Does Homocysteine Impact Reproductive Health for Men and Women?
Homocysteine is a naturally occurring amino acid by-product in the body, which can influence fertility and reproductive health in both men and women. While homocysteine is mostly known for its link to heart and overall health, higher levels have been shown to affect fertility. Research suggests it may affect sperm quality, ovulation, egg quality, embryo development, and pregnancy health. These findings suggest possible links, but they do not prove that homocysteine directly causes reproductive problems. The evidence is still mixed.
What is homocysteine?
Homocysteine is made when the body breaks down methionine, an essential amino acid obtained from high protein foods like meat, fish, eggs, and certain plant-based options. The body usually keeps homocysteine levels low with the help of B vitamins, especially vitamin B6, vitamin B12, and folate. This process is called methylation. Unlike some other amino acids, homocysteine is not used to build proteins. A normal blood homocysteine level is usually below 15 µmol/L but can vary between populations and individuals.
What can cause high homocysteine levels?
Several factors can contribute to elevated homocysteine:
- Low intake of B vitamins, especially B6, B12 and folate, which are needed for homocysteine metabolism
- Genetic factors, including certain MTHFR gene variants that may reduce the efficiency of homocysteine breakdown
- Medical conditions, including cardiovascular and kidney disease
- Certain medications are potential contributors
- Thyroid-related factors can affect this level
- Age and sex where elevated homocysteine appears to be more common among men and may increase substantially in older age groups
HOMOCYSTEINE AND REPRODUCTIVE HEALTH
Reproductive health is closely connected to overall health. Elevated homocysteine has been associated with systemic effects, including damage to blood vessels and increased oxidative stress. These mechanisms may also have implications for reproductive tissues and cells. Research suggests relationships between healthier, lower homocysteine levels and better embryo quality, greater chances of conception and healthier pregnancy outcomes, although research findings on individual reproductive outcomes have not been consistent.
Homocysteine and sperm quality
Male reproductive health is important to focus on in relation to homocysteine levels, because men may be more likely than women to have elevated homocysteine levels. Research suggests that healthier homocysteine levels in both blood and seminal fluid may be associated with better sperm parameters, including sperm count, sperm motility or movement, and sperm morphology or shape and structure.
Elevated homocysteine may contribute to lower sperm health and DNA integrity through oxidative stress, which has been linked to sperm DNA damage. Although sperm DNA quality is not measured as part of every standard semen analysis, the parameters that are measured and impacted by high homocysteine levels determine whether there will be difficulty in conceiving. The DNA damage that it may cause is also important, as sperm contributes half of the genetic material required to form an embryo and can potentially influence reproductive health.
Homocysteine and ovulation
For women, there is a possible association between homocysteine levels and regular ovulation. Research involving healthy women has shown that those with healthier homocysteine levels around the time of ovulation were more likely to ovulate regularly than those with elevated levels. This suggests that homocysteine may be associated with the hormonal and metabolic processes involved in releasing an egg. This association is made with caution, as there are many factors that contribute to regular ovulation.
Homocysteine and egg quality
Some studies have shown the possibility that elevated homocysteine can potentially affect egg quality through increased oxidative damage, much like what happens with sperm DNA. Additionally, studies have examined homocysteine levels in both the blood and follicular fluid which is the fluid surrounding developing eggs within ovarian follicles. Lower or healthier levels have been associated with better egg quality.
Homocysteine and embryo quality
Since quality and chromosomal integrity of both egg and sperm affect embryo development, homocysteine may indirectly impact embryo quality and reproductive outcomes, along with many of the other factors that influence this.
Homocysteine and pregnancy health
Maternal homocysteine levels after conception also play a significant role in pregnancy health. One large Canadian birth-cohort study found an association between increasing maternal homocysteine levels and pregnancy complications; with an increase of 5 µmol/L seen as significant. However, this is presented as an association rather than proof that homocysteine alone causes pregnancy complications. Pregnancy health is influenced by many genetic, medical, environmental and lifestyle factors.
WHAT CAN BE DONE TO SUPPORT HEALTHY HOMOCYSTEINE LEVELS?
There are several approaches for people concerned about elevated homocysteine, particularly those planning a pregnancy.
Ensure adequate B vitamins
Because vitamin B6, vitamin B12 and folate are involved in breaking down and recycling homocysteine, adequate intake of these nutrients is considered important. These nutrients can be obtained through a healthy diet and, where appropriate, prenatal or other supplements recommended by a healthcare professional.
Discuss genetic factors with a doctor
MTHFR gene variants are one factor that can affect homocysteine level management in the body. It is recommended to speak with a doctor about whether genetic testing is appropriate, rather than assuming that everyone trying to conceive needs such testing.
Avoid smoking and excessive alcohol consumption
Smoking and excessive alcohol intake are associated with elevated homocysteine levels. Avoiding these behaviours may also benefit reproductive health in other ways.
Support cardiovascular health
Because homocysteine and cardiovascular health are closely linked, regular physical activity, healthy blood-pressure management and attention to dietary factors that support cardiovascular wellbeing are encouraged. These habits may contribute to better overall metabolic health as well as healthier homocysteine levels.
Consider a blood test
For someone concerned about their homocysteine level, it is recommended to discuss homocysteine blood testing with a healthcare professional first. The results can then be interpreted alongside the individual’s diet, medical history, medications and reproductive circumstances.
KEY TAKEAWAY
Homocysteine may be an important link between general metabolic health and reproductive health. Elevated levels have been associated with poorer sperm parameters, irregular ovulation, reduced egg quality, embryo quality and pregnancy complications, although the strength of evidence varies across these outcomes and association does not necessarily prove a connexion. For people trying to conceive, focusing on overall health, ensuring adequate intake of folate and vitamins B6 and B12, avoiding smoking and excessive alcohol, maintaining cardiovascular health and seeking medical advice if elevated homocysteine is suspected, is advised.
The key takeaway is that, rather than homocysteine being a single explanation for infertility, it is one potentially relevant factor within the wider picture of reproductive health.
Read more about these guidelines in this blog by Ovaterra.
