Study finds a high-fibre diet can improve immune response to vaccines

A study by the Malaghan Institute's Translational Immunology team has found that a high fibre diet can improve the immune response to the first dose of a vaccine.

Published in Frontiers in Immunology, the finding has implications for how we might tailor our diets to stimulate the best protective effect from novel vaccines.

The study, funded by High Value Nutrition Ko Ngā Kai Whai Painga National Science Challenge, investigated immune responses to the influenza vaccine. Participants were asked to report on their diets, with samples of their gut microbiome tested to understand which types of bacteria were prevalent prior to vaccination. After being given the influenza vaccine, participants’ blood was then analysed to assess the resulting antibodies they produced and determine how responsive their immune system was to the vaccine.

“Initially, our goal was to see if there were any specific types of bacteria that could predict the immune response to the vaccine,” says the Malaghan Institute’s Dr Alissa Cait. “Interestingly, we found that for participants who were receiving their influenza vaccine for the first time, those who had the best immune responses had a prevalence of fibre-specific bacteria in their gut.”

Our bodies need gut bacteria to fully digest our food, and our gut microbiome is often a reflection of our diet. A large amount of fibre-specific bacteria indicates those participants ate a diet high in fibre.

“These results suggest that those who consume a diet rich in fibre from foods such as fruits, vegetables and grains seem to produce a better immune response to the first dose of a vaccine due to specific colonies of bacteria that are cultivated in their guts,” says Dr Cait.

As well as helping us digest our food, the by-products of these bacteria fermenting fibre are molecules called short-chain fatty acids. It’s these molecules, not the fibre on its own, that have been shown to influence our immune response.

“Our bodies actively transport short chain fatty acids from our gut to our blood system where they circulate around the body,” says Dr Cait. “Our previous research has shown that these molecules appear to have a balancing effect on our immune system – dampening allergic and autoimmune responses while stimulating immune responses towards invasive organisms like viruses or bacteria – and vaccines.”

The results from the study indicate that diet is most influential when a person is receiving the first ever dose of a vaccine. For subsequent vaccinations for the same disease (like the seasonal flu jab), factors such as the immune memory seem to have a greater impact on the resulting immune response.

For people receiving their first dose of the COVID-19 vaccination, Dr Cait suggests that slight alterations to diet to include more fibre may have additional protective benefit.

“These results suggest that we can develop strategies to improve the protection we get from vaccines simply by eating a more balanced diet.” says Dr Cait. “It’s the age-old advice, eat a balanced diet and reap a multitude of health benefits. Now we can potentially add improved vaccine protection to this long list.”

As part of Vaccine Alliance Aotearoa New Zealand’s Ka Mātau, Ka Ora clinical study into COVID-19 vaccine immune responses in New Zealanders, Dr Cait and her team are now investigating if the amount of dietary fibre participants consume is having an effect on the number of antibodies participants produce after receiving the Pfizer-BioNTech vaccine. They hope this will provide more insight into how we can practically optimise our diets to achieve more protection from vaccines developed in the future.