Eating a “diverse and varied” diet provides the best chance of boosting the immune system to fight Covid-19, according to a scientist.

Philip Calder, a professor of nutritional immunology at the University of Southampton, has produced a report advising the public to ensure they eat a mixed diet to help combat the virus.

His research also shows that supplements are a “safe, effective and low cost way to support an optimal immune system”.

A university spokesman said: “A diet with a diverse and varied mixture of vegetables, fruits, nuts, seeds and pulses, along with some meat, fish and dairy products provides the vitamins, minerals and other nutrients the immune system needs for optimal function.”

Meat is important as a good source of nutrients such as iron and vitamin B12, so people who do not eat meat should consider supplements.

Prof Calder said: “The strength of somebody’s immune systems will not influence whether they get coronavirus; handwashing and social distancing are the best ways to avoid that.

“However, the immune system helps the body deal with the virus if they are infected and what we want is a system that functions properly when it’s challenged with bacteria and viruses.”

The university spokesman added: “Among the foods Professor Calder recommends are a variety of fruits and vegetables which are a good source of vitamins and minerals that are important for supporting the immune system.

“Foods that are high in fibre are also important as some of the undigested fibre in the gut can promote the growth of good bacteria which interact with the immune system to make it work better.

“The third recommendation is oily fish which is a source of omega 3 fatty acids that help to regulate and control the immune system.

“Finally, meat is important as a good source of nutrients such as iron and vitamin B12, so people who do not eat meat should consider supplements.

“Whilst consuming commercial probiotic products can have a role to play – by seeding good bacteria in the gut – Professor Calder recommends plant-based food and fibre as an alternative as these provide an environment to grow the good bacteria that are already in the large intestine.”

Professor Calder added: “The present situation with Covid-19 shows that we cannot just rely on vaccinations to limit the impact of respiratory infections.

“Improving our nutrition is a very straightforward step that we can all take to help our bodies deal with infections and limit the emergence of new, more virulent strains of viruses.

“We therefore strongly encourage public health officials to make sure nutritional strategies are included in all their messaging about coping with viral infections.”