Cholesterol.
Wrongly accused

Thijs R. Klompmaker
Amsterdam
Ortho 2006; 24(6) Ahead of print

A response to this article:
Unilever responds to 'Doubts about plant sterols'
Ortho 2006; 24(5):225. (In Dutch)

Cholesterol is seen as a risk factor regarding heart disease. Unilever took the opportunity to produce and sell products that lower total cholesterol by means of phytosterols, including in healthy people. De Graaf and Schuitemaker showed in their review that absorption of the plant sterols involved seems realistic, increasing heart disease risk. [1] The question is whether such products should be allowed. More fundamentally is the question what the cause is of elevated cholesterol levels.

Irresponsible

In the previous issue of Ortho, Unilever responded to the initial article about plant sterols. [2] As LDL cholesterol is associated to heart disease, Unilever claims that it is safe and solely has positive effects to lower total cholesterol in healthy people using plant sterols: ‘Becel Pro-active to prevent heart disease’. Unilever assumes it is desirable to lower elevated cholesterol levels by any means. This is irresponsible, as cholesterol is essential in many ways.

Super nutrient

Cholesterol is a super nutrient. Its not just the precursor for vitamin D and bile acids, but also for sex-hormones as testosterone, progesterone and oestrogen. Its also one of the main structural components in the brain. Low cholesterol inhibits brain-functioning [3], whereas a diet rich in cholesterol improves cognitive functions. [4] In elderly, lower cholesterol levels are associated with increased infection rates and heart failure risks. [5] Because cholesterol is so important, decreased cholesterol levels evoke depression and aggression, as a warning sign. Low cholesterol is associated to violent [6][7][8] and suicidal behaviour. [9][10][11] This may be explained by the indirect stimulatory effect of cholesterol on serotonin activity. [12] Because cholesterol is so important, the human body can produce most of the cholesterol it needs. A too low intake of dietary cholesterol, however, may obviously lead to deficiency symptoms.

Good and bad cholesterol

There is no good and bad cholesterol, as there is no good and bad glucose. There is only one molecule that carries the name cholesterol, and its properties do not differ. Nevertheless, one talks about good and bad cholesterol depending on the lipoprotein that transports the cholesterol; HDL or LDL. Not because one is better than the other, but purely because associations between these carriers and heart disease risk. Whether this relationship is causal, is unclear. As repeatedly getting a tan may be associated to skin cancer, but not the cause; the tanning is only a symptom of the reaction of the skin to sun exposure. In the same way, elevated LDL may just be a symptom, and not the cause. Fighting symptoms in healthy people seems dubious at least. Particularly as we do know what may cause elevated cholesterol levels.

Cholesterol regulation

As cholesterol is essential in many ways, we need to be extremely careful, and solely address the actual cause of elevated cholesterol. That what primarily influences the regulation of cholesterol level, is cholesterol itself, as more cholesterol is transformed in bile acids and less new cholesterol is produced when cholesterol levels increase. When cholesterol levels decrease, more cholesterol is produced and less cholesterol is transformed into bile acids. Indirectly, fat consumption is also of influence, as bile acids are required to digest dietary fat. Bile acid production, however, is also subject to feedback mechanisms, and therefore not a de-regulative factor. Oxysterols also influence this feedback system, as they strongly resemble cholesterol.

Oxysterols

As intermediates in the transformation of cholesterol into bile acids and vice versa, there are a number of Oxysterols naturally present in our body. Natural oxysterols such as 7 alpha-, 27-, and (24S)-hydroxycholesterol co-regulate cholesterol homeostasis. [13] They inhibit cholesterol production and stimulate transformation of cholesterol into bile acids. [14] Unfortunately, there also are oxysterols that inhibit the transformation of cholesterol into bile acids [15] and stimulate LDL production. [16] Unfortunately, we do ingest such oxysterols, due to our diet. Due to its double bond in its molecule, cholesterol already spontaneously oxidizes at 100 degrees Celsius. [17] This may result in the oxidation of 30% of dietary cholesterol into harmful oxysterols such as 7-keto-cholesterol, 7-beta-cholesterol, 5-beta,6-beta-epoxycholesterol and 5-alpha,6alpha-epoxycholesterol. About 6% of these oxysterols actually get absorbed [18], causing an increase in the levels of cholesterol and oxysterols combined. Of course we shouldn’t blame cholesterol, which is essential and harmless. Some oxysterols are cytotoxic and impair LDL-receptor functioning, cell membrane permeability and production of prostaglandins. [19] Oxysterols are over-represented in LDL [20] and responsible for the harmful properties of LDL [21], which might explain the LDL-heart disease association. Oxysterols such as particularly 7-keto-cholesterol and 7-beta-hydroxycholesterol cause heart disease. [22][23][24] Atherosclerotic plague contains relatively high levels of oxysterols. [25] Dietary oxysterols are also bad for your defence. [26]

Prevention

Preventing signals that are associated with a disease is not preventing that disease. The Becel Pro-active claim could only be justified if research would show that the consumption of Becel would lead to a decreased heart disease risk. There never was such a study. The only thing that Unilever has, is an association with a signal. Whereas prevention is easy and doesn’t cost anything. All we need to do, is stop intensively heating food that naturally contains cholesterol. So, no more well-done beef, products containing egg powder, fried chicken, or hard-boiled eggs. Raw-fish sushi seems perfect.

SOURCES

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