It seems like nutrition experts are always changing their minds about the best way to eat. That’s partly because the nature of science is constant exploration; the scientific method is about continually testing, refuting, and revising hypotheses, not coming up with one definite answer and staying there.
Another, deeper issue with nutrition science is how we conduct it. Randomized, controlled trials (RCTs) are the gold standard of health research, because they are the only type of study that can determine a causal relationship between an intervention (e.g. a low-fat diet) and an outcome (e.g. incidence of heart disease). But, RCTs are especially difficult to conduct in nutrition because they require people to accurately report their food intake and adhere to strict diets, sometimes for long periods of time (and we all know how that usually goes).
Instead, much of what we know about nutrition is based on evidence from observational studies, which can only tell us about associations (e.g. high trans fat intake is associated with a higher incidence of cardiovascular disease) — not about causation. Sometimes, these studies gain momentum: Dietitians and other health experts start discussing them, journalists report on them, and before you know it, the data are taken as fact before all the facts are in.
Given these issues with the science, it’s only natural that nutrition guidelines would be constantly changing. That said, some sound ideas about nutrition have emerged from decades of observational research coupled with results from RCTs. So, what nutrition advice can we actually trust right now? The 7 ideas that follow are a good start. They’re culled from the best available science to date in this ever-changing landscape.