Why Nutrition Research Seems So Confusing
About 30 years ago, butter was bad for you and margarine became a healthy alternative. Left and right, healthy consumers tossed out the buttery saturated fat and replaced it with tubs of partially hydrogenated oils. The flavor was not as palatable, but the health benefits were worth it.
Then, all of a sudden (or so it seemed), the thinking changed. The medical community woke up and realized the health implications of eating trans fats, which largely come from these man-made partially hydrogenated oils.
Now the thinking goes that butter is a "healthy" fat and margarine is the worst thing ever.
This narrative is all too familiar to me. Daily I have discussions with patients about why it seems that medical or nutrition professionals "suddenly" changed their minds about the health benefits or drawbacks of food/supplements/medication/lab targets/diet trends. These patients are always so frustrated by this seeming lack of consistency.
Nutrition science is nuanced. It's not black and white, but rather all shades of grey. In order to understand why there are so many differences of opinion about nutrition, I want to review a few of the most common misunderstandings about scientific research in general.
Misunderstanding #1: We're Constantly Learning
Science is not static. And anybody using scientific research (doctors, veterinarians, dietitians, physical therapists, farmers, etc., etc.) knows that it's not about what you know, but rather what you're learning. I graduated with my master's degree only four years ago, but already there are things that I learned that are out of date.
For example, a couple of years ago I always advised to choose low- or non-fat dairy products. Recently, however, research has been coming out showing that the saturated fat in dairy is not necessarily linked to higher cholesterol and heart disease.
So what do I do? I keep up with the latest research and adjust my nutrition advice.
The hallmark of a good scientist is not to be right all the time, but to recognize when new information has made previous assumptions obsolete and to appropriately adjust her thinking. So please, be patient with your healthcare professionals when they appear to change their minds. Likely they are merely keeping up with the latest, most accurate science.
Misunderstanding #2: Mistaking Association for Causation
Let me tell you a story to help explain the difference between research at the population level (epidemiology) compared to research at the individual level (randomized, controlled trials).
A researcher went to neighborhood in which half of the houses were blue and half of the houses were green. After talking to all of the people, he found that the kids who lived in blue houses were really good at playing basketball. He also found that the kids who lived in green houses were really bad at playing basketball. So, the researcher concluded that living in a blue house makes you good at playing basketball, but living in a green house makes you bad at playing basketball.
Little did the researcher know that (coincidentally) the kids who lived in blue houses had gone to basketball camp that summer, while the kids who lived in green houses did not.
This same mistake has been made by the media regarding artificial sweeteners - in epidemiological studies, in which observations have been made about groups of people,
It's true that people who drink more diet sodas tend to be more overweight. This doesn't mean, however, that diet sodas cause people to gain weight (in fact, many quality research studies have shown that replacing sugar with aspartame actually results in weight loss). Here are a couple of other possible explanations for the correlation between artificial sweeteners and weight gain:
People who drink diet sodas tend to have other less healthy behaviors (exercise? drink less water?)
We feel good about saving calories on diet instead of regular, so we go ahead and splurge on other high-calorie foods
Diet soda pairs really well with french fries (and other types of junk food)
Misunderstanding #3: One New Research Study Finding Does NOT Debunk All Current Standing Knowledge
Another reason for all of the confusion is that the media is out to sell news - and shocking, new information is what sells. Thus, if only one new study is published that contradicts the commonly accepted knowledge of the day, it's all over the headlines. I mean, what do people love more than to hear how wrong Western Medicine is? However, this isn't how science works.
Research is (or should be) done by using the scientific method. In this, a researcher can only prove that the null hypothesis is false. I know, I know - this sounds like a double negative. It is, actually. The null hypothesis states that there is no difference between two groups being tested. The aim of research is to prove the null hypothesis wrong, to further support the hypothesis.
For example, if the researcher from the above example wants to confirm that living in a blue house makes a kid good at playing basketball, this would be the hypothesis and null hypothesis of the study:
Hypothesis: Living in a blue house rather than a green house makes a kid good at playing basketball.
Null hypothesis: There is no difference between living in a blue house and living in a green house on a kid's basketball skills.
From there, the researcher needs to design the study to try to prove that the null hypothesis is not true (best done by randomly selecting kids and assigning them different colors of houses to live in, then waiting a year and measuring basketball skills at set intervals during that time).
Now, let's say that it happened that the researcher did this and did prove the null hypothesis false -- he found that there was a difference between kids living in blue houses versus kids living in green houses. This still does not prove that living in a blue house makes a kid good at playing basketball. In order to turn a hypothesis into a scientific theory, this study needs to be repeated multiple times to see if the finding is real or if it's just a coincidence.
It takes a long, long time before nutrition recommendations are changed because it takes many repeated, quality studies to confirm that the results weren't an anomaly and can be repeated.
The next time you wonder why your dietitian (or doctor or farmer) recommends what she does, ask. A good healthcare professional will be familiar with the latest research and help explain the nuance.
The next time you meet somebody who has all of the answers in an easy black-and-white formula, beware. As the philosopher Bertrand Russell so wisely stated, "...fools and fanatics are always so certain of themselves, and wiser people so full of doubts."
Don't be afraid when information doesn't fit into neat and tidy categories. Learn to love the grey area - ask questions and seek answers. Never be afraid of not knowing, but always seek the truth.
With love, from Peas and Hoppiness