High blood cholesterol is a major cause of heart disease. A person with high blood cholesterol has three times higher risk of heart attack than a person with normal cholesterol level.
Common prevention and treatment for high cholesterol are: dietary approach, which includes avoiding or reducing intake of high cholesterol foods and consuming cholesterol-lowering foods; regular physical activity; and medical intervention, such as with cholesterol-lowering drugs. An additional, recent, promising approach for lowering cholesterol is probiotics.
What are probiotics?
Probiotics are living microorganisms taken as suplements and that benefit the host by improving gut microbial balance. The most common probiotic bacteria are lactobacilli and bifidobacteria. They are generally consumed in the form of fermented dairy products such as yoghurt.
Cholesterol lowering benefits of probiotics
One of the first recorded observations on the effect of bacteria on lowering blood cholesterol dates back to the early 1960s. Scientists observed that Maasai warriors in Kenya had lower cholesterol level after consuming 4 l/day milk fermented with a wild strain of bacteria called Lactobacillus. Since then, several animal and human studies have shown that probiotics lower total and LDL blood cholesterol. In a 10-week study of 48 humans with high cholesterol, daily after dinner consumption of 200 g/day yoghurt containing Lactobacillus acidophilus reduced blood cholesterol by 2.4%. In another 4-weeks study of 32 humans with cholesterol level ranging 220 – 280 mg/DL, consumption of low-fat yoghurt containing Bifidobacterium longum BL1 not only did it decrease total and LDL-cholesterol but also increased HDL-cholesterol. In a 6-weeks study of 58 middle-aged men, intake of 200 ml/day a fermented milk product, containing Enterococcus faecium and two strains of Streptococcus thermophilus, reduced total cholesterol by 6% and LDL-cholesterol by 10%.
There are also several studies that reported no significant cholesterol-lowering effects from probiotics. It is not clear whether their findings are due to the duration of the study subjects were treated with the probiotics or cholesterol level of the subjects or type of probiotics or dosage issues or just probiotics lack cholesterol-lowering effects.
How probiotics lower blood cholesterol
There are several hypotheses on how probiotics lower cholesterol; all of them studied in vitro only. First suggested mechanism is probiotics release enzymes that breakdown bile acids; which are synthesized from cholesterol. The brokendown bile acids are eliminated, much easier than coupled bile acids, in feces. To maintain balance of bile acids level, the body uses its serum cholesterol to produce new batch of bile acids and make up for the bile acids amount lost in feces. Second suggested mechanism is probiotics reduce the absorption of cholesterol into the bloodstream by binding it in the small intestine. Third suggested mechanism is probiotics reduce cholesterol flowing to the bloodstream by using it up themselves for their own growth. Fourth suggested mechanism is probiotics reduce cholesterol flowing to the bloodstream by converting cholesterol in the intestine to a form (coprostanol) that is excreted in feces.
Probiotics are foreign microbes to human gut and don’t make permanent residence in the gut. They are excreted in feces. Therefore, to benefit from their cholesterol-lowering effects, in the long-term, one would have to consume them on daily basis.
Probiotics safety and potential side effects
Priobiotics generally cause no disease but in persons with compromised immune system, they could be infectious. Some strains have also been found to exhibit antibiotic resistance. And there are suggestions that this antibiotic resistance may be transferred to other microbes in the gut.
A safety analysis of probiotics, in children upto 18 year olds, evaluated in more than 70 studies, found no evidence of harmful effects.
There are ample indications that probiotics may lower blood cholesterol. Their mechanisms and dosage are still vague and are still under active investigation, as is itself the effect of probiotics on cholesterol lowering.
Dora I., A. Pereira, and Glenn R. Gibson. 2002. Effects of Consumption of Probiotics and Prebiotics on Serum Lipoid Levels in Humans. Critical Reviews in Biochemistry and Molecular Biology, 37(4): 259-281.
Kieran M. Tuohy, Francesca Fava and Roberto Viola. 2014. The way to a man's heart is through his gut microbiota’ – dietary pro- and prebiotics for the management of cardiovascular risk. Proceedings of the Nutrition Society, 73(02): 172 – 185.
Lay-Gaik Ooi and Min-Tze Liong. 2010. Cholesterol-lowering Effects of Probiotics and Prebiotics: A Review of in Vivo and in Vitro Findings. Int J Mol Scie, 11(6): 2499-2522.
M. Van den Nieuwboer, R.J. Brummer, F. Guarner, L. Morelli, M. Cabana, E. Claassen. 2015. Safety of probiotics and synbiotics in children under 18 years of ages. Beneficial Microbes, March 2015. In press.