Browse evidence-based analysis of health-related claims and assertions
Eating less saturated fat didn’t help men who already had a heart attack live longer without another heart attack.
Quantitative
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.
Descriptive
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.
Correlational
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.
This review looked at data from over 347,000 adults followed for an average of 14 years — so if saturated fat had even a moderate effect on heart disease, this study would have been able to find it.
Even when researchers accounted for how many total calories people ate or how much other fats they consumed, the link between saturated fat and heart disease still didn’t show up.
The studies in this review didn’t all agree with each other, but the reason for the disagreement wasn’t because of differences in how old the people were, how long they were followed, or how good the studies were.
One study looked at whether eating more unsaturated fat compared to saturated fat helps the heart — and found no link, even though other research has suggested it might.
Studies that found a link between saturated fat and heart disease may be more likely to get published than those that found no link, which could make the overall picture look more uncertain than it really is.
Different studies used different ways to measure what people ate — some asked about food habits over a year, others just asked what they ate yesterday — which might make it harder to see real links between diet and heart disease.
We don’t have enough reliable data yet to say if swapping butter for bread or olive oil makes a difference in heart disease risk, because not enough studies provided the right information.
Whether you're young or old, male or female, eating more saturated fat doesn't seem to affect your heart disease risk any differently, according to this big review.
Overall, eating more saturated fat doesn't seem to increase your risk of having any kind of heart disease or stroke, according to a large review of 21 long-term studies.
Eating more saturated fat doesn't appear to raise your risk of having a stroke, according to a review of 8 long-term studies of adults.
Eating more saturated fat, like butter or fatty meat, doesn't seem to raise your risk of heart disease, according to a big review of 16 long-term studies of adults.
We can’t be sure if saturated fat is good or bad for you because the studies are all over the place—some say one thing, others say the opposite, and the measurements aren’t very accurate.
Some studies say trans fats raise diabetes risk, others don’t—this might be because some studies account for healthy foods like whole grains and nuts, and others don’t.
Some types of saturated fat in your blood—especially from processed carbs—are linked to higher diabetes risk, while others from dairy are linked to lower risk.
If you swap out trans fats (like in fried foods) for healthy fats like those in fish or nuts, your risk of heart disease drops a lot—what you replace it with matters more than just cutting fat.
There’s a hint that eating more saturated fat might raise the risk of dying from heart disease, but the data is too messy and uncertain to say for sure.
Eating trans fats doesn’t clearly raise or lower the risk of a certain type of stroke called ischemic stroke—the results are mixed and not reliable.