Sourdough, sauerkraut, kimchi, kombucha… these are just some of the products on the market that appeal to the interest in optimising your gut microbiome. The public has latched onto the concept of the gut microbiome being key to health, so such products have become incredibly mainstream. Heck, I even tried a kombucha gelato at a market not too long ago, which kind of (okay, completely) defeats the purpose of it (but was surprisingly delicious). One of the benefits of a healthy microbiome may be improved cholesterol levels. Seeing as cholesterol has a significant impact on cardiovascular disease, which is the primary cause of death worldwide, that’s something not to be sneezed at.
- It seems that probiotics (and prebiotics) may improve cholesterol status among people who begin with unhealthy levels. However, they seem less powerful than statins.
- It seems that probiotic/prebiotic supplements need to be used for at least 8 weeks to have a significant impact.
- People who are under 50-60 years of age, and have diagnosable cardiometabolic risk factors, are most likely to benefit.
- More research is required to ensure there is a cause-effect relationship (as opposed to an association) between the microbiome and cholesterol. We also need research to address gaps in our knowledge, such as the mechanisms by which probiotics and prebiotics exert their effects, and the strains which are responsible in different conditions.
Unhealthy cholesterol levels are extremely common. Even my uncle, who’s one of the fittest 60 year olds I know, has had it for some time.
Phrases such as ‘high cholesterol’ and ‘cholesterol-lowering’ are often used for simplicity’s sake, but in reality we usually don’t want to simply lower cholesterol. We want to resolve dyslipidaemia- abnormal cholesterol status. We may or may not wish to lower the total amount in our blood. But we definitely want to avoid high LDL- (and VLDL-) cholesterol and triglyceride (fat) levels, and low HDL-cholesterol levels within our blood. In fact, the relative abundance of these different types of cholesterol may be more important than the total cholesterol value itself.
|LDL- and VLDL-cholesterol = ‘bad’ as it increases cholesterol deposition on artery walls|
HDL-cholesterol = ‘good’ as it takes cholesterol out of the blood to the liver- preventing it from being deposited on artery walls
It’s believed that improving cholesterol levels is one of the most effective ways of reducing the impact of cardiovascular diseases. While the commonly used cholesterol lowering drugs (statins) are effective, they can have side effects. In the hope of avoiding side effects, there is interest in nutritional interventions that could achieve the same things. Just one of these potential tools are probiotics and prebiotics. Other potential nutritional strategies that are under investigation include supplementation with antioxidants (CoQ10, polyphenols, selenium), some minerals (zinc, potassium, magnesium, and calcium), vitamin D and garlic. There is no doubt that cholesterol is sensitive to dietary (and other lifestyle) factors… However, whether dietary changes are as powerful as statins in cases of pathophysiology is another question entirely.
Cholesterol meets the microbiome
We know that the gut microbiome is associated with diverse physiological functions not limited to immunity. Some of its roles include assisting nutrient absorption and regulating fat metabolism. A disturbed microbiome could contribute to chronic cardiometabolic disorders, including unwanted changes to cholesterol levels.
Can improving your microbiome be a way to manage cholesterol, then?
There is definitely an association between regular consumption of probiotics and prebiotics and better cholesterol. Since probiotics and prebiotics are designed to improve your microbiome, it might be reasonably expected that any effects would be mediated via the microbiome. However, some studies fail to report the impact of probiotic supplements on the microbiome. Some have assessed the change in microbial populations over the course of the study, but not with the most accurate tools available. Call me pedantic, but I’d like to see a direct assessment on microbiome AND cholesterol effects to be standard in the research.
Getting back to the effect of probiotics and prebiotics: As far as a cause-effect relationship is concerned, there are some inconsistent results. A 2021 review of the overall evidence suggests that use of probiotics might improve cases of poor cholesterol status. It seems that 8-weeks or more of supplementation is most effective. Also, people under 50–60 years of age and those who are most at risk of cardiometabolic disease may benefit most. For example, if you already have elevated cholesterol or blood triglycerides, metabolic syndrome, or high blood pressure.
However, any effect still appears modest compared with statins.
From small studies, it appears that various products including kefir, fermented milk with probiotics, fermented plant extract with prebiotic effects (composed of fruits, vegetables, and herbs with added oligosaccharides, yeast, starch, and dietary fibers), have potential for these modest benefits. Different pro-/prebiotics may act on target different subfractions (eg: HDL, LDL, triglycerides). In some cases there was also a reduced oxidation of LDL-cholesterol (which contributes to problems such as plaque buildup in arteries and endothelial dysfunction). More research is required to identify the specific actions and relative merits of different products.
