Cholesterol is poorly understood by the general populous. In fact, for years it has been misunderstood by the medical community as well. Finally we are starting to get somewhere on this topic, but it seems to be moving slowly. Let’s start out with a few simple biochemical truths:
- About 3/4ths of our body’s cholesterol is endogenously synthesized (made inside the body). The remaining 1/4th comes from the diet. The body can synthesize all necessary cholesterol if none is eaten.
- The main factors that increase cholesterol synthesis are low cholesterol levels and the hormone insulin.
- Insulin is secreted mainly in response to dietary carbohydrate.
The cholesterol raising abilities of saturated fats has been covered to death over the past 25 or so years. In reality, certain saturated fatty acids (probably the long-chain ones) do seem to elevate serum LDL cholesterol. Historically, human intake of saturated fats was between 10 and 15% (1), which is probably an appropriate level. Excessive intake of dairy, especially cheese, and grain-fed beef (higher in saturated fat than grass-fed (2)) has pushed many people above this level, which likely increases their LDL cholesterol, and that is not a good thing.
As we are beginning to learn, however, not all saturated fatty acids have this ability. Stearic acid, for example, the main saturated fat found in beef, does not seem to have these LDL elevating characteristics. In fact, it seems that stearic acid has no different affect on cholesterol than carbohydrates or oleic acid, the monounsaturated fatty acid found in olive oil (3). Soon the broad generalizations involving saturated, monounsaturated and polyunsaturated fats will be no more. Instead, we will be discussing specific fatty acids, so get used to names like myristic acid, palmitic acid and arachidonic acid.
My intention here, though, is to remind folks that insulin is massively important in cholesterol homeostasis. Specifically, when insulin is elevated, cholesterol synthesis increases. Certainly other factors play in, but insulin is clearly recognized to play this role. In other words, this is not controversial.
As mentioned, carbohydrates are the main regulator of insulin levels. When we eat carbohydrates, our blood sugar increases, which causes a release of insulin in order to bring blood sugar back down to a safe level. Refined carbohydrates, like white bread or rice, cookies or soda, cause this elevation of blood sugar and insulin to happen very rapidly. Repeatedly spiking insulin levels (e.g. cereal for breakfast, soda all day and spaghetti every night) can lead to permanently elevated insulin levels, which is associated with almost every chronic illness known to man (heart disease, obesity, diabetes, cancer, metabolic syndrome, and I am willing to bet also erectile dysfunction). One reason chronically elevated insulin relates to these problems is its stimulatory effect on cholesterol synthesis.
In terms of a physiological mechanism, the connection between refined carbohydrates and elevated LDL cholesterol is incredibly simple compared to the effects of saturated fats on cholesterol. Next time an “authority” on health is scaring you about saturated fats, take a second and remind yourself of the incredible danger of your beloved carbohydrates.
1 – Saturated fat consumption in ancestral human diets: Implications for contemporary intake
3 - Effects of stearic acid on plasma lipids and lipoproteins in humans
