3 more health myths you (probably) believe—and the real science behind them

Topics: Industry, Research and Development, Patient Populations, Children, Public Health, Food/Nutrition

By Jackie Kimmell, senior analyst

As American Health Line mentioned in a previous explanation of the science behind four common health myths, it can be hard to distinguish myth from fact in the world of health.

Even for those of us who work in health care, it can be difficult to keep up with the stream of new scientific studies, understand contradictory evidence, and dispel wrong assumptions. Therefore, American Health Line has dug into three more common health myths to help you understand their origin and the scientific evidence behind them.

1. Sugar makes kids hyper. 

This myth was likely born in 1973 when allergist Benjamin Feingold published his popular Feingold Diet, which suggested to parents that they should avoid food additives in their children's diets. Refined sugar in children's diets soon also fell under scrutiny.

It took only a few years for the public to jump from viewing refined sugar as unhealthy to it causing children to act hyper and misbehave.

However, since then, an array of studies have refuted this often-believed myth. A 1995 meta-analysis of 23 studies in JAMA found no effect from sugar on the cognitive performance or behavior of children. Researchers did note, however, that they couldn't rule out that sugar has a small effect on a small subset of children.

Just as in adults, increased blood sugar in children might lead to an energy boost if a child is feeling lethargic because of low-blood sugar levels (known as hypoglycemia), but this boost would come only from returning them to a normal energy state. For children with normal blood sugar levels, eating sugar will just lead the child's body to convert those extra sugars to fat, not energy.

The reason the myth has persisted might actually be due to parents convincing themselves that it is true. One study showed that parents actually perceive their children as being more hyperactive after being told they had a sugary drink, even though their children were given nothing.

2. You need to take a daily multivitamin.

The number of U.S. residents taking multivitamins decreased over the past decade—the 37% who reported taking them in 2000 had fallen to 31% in 2012—in part because the science supporting multivitamins has largely been inconclusive.

Catherine Price, a science journalist, has said there are 13 vitamins that scientists believe are associated with good health. Those vitamins can be gleaned from everyday food, but most U.S. residents don't eat the recommended amounts of fruits and vegetables, so many turn to consuming their vitamins and minerals in a pill form instead.

But to date, there's been limited evidence that a daily multivitamin has a causal impact on long-term health.  A meta-analysis conducted for the U.S. Preventative Services Task Force found that there was no clear evidence of dietary supplements on total mortality, cardiovascular disease, or cancer. Another study found no impact of multivitamins on cognitive decline, and another found no link to the risk of repeat cardiovascular events.

Other studies have found that multivitamins could, in fact, be harmful. One study of 38,000 women from age 50 to 60 found that daily multivitamin use was actually associated with a slightly (6%) increased risk of total mortality.

This is might be because, while vitamins seem intuitively appealing (if minerals and vitamins are good for you, taking them in a pill should be good for you too), the excess amounts often found in supplements can be too much for the body. For example, studies have shown that too much beta carotene and vitamin E can lead to cancer, and excess vitamin A can cause liver damage, coma, and mortality.

The fact that U.S. residents spent $28 billion on dietary supplements in 2010 led an editorial in the Annals of Internal Medicine to declare: "Enough is enough. Stop wasting money on vitamin and mineral supplements." 

However, for those at risk of deficiencies, multivitamins can be useful. Those with inflammatory bowel disease, celiac disease, or those who have had gastric bypass surgery might need a vitamin to meet their dietary needs.

3. You use only 10% of your brain.

The myth that we use 10% only of our brain is sometimes misattributed as having originated with Albert Einstein, although no record exists of him making such a claim. It could also possibly come from famous American psychologist William James, who liked to argue that humans were meeting only 10% of their full potential. When famous journalist and adventurer Lowell Thomas wrote the 1936 introduction to Dale Carnegie's How to Build Friends and Influence People, he apparently misunderstood James' aphorism and claimed James had said we use only 10% of our brain.

However, this claim has been soundly disproved three times over. First, advanced brain imaging—including PET scans, MRIs, and EEGs—have shown that almost all of the brain is engaged when undertaking any given task.

Second, the idea that we would only be using 10% of our mental capacity seems implausible given natural selection, as it is unlikely that we would have evolved to squander energy on a 90% useless organ—especially given how metabolically expensive brain tissue is to grow and run.

Finally, clinical neurology suggests that there's no area of the brain which can be destroyed, either due to a stroke or head trauma, which will not leave a patient with some sort of functional problem. If the myth was actually true, only 10% of brain damage would actually cause functional deficits.