Cholesterol, Diet, and Heart Health: What Science Says today
As a generally healthy adult, I didn’t prioritize yearly physicals and blood work. Once I hit my 40s, I realized, “Oh, this is the decade screening exams begin,” so I found a primary care physician and started the screening journey. Part of said journey is blood work, and part of that is cholesterol. As a physician, I understand what cholesterol is, what it does, and why it matters, but there are many people who do not. So let’s dive into cholesterol and make sense of it all.
What is Cholesterol?
Cholesterol is a fat-based molecule that circulates in our bloodstream and is vital for forming cell membranes, synthesizing hormones, and storing fats.1 Our bodies make their own cholesterol, and we also obtain it from animal-based foods like meat and dairy.2 Cholesterol exists in two main forms:
- Low-density lipoprotein (LDL) – Often called “bad” cholesterol because it is thought to increase the risk of heart disease and stroke.
- High-density lipoprotein (HDL) – Known as “good” cholesterol because it transports fat molecules to the liver for removal from the body.
What are Target Cholesterol Levels?
According to the 2013 American College of Cardiology and American Heart Association (ACC/AHA) guidelines,3 target cholesterol levels are:
- Total cholesterol: < 200 mg/dL
- LDL cholesterol: < 70 mg/dL in high-risk individuals, <100 mg/dL in the general population
- HDL cholesterol: Men > 40 mg/dL, Women > 50 mg/dL
The Cholesterol Hypothesis Controversy
Since the 1970s, the cholesterol hypothesis has held that higher LDL levels directly increase the risk of cardiovascular disease (CVD), such as heart attacks and strokes. However, there is emerging evidence challenging this idea,4,5 revealing that our understanding of cholesterol, diet, and heart disease is more complex than initially believed.
One key issue is that earlier studies lacked today’s detailed understanding of nutrition and advanced measurement tools. The ACC/AHA have noted that studies investigating the link between cholesterol and risk of CVD have produced mixed results.5
Here is what we know:
- Saturated fats are independently linked to CVD,6 and directly increase triglyceride production in our bodies.2
- Triglycerides play a role in the producing LDL7 and are independently linked to CVD.8
- LDL is attached to a molecule called apolipoprotein B, which is directly linked to atherosclerotic plaque formation.9
- Foods high in saturated fats and triglycerides often contain cholesterol, but the reverse isn’t always true. For example, while bacon is high in saturated fats, triglycerides, and cholesterol, eggs and shrimp are high in cholesterol but low in saturated fats. Studies show no clear link between eating eggs and CVD.5
- Red meat is high in saturated fat.10 When prepared at high temperatures, it is a source of advanced glycation end products (AGEs), which increase inflammation.2
While the cholesterol hypothesis was a major step forward in understanding heart health, new insights point away from LDL as the main culprit, and instead point towards red meats, saturated fats, triglycerides, and apolipoprotein B.
Putting it all Together
Cholesterol levels may not directly cause atherosclerosis or heart disease, but some of the foods high in cholesterol can contribute to these conditions due to the other elements in those foods. The typical Western diet–which includes a lot of saturated fats, refined grains, red and processed meats, and very few fruits and veggies–is bad for us and causes cardiovascular disease.
Replace the “bad stuff” with healthier options. The DASH diet and Mediterranean diet are good options. They emphasize whole grains, fruits, veggies, lean proteins, and only occasionally include red meat. Instead of stressing over specific cholesterol numbers, swap your butter for extra virgin olive oil, swap your red meat for fish and nuts, add lots of veggies, and swap your cakes and pies for fruit. Not only will your cholesterol numbers improve but more importantly, you will lower the other risk factors such as triglycerides and apoprotein B.
References
1. Tabas I. Cholesterol in health and disease. The Journal of clinical investigation. 2002;110(5):583-590.
2. Kelly J, Clayton JS. Foundations of lifestyle medicine board review manual. American College of Lifestyle Medicine; 2021.
3. Egan BM, Li J, White K, et al. 2013 ACC/AHA cholesterol guideline and implications for healthy people 2020 cardiovascular disease prevention goals. Journal of the American Heart Association. 2016;5(8):e003558.
4. Ridker PM. LDL cholesterol: controversies and future therapeutic directions. The Lancet. 2014;384(9943):607-617.
5. Carson JAS, Lichtenstein AH, Anderson CA, et al. Dietary cholesterol and cardiovascular risk: a science advisory from the American Heart Association. Circulation. 2020;141(3):e39-e53.
6. Perna M, Hewlings S. Saturated fatty acid chain length and risk of cardiovascular disease: a systematic review. Nutrients. 2022;15(1):30.
7. Laufs U, Parhofer KG, Ginsberg HN, Hegele RA. Clinical review on triglycerides. European heart journal. 2020;41(1):99-109c.
8. Cullen P. Evidence that triglycerides are an independent coronary heart disease risk factor. The American journal of cardiology. 2000;86(9):943-949.
9. Sniderman AD, Thanassoulis G, Glavinovic T, et al. Apolipoprotein B particles and cardiovascular disease: a narrative review. JAMA cardiology. 2019;4(12):1287-1295.
10. Bergeron N, Chiu S, Williams PT, King SM, Krauss RM. Effects of red meat, white meat, and nonmeat protein sources on atherogenic lipoprotein measures in the context of low compared with high saturated fat intake: a randomized controlled trial. The American journal of clinical nutrition. 2019;110(1):24-33.