One of my earliest memories of health was my dad’s diagnosis with familial hypercholesterolemia – a fancy way of saying that his high cholesterol is genetic. I remember dad wearing matching workout suits to the gym and dramatically changing his diet per his doctor’s orders. A six-month no-avocado, no-egg, no-elk diet cast an ominous cloud over the household, resulting in a storm of fury when lab results indicated an increase in dad’s “bad” cholesterol!
Contrary to a half-decade of recommendations to consume a low-fat diet for optimal heart health, it is not the consumption of excess saturated fats that elevates small, dense low-density lipoproteins, or LDLs (which lead to heart disease). Rather, research shows that excess consumption of carbohydrates elevates levels of small, dense LDLs in the blood! (Note: large, buoyant LDLs do not appear to lead to heart disease).
The Nurse’s Study (2000) found a direct relationship between high intakes of refined carbohydrates and an increased risk of stroke, even after accounting for other risk factors. Also, a diet high in refined carbohydrates contributes to lower levels of high-density lipoproteins (HDLs) – the cholesterol that helps protect the body from plaque build-up in the arteries – and higher levels of triacylglycerols (commonly, “triglycerides” or TAGs). Low HDL with high TAGs is a risk factor for developing The Metabolic Syndrome, diabetes and cardiovascular disease.
One in three Americans die from heart disease, and with a huge body of quality, current research linking refined carbohydrates and low-fat foods to cardiovascular disease, why are so many people still consuming a heart unhealthy diet?
“Low-fat” has been engrained in our culture for decades, reinforced by marketing efforts of low-fat food companies and unsupported by media claims. There may also be a misunderstanding of how carbohydrates convert into fats, of which cholesterol is only one.
Carbohydrates are one type of macronutrient that provides energy to the body. In our digestive tract, carbohydrates are broken down until they become single-sugar molecules – glucose, fructose or galactose. Glucose is the main fuel for cells, organs, muscles and the only fuel source for the brain. Simple sugars are 2-molecule carbohydrates, such as glucose-fructose (white sugar) or galactose-glucose (lactose, found in milk). Complex carbohydrates contain 3+ molecules of sugar, and are typically from nature.
Carbs come from fibrous plants – fruits, vegetables, grains and legumes – as well as from animals in the form of dairy. Additionally, the majority of boxed foods on grocery store shelves are packed with carbohydrates, most of which have been refined, preserved, and fortified. Pizza, pasta, breads, crackers, baked goods and countless other standard American restaurant foods are high in carbohydrates from processed grains and sugars.
Here’s how it works: refined (simple) carbs are digested rapidly and absorbed into the bloodstream, travel to the liver to be metabolized, and produce energy molecules. When this energy exceeds the body’s needs, these molecules become fatty acids, and then produce triacylglycerides, including low-density lipoproteins (VLDLs). In the bloodstream, VLDLs interact with LDLs, producing some small, dense LDLs, which are absorbed into artery walls and are more prone to becoming atherosclerotic plaque.
Refined carbs offer little in terms of nutrients needed for cellular energy and brain function, and a lot in terms of too much sugar and, ultimately, storage of unhealthy fats. To lower elevated levels of LDLs, consume fewer refined carbohydrates and mostly whole foods.
Gropper, S.S., & Smith, J.L. (2013). Advanced Nutrition and Human Metabolism (6th ed.). Belmont, CA: Wadsworth, Cengage Learning.
How Carbohydrates Affect Cholesterol Levels. (2017). Manna Health Products. Retrieved from https://www.mannaplus.co.za/how-carbohydrates-affect-cholesterol-levels/
Kresser, C. (n.d.). The diet-heart myth: Find out how 50-year old science is hurting your heart. ChrisKesser.com. Retrieved from: http://chriskresser.com/the-most-important-thing-you-probably-dont-know-about-cholesterol
Ma, Y., Chiriboga, D. E., Olendzki, B. C., Li, W., Leung, K., Hafner, A. R., … Hebert, J. R. (2006). Association between Carbohydrate Intake and Serum Lipids. Journal of the American College of Nutrition, 25(2), 155–163.
McGuire, M., & Beerman, K. (2013). Nutritional sciences: From fundamentals to food (3rd ed.). Belmont, CA: Wadsworth, Cengage Learning.