The Damaging Effects of Low Cholesterol
by Nieske Zabriskie, ND
Despite all of the negative reports regarding cholesterol, this life-sustaining lipid is essential for several important functions required for optimal health. Cholesterol is a vitally important component of cellular membranes; serves as a precursor molecule for the synthesis of steroid hormones, vitamin D, and bile acids; and plays a role in nerve conduction, brain function, and mood. Without cholesterol, we wouldn’t be able to exist.
The majority of cholesterol in the body is synthesized in the liver and the intestines. Cholesterol is transported through the blood as lipoproteins, which are lipid-protein complexes that differ in their content of lipid and protein. Dietary intake of saturated fats also impacts total cholesterol levels. However, diets low in cholesterol and saturated fats modulate low-density lipoprotein (LDL) cholesterol by only approximately 10 percent.1 Fats and carbohydrates are converted to triacylglycerols in the liver, which are then packaged into very low-density lipoproteins (VLDLs). VLDLs are released into the circulation to be transported to various tissues for storage or utilized for energy production. In the circulation, VLDLs lose triacylglycerols and are converted to intermediate-density lipoproteins (IDLs) and LDLs.
Of particular concern is the amount of small, dense LDL particles. Research indicates that these particles are more likely to be related to suboptimal cardiovascular health and blood flow than larger, “fluffy” LDL particles.2 High-density lipoproteins (HDLs) are also involved in transport. However, these lipoproteins acquire cholesterol from peripheral tissues and transport this cholesterol back to the liver for incorporation into bile acids, which is known as reverse cholesterol transport. Current standard medical guidelines suggest that total cholesterol should be below 200 mg/dL, LDL below 100 mg/dL, triglycerides below 150 mg/dL, and HDL above 40 mg/dL for men and 50 mg/dL for women.
Yet, there remains a degree of controversy on the topic, as heart disease is not merely determined by these indices, and without a more comprehensive approach looking at LDL size (small dense) or (large buoyant), lipoprotein A, fibrinogen, homocysteine and cardio-CRP, one misses the proverbial boat when it comes to protecting the heart.
Cholesterol: Why We Can’t Live Without It
The majority of cholesterol is incorporated into bile acids in the liver. Bile acids are stored in the gallbladder and released into the intestines in the presence of dietary fats. Bile acids function to emulsify fats allowing for absorption of fats and fat-soluble vitamins. Over 90 percent of bile acids are recycled through circulation and reused by the liver. The complexity of this pathway to maintain adequate cholesterol within the body suggests the importance of this lipid.
Cholesterol is also an important component of cellular membranes, where it modulates the fluidity and permeability of the membrane. Without cholesterol, some membranes would crystallize at physiological temperatures. In addition, steroid hormones are derived from cholesterol, including cortisol, estradiol (a form of estrogen), testosterone, dehydroepiandrosterone (DHEA), progesterone, pregnenolone and aldosterone. Vitamin D is also synthesized from cholesterol.
