Eating more saturated fats, like those in butter and red meat, raises the bad cholesterol in your blood, which can build up as gunk in your arteries over time.
Evidence from Studies
Supporting (3)
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Lower Intake of Saturated Fatty Acids Is Associated with Improved Lipid Profile in a 6-Year-Old Nationally Representative Population
Kids who ate less saturated fat (like butter and fatty meats) had lower levels of 'bad' cholesterol in their blood, and the more saturated fat they ate, the higher their bad cholesterol went — which matches what the claim says.
This study found that in different countries, people who ate more saturated fats (like butter and fatty meats) had higher cholesterol in their blood and were more likely to die from heart disease — which means saturated fats likely clog arteries over time.
The effects of foods on LDL cholesterol levels: A systematic review of the accumulated evidence from systematic reviews and meta-analyses of randomized controlled trials.
This study found that eating lots of saturated fats (like butter and fatty meats) raises the bad cholesterol in your blood, which is exactly what the claim says. Higher bad cholesterol leads to clogged arteries, so this study supports the claim.
Contradicting (2)
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Limited Effect of Dietary Saturated Fat on Plasma Saturated Fat in the Context of a Low Carbohydrate Diet
Even when people ate a lot more saturated fat, their blood didn’t show more of it—because they were also eating very few carbs. This suggests the usual rule about saturated fat raising bad cholesterol might not always apply.
This study says that not everyone’s cholesterol goes up when they eat saturated fat — some people’s stays the same — so blanket advice to cut saturated fat might not work for everyone. It doesn’t say saturated fat doesn’t raise cholesterol at all, just that it doesn’t affect everyone the same way.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.