Walter Willett

What Walter says, topic by topic

فيتامين B12

On a 2020 Long Island panel, Willett said someone who chooses to go fully vegan can do so, but will need to pay attention to where their vitamin B12 comes from¹.

What all the experts say about vitamin B12

Omega-3 fats

On the same panel Willett said that for most people eating fish once or twice a week is good, since without it they may fall short of ideal omega-3 intake².

He also described a pooled analysis of his three large cohorts. Compared with carbohydrate, saturated fat went with higher mortality, while plant monounsaturated and especially polyunsaturated fats went with lower mortality and less heart disease³. He called the idea that omega-6 fats are inflammatory a myth, saying dozens of studies show they tend to lower inflammatory markers³.

What all the experts say about omega-3 fats

Oil

Willett does not ask people to give up oil. On the 2020 panel he said no trial can compare olive oil with soybean oil over decades, so cohort data has to guide the choice, and that when people eat oils, unsaturated ones are better than highly saturated palm oil⁴.

He added a planetary point: palm oil gets most of the criticism, but soybean oil also has a large footprint, and feeding about 10 billion people will leave big footprints whatever the choice⁵.

What all the experts say about oil

البروتين

Willett argues that red meat studies depend on what the meat is compared with. On the 2020 panel he said that against a healthy diet built on plant proteins such as nuts, legumes and soy, red meat raises LDL in trials and goes with more cardiovascular disease in cohorts⁶.

What all the experts say about protein

Calcium, dairy and bones

Willett, who grew up on a Michigan dairy farm, does not ask everyone to drop dairy. On the 2020 panel he said that replacing dairy with plant proteins such as nuts, legumes and soy improves blood lipids in trials and goes with less heart disease in long-term studies⁷.

He said bones do not depend on large amounts of dairy, though people need some calcium, and a small amount of dairy can fill gaps for those who lack other sources⁸. He suggested that cutting down to one serving a day would be a big step, provided it is not replaced with sugary drinks⁹.

He also linked dairy to fat quality: in his cohorts, most saturated fat came from dairy and red meat, which he called one more reason that a lot of either is not good for health¹⁰.

What all the experts say about calcium, dairy and bones

Starches

On the 2020 panel Willett said that a large body of data shows the share of calories from fat matters little, while the quality of both fat and carbohydrate matters a great deal¹¹. He set intact whole grains apart from refined starches, and said many diets around the world get too much of their energy from carbohydrate, more and more of it refined¹¹.

What all the experts say about starches

Fish and eggs

Willett sees a place for fish. On the 2020 panel he said every step toward a healthy plant based diet helps, and that the data he has suggest pescatarians do slightly better than vegans, though not enough to separate the two sharply¹².

What all the experts say about fish and eggs

Whole grains, bread and flour

Asked in 2020 about a low-carb author’s claim that even whole-grain cereal and pasta raise disease risk, Willett answered that intact whole grains behave very differently in the body from refined starches, and that the quality of carbohydrate counts for far more than its share of calories¹¹. When he describes the healthy diet that other foods should be measured against, whole grains sit alongside plant proteins, fruit and vegetables⁶.

What all the experts say about whole grains, bread and flour

Meat

Willett says the verdict on red meat depends on what it is compared with. On the 2020 panel he explained that many older analyses set red meat against the rest of the typical American diet, which is full of refined starch and sugar, so finding no difference only showed that red meat was as poor as that background diet¹³. He noted that only about 5% of Americans meet the dietary guidelines and that his group scores the national diet at around 50 out of 100, “a pretty low F”¹³. Measured against a mostly plant protein diet, he said, red meat raises LDL in trials and goes with more cardiovascular disease in cohorts⁶.

He was also critical of a 2019 review in a medical journal that told the public it could keep eating red meat. He said its author list held only one senior nutritionist, a person without research in the field, and he cited newspaper reports that raised conflict-of-interest questions about the review¹⁴. More broadly, he argued that far too much nutrition research is paid for by industry, sometimes indirectly, and that public money through the NIH is the main route to less biased studies¹⁵.

