Men who don't eat enough protein have poorer sperm and are more likely to have overweight children

Men who don't eat enough protein have poor sperm and are more likely to have children who will face a lifetime of obesity, research suggests.

Mice fed diets containing half the recommended amount of protein had lower quality sperm and seminal fluid – which carries swimmers.

Their offspring were fatter and had signs of type 2 diabetes when they were the human equivalent of 30 years old, the study found.

Researchers say this is because a dietary imbalance of protein affects the quality of DNA being passed down from the father to the child.

However, the Nottingham University team remain unsure as to how a lack of the nutrient, found in meat and lentils, can weaken sperm.

Mice fed diets containing half the recommended amount of protein, found in high quantities in meat, had poor quality sperm and seminal fluid – which carries swimmers (stock)

An array of studies have shown that sperm from men who are overweight, smoke or drink excessively are of poorer quality.

However, little trials have delved into the impact of such lifestyle factors on the long-term health of a father's children.

The new experiment shines light on that gap – by examining the offspring of mice when they were 30.

Researchers led by Dr Adam Watkins fed male mice a diet that was either made up of 18 per cent or nine per cent protein.

Guidelines in the UK and US urge adults to ensure around 20 per cent of their daily calorie intake is from protein.

Sperm samples were collected from the dead male mice, so scientists could analyse the difference between the two groups.

Rodents on the diet lacking a sufficient amount of protein produced poorer sperm, according to Dr Watkins.

Their sperm had fewer chemical tags on their DNA that regulate gene expression, compared to mice fed a normal diet.

Their seminal plasma – the fluid that carries sperm and provides them nutrients through their journey to fertilise an egg – was also of a poorer quality.

Researchers used the sperm collected from the dead male mice to impregnate female mice, who had all been given a normal diet.

Researchers say this is because a dietary imbalance of protein affects the quality of DNA being passed down from the father to the child through their sperm (stock image)

The health of their offspring was then analysed when they turned four months old - the equivalent of around 30 in humans.

They were fatter than their counterparts, according to the study published in the Proceedings of the National Academy of Sciences.

And they also showed signs of type 2 diabetes – a silent killer that can shave years off a sufferer's life - and had slower metabolisms.

The seminal plasma of the protein-lacking mice suppressed maternal uterine inflammation, deemed essential for a healthy pregnancy.

Dr Watkins said: 'It is well understood that what a mother eats during pregnancy can affect the development and health of her child.

'As such, there is a lot of information available to women who want to become pregnant about the importance of a healthy lifestyle and good dietary choices both for their own health and that of their child.

'Interestingly, little, if any, advice is available for the father.

'Our research using mice shows at the time of conception, the diet and well-being of the father influences the long-term growth and metabolic health of his offspring.

'Our study not only identifies what impact a poor paternal diet has on the health of his offspring but also starts to uncover how these effects are established.'

Professor Kevin Sinclair, involved in the study, said: 'It is important to recognise that sperm contribute more than just half of the genes that make up a child.

'During natural conception sperm deposited in the female reproductive tract are bathed in seminal plasma which can in itself influence pregnancy outcomes.

'Our study shows that the composition of seminal plasma can be altered by father's diet, and that this can also influence offspring wellbeing.'

HOW DO SPERM MOVE?

Sperm are vital in human reproduction and the motility of the male cells is crucial. 

In order to help the sperm cells move, they evolved a 'tail' which is called  a flagellum.

Sperms' tails play a critical role in their ability to swim and consequently fertilise an egg.

Sperm are vital in human reproduction and the motility of the male cells is crucial. Sperms' tails play a critical role in their ability to swim and consequently fertilise an egg

Sperm tails consist of around 1,000 building blocks, including structures known as tubulins, which form long tubes.

Attached to these tubes are moving molecules called motorproteins.

These pull and bend sperm tails, enabling them to swim. 

The movement of the tail is powered by a mitochondria, the powerhouse of a cell, which produces energy.