Are egg yolks really that bad? Do they increase cholesterol and lead to heart disease? These are some of the questions I’d like to refute in today’s post.
It all goes back to Ancel Keys and the Seven Countries Study, which found an association between countries where fat consumption was the highest and increased rates of heart disease. This sparked the fat-phobia movement– healthful foods such as eggs and dairy products (I will cover dairy in later blog posts!) were demonized, and fat-free, but not necessarily more healthful, foods were advertised for consumption.
However, the new U.S. dietary guidelines removed the limits on dietary cholesterol. Only about 20-25% of our blood cholesterol comes from our diet. The remaining 75-80% of the cholesterol is synthesize in our bodies (within our bodies, 20% of cholesterol is synthesized in our liver and the remaining 80% is synthesized by other cells in our bodies).
Dr. Peter Attia, MD has talked widely on the effects of dietary cholesterol on serum levels of cholesterol which I would like to summarize below:
- There are two many types of cholesterol, esterified cholesterol OR unesterified/free cholesterol (active form)
- Our bodies can only absorb unesterified/free cholesterol through the cells in our gut (called enterocytes, specifically through the NPC1L1 transporter shown above)
- >50% of the cholesterol we ingest from food is esterified cholesterol – thus we don’t absorb much of it
- AND if our gut cells (“enterocytes”) do absorb too much through the NPC1L1, this process is tightly regulated and will just kick out the excess cholesterol back into our gut lumen through the ABCG5/G8 transporter shown above
I’d also like to highlight the functions of cholesterol. Cholesterol is important for maintaining cell membranes and structures. It also helps cells adjust to changes in temperature and is used by nerve cells for insulation. Further, cholesterol is important for synthesizing hormones such as the sex hormones testosterone, progesterone, and estrogen. The liver uses cholesterol to make bile, which processes and digests the fats we consume. Finally, our bodies need cholesterol to make vitamin D. With the already low level of sun exposure in our society today, it is important to have cholesterol for those times when we are exposed to the sun to convert cholesterol into vitamin D!
Before the new US dietary guidelines, it was recommended not to exceed consumption of more than 300 mg of cholesterol a day. One large egg contains 212 mg of cholesterol, so one could see why eggs were criticized as raising cholesterol. However, in one study, eggs actually increased HDL (good) cholesterol in adult men and favored the formation of larger LDL (we want larger cholesterol because it doesn’t stick to the arterial walls and clog them!). In another study, egg consumption increased both the formation of large LDL and HDL. This does not necessarily link egg consumption to atherosclerosis or heart disease. A meta-analysis published in 2013 compiled 17 prospective studies on egg consumption and health. The researchers found that eggs had no association with either heart disease or stroke in healthy individuals. A study in 2006, found that same results between dietary cholesterol from eggs and rates of CHD.
All of these results may indicate that eating eggs and cholesterol does not have an association with heart disease.
Further, eggs are rich in nutrients: Eggs are rich in the antioxidants lutein and zeaxanthin, which is important for eye health, specifically cataracts and macular degeneration. One study found that consuming 1-2 egg yolks a day for just a month and a half increased serum levels of lutein 28-50% and zeaxanthin by 114-142%. Eggs contain all of the amino acids and are high in vitamins D, B-12, B-2, B-5, B-6, iron, selenium and choline (which is important for brain health).
Finally, eggs are satiating and may help individuals lose weight. In one study, overweight men and women were either provided a breakfast of 2 eggs or bagels on a calorie-restricted diet. After 2 months, the egg group had greater reduction in BMI, more weight loss, reduction in waist circumference, and body fat, even though both breakfasts contained the SAME number of calories.
Conclusion: Eat eggs! And eat the yolks. They are highly nutritious folks! If you can, opt for pasture-raised eggs that feed on grass and natural seed versus corn-fed or caged eggs. They will be much more nutritious and have better fat content. No more yolking around, this blog post is EGGCELLENT news.
Check out my veggie scramble for a great breakfast idea to incorporate eggs into your diet and start your morning off with a nutritious, high-protein meal.