Refrigerated raw sauerkraut, Korean kimchi, tempeh, kefir, and yogurt–these fermented foods all have something healthy in common. They harbor live active cultures of “good” bacterial strains that can keep the gut robust and strong. In fact, studies suggest these probiotic foods might do everything from boost mood to stimulate the immune system to fight cancer. Some benefits are exaggerated, so here’s a look at where the research stands. (Shopping tip: pasteurization kills “good” bacteria so unrefrigerated jars of sauerkraut on supermarket shelves aren’t probiotic-rich.)
Immune Booster: Yes.
Scientists estimate that over 100 trillion microbes reside in the large intestine of adults. Since the gut accounts for the largest part of your immune system, keeping the gut populated with a healthy balance of “good” bacteria will keep the immune system functioning optimally.
Weight loss aid: Looks promising.
It’s well documented that obese people have less microbial diversity in their guts than lean people. But a Washington University study goes one step further, making a strong case for including fermented foods as part of a weight loss strategy. These researchers took gut microbes from lean and obese twins and introduced them into the g.i. tracts of mice. The animals populated with lean bacteria stayed slim while mice taking in bacteria from obese people quickly gained weight, even though both groups ate the same amount of food.
Cancer Fighter: Maybe.
While studies show that “bad” bacteria in the gut can produce compounds that promote colon cancer, it’s not a slam-dunk conclusion that healthy doses of “good” bacteria will reverse the cancer process according to the American Institute for Cancer Research. More research is needed.
Mental Health Aid: Stay tuned.
Preliminary studies find that people taking oral probiotics, or doses of “good” bacteria, can reduce anxiety and improve mental outlook. In fact, Harvard scientists speculate that microbes in fermented foods, strains like lactobacillus and bifidobacteria, may influence many areas of brain health and even impact illnesses like depression.
*Shopping tip: pasteurization kills “good” bacteria so unrefrigerated jars of sauerkraut on supermarket shelve aren’t probiotic-rich.