(Reuters Health) - Men with infertility may have better-quality sperm when they take certain nutritional supplements and medicines, but there’s little evidence about whether that leads to pregnancies and births, a research review concludes.

Approximately one in eight couples fail to conceive after one year of trying and seek medical treatment for infertility, researchers note in European Urology. Although male infertility is the cause roughly half the time, research to date hasn’t provided a clear picture of which drugs and supplements may be able to improve sperm quality and quantity.

For the current analysis, researchers examined data from 61 experiments that tested the effectiveness of a wide range of drugs and supplements for improving semen parameters and the odds of a live birth.

They looked for improvements in three things that can make conception more likely: sperm concentration, or the amount of sperm released when men ejaculate; sperm morphology, or the number of sperm in the ideal size and shape with an oval head and a long tail; and motility, or the ability of sperm to move through the female reproductive tract to reach an egg.

“This systematic review has identified several medical and nutritional treatments options that appear to improve semen parameters,” said senior study author Dr. Muhammad Imran Omar of the University of Aberdeen in the UK.

“In spite of this, there are limited data suggesting pregnancy and live birth rates are increased,” Omar said by email.

Only four of the studies in the analysis reported birth rates, and there were too few births across all of the studies to assess what interventions might work best, the study authors note.

Roughly half of the studies looked at pregnancy rates, but here too, the total number of pregnancies was too low to draw firm conclusions about whether or how specific drugs or supplements might help.

Coenzyme Q10, a nutritional supplement that acts as an antioxidant and is commonly taken for a variety of heart conditions, was tied to gains in sperm count, motility and shape in three of four studies lasting three to six months. But the quality of the evidence was deemed “low,” researchers point out.

Six studies examined nutritional supplements with L-carnitine, an amino acid that can help the body burn fat for energy. Sperm count and motility appeared to improve with L-carnitine, but not the size and shape of sperm. These results were also rated “very low certainty.”

Follicle-stimulating hormone (FSH) used by men, a prescription drug that can stimulate the production of sperm in men and eggs in women, was tied to higher pregnancy rates in five studies, but the evidence was also of low certainty. FSH also appeared to improve sperm count and shape but not motility, again, with very low certainty.

Tamoxifen, a cancer drug that is also prescribed to improve sperm quality, was tied to better sperm count, motility and shape but not to improved pregnancy rates. This evidence was “low” or “very low” quality.

Pentoxifylline, a drug typically prescribed to improve blood flow in people with artery disease, appeared to improve sperm count, motility and shape in three studies lasting three to six months. But researchers considered the evidence low-certainty.

Kallikrein, an enzyme that improves blood flow, didn’t look like it improved pregnancy rates but it was tied to improved sperm count and motility.

Wide variation in the size, duration and design of the smaller studies in the analysis make it hard to draw firm conclusions about which drugs or supplements might be best for men to take when they have infertility, the researchers conclude.

“Most of the studies have only investigated changes to sperm quality and not whether men who are given these interventions are more likely to get their partner pregnant,” said Dr. Allan Pacey, an andrology researcher at the University of Sheffield in the UK, who wasn’t involved in the study.

“It is a logical assumption that if sperm quality is improved that more babies will follow,” Pacey said by email. “But it is just that: an assumption.”

SOURCE: bit.ly/2ttyxMx European Urology, online January 9, 2019.