From the benefits of gluten-free to those of Mediterranean and Palaeolithic diets, many claims that one dietary strategy are better than another for health and weight loss are simply 'unjustified' and 'sometimes utter nonsense', according to a new review.
Mixed messages in media headlines and competing claims over which dietary strategies are 'the best' for weight management and health routinely refute both the conventional wisdom and one another, warns Dr David Katz - the author of a review that aims to unravel the scientific basis for a variety of claims made by proponents of different dietary strategies.
The invited review, titled 'Can We Say What Diet Is Best for Health?' appears in the Annual Review of Public Health, in which Katz asserts that such claims are almost entirely unsubstantiated and often 'nonsense'.
“The basic theme of optimal eating for human health and weight control is very strongly supported by a vast and diverse literature,” explained Katz, who is director of Yale University’s Prevention Research Center. “But arguments about the best variant on that theme are mostly unfounded, sometimes utter nonsense, and often about attempts to sell something to a public that is particularly gullible on this topic.
"Most of the competing claims about diet invoke either a particular scapegoat or panacea, and that seems to conform to the prevailing variety of wishful thinking.”
Competing claims, but the same basic themes
Katz noted that while many of the 'competing' claims of being the best dietary strategy seem to be at odds with each other - in fact, most of the diets are variations of the same basic nutrition patterns - which are all linked to health benefits.
“From altitude, it’s pretty clear that Michael Pollan pretty much nailed the description of an optimal diet when he recommended eating ‘food, not too much, mostly plants'," he said. "But importantly, that theme can be represented by a diet low or high in fat, low or high in carbohydrate, lower or higher in protein. It can be represented by a Mediterranean diet, a traditional Asian diet, a Paleo diet, a vegetarian diet, or a vegan diet."
"If any one of these is ‘best’ we lack the evidence to say so; there are, not surprisingly, no lifelong studies that randomly assigned people to optimized vegan or Paleo diets. Who would sign up?" said Katz.
What about grains, and gluten free?
The Yale expert also refuted the currently popular concept that wheat or grains are particularly to blame for weight or health problems.
“People with celiac disease or lesser forms of gluten sensitivity clearly need to avoid gluten and its sources, just as people with peanut allergies need to avoid peanuts," said Katz. "But whole grains figure in the diets of some of the longest-lived, healthiest people on the planet, as highlighted by the Blue Zones project."
"Like most other competing claims about diet, these seem convincing because the authors only cite the work that supports their point of view, ignoring a vast literature that refutes it.”