Foods with similar nutrition labels can have very different effects on gut microbiomes, research finds.

A recent study, the results of which feature in the journal Cell Host & Microbe, looked at participants' diets and stool samples over the course of 17 days to examine the discrepancies between how different foods influence the gut microbiome, even when they seem to be nutritionally similar.

A healthy human gut microbiome includes a wide variety of diverse bacteria, and the scientific community has been interested to see how the gut microbiome relates to both health and disease. For this study, the researchers recruited a total of 34 participants whom they instructed to record everything that they ate for 17 days. The team collected stool samples daily.

To discover how each participant's microbiome changed every day in response to the food that they ate, researchers performed shotgun metagenomic sequencing on the stool samples. Doing this also allowed them to note the effects of microbiome changes on enzymes and metabolic functions.

How nutrients can alter the gut microbiome

Before the research began, the study authors believed that they would be able not only to identify links between certain dietary nutrients and specific strains of microbes but also to determine why microbiomes differ among individuals. However, they found instead that foods that shared a comparable nutritional profile did not necessarily have a similar effect on the microbiome.

Senior author Dan Knights, who works in the Department of Computer Science and Engineering and the BioTechnology Institute at the University of Minnesota in Minneapolis, notes that these findings presented a different challenge. "We had to scratch our heads and come up with a new approach for measuring and comparing the different foods," he explains.

The researchers then developed a structured hierarchy of foods, which allowed them to identify closely related foods across which they could share statistical data.

They found that related foods, for example, the leafy greens spinach and kale, had a comparable effect on the microbiome, while foods that were not closely related but had very similar nutritional profiles differed in their effects.

Nutrition labels at a glance

Manufacturers pack a lot of information into a nutrition label, and it can help people choose what to eat and what to avoid. For example, every nutrition label in the United States notes what constitutes a serving size, and following that, what each serving size contains.

The calorie content usually sits near the top of the label, and total fat, cholesterol, and sodium are next on the list. Nutrition labels also note the number of carbohydrates, including dietary fiber and sugar, and how many grams of protein each serving provides. Additionally, nutrition labels indicate which vitamins and minerals, such as vitamins A and C, calcium, and iron, the food contains.

What this study uncovered is that while certain foods may have comparable amounts of vitamin A, carbs, or protein, they do not necessarily result in a similar gut microbiome.

The gut microbiome and overall health

Future research may help pinpoint ways to actively change someone's gut microbiome to bring about a positive health shift, but as this group of researchers found out, it is not simply a matter of matching a food's nutritional profile.

"The microbiome has been linked to a broad range of human conditions, including metabolic disorders, autoimmune diseases, and infections, so there is strong motivation to manipulate the microbiome with diet as a way to influence health," says Knights.

"This study suggests that it's more complicated than just looking at dietary components like fiber and sugar. Much more research is needed before we can understand how the full range of nutrients in food affects how the microbiome responds to what we eat."

—Dan Knights