Food Bytes is a weekly blog post of “nibbles” of information on all things food and nutrition science, policy and culture.
This week’s food bytes focuses on the complications of understanding what is a healthy diet because there seems to be much havoc and confusion in the space. The more havoc, the more people want to dissect the havoc or relish in it. And we seemed to be inundated these last two weeks with diet news.
Tamar Haspel is a fantastic food columnist for the Washington Post. There was a lot of twittering and conversation, which she does not shy away from, about her recent article entitled “Here’s what the government’s dietary guidelines should really say.” She hauls the science of nutrition over the coals leaving no one left standing. In her article, she presents two main criticisms. Her first issue is the flawed nature of nutritional sciences. Errors abound in the way diet data is collected, the way observational studies assess impacts of those diets on outcomes, and the ways in which confounding factors are taken into account. Her second issue is the conflicts of interest in nutritional science. She highlights not just perverse industry-funded research, but also, the nutrition experts’ often ideological world views, or “fanatical opinions that abound in nutrition” which shape interpretations of the data in misleading ways. These two issues, the imperfect science and the conflicts of interest, interact and influence each other.
Following her merciless critique, Haspel concludes that “In the two decades I’ve been writing about nutrition, my confidence in what we know about food and health has eroded.” She is not alone. Many people are very confused about what is healthy and what is not. What will kill you and what will keep you alive. What is sustainable, and what will ruin the planet. She is left feeling certain about three simple things: (1) eat a wide variety of foods with their nutrients intact; (2) keep your weight down; and (3) get some exercise. Sounds about right.
Timeline of the nutrition science field
Do former New York Times writer Mark Bittman and Yale Professor David Katz agree with these sentiments? Largely yes. They argue, “eating well remains difficult not because it’s complicated but because the choices are hard even when they’re clear.” But they have answers. Lots of them. They thought of every question imaginable about diets and health and tried to answer them. Many of the answers are a bit “take my word for it,” but I give them the benefit of the doubt. Although some could wonder why we trust Bittman over credible scientists, but I digress. They argue that future conversations are no longer needed. Yeah, if it were only that easy boys…
Katz also delves deep into why we are eating as if we know less about food than ever before. He argues that humans have been bamboozled by prominent ideologues in the field of nutrition who have built careers defending just one point of view. Similar sentiments to what Haspel highlighted. He argues:
“Where humans practice any reasonable variant on the theme of wholesome foods, mostly plants, in a balanced, time-honored assembly; wherever they eat mostly vegetables, fruits, whole grains, beans, lentils, nuts and seeds, and drink mostly water, they tend to live long, prosper with vitality, and go late and gentle into that good night. It is not the job of “science” to tear down this established foundation: It is the job of science to build upon it.”
I think what Katz is getting at is that the science of nutrition has come a long way, and there is lot of agreement about the science, but we need to build further on that evidence base. At least, I hope that is what he means. Well-respected Dariush Mozaffarian (Dean and Jean Mayer Professor at the Tufts Friedman School of Nutrition Science and Policy) and colleagues have shown a timeline of the nutrition field and how far the science has come. In the final piece of their timeline - the future - they argue, “Public health future nutrition policy must unite modern scientific advances on dietary priorities with creative new approaches for trusted public communication and modern evidence on effective systems level behavior change.” Trusted public communication. Sounds quite similar to what is being argued by Katz and Haspel. The question is, how do we ensure the science and the way it is communicated by scientists, media and journalists, is trustworthy?
Global Burden of Disease Lancet study: impact of diets on mortality
But the chug and churn of nutritional sciences continues amidst the havoc. Here are three studies published these past two weeks that show the impact of diets on health, at three different levels: at the dietary pattern/whole diet level, the food group level and the individual nutrient level.
The Global Burden of Disease project out of the University of Washington just published a Lancet paper on the impact of suboptimal diet on noncommunicable disease mortality and morbidity (Full discloser: The Food Archive archiver is an author on this paper). The estimates (and modeled data) show that 11 million deaths and 255 million disability adjusted life years (DALYs) were attributable to dietary risk factors. High intake of sodium (3 million deaths and 70 million DALYs), low intake of whole grains (3 million deaths and 83 million DALYs), and low intake of fruits (2 million deaths and 65 million DALYs) were the leading dietary risk factors for deaths and DALYs globally and in many countries.
Sabrina Schlesinger and authors published a systematic review looking at the impact of food groups on risk of overweight, obesity and weight gain. They found that increased consumption of whole-grains, fruits, nuts, legumes and fish consumption had a negative association with overweight and obesity. Positive associations were found for refined grains, red meat, and and sugar sweetened beverages and overweight, obesity and weight gain.
And last, a Nature paper examined the impact of carbohydrate, a macronutrient, quality on health. They argue that the quality of carbohydrate-rich foods (high in fiber and whole grains) rather than quantity has the strongest effect on decreased mortality and reduced incidence of cardiovascular diseases, type 2 diabetes mellitus and colorectal cancer.
Still confused? Everyone is sort of saying the same thing that Michael Pollan said so simply a decade ago, now a mantra for many: Eat food, mostly plants and not too much.