Brenda and I have talked at length, here on the blog and also in our books, about the importance of gut bacterial balance to weight management. Having the wrong microbes in your gut predisposes you to weight gain, the topic of our last book, The Skinny Gut Diet. Following this line of thinking, researchers have tested the effects of pre- and probiotics on a range of metabolic abnormalities in humans. A recent systematic review and meta-analysis published in the journal Clinical Nutrition found that prebiotics and synbiotics (prebiotics plus probiotics) had a beneficial effect on a range of metabolic abnormalities in overweight or obese adults.1
Remember that prebiotics are compounds—usually soluble fibers—that act as food for the beneficial gut bacteria. They help to increase the levels or activity of the beneficial bacteria in the gut.
The analysis included 513 overweight or obese adult participants from thirteen different clinical trials. Nine of the trials administered prebiotics, and four of the trials administered synbiotics. The prebiotics were mostly inulin-type fibers at doses ranging from 5.5 to 21 grams per day, while the synbiotics were composed of a maximum of 2.5 grams of the prebiotic FOS (fructooligosaccharide) along with 270 million to 5 billion cultures of Bifidobacterium, and/or Lactobacillus, and/or Streptococcus probiotic bacteria daily.
Prebiotic supplementation was found to reduce total cholesterol and LDL-cholesterol (“bad” cholesterol) concentrations, while also reducing triglycerides and increasing HDL-cholesterol (“good” cholesterol) in participants with diabetes. Synbiotic supplementation was found to reduce fasting insulin and triglyceride levels.
“The supplementation of prebiotics or synbiotics could take part in the management of obesity-related comorbidities, such as dyslipidemia and insulin resistance.”
Some of the studies reported abdominal symptoms such as bloating, pain, and nausea, but they also noted improvement of symptoms during the supplementation and no withdrawal of participants from the studies, which the researchers believe is due to an adaptation period. Some people have difficulty tolerating inulin-derived prebiotics (including FOS), which are fermented in the digestive tract to a high degree and can trigger symptoms.
The authors of the review did not look at the effects of taking probiotics alone for some reason. Previous studies administering fermented milk and yogurt containing probiotics have found beneficial effects on cholesterol levels.2 Another study found that a high-dose, multistrain probiotic reduced total cholesterol, triglycerides, and LDL-cholesterol, as well as increased HDL-cholesterol in overweight adults.3 More studies are needed to determine the effects of probiotics alone on metabolic abnormalities in overweight and obese adults.
The really good news is whether you take prebiotics, synbiotics, or just probiotics, they all seem to have a significant benefit on mitigating metabolic syndrome (high cholesterol, LDL, triglycerides, insulin, blood sugar, and blood pressure, and low HDL, along with increased waist size). Metabolic syndrome is now the world’s greatest health challenge.
Since fiber is critical, it would be wise to eat an 80%+ plant-based diet or at least take prebiotics in addition to probiotics. As we have stated many times: Taking beneficial bacteria plus prebiotic fibers leads to major benefits in immune balance by modulating inflammation. In other words, you will have appropriate inflammation if attacked by an infection, but not the inflammation that is the foundation of metabolic syndrome, autoimmunity, allergies and most all disease conditions.
Start out slow with these products and increase gradually. If there is too much gas, bloating, or abdominal discomfort, stop for a few days and start back on a lower dose. You wouldn’t think of doing a marathon without training, likewise it may take time and persistence to retrain your intestinal response to good bacteria and fiber. Those on an 80 percent or more plant-based diet usually adapt quicker since they are already eating plenty of fiber, the foods preferred by beneficial bacteria.
- Beserra BTS, Fernandes R, do Rosario VA, et al., “A systematic review and meta-analysis of the prebiotics and synbiotics effects on glycaemia, insulin concentrations and lipid parameters in adult patients with overweight or obesity.” Clin Nutr. 2014; online ahead of print.
- Pereira DI and Gibson GR, “Effects of consumption of probiotics and prebiotics on serum lipid levels in humans.” Crit Rev Biochem Mol Biol. 2002;37(4):259-81.
- Rajkumar H, Mahmood N, Kumar M, et al., “Effect of probiotic (VSL#3) and omega-3 on lipid profile, insulin sensitivity, inflammatory markers, and gut colonization in overweight adults: a randomized, controlled trial.” Mediators Inflamm. 2014;2014:348959.