Cholesterol is a fat naturally present within our cells and blood. The liver and intestines produce all the cholesterol necessary for health by contributing to cell production, nerve fibers, bile acids, and hormones such as estrogen and testosterone. Healthy people typically make far more cholesterol than they ingest from food. Recent discoveries in nutrition research have incited an upheaval of misinformation regarding “good” and “bad” cholesterol. Increasing evidence is challenging the long-held notion that high cholesterol levels increase the risk of cardiovascular disease.
The lipid thesis linking dietary cholesterol with heart disease risk gained traction during the 1960s, based on available scientific information. Since then, mounting clinical data conflicted with this notion. Research indicates that dietary cholesterol has little effect on the balance of low-density lipoprotein (LDL) and high-density lipoprotein (HDL), the two types of cholesterol created in the body. Numerous studies reveal a startling absence of connection between cholesterol intake and occurrences of heart disease. Some countries and health organizations have adjusted their nutritional recommendations due to this research and the negative ramifications of cholesterol restrictions. Nevertheless, the outdated thesis widely persists, perhaps in part because cardiovascular disease continues to claim more lives than any other ailment.
Much published research indicates high cholesterol intake correlates with greater cardiovascular disease risk, leading to the recommendation that individuals decrease their consumption of cholesterol-rich foods. Particularly, foods that trigger the production of “bad” LDL cholesterol became targets for elimination. By 2015, however, Harvard Medical School had already acknowledged a growing consensus among nutrition scientists that cholesterol in food has a small impact on cholesterol levels in the blood. Research from across the globe supports this consensus. Unlike the U.S., countries including Canada, European nations, India, Korea, and Australia do not specify a maximum cholesterol consumption limit in their dietary recommendations. Existing data from these regions do not confirm a link between LDL cholesterol and heart disease.
Trans fats are naturally present in trace amounts in meats, dairy products, and some edible oils. The prevalent trans fats in commercially prepared foods — PHOs — derive from partially hydrogenated oils, liquid vegetable oils that are processed with added hydrogen. Their shelf-stability has made them the fats of choice for food manufacturers worldwide. Massive bodies of research show that PHOs elevate LDL cholesterol levels and lower HDL cholesterol levels. This imbalance triggers inflammation, a major culprit behind atherosclerosis. The U.S. Food and Drug Administration has stated that removing trans fats from processed foods could save thousands of lives from heart attacks and deaths annually. In 2015, the FDA issued a final determination that PHOs are not safe for inclusion in foods.
The pervasive use of industrial vegetable and seed oils has spiked global consumption of linoleic acid, an omega-6 polyunsaturated fat. Older research cites oxidized LDL cholesterol as a primary catalyst for atherosclerosis formation. However, oxidized linoleic acid, the most prevalent oxidized fatty acid within LDL, is at the root. A 2018 British Medical Journal study summarized extensive evidence showing that this omega-6 fat incites oxidative stress and low-grade inflammation, leading to cardiovascular disease.
Dairy fats have been subject to negative bias due to their high cholesterol levels. Federal dietary guidelines have long advised limiting the intake of whole-fat dairy products, sources of saturated fats believed to impact blood lipids adversely. Consequently, western cultures favored low-fat dairy products. However, little evidence supports this presumption. A nine-year multinational study published in The Lancet in 2018 links dairy consumption with a lower risk of heart disease and mortality. Recent meta-analyses suggest that full-fat dairy products carry significant anti-inflammatory benefits and greater bioavailability of nutrients. Generally, milk appears to exert a neutral effect on heart health, while fermented dairy products such as yogurt, cheese, and kefir may have a positive cardiovascular impact. According to a 2018 review, some saturated fats in dairy products are associated with lower occurrences of coronary heart conditions.
Eggs are a prime example of vastly conflicting evidence regarding foods and cardiovascular health. Some studies show little or no correlation between consumption of this high-cholesterol food and heart disease, but research published in JAMA in 2019 did find such an association. However, the Harvard School of Public Health recommends interpreting the findings in the context of other research, which suggests that low to moderate egg consumption does not lead to a greater risk of cardiovascular disease in most healthy individuals.
A serving of shrimp supplies almost 60% of the daily recommended intake of cholesterol. Nutritionists once cautioned against eating shrimp because of the prevailing belief that cholesterol is injurious to health. Now, dieticians acknowledge that this seafood is beneficial in moderation as a source of vitamins, minerals, and antioxidants. It is important to check the source of shrimp, however, to avoid pollutants or undesirable additives.
In the 1970s, some scientists purported that refined carbohydrates are at least partially responsible for coronary heart disease. This perspective languished in the shadow of the lipid thesis. Today, it is gaining momentum as current research relegates a smaller role of saturated fats in high cholesterol blood levels. Recent studies increasingly support a link between carbohydrate-rich foods and heart disease. Consumption of refined carbohydrates increases the risk of cardiovascular illness while complex carbohydrates found in vegetables and whole grains protect against the same. A 2018 study published in Nutrients suggests that an additional one or two daily servings of carbohydrates may – dependent on the type – lower or raise risk by up to 20%.
Red meat has suffered ill repute as a heart health villain because of its high cholesterol and saturated fats. Many people forgo it in favor of leaner meats to avoid excess consumption of fats that are believed to elevate blood cholesterol levels. A 2017 review published in the Journal of Preventive Medicine suggests that sodium, preservatives, and other processing ingredients are the compounds that amplify the risk of cardiovascular disease. This suggests that, while there may be other reasons to reduce consumption of red meat, “bad” fats are not the primary cause.
Consistent data is lacking regarding the impact of alcohol on high cholesterol. Generally, moderate alcohol consumption may incur some cardiovascular benefits while excessive intake increases the risk of many dangerous health conditions. Harvard Medical School physicians recommend no more than one drink per day. A standard serving carries 14 grams of pure alcohol, and may be consumed in:
- 5 ounces of wine
- 12 ounces of regular beer
- 1 ounce of 100-proof spirits
- 1 1/2 ounces of 80-proof distilled spirits