|I'm fairly certain that dark chocolate and black coffee are good for me. Your results may vary. How about this New Year's Resolution? Ignore all news reports about nutrition research in 2016.
Real Clear Science
"The problems with nutrition science begin with how most of its research is conducted. The vast majority of nutrition studies are observational in nature [i.e., correlational, not experimental] -- scientists look at people who eat certain foods and examine how their health compares with the health of people who don't eat those foods or eat them at different frequencies. But as I reported earlier this year, these sorts of studies have a high chance of being wrong. Very wrong.
In 2011, statisticians S. Stanley Young and Alan Karr teamed up to analyze twelve randomized clinical trials that scrutinized the results of 52 observational studies. Most of the observational studies showed various vitamin supplements to produce positive health outcomes. However, the superior clinical trials disagreed.
"They all confirmed no claims in the direction of the observational claims," Young and Karr revealed in Significance Magazine. "We repeat that figure: 0 out of 52. To put it another way, 100% of the observational claims failed to replicate. In fact, five claims (9.6%) are statistically significant in the clinical trials in the opposite direction to the observational claim."
Observational studies are common in nutrition research because they are relatively cheap and easy to pull off. But you get what you pay for. These studies are often shoddy, primarily because they cannot effectively control for confounding variables. Most also suffer from another key drawback, one that may render them totally meaningless: self-reported data. Subjects report their food consumption by remembering what and how much they ate. Memory is not a recording; it is a reconstruction, making it prone to error. In fact, a 2013 study found that the majority of respondents in the CDC's National Health and Nutrition Examination Survey(NHANES), a survey program that provides data for a plethora of epidemiological studies, reported eating fewer calories than the bare minimum they would need to survive! Something is seriously flawed here.
Unfortunately, when nutrition scientists employ the gold standard of scientific research -- randomized, controlled trials -- the quality of evidence isn't always much better. As health researcher Aaron Carroll wrote for the New York Times:
A 2011 systematic review of studies looking at the effects of artificial sweeteners on clinical outcomes identified 53 randomized controlled trials... only 13 of them lasted for more than a week and involved at least 10 participants. Ten of those 13 trials had a Jadad score — which is a scale from 0 (minimum) to 5 (maximum) to rate the quality of randomized control trials — of 1. This means they were of rather low quality... The longest trial was 10 weeks in length.
The ultimate point of nutrition research is to apprise the public of what they should and should not eat. What really is healthy? What isn't? But this endeavor may have been doomed from the start. As was recently showcased in research published to the journal Cell, what's healthy for one person may not be healthy for someone else. Tina Hesman Saey summarized the study over at ScienceNews:
"The researchers made the discovery after fitting 800 people with blood glucose monitors for a week. The people ate standard breakfasts supplied by the researchers. Although the volunteers all ate the same food, their blood glucose levels after eating those foods varied dramatically. Traits and behaviors such as body mass index, sleep, exercise, blood pressure, cholesterol levels and the kinds of microbes living in people’s intestines are associated with blood glucose responses to food, the researchers conclude."
Between poorly conducted research, pervasive corporate influence, and the simple fact that everybody reacts to specific foods differently, nutrition science as a whole must be taken with a gigantic grain of salt."