The vast numbers of bacteria living in our large intestine make up a rich ecosystem known as the gut microbiome. The gut microbiome is being intensively researched at the moment for potential effects on our health: conditions as diverse as kidney disease, obesity, sleep disorders and mental disorders are linked to specific changes in the bacteria in our gut (1-5). For example, a certain gut microbiome pattern is seen in people who suffer from obesity, and this could mean that obese people get more energy from the diet than people with a normal body weight, contributing to obesity (6, 7).
NUTRI-FACTS covered the basics of the gut microbiome in a recent Topic of the Month. An important concept in how we can use the gut microbiome to improve health is changing the relative numbers of different types of bacteria. One way to do this is with probiotics, otherwise known as “good bacteria.” Consuming products containing good bacteria such as probiotic yogurt means that the gut microbiome contains more of the bacteria that have been consumed (8). A second way, the prebiotic approach, is to make changes to the diet to encourage or discourage the growth of certain bacteria. This approach works because our diet forms the diet of our gut bacteria as well. Bacteria can be quite picky about their food preferences, and will grow well or poorly depending on the food that that they get from us. For example, the addition of a dietary fiber to the diet can lead to changes in the abundance of certain bacteria, and an improvement in bowel health (9).
A new concept in gut microbiome research is the broadening of what we classify as prebiotics (10). In the past, prebiotics had to be consumed by gut bacteria to be considered a prebiotic. However, we know that other components of the diet are not necessarily used as food by bacteria, yet they may still be able to change the composition of the gut microbiome.
An example of this is resveratrol, which is found in red wine, berries and peanuts. In nature, resveratrol helps leaves and grape vines ward off attacks from molds (11). A study performed in test tubes showed that resveratrol can slow the growth of certain “bad bacteria” including Escherichia coli and Enterococcus faecalis, while “good bacteria” such as Lactobaccillus are stimulated. Resveratrol has therefore attracted attention for its role in changing the composition of the gut microbiome.
There are three potential ways resveratrol can affect the gut microbiome: it can make changes to the actual bacteria in the gut, it can modify what the bacteria produce, and it can affect how the cells lining the gut work, as described in a recent review article (12).
Several researchers have been able to show that resveratrol may change the gut microbiome of the obese so that it resembles that of someone of a normal body weight. For example, mice fed a high fat and sugar diet develop obesity, and their gut microbiome changes in the same way that humans do: the proportion of Bacterioides bacteria increases and the proportion of Firmicutes bacteria decreases. In mice fed resveratrol, the obesity-related changes in the gut microbiome were reversed, and the gut microbiome resembled that of a normal-weight mouse despite a diet that promoted obesity (13).
A second interesting study gives evidence that resveratrol can affect concentrations of certain compounds produced by the gut microbiome. It showed that resveratrol could change the amount of a cardiovascular risk factor produced in the gut, and this lead to less plaque build-up in the arteries of mice (14).
Thirdly, resveratrol can affect how the cells lining the large intestine function, which affects the gut microbiome. This could be important for leaky gut syndrome (15). For example, resveratrol helped protect intestinal cells after they were damaged by a food toxin, and prevented bad bacteria from entering them (16). A related study found that resveratrol could boost production of proteins in intestinal cells that help prevent leakage of nutrients between cells, and this was related to changes in the gut microbiome (17).
Altogether, these studies show the potential for resveratrol to have beneficial effects on human health by modifying the gut environment. It can change the relative numbers of different bacteria in the gut. It affects the compounds that the gut microbiome makes, and it helps the large intestine to function properly. Research, still in its early days, shows promise for further effects of resveratrol on the gut microbiome.