For decades, microbiologists and dietitians have advocated including fermented foods in a nutritious diet. Now, new research is helping scientists understand  how much fermented food should be consumed daily. This study is the first large-scale estimate of live microorganisms in the average U.S. diet.

“Ultimately, we want to understand if there should be a recommended daily intake of these microbes to keep us healthy, either through the foods or from probiotic supplements,” said Maria Marco, a professor in the food science and technology department at UC Davis (and a TFA Advisory Board member). “In order to do that, we need to first quantify the number of live microorganisms we consume today in our diets.”

The study, published in the Journal of Nutrition, was co-authored by ten scientists regarded as experts in the field of fermented foods and probiotics. They examined the number of live microbes in more than 9,000 foods eaten by 75,000 adults and children. 

From a UC Davis press release on the study: Around 20% of children and 26% of adults consumed foods with high levels of live microorganisms in their diet. Both children and adults increased their consumption of these foods over the 18-year study period.

“This trend is going in the right direction. Exposure to friendly microorganisms in our foods can be good for promoting a healthy immune system.” said Marco.

Foods for gut health

Study authors examined the National Health and Nutrition Examination Survey to create their estimate. This resource contains extensive information on the foods consumed daily by Americans. Food science and fermentation experts assigned each food an estimated range – high, medium, or low – of live microbes per gram.. Foods in the high category included yogurt, fermented pickles and kimchi. Fresh, uncooked fruits and vegetables were represented in the medium category.

The analysis was funded by a grant from the International Scientific Association for Probiotics and Prebiotics (ISAPP.) ISAAP notes that the microorganisms quantified in this study are not necessarily probiotics.

“By definition, a probiotic must be well-defined and have a demonstrated health benefit at a quantified dose. Live microbes associated with food as a category, however, do not generally meet the criteria of a probiotic,” said corresponding author Mary Ellen Sanders, executive science officer for the ISAPP.

The publication is part of a larger global effort to determine how live dietary microbes might contribute to health.

“There is no doubt that the microbes we eat affect our health. When we think of microbes in our food, we often think of either foodborne pathogens that cause disease or probiotics that provide a documented health benefit,” said co-author Colin Hill, a professor of microbial food safety with University College Cork, Ireland. “But it’s important to also explore dietary microbes that we consume in fermented and uncooked foods. It is very timely to estimate the daily intake of microbes by individuals in modern society as a first step towards a scientific evaluation of the importance of dietary microbes in human health and well-being.”

Other scientists co-authoring the paper were ISAPP board members Robert Hutkins (TFA Advisory Board Member), Dan Merenstein, Daniel J. Tancredi, Christopher J. Cifelli, Jaime Gahche, Joanne L. Slavin and Victor L. Fulgoni III.