Peanut allergies have been on the rise in Western countries the past couple of decades, and researchers are having trouble figuring out why. Now a new study has found a link between peanut allergies and gut bacteria, with a high-fiber diet reducing the incidence of peanut allergies, providing hope for those who have this potentially deadly food allergy.
The study comes from Jian Tan of Monash University in Melbourne, Australia, along with other researchers. The researchers published their study results in the June 21st issue of the journal Cell Reports. Although other researchers had noticed that those in Western countries eating a Western diet seemed to have much higher rates of peanut allergies than those in other countries with a more traditional diet, the reasons were not clear. Some speculated that peanut allergies were linked to a lack of microbes in a cleaner environment, called the hygiene hypothesis, some suspected a link to body fat, and some suspected a link to gut microbes since the rise in food allergies seemed to coincide with a rise in processed foods. The researchers in the current study decided to see if gut microbes did play a role in food allergies and if fiber could help reduce the severity of the allergies.
For their study, the researchers used a group of mice bred to have a peanut allergy. When the researchers fed a high-fiber diet to the peanut allergy mice, a healthy population of bacteria formed in their guts. When exposed to peanuts, these mice then had less of an anaphylactic reaction, which is a severe allergic reaction, than their counterparts who were fed a diet with average fiber, sugar, and calories. The researchers then fed fatty acid byproducts, the results of fiber being broken down, to other mice for three weeks prior to peanut exposure. This also reduced the incidence of an allergic reaction. Not only that, when the researchers gave mice with no gut microbes the gut bacteria of the fiber-fed mice, these mice also had less of a reaction to peanuts than the low-fiber mice.
In the mice and other animals, gut bacteria break down dietary fiber into short-chain fatty acids and other byproducts. The researchers showed that these fatty acids bind to certain receptors on T regulatory cells, which are immune cells that suppress an immune response. This means that when there are more byproducts of fiber, there will be less inflammation in the gut in response to allergens, such as peanuts, since the immune response is suppressed by the fatty acids. The high-fiber diet seems to increase food tolerance in mice with a peanut allergy.
The current study involved mice, but there is evidence the same would hold true in humans. Others have found that children living in rural Africa eat twice as much fiber as children in Europe, and they have different gut bacteria which produce more short-chain fatty acids, the same type of fatty acids that seem to reduce an immune response to peanuts in the mice. Tan and team say that more research would be needed before trying this method in humans, including figuring out exactly which form of fiber seem to be best at reducing the food allergies.
The researchers are also unsure if a mother can reduce her chance of a baby with peanut allergies by consuming more dietary fiber herself. Although babies cannot eat solid foods containing fiber, these short-chain fatty acids can be transferred through breastfeeding, so there is potential. More research would be needed to determine if mothers can reduce their child’s food allergies this way.
The study does provide hope that Western countries can reverse this trend toward more peanut allergies. Not only that, some are speculating whether those with peanut allergies can reduce their reactions by increasing fiber in their diets. In a different study, researchers gave children a type of bacteria that produces short-chain fatty acids while gradually introducing peanuts into their diets. At the end of the study, the researchers found that more than 80 percent of the children no longer had a bad reaction to peanuts.
Peanut allergies are among the most common food allergies, especially in children. Between 1997 and 2008, the number of children in the United States with a peanut allergy more than tripled. Some have a greater reaction to peanuts than others, ranging from mild irritation when eating a peanut to a severe allergic reaction, called anaphylaxis, even when exposed to trace amounts of peanut. Symptoms of anaphylaxis can include swollen lips or a skin rash; gastrointestinal upset like cramping, diarrhea, and vomiting; difficulty breathing; and reduced blood pressure with a weak pulse, paleness, confusion, and loss of consciousness. In the worst cases, peanut exposure can even cause death. Those with a peanut allergy must avoid peanuts, or foods and utensils that have come into contact with peanuts, and carry an epinephrine auto-injector such as an EpiPen which can help control their symptoms until they reach a hospital for medical help.