Cholesterol, Immunity, and Infectious Disease

Cholesterol plays an important role in immunity, especially with bloodborne pathogens. One study here explained that total cholesterol (TC) fluctuates wildly during acute infections indicating cholesterol may have immune mediated activity. The article reviewed 19 cohort studies that revealed a correlation between increased death from respiratory and gastrointestinal diseases (both infectious) and low TC.

It also showed that people admitted to hospitals due to an infectious disease also had low cholesterol. Some common diseases noted were genitourinary infections, skin, and subcutaneous (just below the skin) infections. HIV and death from AIDS were also associated with lower cholesterol levels.

Patients with low TC suffering from chronic heart failure had a poorer prognosis after surgery and lower long-term survival rates. This also included patients recovering from abdominal surgeries. Another interesting note was that people suffering from hepatitis B including asymptomatic carriers also have lower TC levels.

Although the evidence shows that young and middle-aged men are at risk for heart disease with high cholesterol (this can be controlled through diet) their risk becomes negated when they get close to 50. As one gets older, higher cholesterol is associated with longevity 1, 2 in both men and women. This may be due to not only the cardioprotective effects of higher cholesterol but also to innate immunoprotective mechanisms associated higher TC.

Interestingly, eating a diet lower in fiber increases serum cholesterol due to the gut’s increased ability to reabsorb cholesterol in the absence of fiber. In addition to this, diets higher in linoleic and linolenic acids (essential fatty acids) may help prevent or reverse atherosclerosis (yes, atherosclerosis can be reversed).

Another article showed that one cause of cardiovascular disease may result from bacterial communities reinfecting arterial walls. Suppressed immune response related to low cholesterol may be a contributing factor.

If you want to reduce your risk of infection and improve immunity response mechanisms, one thing to consider is maintaining healthy cholesterol levels. Cholesterol may also play a role in a number of autoimmune disorders.

Low Total Cholesterol and Mortality Rates

This is an exploration of mortality rates associated with low cholesterol. The review was published in Circulation: Journal of the American Heart Association. In this review, the National Heart, Lung, and Blood Institute held a conference seeking to understand why lower total cholesterol (TC) levels are associated with some cancers, respiratory and digestive diseases, trauma, and residual deaths.

Apparently, men are more susceptible to this correlation than women. They examined 19 cohort studies from the U.S., Europe, Israel, and Japan. TC is a calculation of cholesterol measurements of LDL, HDL, and triglycerides.  The review noted high rates of cerebral hemorrhage with lower average TC. The rate of cerebral hemorrhage decreased as average TC went up in prospective populations. This was true in the Multiple Risk Factor Intervention Trial (MRFIT) in addition to increased incidence of colon cancer with lower TC. This may be related to what I wrote in an earlier post.

For women, 6 of the 11 studies showed no variation in cancer death rates across all spectrum of TC levels. There was an increased cancer risk in men when their TC levels fell below 180 mg/dL. In non-cancer and non-cardiovascular death rates, both men and women had similar risk findings. When TC was below 160 mg/dL there was a 40% increase of mortality compared to 160-199 mg/dL levels. Risk was also reduced by 10% when TC levels were between 200-240 mg/dL compared to the reference class (TC between 160-199 mg/dL levels).

This increase in non-cardiovascular deaths raises the issue of the dangers associated with taking cholesterol lowering drugs. These dangers are real and should not be taken likely (as mentioned in the study). Once again, when the data was pooled together, TC below 160 mg/dL was associated with highest risk of mortality.

Unfortunately, some of the data did not differentiate between age or sex but we can assume that having TC this low for anyone is quite risky. The review did take into account people with diabetes, smokers, CVD, alcohol intake, and other possible factors that might skew the data. Some of the research also separated participants further by age and gender.

Findings for all-cause mortality (ACM [death from any cause]) for those with TC between 200-240 mg/dL had the lowest incidence. The rate of death increased the TC went down below 199 mg/dL (are you seeing a trend yet?). Interestingly enough, the American Heart Association, the journal’s parent organization, say that total cholesterol should be below 200 mg/dL. This is the range that has been demonstrated by the AHA to increase risk death from all causes. The standard protocol for primary care providers is to prescribe statin medication when TC is above 200 mg/dL which will place patients well within the range of increased risk of death. 

There are also other health risks associated with direct effect of statin use in addition to health benefits not associated with TC lowering mechanisms. Statins act on many mechanisms in addition to reducing cholesterol synthesis in the liver. A benefit-risk analysis of statin use will be explored in a future post.

It is safe to say that total cholesterol levels appear safest when they remain in the range between 200-240 mg/dL. This is my target. Unless you have a very rare disease, it is completely controllable through diet which will be discussed later. Don’t forget exercise will increase your total cholesterol level (by increasing HDL) as it improves your health.