Let’s face it, research can be confusing. When a major new study in the field of nutrition is released to the media, I hear the same questions all the time.
1) Why do they say that this is unhealthy now, ten years ago they said this was good for me?
2) Why do they say this is healthy now, 10 years ago they said this was bad for me?
3) Should I listen to these results and change my diet?
3) Was this a well designed study?
4) Two different newspapers reported the results differently, what is going on?
5) The government health websites tells us to do one thing, my doctor another and the media has it’s own ideas. Who should I listen to?
I figured I’d use this post to explain a bit about the research process and hopefully give you a better understanding of nutrition research in general.
The Scientific Method
In reality, one study does not tell you much, even if it is well designed. In order to change nutrition policy with confidence, you really want to see agreement among different types of research. For example, population studies, cohort studies, randomized controlled trials, animal studies and biomarker studies are all different types of research each with their own strengths and weaknesses. You’d really like to see most, if not all of these lines of research pointing in the direction of the hypothesis before making or changing nutrition recommendations.
It is also important to realize that it is totally normal to have studies that contradict each other. Each study has its own unique methods, including different subject characteristics, different doses of the nutrient or supplement and different duration of follow up. The way Dr. Willett at Harvard used to talk about it was very helpful. He used to say that coming up with nutrition policy was like having a big scale with lots of stones. The stones represent research studies. Each time a study shows an association between a nutrient and disease, you put a stone on one side of the scale. When a study does not support the association, you put a stone on the other side. If a study is really well designed, it’s a big stone. If the study has design flaws, it’s a tiny stone. Over years, and even decades, as the research begins to mount, the scale tips to one side. That is when the recommendations are made.
If you think about it this way, you’ll expect to see studies that go against a recommendation now and again and you also won’t put too much weight on a single study. It’s the accumulation of research from many different areas that leads us to make a recommendation, and this takes time.
The Media’s Play In This
The media is a big reason why people are confused by nutrition research. When a study comes out, they are very quick to over-inflate the importance with catchy, dramatic headlines and over-generalized stories. I understand that they are trying to sell newspapers, but they are definitely adding to the confusion by sending the message that one study can overturn years and even decades of research. Always take the media’s stories on nutrition research with a grain of salt.
Nutrition Science Is A Young Science
The truth of the matter is that we have only been studying nutrition and disease in large numbers of subjects for a few decades. Nutrition science is a young science and we are still perfecting our research methodology. Therefore, understand that sometimes recommendations that were made 20 years ago may not turn out to be true once we look at the problem with better and more modern methods. This may also be true 20 years from now. Trans fat is a great example. Decades ago, it was thought that trans fat was a better option than saturated fat to reduce risk of heart disease. Now we know that it is far worse for you. Our methods evolved and our studies taught us the error of the early recommendation. As of right now I can say this with confidence; research methods have dramatically improved in the last few years and we are now beginning to understand a lot about how nutrition can affect our health.
Publishing an article
When researchers want to publish a scientific paper, they will submit to the most prestigious journals first and then if they get rejected, submit to lesser journals with more relaxed acceptance standards. Therefore, if an article appears in a less competitive journal, it has likely been rejected by several journals already. Usually it will have been rejected for design flaws or because it doesn’t really add much to our current understanding of that particular nutrition and health topic. So I always tell people to find out where the article was published. If it was in one of the big 3 journals for nutrition literature, definitely give it more weight, if not give it a little bit less weight. The top 3 journals for nutrition research are:
New England Journal of Medicine
#2) The Journal of the American Medical Association
#3) The American Journal of Clinical Nutrition.
Some Final Tips
So the next time you see a big nutrition study in the newspaper or TV news, consider the following.
1) This is just one study. How does this fit into the context of the rest of the research on this subject?
2) If it goes against what we have been recommended, this is to be expected from time to time.
3) The media is probably making a bigger deal of this than it should.
4) If this was published in one of the big 3 nutrition research journals, pay attention to it a bit more. If not, pay attention to it a bit less.
5) Always keep in mind that nutrition science is a young science and there will be some contradictions from time to time, which is true for all evolving, researched based science. The good news is that our methods are getting pretty good and these should be fewer and fewer as time goes on.