Obesity and metabolic disease affect male fertility. However, little is known about how fat (lipids) from food in blood and other bodily fluids affect the motility of sperm. By examining samples of serum and semen from 60 men, researchers have shown that the lipid composition of blood is reflected in the lipid composition and thus the fitness of sperm. The results indicate that what you eat today can determine the quality of your sperm 3 months from now.
For women hoping to conceive, there is almost endless advice – cut caffeine and alcohol, exercise moderately, pop prenatal vitamins. But babymaking takes two, and “the male side is completely ignored,” says Albert Koulman, a biochemistry researcher at the University of Cambridge who studies metabolism in pregnancy and early life. According to Koulman, that’s missing half the equation.
Recent research suggests that diet could affect the motility of sperm, or the ability to “swim” effectively. A new study, published in October in the International Journal of Molecular Sciences, explores the idea that a man’s ability to regulate lipid molecules may determine the power behind his sperm.
Scientists think that changing the diet could be much easier and less invasive than existing interventions for male infertility. “A lot of money is going into fertility,” Koulman says. “There are cheaper options that are could be just as effective or more effective.”
What’s in sperm?
A team of researchers, including Koulman, set out to follow the path of how what we eat provides the building blocks for sperm. Could the composition of blood and seminal fluid, the liquid that carries sperm out of the reproductive tract, provide clues as to why some sperm swim with ease while others struggle?
First, a quick primer on how sperm are produced. When we digest food, components of carbohydrate, protein and lipids are distributed to the rest of the body through the bloodstream. These small molecules are used as both energy sources and building blocks to assemble new cellular machinery, including sperm. So the content of the blood that flows to the seminiferous tubes in the testes, where sperm get their start, determines what components are available to construct both sperm and seminal fluid.
“We still have a very basic understanding of what makes sperm work, or their composition,” says Claire Meek, another University of Cambridge researcher who studies metabolism in pregnancy and early life and was involved in the study. Awareness is growing that “lipids are almost certainly key regulators of sperm function and structure, but we know very little about what that really means”.
“When you think about it, sperm have loads of different jobs to do,” Meek explains. “They have remarkably diverse roles for one type of cell.”
As for structure, lipids make up the membrane surrounding the sperm – the membrane around the head has to be strong enough to keep the precious genetic payload from being damaged, while a rigid membrane around the tail could make propulsion easier.
And while historically it was thought that sperm could only draw energy from simple sugars such as glucose, recent research indicates that lipids are also a vital energy source. Of all the proteins a sperm cell can produce, about one quarter are thought to be devoted to breaking down lipids for fuel.
Lipids seem to play an important role in seminal fluid as well. After ejaculation, the sperm relies on the contents of the seminal fluid for energy to sustain it on its quest to fertilise an egg (a sperm cell just doesn’t have enough onboard storage capacity to carry all the fuel needed).
“An energy issue”
The researchers recruited 60 men who had been referred for an initial consultation for couples’ infertility and collected samples of their seminal fluid, sperm and blood serum (blood with all the cells removed). Or at least they tried to – one of the biggest hurdles for this study was the logistical challenge of asking volunteers to produce a semen sample at home and get it to the laboratory before an hour had passed.
While 60 men successfully gave blood serum and seminal fluid samples, only 26 made it to the laboratory quickly enough for their sperm to be analysed.
For these 26 men, the researchers analysed all three components – blood serum, seminal fluid and sperm cells – to see what kinds of lipids were present and in what proportion. They also classified each man’s sperm as high motility or low motility, which is inherently challenging.
“Part of the issue is that no one really has a very good definition of what is normal motility and not normal motility,” Meek says. For this study, they used criteria established by the World Health Organization.
Koulman and Meek agree the most striking result from the analysis was that men with more motile sperm had greater differences between the lipid composition of their blood serum, their seminal fluid and their sperm. In other words, their bodies were better able to control what went into the sperm and what went into the seminal fluid.
“You could argue that this is really an energy issue – it actually takes energy to maintain differences in concentration,” Meek says.
Koulman adds he has seen a similar phenomenon in breast-milk. “A mother’s poor nutritional status leads to a less specific lipid profile in the breast-milk,” meaning not having an optimal variety or proportion of lipids, he explains.
The researchers emphasise that this study was small and has limited generalisability to the whole population – they certainly cannot make any suggestions about what to eat and what to avoid to improve the quality of your sperm. Instead, the authors see it as a proof-of-concept study that should encourage future research.
As for the next steps, Koulman and Meek say that they are curious to see what including information about each person’s diet could reveal. But since sperm take about 3 months to mature, researchers would ideally need to take blood samples and gather information on diet months before collecting semen samples. In other words, what you eat today would theoretically determine the quality of your sperm 3 months from now.
The researchers reiterate that very fundamental aspects about male fertility – such as a normal baseline for sperm motility – have not been pinned down. In no small part, that is because “recruiting men is actually really difficult” for scientific studies versus women, Meek says. The current study was able to recruit participants from a pool of men who were already providing semen samples as part of fertility analysis, while “healthy men basically don’t volunteer”.
“It is quite hard to ask, ‘Can I have some sperm?’”, Meek admits. Add to that the challenge of getting a sample into the lab while it’s still fresh and “it’s quite a difficult scenario to get that from healthy men within the context of normal life”.