Cholesterol: You Eat it and You Need It

Cholesterol: You either love it or you hate it... but you should love it!

It is a precursor to vital compounds produced in the body, including testosterone, estrogen, DHEA, cortisol, aldosterone, vitamin D, and even cell membranes (Gropper 2021).

Cholesterol is the most abundant lipid in the brain and is especially important to the health and function of the myelin sheath that protects nerve cells (Vitali 2014).

No doubt cholesterol is essential to health. Of course, if it becomes oxidized, it can become damaging and contribute to atherosclerosis... but that is another lecture!

The question at hand is what happens to the cholesterol we eat and whether it contributes to cardiovascular disease.

Summary of Cholesterol Absorption (Li 2001)

Dietary cholesterol, which is cholesterol we get from food, plays a big role in maintaining the right balance of cholesterol in our bodies. The process of absorbing this cholesterol starts in our intestines. Here, cholesterol from our diet combines with other substances to form little packets called micelles. These micelles make contact with cells in our intestines that help absorb the cholesterol.

Now, our intestines are pretty selective; they control not just how much cholesterol is taken up but also which types of similar substances (called sterols) are allowed in. Every day, our intestines absorb a good amount of cholesterol along with other sterols.

Once cholesterol is absorbed in our intestines, it's modified by a special enzyme and packed into particles called chylomicrons. These chylomicrons leave our intestinal cells, travel through our body's transport system, and deliver cholesterol to where it's needed.

Some other chemicals, like bile acids, which help with digestion, are not absorbed in the same place as cholesterol but are taken up elsewhere in our intestines and sent back to the liver. This cycle is part of something called enterohepatic circulation.

The chylomicrons mainly deposit their other contents, the triglycerides, into tissues around the body, while most of the dietary cholesterol is sent to the liver. The liver, seeing this influx of cholesterol, responds by making less of its own cholesterol. Then, the liver either packages its own cholesterol into different particles for distribution throughout the body or turns it into bile acids and puts them into bile for digestion, completing another loop of the enterohepatic circulation.

Dietary Cholesterol, Blood Lipids, and Cardiovascular Risk (Berger 2015)

A systemic review and meta-analysis of 40 studies found that eating more cholesterol doesn't necessarily increase your risk of developing cardiovascular diseases (CVD), like heart disease. Most of the cholesterol in our bodies is actually made by our bodies (it's endogenous), and it's only one part of the complex process that leads to diseases like atherosclerosis, where your arteries get hard and narrow.

The relationship between eating cholesterol and the levels of cholesterol in your blood is somewhat complex. Up to a certain point (around 600 mg per day), eating more cholesterol does lead to a bit higher levels of cholesterol in your blood. However, for intakes above this amount, the impact on blood cholesterol levels isn't that strong for most people. The studies even found that if you eat over 900 mg of cholesterol per day, the increase in blood cholesterol levels isn't statistically significant, meaning it's likely not a real, consistent effect. This matches previous observations where blood cholesterol levels seem to hit a plateau even if you keep eating more cholesterol.

However, the relationship between eating cholesterol and the risk of heart disease can be influenced by other factors in your diet. For instance, eating more saturated fats and getting a high percentage of your calories from fats, both of which often go hand in hand with eating more cholesterol, have been linked to a higher risk of heart disease. On the other hand, eating more fiber and plant-based proteins, which are usually associated with eating less cholesterol, have been linked to a lower risk of heart disease.

Optimal Takeaways

• Cholesterol is a vital compound in the body and is required for the production of hormones, vitamin D, bile acids, cell membranes, and brain tissue.
• You eat cholesterol, and you make cholesterol.
• Dietary cholesterol is absorbed through a complex process requiring de-esterification and re-esterification.
• The absorption of dietary cholesterol signals the liver to produce less cholesterol for the day to maintain cholesterol balance in the body.
• Dietary cholesterol alone does not appear to increase the risk of cardiovascular disease but may be consumed along with too much saturated fat and not enough plant-based foods.

References

Berger, Samantha et al. “Dietary cholesterol and cardiovascular disease: a systematic review and meta-analysis.” The American journal of clinical nutrition vol. 102,2 (2015): 276-94. doi:10.3945/ajcn.114.100305

Gropper, Sareen S.; Smith, Jack L.; Carr, Timothy P. Advanced Nutrition and Human Metabolism. 8th edition. Wadsworth Publishing Co Inc. 2021.

Lu, K et al. “Dietary cholesterol absorption; more than just bile.” Trends in endocrinology and metabolism: TEM vol. 12,7 (2001): 314-20. doi:10.1016/s1043-2760(01)00433-7

Vitali, Cecilia et al. “HDL and cholesterol handling in the brain.” Cardiovascular research vol. 103,3 (2014): 405-13. doi:10.1093/cvr/cvu148

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