system
Given the following post, respond as if you're commenting on Reddit:
human
How does diet affect the risk of heart disease?

There is a lot of conflicting information out there. The common story is that (saturated) fat and cholesterol in meats are the primary culprits, but now a lot of (pop) science seems to claim that those are relatively harmless and sugars are instead the main culprits. What does the actual scientific evidence support?
gpt
I don't have a lot of time to go into an in-depth answer, but cholesterol and fats were vilified mainly because when you looked at the hearts and blood vessels of people with cardiovascular disease, you see a lot of plaques which grow and harden and constrict the blood vessels around the heart and the rest of the body. And what are these plaques largely made of? Fats and cholesterol (and a bit of calcium). So naturally scientists looked into does the amount of fats (particularly saturated fats) consume affect the amount of fats and cholesterol blocking up their arteries? And they found that yes they did.

But fairly recently a group decided to look at weather a diet with increased saturated fats was worse for your health than a diet high in refined sugar. And surprisingly what they found is that actually the high sugar diet produced much a much more profoundly negative affect in the heart in just a few weeks. The high fat group had increased ldl levels (the "bad cholesterol"), they also had increased levels of hdl (the "good cholesterol") which would mitigate a lot of the bad consequences of the ldl cholesterol. The high sugar group on the other hand showed higher levels of total cholesterol, higher ldl levels and lower hdl levels. This is likely due to the sugar causing the liver to release a lot of harmful fats into the bloodstream.

Large amounts of sugars can also lead to insulin resistance and eventually can contribute to developing type 2 diabetes, which (amongst a lot of other things) increases your chances of developing heart disease. Sugar also increases your blood pressure.

So what about the studies before that linked high levels of fats in the diet to cardiovascular disease? Well it is true that people who eat more saturated fats are more likely to develope heart disease, what the researchers didn't take into account is that people eating a lot of saturated fats are much more likely to be consuming a lot more sugar, especially refined sugars.

So really the bottom line is to moderate your intake if refined/added sugars but you probably shouldn't load your diet up with high saturated-fat foods either, everything in moderation. Really avoiding any heavily processed foods which are usually very high in fats and sugars is a safe bet.


Sources: Undergrad in biochemistry, currently doing a PhD in Diabetes Complications.