Ask Dr. Mozaffarian
After the fireside conversation, Nantucket asked its questions, on nutrition science, GLP-1 medications, regenerative agriculture, saturated fat, and the new Dietary Guidelines. Here are Dr. Dariush Mozaffarian's answers, straight from the source.
The Big Picture
How Food Is Medicine fits into health, the food system, and the misinformation surrounding both.
How can Food Is Medicine improve health while strengthening local food systems?
Food Is Medicine can do both by using healthcare dollars to help patients obtain the minimally processed, nourishing, delicious foods that improve health — fruits, vegetables, nuts, beans, whole grains, seafood, plant oils, yogurt, and more — while intentionally sourcing more of those foods from local and regional producers.
Done well, that creates a virtuous cycle: patients get healthier, healthcare systems spend less on preventable disease, and farmers gain a reliable new market for producing healthier food.
How can we separate nutrition facts from misinformation?
Start with the totality of the evidence, rather than a single study, influencer, nutrient, or frightening headline — and ask whether findings are consistent across randomized trials, long-term studies, mechanistic evidence, and different populations.
One of the biggest mistakes in nutrition has been reducing food to individual numbers like calories, fat, or protein; we eat foods, and their overall composition, processing, and biological effects matter.
What's the biggest misconception about diet and food?
There are so many — Dr. Mozaffarian covers these in his book. As just one example, many mistakenly believe that maintaining health and weight is mainly about calories and personal willpower.
Foods with the same calories can have very different effects on hunger, hormones, the microbiome, metabolic rate, fat storage, and long-term weight — so food quality and biology matter enormously.
What evidence do you have that our food is creating more problems than cars?
The comparison is actually striking: poor diet contributes to hundreds of thousands of U.S. deaths each year, while motor-vehicle crashes account for fewer than 1% of U.S. deaths. Globally, unhealthy diets are among the leading causes of premature mortality.
Environmentally, food and agriculture are enormous drivers of greenhouse gases, freshwater use, deforestation, biodiversity loss, and soil degradation. We've spent decades making cars safer while giving far less attention to making our food system safer.
Science & Policy Deep Dive
On GLP-1s, GMOs, regenerative agriculture, supplements, saturated fat, and the new Dietary Guidelines.
What role should GLP-1 medications play in obesity treatment — and the future of Food Is Medicine?
GLP-1 drugs are an important medical advance and should be used when appropriate — they can produce substantial weight loss and reduce cardiovascular, kidney, and other complications.
But medication doesn't eliminate the need for good nutrition: Food Is Medicine can help patients preserve muscle and nutritional adequacy, manage gastrointestinal side effects, improve diet quality, and sustain better health during and especially after treatment.
How should we think about GMOs, glyphosate, and food safety?
We shouldn't lump GMOs and glyphosate together. Genetic engineering is a technology — a tool that could be used for good or ill. Glyphosate is a specific chemical exposure. Each should be judged on its own evidence.
There is no evidence that GMOs per se have any effect on health; so far, reviews of the evidence don't suggest much health impact either way. The bigger problem is for farmers, who are pressured to buy GMO seeds and pesticides instead of shifting to natural, regenerative practices that are better for the earth and their long-term sustainability and bottom line.
Glyphosate is clearly harmful at higher exposures, such as to farmers who are spraying it. At the low levels found in food, there's actually true scientific controversy over its relevance — another example of the need for much more investment in nutrition science and research.
Can regenerative agriculture feed the world — and why does it matter for health?
The question isn't whether every farm can or should follow one rigid definition of "regenerative agriculture." Rather, we must change how we grow food in order to produce enough nutritious food while restoring soil, water, biodiversity, climate resilience, and farmer livelihoods.
Preliminary evidence suggests that regeneratively grown crops and livestock may be more nutritious — another key area for more research investment. Ultimately, regenerative agriculture is critical for health because if we don't change what we're doing, we won't be able to grow any food long-term.
Which supplements actually clear the bar of real, evidence-backed necessity — and does creatine belong in that category?
For most healthy people, supplements should fill a demonstrated need — folic acid around pregnancy, B12 for vegans or people with impaired absorption, iron for iron deficiency, vitamin D when clear deficiency exists — rather than compensate for a poor diet.
Fish oil has fairly strong evidence for improving heart disease, but Dr. Mozaffarian still favors eating the food where possible.
Can you elaborate on your claim that saturated fat doesn't cause heart disease? How new is this evidence?
The facts are best phrased more carefully: saturated fat by itself is a poor way to judge whether a food causes heart disease. The evidence has been accumulating for well over a decade.
Replacing certain types of saturated fat with polyunsaturated fats lowers coronary risk, while replacing other types may not; replacing saturated fat with refined starch or sugar does not influence risk; and foods rich in saturated fat — yogurt, cheese, butter, red meat — have quite different health effects from one another.
What about the 2025–2030 Dietary Guidelines calling butter and beef tallow “healthy fats,” and putting red meat at the top of the pyramid?
The biggest advance in the new Guidelines is being missed in that debate: for the first time they explicitly tell Americans to limit highly processed foods, sugary drinks, refined carbohydrates, and problematic additives, and to prioritize real, minimally processed foods.
Dr. Mozaffarian wouldn't interpret the pyramid as an instruction to load up on red meat, butter, or tallow — a pyramid should be read by the space devoted to each food, and the space devoted to animal and plant foods there is actually pretty good. He does agree that butter isn't the healthiest fat: plant and seafood fats have the strongest evidence for benefit, while butter and dairy fat are generally neutral. Unprocessed red meat should be consumed in moderation, particularly due to pro-inflammatory and pro-carcinogenic risks; processed meats should be avoided.
The science, evidence, and implications in full
These brief answers only scratch the surface. Dr. Mozaffarian's book, Food Is Medicine, covers these questions in far greater detail.