must look for the consensus out of the many research studies. Since most of us can’t put the time into reading all that research, one of the best ways is to use good online sources like Nutrition.gov or the USDA National Agriculture Library. You can also talk to a dietitian. Either way, rely on the experts to sift through the latest claims and scientific discoveries to steer you down the right path.

View the full spring 2011 issue of the ACSM Fit Society® Page supported by Liberty Mutual online.

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