Why You Don't Know What to Eat

Why is it that no one seems to have a straight answer on what to eat?

We know that good nutrition and good health are inextricably linked. What we eat directly influences our health, our weight, and our future. Wouldn’t you think that the health care providers, the media, the weight loss experts, the diabetes experts, the heart health experts, and so many more...wouldn’t you think that they could all agree on what’s healthy and what’s not??

Though it may be hard to believe, it’s just not that simple. Here’s why.

Most of the confusion comes from how we actually conduct nutritional studies. A lot of nutritional studies are what we call observational.  Basically, researchers observe what people eat and compare their health outcomes. The gold standard of research is a randomized controlled trial where you control the variables that could have an impact on the outcome and randomize subjects to a treatment group or a control group. The goal with a randomized controlled trial is that the two groups are the same except for the treatment. This allows us to evaluate how the treatment works and allows us to declare that the treatment causes an effect. For example, this new chemotherapy drug causes an improvement in survival in breast cancer patients compared to using the standard chemotherapy. We try to make everything the same about the patients except for the treatment they receive (new chemo or old chemo).

An observational research study is about as far away from a randomized controlled trial as you can get.  While you can try to observe and document a lot of variables such as specific types of foods eaten, whether or not the person smokes, how much exercise does the person get, etc., you are never going to be able to control all of those factors, and you don’t know how much influence those factors have on the health outcome. You also cannot state a cause and effect with this kind of research. All you can say is that a certain behavior or food is associated with a health outcome. But you can’t say it causes that outcome.

In addition to this problem of controlling variables, you have the problem of how you actually collect the data. If you want to know what someone eats, how do you ask them? Do you have them fill out a food journal for a couple of days? Do you ask them what they ate yesterday? Do you ask them how frequently they had a specific food in the last year? How many of you think you could answer those questions with any degree of reliability? And do your answers really reflect what you eat on a day-to-day basis? Well, that is how food consumption data is usually gathered in most nutrition studies.

And finally, it takes a long time for health conditions to develop. This means these studies need to be conducted over many years. A lot can happen in that time. Diets change. Health habits change. Weight changes. All of these things have an impact on the development of chronic disease and may not be tracked all that well in an observational study.

So, part of the reason why you get conflicting information about nutrition is that it is difficult to draw firm conclusions from these studies for the most part.  The researchers draw conclusions similar to saying X food may be associated with the development of Y disease.  But the headline that you read in the paper or that makes the evening news is “X food causes Y disease” or “X food is terrible for us.”  In actuality you can’t make those kinds of statements based on the study.

This is probably the main reason why you hear so much conflicting information—especially in the news media. These studies can be difficult for nutrition experts and doctors to interpret much less health reporters for newspapers or the evening news. The best advice may be to not rely on any one study to formulate your diet but rather multiple sources. If it doesn’t make sense to you to eat the way the latest newspaper headline promotes, just wait, and next week there will be a new headline.