Approximately 25 percent of the total amount of cholesterol in the body is localized to the brain, mostly found in myelin.3 Myelin consists of several layers of tightly compacted membranes wrapped around nerve cell axons and functions to provide electrical insulation to ensure the rapid propagation of nerve conduction. Animal models indicate that only minimal changes of the nervous system myelin lipid composition are tolerated and depend on adequate cholesterol synthesis.4
The fact that low cholesterol can also be associated with increased mortality is often ignored.5-6 Another interesting paradox suggests that although high serum lipids are associated with suboptimal cardiovascular health, low cholesterol is also associated with heart health in individuals with advanced cardiac dysfunction.7
Adequate Cholesterol and Brain Health
Mood has been associated with serum cholesterol concentrations. In one study, researchers demonstrated that increased HDL was negatively associated with mood while higher LDL and triglycerides were positively associated with mood.8 Another study evaluated 4,115 men and 4,275 women aged 18 or older for serum lipid levels and mood. The results demonstrated a U-shaped curve, meaning that both low and high serum lipids were associated with a negative mood. In fact, the strongest association was found in men with low LDL cholesterol, showing over 5-times the likelihood of having mood changes with LDL levels below 169 mg/dL.9
In another interesting study, 326 healthy women between 52-63 years of age were evaluated for serum lipid levels and memory. The results of the study revealed that the women with the lowest LDL cholesterol levels also had the lowest performance on the memory tests. Additionally, lower performance was seen in the women whose LDL cholesterol levels declined over the previous three years. The researchers concluded that higher serum concentrations of LDL and relatively recent increases in total cholesterol and LDL concentrations are associated with better memory in healthy middle age women.10 A related study also showed that low total cholesterol was associated with declining cognitive function in elderly subjects with evidence of some cognitive changes.11
Balanced levels of HDL cholesterol also play a role in cognitive health. In one study, researchers evaluated cognitive function and serum lipid levels in older adults with normal cognition. They found that higher HDL cholesterol was associated with better performance on cognitive tests as well as increased gray matter volume, particularly in regions of the brain associated with neurodegenerative conditions.12 A similar study showed that low HDL cholesterol was associated with more significant white matter changes, which are commonly found in elderly individuals with suboptimal cerebrovascular health and due to age-related cognitive changes.13
Enhanced Physical Performance with Age
In addition to cognitive performance, adequate cholesterol levels also impact functional performance and strength. Researchers assessed 1,064 subjects between 55-85 years of age for functional performance using the chair stand, 3-meter walk, and putting on and taking off a cardigan, at the beginning of the study and again after 3 years. In addition, serum protein (albumin) and total cholesterol were measured at the beginning of the study. The data showed that the women with more optimal total cholesterol concentrations had 2.5-times the likelihood of maintaining functional status compared to women with lower serum total cholesterol concentration. In the men, the subjects with more optimal albumin and total cholesterol concentrations were 3-times more likely to maintain functional performance compared to men with lower levels.14
Supporting Balanced Cholesterol
There are many natural ways to support healthy, balanced cholesterol levels such as eating a Mediterranean diet and exercising.
Animal studies show that a sedentary lifestyle can reduce the body’s ability to process fats. Leg muscles tend to increase production of a fat-processing molecule known as lipoprotein lipase when a person is standing or walking around.15-17
Sitting means this molecule is in shorter supply. The lipoprotein lipase enzyme is involved in releasing fatty substances from very low-density lipoproteins (VLDLs) in the blood, making them more likely to be used for energy than deposited in arterial walls.15,17 When a person sits, the muscles relax, and the enzyme activity plummets by as much as 95 percent, leaving fat in the bloodstream.15,17
Due to its role in fat processing, lipoprotein lipase plays an important role in reducing LDL and increasing HDL (the good cholesterol).15,18
In fact, after two hours of sitting, healthy cholesterol drops by 20 percent.15
One study found that increased sitting time was associated with increased levels of the inflammatory markers CRP and IL-6 in women.19
Therefore, taking frequent breaks throughout the day to stand and walk around can help support a healthy inflammatory response while at the same time enhance cardiovascular health and support healthy cholesterol levels.
Beyond Cholesterol
Supporting balanced cholesterol levels receives the lion’s share of attention when promoting cardiovascular health. But despite the attention given to cholesterol, other factors have been shown to be equally, if not more important players in cardiovascular health. Research indicates that white blood cell count, fibrinogen, the inflammatory marker C-reactive protein (CRP), the markers of kidney function uric acid and creatinine, and glucose are important to maintain in healthy ranges. In fact, one study showed that the strongest correlation with suboptimal cardiovascular health was fibrinogen concentration.20 Researchers also report that circulating levels of inflammatory markers such as CRP are likely indicators for future cardiovascular health.21
Conclusion
Although cholesterol reduction is given a great deal of attention, cholesterol levels that are low also have health consequences, as cholesterol has several essential physiological functions. To optimize cardiovascular health and cholesterol, factors such as promoting a healthy inflammatory response, minimizing time spent sitting and lifestyle management through diet are critical to address.
References
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