Posts Tagged: microbes

Should there be more microbes on your plate?

Should there be a recommended daily intake of friendly microbes, often found in foods such as kimchi and yogurt? For the first time, scientists have measured the amount of friendly microbes in the food Americans eat. Photo by Leah Mytchyk on Unsplash

Scientists make the first large-scale estimate of live microorganisms consumed in the U.S. diet

Our diets provide us with the building blocks we need to stay healthy and fight disease. The nutrients in foods and beverages can be tallied up to know if we are getting what our bodies need. Yet what if a nutrient has been overlooked? For instance, friendly microbes in raw and fermented foods have not been measured as part of our diets — until now.

“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. “In order to do that, we need to first quantify the number of live microorganisms we consume today in our diets.”

Marco co-authored a new study with a group of scientists that examined the number of living microbes per gram of more than 9,000 different foods consumed by nearly 75,000 adults and children. It found that 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. The study, published in the Journal of Nutrition, is the first large-scale estimate of how many live microbes are consumed by Americans every day.

“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 the estimate. The health and dietary database contains extensive information on the foods consumed by Americans daily. Food science and fermentation experts assigned each food an estimated range of live microbes per gram, creating categories of foods with low, medium and high levels of live microbes. Foods in the high category included fermented dairy foods such as yogurt, fermented pickles and kimchi. Fresh, uncooked fruits and vegetables were also good sources of live microorganisms, represented in the medium category.

The analysis was funded by a grant from the International Scientific Association for Probiotics and Prebiotics, or ISAPP. 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, Dan Merenstein, Daniel J. Tancredi, Christopher J. Cifelli, Jaime Gahche, Joanne L. Slavin and Victor L. Fulgoni III.

Editor's note: Maria Marco is affiliated with UC Agriculture and Natural Resources as an Agricultural Experiment Station faculty member.

Changes in breast milk sugars impact babies’ health and growth

When it comes to nursing moms and their babies, an elegant web of cause and effect connects climate, breast milk, gut microbes and infant health.

That web was clearly illustrated by a recently published study involving 33 women and their babies in the West African nation of The Gambia. The research team, including scientists from UC Davis and UC Agriculture and Natural Resources, found that complex breast milk sugars called oligosaccharides helped protect nursing babies from illness and also influenced the mixture of microbes in the infants' guts.

The researchers also showed that changes in food availability from season to season could affect the composition of the women's breast milk and the protective quality of the babies' gut microbiota. And those changes, in turn, impacted the health and growth of the breastfed infants.

UC research in The Gambia has revealed microbial changes in breast milk characteristics during the country's two distinct seasons - when food supplies differ significantly. (Photo: Wikimedia Commons)

Composition of breast-milk sugars and infant health

Oligosaccharides occur abundantly as more than 200 different chemical structures in human breast milk. It's been known for some time that these complex sugars contribute to infant health by supporting the growth of beneficial bacteria in the baby's gut. And these gut bacteria have been shown to play a key role in fending off infectious illnesses.

But little has been known about how changes in the composition of the breast milk sugars might affect the health and growth of infants, especially those living in areas where infection rates are high.

To explore that relationship, the researchers monitored the composition of the oligosaccharides in the mothers' milk and examined the infants' gut microbiota at 4 weeks, 16 weeks and 20 weeks after the babies were born. Then they analyzed the data, looking for possible relationships to the health and growth of the babies and the status of their gut microbes.

They found that two of the oligosaccharides, lacto-N-fucopentaose and 3′-sialyllactose, had a direct relationship to the babies' health and growth. High levels of the former were associated with a decrease in infant illness and with improved growth, measured as height for age, while the latter proved to be a good indicator of infant growth, measured by weight per age.

“Our findings provide evidence that specific human milk oligosaccharides can alter the composition of breast milk, making it more protective against infection and allowing the infant to invest energy in growth rather than fending off disease,” said the study's corresponding author Angela Zivkovic, an assistant professor of nutrition at UC Davis.

Influence of wet and dry seasons

The researchers also were curious how seasonal shifts in food availability, which significantly impact the mothers' diets, might be reflected in breast milk composition and infant health.

The Gambia has two distinct seasons, the wet season from July to October and the dry season from November to June.

The wet season is also known as the “hungry” season because it is the time of year when food supplies tend to be depleted, infection rates rise and the farming workload is highest. In contrast, the dry, or “harvest,” season is characterized by plentiful food supplies as well as significantly higher energy stores and less illness among the local people.

The researchers found that mothers who were nursing during the wet or “hungry” season produced significantly less oligosaccharide in their milk than did those nursing during the dry season.

In examining the makeup of the babies' gut microbiota, the researchers noted that most of the bacteria belonged to the Bifidobacteria genus. They also discovered that higher levels of Dialister and Prevotella bacteria were accompanied by lower levels of infection.

In addition, higher levels of Bacteroides bacteria were present in the infants' guts that had abnormal “calprotectin” – a biomarker associated with intestinal infections.

“We are very interested in which specific dietary factors influence the oligosaccharide composition of mother's milk,” Zivkovic said. “If we can find the mechanisms that change the composition of breast milk sugars, we may have a new approach for modifying the infant microbiota and ultimately influencing the health and vigor of the nursing baby.”

The study by Zivkovic and colleagues appears online in the journal Scientific Reports. The research is part of a long-running, cross-disciplinary project at UC Davis examining milk and its role in nutrition.

Funding for the study was provided by the National Institutes of Health, UK Medical Research Council, Bill and Melinda Gates Foundation, Alfred P. Sloan Foundation, and Peter J. Shields Endowed Chair in Dairy Food Science at UC Davis.

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