Nutrition studies don't cut the mustard

Most people think moderate drinking is good for your heart. It's one of those nutrition success stories everybody likes to hear, like chocolate and coffee are great sources of antioxidants. Wouldn't it be great if your health was guaranteed just by indulging yourself? Of course, reality kicks in with a new study: International study questions health benefits of moderate drinking. This is not news, the BBC reported on a study with a similar conclusion back in 1999.

It is not uncommon that nutrition studies disagree with each other. It is hard to study nutrition, since you cannot just take two groups of people and lock them in a controlled environment for decades to study the effects of dietary changes in one group. Most people these days think you can do that with animals, but of course, animals aren't humans.

A popular type of nutrition study without ethical problems is a population study. You take a group of people with certain characteristics (say: moderate drinkers), and a group of people that don't have those characteristics (say: non drinkers). You then find out which group has more heart-disease, death, cancer or whatever else you want to study. Of course there are problems with these kinds of studies. It turns out that most of the studies that reported that moderate drinkers had less heart disease did not control for the fact that people who are already ill or take medications are likely to be non drinkers. I think this is unbelievably stupid, but it happens all the time.

Another example: most people think that being underweight is unhealthy; perhaps even unhealthier than being overweight. This is not true. Smokers and people who have serious illnesses are more likely to be underweight. An active non smoking healthy individual with a BMI of 17 is at less risk for death than someone with a BMI of 21. (Source: Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating)

So, what should you do? If those studies can't be trusted, and seem to disagree all the time, how do you know what you should eat? It's not that bad. There may be scientific dispute over details; there is no controversy at all over the bottom line: fruits and vegetables are essential to good health. And don't forget to exercise.

April 1, 2006