It seems like every day there is a new health claim, superfood, or "surefire diet trick" that is making headlines across the U.S. But how many of these claims are actually supported by the science they're discussing? That's a surprisingly tricky question to answer. To help you navigate the health news minefield, Dr. James J Kenney debunks a few of the latest stories...
Have you seen the article that insists, "Exercise May Actually Suppress Your Appetite?" Sounds like great news, right? Well, it would be, if that's what actually happened over the long term. Dr. Kenney took a look at the data and concluded, "Sadly but not for long. The impact of aerobic exercise on food intake is to actually increase it, not to reduce it. At best, the increase in ad libitum energy intake does not completely negate the calories burned. Anyone who has burned a lot of calories exercising knows the result is increased food intake and not a reduced appetite overall. If exercise reduces hunger, then how do we explain the huge calorie intake of athletes training for the Olympics? Yes, there may be a transient drop in appetite after exercising -- especially if body temperature is increased, but this temporary drop is more than compensated for later after body temperature returns to normal."
The bottom line? Yes, you may not feel like chowing down immediately after exercising, but this short-term effect does not last, and may even be outweighed in the longer term.
The article, "Breast Cancer Checks Save Lives Despite Over Diagnosis" also makes claims that call for further consideration. According to Dr. Kenney, "A lot of assumption were made that likely grossly exaggerated the benefits of mammograms and probably also somewhat overestimated the harm. Most data from better quality studies suggests the actual reduction in breast cancer mortality from screening mammograms is at best 5-10%, and probably is somewhat less than 5%. In that case, 12 women would have been subjected to treatments for breast cancer that they would never had known about without the screening for each death from breast cancer prevented. So in the USA, we have more than 200,000 women diagnosed with breast cancer each year and about 40,000 deaths from breast cancer. At best this number is being reduced by perhaps 2,000 to 3,000 per year via millions of mammograms. An important question (not considered in this analysis) is of the millions of mammograms, how many cases of breast cancer are actually being caused, especially in women who start at age 40 and get one every year? It could easily be 2,000 or more, but we have no good data on this. If so, the net impact of all those screening mammograms would be 12 women treated and dozens more made nervous wrecks because of false positives for each women whose breast cancer was diagnosed earlier because of screening. And how many of those women treated for breast cancer that was over-diagnosed will end up dying prematurely from the 'treatment' (radition, surgery, chemo)? Again we do not know. But this we do know: There is no credible data from any quality study that shows anything close to a statistically significant reduction in total mortality as a result of screening mammograms. By contrast, regular exercise, staying thin, limiting post menopausal estrogen, a healthful low-fat diet, and getting adequate sunshine all likely reduce the risk of breast cancer far more than screening mammograms. And most of these strategies are also known to increase longevity."
Here's the bottom line: there aren't high-quality studies that have successfully linked increased breast cancer screenings to increased survival rates. Instead, take other steps to prevent breast cancer -- steps that do have that scientific data to support them. These steps include eating healthfully and exercising regularly.
Dr. Kenney also evaluated the latest claims about omega-3 fatty acids and other supplements in the article, Fish Oil Benefits: New Science. Check it out, then read some of his additional thoughts on supplements below...
"Looks like it is better to eat seafood. The problem with the latest meta-analysis is that they used supplements in most of these studies and none of them assessed EPA/DHA status before giving people a supplement or placebo. Most likely a lot of people already had an adequate intake of omega-3s, in which case the supplements would do no good and might cause harm. Supplements of vitamin A or iron do more harm than good unless given to people who are shown to be deficient. It looks like the benefits of telling everyone with heart disease to take fish oil supplements without assessing their nutritional status for these essential nutrients seems a bit questionable. The good news was the meta-analysis did show a pretty strong trend to reduce cardiovascular disease deaths with fish oil supplements versus a placebo (except for stroke where there was a slight -- n.s. -- trend toward increased risk). That may because in higher doses fish oil supplements may increase bleeding and that could increase hemorrhagic stroke risk."
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