Probiotics have been studied as a means of improving serum lipid patterns. If effective, probiotics could be a tool for dietary modification to promote heart health. It turns out that the gut, and the microbes it contains, plays an important role in the level of circulating lipids. Bile salts, which are released into the small intestine to help digest dietary lipids, are made by the liver from cholesterol and are enzymatically transformed by gut microbiota. These transformed bile acids, which are more likely to be excreted, must be replenished. To do so, the body utilizes available cholesterol, thereby decreasing the cholesterol pool. The gut microbes, therefore, can impact the circulating level of cholesterol.
Currently, adding probiotics to your diet has not made the list of ‘go to’ recommendations for heart health (for example, see here, here, and here). Fair enough, as evidence on the role of probiotics to improve serum lipids is emerging, but let’s look at the evidence – it might be time for probiotics to be included in these recommendations.
The systematic review and meta-analysis process can provide a ‘one-stop shop’ for evidence on any given research topic. Done correctly, this approach is an unbiased method to consider evidence in totality. A 2015 meta-analysis reviewed randomized controlled trials on probiotics and serum lipids. Thirty studies (on 1624 participants) were included in the analysis. These studies tested strains of Lactobacillus acidophilus, Bifidobacterium lactis, Lactobacillus plantarum, Lactobacillus helveticus, or Enterococcus faecium. The review found that probiotics reduced total cholesterol by an average of 7.8 mg/dL and LDL cholesterol by 7.3 mg/dL. This is a modest reduction of a few percentage points. Probiotics were not found to impact HDL cholesterol or triglycerides. The review noted that effects were stronger for subjects with higher baseline cholesterol levels and for longer treatment duration (12 weeks was the longest study tested). Some strains appeared to be more effective than others.
Another meta-analysis conducted in 2017 looked only at studies conducted with Lactobacillus probiotics. Fifteen randomized, controlled trials, with 976 subjects were included overall. Unfortunately, this meta-analysis included 2 studies that tested ‘Lactobacillus sporogenes’, which is NOT a Lactobacillus, but is likely a Bacillus species; these 2 studies should have been excluded from analysis. Overall reductions in total cholesterol and LDL, but no effect on HDL or triglycerides, were observed. Data grouped according to probiotic species showed that L. plantarum showed significant reduction of TC and LDL cholesterol, and L. reuteri reduced LDL cholesterol.
Since these reviews were published, a few additional trials have emerged. Costabile et al. (2017) selected L. plantarum ECGC 13110402 from among 353 other Lactobacillus strains based on characteristics thought to be of value in reducing total cholesterol, especially a high bile salt hydrolase activity. This randomized, placebo-controlled study included only 46 subjects and treatment duration was 12 weeks. Regarding serum lipid results (many other measures were also performed), the probiotic modestly (4.5% for all subjects and 7.4% for normal cholesterol subset) increased HDL (‘healthy’ cholesterol) compared to placebo. LDL levels dropped in the normal cholesterol group compared to placebo.
In another study, administering B. lactis BB-12 (3.1x10e9/d) did not change any serum lipid parameters over a 4-week intervention period (Lee et al. 2017).
Taken together, the evidence suggests that some probiotics may modestly improve serum lipid profiles. Additional studies are needed to clarify which probiotic strains and doses are most effective and which populations would most benefit and to what extent. In addition, studies to identify mechanisms of this effect are needed. Some probiotic strains deconjugate bile salts, which may result in lower serum cholesterol levels. But this may be an oversimplification, as this 2015 review cautions. Considering the excellent safety record of Lactobacillus probiotics, it seems that dietary approaches to managing serum lipids should include probiotics.
Probiotics may contribute to cardio health through antihypertensive effects. One mechanism: antihypertensive peptides produced during fermentation of milk.