A plant-based diet helps to "feed" the "good bacteria" in our gut. [Photo: Getty]

People in their seventies may benefit from going vegan, an expert has said.

Professor John Mathers from Newcastle University claims swapping meat and dairy for a plant-based diet helps feed the good bacteria in our gut.

These bugs typically decline with age as the gut barrier becomes leakier, allowing substances from the digestive tract to enter the bloodstream.

This may trigger inflammation, which has been linked to everything from dementia and heart disease to cancer.

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Speaking at the House of Lords, the professor of nutrition said: A plant-based diet may be more healthy in old life.

It provides the carbohydrates for good bacteria to grow.

Fruits and vegetables are rich in indigestible ingredients called prebiotics.

These act as the fertiliser for the growth of bacteria in our digestive tract.

Prebiotics are different from probiotics, which specifically introduce new bugs into the gut, like some yoghurts.

Dr Marina Ezcurra, from the University of Kent, added: Bacteria in the gut are linked to age-related diseases, including neurodegenerative and cardiovascular conditions, and cancer.

As we get older, gut microbes are more likely to release molecules into the bloodstream, which affects our tissues.

A strong microbiome strengthens the gut barrier against leakage that leads to inflammation.

Prebiotics are said to be more powerful than probiotics for long term health.

They change the pattern of organisms in the gut, which continues for some time after a person has stopped consuming prebiotics, Professor Mathers said.

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Leaky gut syndrome is not officially recognised as a condition.

However, some claim the immune system reacts to substances that have escaped out of the porous bowel and into the bloodstream.

According to the NHS, certain conditions and drugs can make the intestine more permeable, however, there is little evidence it causes any significant, widespread problems.

For those considering going vegan,the health service adds they should be able to get most of the nutrients they need from a varied and balanced diet.

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Their diet should be made up of at least five portions of fruit and vegetables a day, as well as dairy alternatives, beans and lentils.

However, vitamin B12 is only found naturally in meat and dairy.

Vegans therefore rely on fortified cereals, drinks and yeast extract, like Marmite.

With veganism not being for everyone, Professor Mathers admits the benefits likely vary from person-to-person.

Diet advice is complex, he said.

We know little of the nutritional needs of old people aged 75 or over.

It depends on any conditions they have and the drugs they take, which lends to a more personalised approach.

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Whether you choose to go plant-based or not, adding more protein to your diet could keep you strong into old age.

The elderly struggle to build muscle so they need more protein to maintain muscle mass, Professor Mathers said.

Vegans can up their protein intake by adding lots of beans, lentils and other pulses to their diet.

Meat, fish and eggs are also rich sources.

While changing your diet in later life may seem overwhelming, the experts stress you cannot underestimate the benefits it could have.

Ageing is damage to the big molecules in our body, like DNA and lipids, Professor Mathers said.

Food influences the processes in cells and tissue that repair that damage.

Nutrition is fundamental.

And the effects could be almost immediate.

Diet changes the microbiome dramatically, Dr Ezcurra said.

If you alter your diet it influences the species in your gut in four days.

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Going vegan in your seventies could ward off disease - Yahoo News