Another issue is that most of the studies are small in size and only lasted for 6-12 weeks. It would be interesting to see what effect longer-term supplementation has.
It’s worth noting that consistent use of pre- and probiotics may be required to maintain any beneficial effects. In the aforementioned study of fermented fruit extract, two weeks after its use was discontinued, harmful C. perfringens and E. coli bacteria started to increase gradually, whereas Bifidobacterium and Lactobacillus species began to decline. Also, total and LDL-cholesterol and blood fats slightly increased. In another study, supplementation with Lactobacilli reuteri reduced the impact of an unhealthy diet on the cholesterol of pigs. But once the supplementation stopped, the benefit disappeared.
Interestingly, in this pig study, supplementation caused the Lactobacilli reuteri bacteria population to become more abundant only in the first 2 (of 4) weeks. After this, improvements to total and LDL cholesterol were maintained, even though the microbiome reverted back to normal. The lack of clarity here and small sample size means more research on this is required… in humans too.
How does the microbiome affect cholesterol levels?
While it seems that the microbiome affects cholesterol metabolism, the mechanisms by which probiotics and prebiotics work is not completely known. It appears that probiotics increase excretion of cholesterol and decrease the amount of cholesterol that is absorbed from the intestines.
Both of these appear to be mediated by a breakdown of bile salts into bile acids and other byproducts. While bile salts are very useful for binding and carrying cholesterol/fats through the intestine, into the body, bile acids are not. Instead, they are easily excreted in the faeces. Cell culture studies suggest that some probiotics may also convert cholesterol to coprostanol, which can be defecated. However, we are not sure precisely which probiotics have this effect.
The increased excretion may have flow-on effects. Cholesterol is also needed to make bile acids. So, to replace the excreted bile acids, the body uses up other cholesterol, leaving less to float around in the blood and wreak havoc.
Probiotics also seem to modulate the metabolism of fats.
Animal and human studies suggest other possible mechanisms, such as increasing the bulk of faeces and reducing the amount of time they spend in the body, which inhibits the formation and reabsorption of biological molecules that include cholesterol in their structure. Prebiotics seem to increase the production of short chain fatty acids which are transferred to the liver, and there inhibit cholesterol synthesis.
However, the potential mechanisms may vary depending on the strain of probiotic bacteria and type of prebiotic.
What microbes are helpful?
The research is too young to construct a complete picture of what are the ‘good’ and ‘bad’ microbes as far as cholesterol is concerned. Furthermore, it is not just the strain of bacteria that matters. Effects may vary depending on the overall physiology of the person, and the type of diet they eat. So, much more research is required, taking into account these variables.
A number of studies suggest that Bifidobacterium species and Lactobacillus species are potentially beneficial, depending on a person’s characteristics. For example, the use of fermented plant extract increased these species, while also reducing cholesterol levels. In a small study of people with metabolic syndrome, Bifidobacterium lactis in a fermented milk was seen to reduce total and LDL cholesterol. A pig study showed Lactobacilli reuteri bacteria containing an enzyme called bile salt hydrolase (BSH) helped breakdown bile salts and therefore increase cholesterol excretion.
There may be other beneficial bacteria too. I came across one study where probiotics containing Sterolibacterium denitrificans converted cholesterol to the more easily excreted coprostanol.
Escherichia coli and Clostridium perfringens are considered harmful to overall health, and possibly this area too. In the study where fermented plant extract improved cholesterol, these bacteria were also reduced.
Taking probiotics and prebiotics seem to provide modest benefits to cholesterol levels, if they start high or if you have other cardiometabolic risk factors. They may be a good complement to other treatments, but do not seem powerful enough to be a substitute for statins. Eight or more weeks of usage may be required to unlock the maximal benefits, and they may be quickly lost once supplementation is discontinued. It is likely these benefits are mediated by the effect of the supplements on the microbiome, which has been associated with a wide range of areas of human health. However, more clinical evidence is required to determine exactly what kind of relationship exists between these variables, the mechanisms involved, and what microbial species are responsible.
We’ve gone into more detail on other fundamental means to improve your microbiome here. Beyond these, improving your microbiome can require an individualised approach, and is thus beyond the scope of this website. This is particularly true if you’ve been diagnosed with a bacterial imbalance such as SIBO. That’s why our friends at The SIBO Doctor have created educational resources such as The SIBO Success Plan.
This program is led by Naturopathic Dr Nirala Jacobi, a world-leader in gut health and SIBO. Over the course of 8 lessons, you’ll become empowered with all the tools you need to finally understand and overcome your SIBO. The SIBO Doctor also offers comprehensive training for health practitioners.
How could you support your microbiome?
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