What all the experts say about meat

Low-fat eating

Willett does not set a fat target, and this is where he parts company with the low-fat plant based doctors. On the 2020 panel he said a large body of studies shows that the percentage of calories from fat is not important, while the kind of fat and the kind of carbohydrate matter a great deal, and that fats from plants carry health benefits¹¹. In his pooled cohorts, plant monounsaturated and polyunsaturated fats went with lower mortality when they replaced carbohydrate³.

What all the experts say about low-fat eating

دهون مشبعة

In 2020 Willett described a pooled analysis of his three cohorts: roughly 130,000 people free of major disease at the start, diets followed for up to about 30 years, and some 30,000 deaths along the way¹⁶. Compared with carbohydrate, more saturated fat went with higher mortality, and trans fat looked far worse; he noted that partly because of such data, trans fat has been banned in the US since 2018¹⁷. He added that feeding trials leave no doubt that saturated fat raises LDL cholesterol, and that the cohort pattern for death and heart disease points the same way¹⁸.

He rejected the claim that saturated fat has been cleared. Meta-analyses such as the one by Ronald Krauss, he said, pooled published papers that compared saturated fat or red meat with the rest of a poor diet rather than with a healthy alternative, so they could not answer the real question¹³. In his cohorts most saturated fat came from dairy and red meat, which he took as one more reason to keep both low¹⁰.

What all the experts say about saturated fat

Cholesterol

Willett rests his cholesterol case on trials as well as cohorts. On the 2020 panel he said feeding saturated fat clearly raises LDL¹⁸, that red meat raises LDL in randomized trials when compared with plant proteins such as nuts, legumes and soy⁶, and that replacing dairy with those plant proteins improves blood lipids in trials⁷.

What all the experts say about cholesterol

Carbohydrates and low-carb diets

Willett judges carbohydrates by quality, not by amount. Responding in 2020 to a low-carb author who argued that too many carbohydrates raise disease risk, he said the share of calories from fat or carbohydrate matters little next to the quality of each¹¹. He added that across much of the world people get too much of their energy from carbohydrate, sometimes around 80% of calories and more and more of it refined, a pattern he called a poverty diet built on the cheapest foods¹⁹.

He also counted refined starch and sugar as the core of the poor American diet that many red meat studies used as their comparison¹³.

What all the experts say about carbohydrates and low-carb diets

Weight loss

Willett speaks about obesity as a population problem. In his opening remarks on the 2020 panel he said projections put about half of Americans in the obese range by 2030, and that the numbers were still climbing despite earlier hopes of a slowdown²⁰. He said the generation that became obese in childhood is now reaching adulthood, and the expected consequences, including rising heart disease, diabetes and colon cancer in younger adults, are now appearing²¹.

He lists keeping a healthy body weight among four behaviors, with not smoking, being physically active and eating a healthy diet, whose effect on lifespan he considers well established²².

What all the experts say about weight loss

Heart disease

In 2020 Willett said the US had cut heart disease deaths among younger adults by about 80%, but that the rate was rising again as people who were obese from childhood reach adulthood²¹. In his cohorts, plant monounsaturated and especially polyunsaturated fats went with less heart disease, while saturated fat went with higher mortality³. Red meat and dairy, when compared with plant proteins such as nuts, legumes and soy, went with more cardiovascular disease⁶⁷.

What all the experts say about heart disease

Longevity and aging

On the 2020 panel Willett said his group had earlier estimated that four habits, not smoking, staying physically active, keeping a healthy weight and eating a healthy diet, could add about 10 years of life²². A paper his group had published days before the panel, he said, showed that those extra years are mostly healthy ones rather than years in a nursing home or with dementia, though anyone can still face an illness that no one yet knows how to prevent²².

What all the experts say about longevity and aging

Each small number links to its reference at the bottom of the page: the video at the exact second, or the page where it was said.