Browse evidence-based analysis of health-related claims and assertions
The amount of saturated fat found in your blood doesn’t seem to predict whether you’ll get heart disease, based on blood tests from many people.
Correlational
Taking flaxseed or walnut oil supplements doesn’t seem to help prevent heart disease, based on clinical trial results.
Taking omega-6 supplements, like those from sunflower or corn oil, doesn’t appear to protect against heart disease, according to clinical trial data.
Taking fish oil supplements doesn’t seem to lower your risk of having a heart attack or other heart disease, according to this review of many clinical trials.
Eating more omega-6 fats—like those in vegetable oils—doesn’t appear to increase or decrease your risk of heart disease, based on this large review.
People who eat more fish or other sources of omega-3s don’t seem to have much lower risk of heart disease, according to this review of many studies.
Eating more saturated fat—like in butter or red meat—doesn’t seem to make people more likely to get heart disease, based on this big review of studies.
People who eat a lot of trans fats (like in fried or processed foods) are more likely to have heart problems than those who eat very little.
The studies didn’t seem to be hiding negative results, but the smaller ones showed odd patterns that might mean some results weren’t fully reported.
Quantitative
None of the studies said, 'Eat less fat to live longer' — in fact, some warned it might not help or could even be harmful.
Descriptive
The diets weren’t just about eating less fat — they also banned butter, added lots of vegetable oil, and cut out eggs, so we don’t know which part actually mattered.
The studies weren’t perfectly done — many didn’t hide who was on which diet, and people had to remember what they ate, which might have messed up the results.
All the studies were done on men who already had heart problems — we don’t know if the same results would apply to women or people without heart disease.
One study that tried to get people to eat only 10% saturated fat actually saw more people die than in the group that ate more fat.
The diets tested in the studies weren’t even the same as the official government advice — they were different and less strict.
Even though people who ate less fat had much lower cholesterol, they didn’t live longer or have fewer heart attacks than those who didn’t change their diet.
Before the government told everyone to eat less fat, no study had actually tested whether eating exactly that much fat helped people live longer.
Eating less saturated fat didn’t help men who already had a heart attack live longer without another heart attack.
In men who already had heart problems, eating less fat didn’t help them live longer, even though their cholesterol went down.
The studies used in this review mostly involved men, so we can't be sure the results apply to everyone, like women or different ethnic groups.
For people who haven't had a heart attack yet, how much fat they eat doesn't seem to affect their chance of dying from heart disease, according to combined data from several long-term studies.
The official advice to eat less fat to avoid dying of heart disease isn't backed up by the long-term studies of large groups of people.
Eating more saturated fat — like in butter or red meat — doesn't appear to raise the chance of dying from heart disease, based on long-term studies of nearly 90,000 people.
Eating more fat in your diet doesn't seem to make you more likely to die from heart disease, according to long-term studies of nearly 90,000 people.