Cholesterol has been a double edged sword for human health. On one side it is an essential component of the basic building blocks of different tissues of the body while at the other its elevated levels in the blood can lead to severe heart complications. According to a recent prediction by the World Health Organization (WHO) heart ailment related diseases will be the major death cause in humans by 2030 affecting nearly 23.6 million individuals all over the world. Higher cholesterol levels have been shown to share significant linkage with 45% Western European heart attacks. Can probiotics with their multi-beneficial effects be tried out in the remedy of the diseased condition by reducing cholesterol levels? It has been seriously considered and in many cases the administration of the probiotic products resulted in significant improvements in the recipients.
Available Methods To Reduce Cholesterol:
It is established beyond doubt that hypercholesterolemia increases heart attack risks by three times as compared to normal cholesterol levels. The cardiovascular diseases have also been associated with food habits and diet intake which could lead to enhanced cholesterol deposition such as diet with high fat content or low vegetables and fruits. Therefore, various methods of reducing cholesterol level in the blood have now been tried. Some of the suggested ones include regulation of diet, exercises and use of drugs. There are therapeutic agents available that can maintain low cholesterol but they not without side effects. Besides, they are also quite expensive in nature and beyond the reach of a large section of the affected population. Therefore, people are always in the lookout for alternative methods to inhibit the problem.
The Usefulness of Probiotics in Lowering Cholesterol:
Lactobacillus and other probiotic strains with their ability to interfere with the host metabolic machinery for different constituents of the diet including fats and lipids have been recommended for lowering the blood cholesterol levels. The lactobacilli have in their repertoire factors that enable it to easily colonize the small intestine the site of enterohepatic cycle. e.g., L. plantarum has been quite robust to pass unharmed through the extreme conditions of the GI tract when administered orally and colonize itself in the intestine. The major concept behind the use of food products with beneficial health effects has been the oral intake of microorganisms. As such lactobacilli strains have been incorporated in fermented milks, baby foods and other therapeutic preparations. There are several available data from in vivo and in vitro studies to signify the importance of probiotics in reducing blood cholesterol. L. fermentum strains have been observed to colonize the small intestinal epithelia preferentially. Once administered orally they can adhere to the epithelial layer of the GI tract and inhibit the microflora that causes an increase in cholesterol levels by the release of certain active agents. Cholesterol acts as an important precursor for the synthesis of bile acids. This property can be exploited by the beneficial microbes to control cholesterol by the conversion of cholesterol into bile acids.
The BSH Theory in Cholesterol Regulation:
The Bile Salt Hydrolase (BSH) theory has been very recently adopted as one of the crucial underlying mechanisms of cholesterol lowering activity by the probiotics. The probiotic strains with elevated BSH activity (as shown in various in vivo studies with animals) have been applied successfully for the reduction of blood cholesterol.
However, the mechanism behind the association between the enhanced BSH synthesis by the various probiotic strains and the hypocholesterolemic effects has not been fully revealed. A number of available probiotic bacteria can yield high levels of BSH expression which needs to be further validated in terms of their application in hypercholesterolemia. It is also noteworthy to mention that the BSH activity should also be evaluated from the aspect of any side effects their high levels might cause to the host. Nonetheless, several studies have found improvements in cholesterol reduction by increased BSH activity. The work by Gilliland and his group demonstrated that there exists a high positive correlationship between the ability of the probiotics to assimilate cholesterol and their capacity to hydrolyze bile salts.
Therefore, the BSH activity of the probiotic bacteria can be used as a hallmark of their selection to be used in lowering cholesterol. This selection criterion becomes all the more prominent with the report that microorganisms that are not able to cause the deconjugation of bile salts do not possess any significant ability to reduce the cholesterol content of the culture medium.
Proposed Mechanisms of Cholesterol Removal:
A number of mechanisms have been put forth in support of the cholesterol removing act of the probiotics. The most common mechanism involves the hydrolysis of bile salts by the different probiotic strains. Bile is an important cholesterol end product that remains stored in the liver. When the salts of bile acids are broken down, their solubility is reduced and in turn leads to intestinal absorption and fecal elimination. Under such conditions more of the blood cholesterol is consumed in the synthesis of newer bile acids thereby reducing cholesterol.
The reduction in the levels of cholesterol by the probiotics has partly been credited to their cholesterol binding ability within the gastrointestinal tract. The report by Usman et al. suggested that L. gasseri strains have been able to reduce cholesterol from the culture medium through the above mentioned capability. The group also demonstrated that the potential of the probiotics to bind cholesterol and thereby sequester it was in large dependent on the specific strains and their growth profiles. In a similar study Kimoto et al. found that live probiotic cells could remove cholesterol from the media more as compared to the heat inactivated dead cells. What was remarkable though was the cholesterol sequestering ability of the dead cells. This goes on to suggest that some receptors present on the surface of these cells might provide for such cholesterol binding affinity. Cholesterol has also been reportedly removed by some probiotic strains via cellular compartmentalization during growth.
Hence, there are enough positive indications for the use of probiotics and related food products for their application in maintaining low blood cholesterol levels that can have potential bigger implications to restrict heart diseases.