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Low cholesterol good for the immune system?

Answered on September 12, 2014
Created March 09, 2011 at 11:10 AM

I just came across this news story.

It claims that:

Lowering cholesterol could help the body's immune system fight viral infections... when the body succumbs to a viral infection a hormone in the immune system lowers cholesterol... Therefore limiting the body's cholesterol would curb the chance for viruses to thrive.

Hence statins have been suggested.

Is is true that lowering statins would help fight infection? Previously I'd read that cholesterol was necessary for the immune system (and Paul Jaminet talks about this here) and that low cholesterol was associated with higher mortality, in part, for this reason. I can see the rationale for starving the infection of fuel, but is cholesterol (rather than glucose or some such, the main fuel?). This relates to another seeming paradox that has confused me- namely immunity and iron. i.e. we know that reducing iron availability mitigates infection, but equally iron deficiency is harmful to the immune system. One might be tempted to conclude that we simply need 'enough' cholesterol/iron etc. but that any excess is harmful, but given that cholesterol is almost entirely regulated internally by the body, why should we think that 'enough' cholesterol is much lower than what we typically have? (Of course, contra this, iron regulation is quite tight too, and we know that there are lots of other downsides to lower cholesterol).

One other possibility that suggested itself to me, is that if the body automatically reduces cholesterol production in response to infection, might an explanation of some people having lower (and so closer to "normal") cholesterol levels, be that they have chronic infections or are otherwise less healthy than those with higher cholesterol (ceteris paribus)?

(Let it be noted that I am very sceptical about any mainstream news reporting of scientific research. So this comes with the qualification that once we come across the actual research, it may well say the exact opposite to what has been reported).

E35e3d76547b18096a59c90029e7e107

(15613)

on March 10, 2011
at 10:27 AM

Thanks for the article Matt, good to know that "inhibition of viral growth is not due to cholesterol deprivation." I was particularly interested to see that some viruses seem to *increase* cholesterol synthesis. And yes it's obviously more complex than good/bad (like iron), since we already know that cholesterol plays numerous vital roles in the immune system.

E35e3d76547b18096a59c90029e7e107

(15613)

on March 09, 2011
at 07:23 PM

Yes, it's a really really bad idea obviously. By fuel I just mean that it's "needed for viruses to grow" according to the article. As to scepticism about cholesterol in the paleo community, I can't help but notice that it's occurred about the same time that many paleo luminaries have rediscovered that they like starch, but in fairness, I think it's probably a correction from the prior rhetorical stance which was a bit overly strong anti-anti-cholesterol.

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5 Answers

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F9a0b72f38860d7601afd5a45bb53394

(3618)

on March 09, 2011
at 06:46 PM

How do we know that we wouldn't be messing things up if we lowered cholesterol ahead of time before the viral infection? Maybe whatever the body's doing depends on having the higher cholesterol before the viral infection and then lowering it afterwards.

Where did all the pro-statin people come from, by the way? Every time I turn around someone is here going "But SERIOUSLY! Cholesterol MIGHT BE BAD!" You're probably not a pro-statin person, but your post on top of everybody else's got me wondering again.

As far as we know, viruses don't use fuel. They are just DNA or RNA snippets in protein shells. No one's found any evidence that they eat anything. (Bacteria "eat", but they're cells.) IF there is a connection between cholesterol levels and fighting viruses, it might have something to do with cell receptors, which are also involved with cholesterol going into cells. But again, maybe whatever happens to the cell receptors also affects cholesterol levels rather than the cholesterol level having a direct effect on the viral infection.

Or, here's a crazy idea, maybe it's the ambulance effect again, and the cells are intaking cholesterol to better fight off the viruses. That would have the result of reduced serum levels but the cholesterol would still be in the body. Now imagine if someone goes on statins to prevent a viral infection--might they actually achieve the opposite effect and get sicker?

I hate the press sometimes. Like now.

E35e3d76547b18096a59c90029e7e107

(15613)

on March 09, 2011
at 07:23 PM

Yes, it's a really really bad idea obviously. By fuel I just mean that it's "needed for viruses to grow" according to the article. As to scepticism about cholesterol in the paleo community, I can't help but notice that it's occurred about the same time that many paleo luminaries have rediscovered that they like starch, but in fairness, I think it's probably a correction from the prior rhetorical stance which was a bit overly strong anti-anti-cholesterol.

2
0bc6cbb653cdc5e82400f6da920f11eb

(19245)

on March 09, 2011
at 10:02 PM

The original study can be found here and it is an open access publication: Host Defense against Viral Infection Involves Interferon Mediated Down-Regulation of Sterol Biosynthesis

The funding of the research comes from public and charitable funding, not from pharmaceutical companies.

The research is extensive and is pretty inpenetrable for a non-expert however the authors provide a summary of the article that is more readable:

Currently, little is known about the crosstalk between the body's immune and metabolic systems that occurs after viral infection. This work uncovers a previously unappreciated physiological role for the cholesterol-metabolic pathway in protecting against infection that involves a molecular link with the protein interferon, which is made by immune cells and known to ???interfere??? with viral replication.

Our initial investigation into how lowered cholesterol might protect against viral infection reveals that the protection is not due to a requirement of the virus for cholesterol itself but instead involves a particular side-branch of the pathway that chemically links lipids to proteins. Drugs such as statins and small interfering RNAs that block this part of the pathway are also shown to protect against cytomegalovirus (CMV) infection of cells in culture and in mice. This provides the first example of targeting a host metabolic pathway in order to protect against an acute infection.

This seems like a facinating bit of new research to me. Cholesterol and its biosynthesis pathways in your body are complex and far more than just cholesterol is either good or bad. This research does not seem to have much to do with blood cholesterol either.

There is a lot of research going on currently into the interactions of viruses and cholesterol pathways.

E35e3d76547b18096a59c90029e7e107

(15613)

on March 10, 2011
at 10:27 AM

Thanks for the article Matt, good to know that "inhibition of viral growth is not due to cholesterol deprivation." I was particularly interested to see that some viruses seem to *increase* cholesterol synthesis. And yes it's obviously more complex than good/bad (like iron), since we already know that cholesterol plays numerous vital roles in the immune system.

2
Medium avatar

on March 09, 2011
at 08:21 PM

This message brought to you by AstraZeneca Pharmaceuticals.

1
1acc4ee9381d9a8d998b59915b3f997e

(2099)

on March 09, 2011
at 08:33 PM

Cholesterol is used by the body to create and maintain cell membranes, amoung other things. To me, it stands to reason that cholestrol falls during a viral infection because the body is busy rebuilding/repairing itself! It seems to me that if the cholesterol level is low in the first place, if the person gets an infection, that their body would have a harder time repairing itself.

1
5edbf85deaf83e13b176df023abb154d

on March 09, 2011
at 01:50 PM

The guy quoted in that article basically says that something MIGHT be the case. From there, the media made a story out of it. The journalist in that article is stretching to make something out of nothing.

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