Research reviewed by Gram found that folate and related B vitamins help support egg development in animal studies, but human evidence remains limited. No supplement has yet been proven to increase live births or slow ovarian aging in women. Most findings come from mice, cattle, pigs, and observational studies, so large human trials are still needed.
Gram Research analysis of a 2026 review in Human Reproduction Update looks at how folate and related B vitamins may support egg health and aging in the ovaries. These nutrients feed a chemical system called one-carbon metabolism, which helps build DNA and controls how genes are switched on and off. The review found promising clues in mice, cattle, and pigs, and some human studies linked low B vitamin levels or certain gene versions to fertility problems. However, the authors concluded that no supplement has been proven to increase live births or slow egg aging in women. Most of the evidence is from animals or observational studies, which can show links but not cause and effect. Large, well-designed human trials are still needed before any clear advice can be given.
Key Statistics
A 2026 review in Human Reproduction Update found that a multi-component supplement containing 5-methyltetrahydrofolate increased the share of cattle embryos reaching the blastocyst stage from 17.1% to 34.9% during egg maturation.
According to Gram research analysis of a 2026 review, a retrospective human study found that combined 5-methyltetrahydrofolate, B12, and B6 supplements were associated with an odds ratio of 1.83 for live birth compared with folic acid alone, though causation was not established.
A 2026 review of folate and fertility found that only 12% of infertile women had optimal red blood cell folate levels, while 44% had adequate vitamin B12.
The Quick Take
- What they studied: The researchers asked whether a group of chemical processes that depend on folate and related vitamins affects egg quality and how eggs age in the ovaries.
- Who participated: This was a review of existing studies rather than a new experiment with its own group of people. It included laboratory work on mice, cattle, and pigs, as well as human studies of women with fertility problems. The total number of people was not reported as a single figure.
- Key finding: The review found that folate-related nutrients appear to play a role in egg development and early embryo growth. In one cattle study, a multi-vitamin containing a active form of folate raised the number of healthy early embryos from 17.1% to 34.9%. Human evidence is weaker: it links low B vitamin levels and certain gene versions to fertility problems, but it does not prove that supplements help women have babies.
- What it means for you: Getting enough folate and vitamin B12 is a reasonable part of a healthy diet, especially when planning a pregnancy. Supplements should be discussed with a doctor, since no supplement has been shown to improve live birth rates or slow egg aging in women. Genetic test results should not be the only basis for treatment decisions.
The Research Details
This paper is a review, meaning the authors gathered and evaluated published research instead of running a new experiment. They searched the PubMed medical database for English-language studies from 2008 to 2026 on folate, related B vitamins, egg development, and ovarian aging. They also checked reference lists of key papers by hand to find additional studies.
The authors sorted the evidence by the type of study and the species or group studied. They gave the most weight to studies that tested how changes in these nutrients affect cells, along with long-term studies that followed people over time and clinical trials. Studies in animals and cells were included to explain how the system works, but they cannot be assumed to apply directly to women.
The review also pointed out gaps in what is known. For example, researchers have not yet measured the key chemicals of this system directly in aging human eggs, and no large trial has tested whether supplements improve pregnancy outcomes.
A review like this helps bring scattered research into one picture. Many studies look at only one piece of the puzzle, such as a single vitamin or a single gene. By combining them, the authors can see which ideas are supported by strong evidence and which are still guesses. This prevents readers from treating early laboratory results as proven medical advice.
The review was published in a respected reproductive medicine journal and was written by experts in the field. Its authors were clear about what the evidence does and does not show. However, a review is only as strong as the studies it includes, and many of those studies were small, used animals, or looked only at associations. The paper itself does not report a single sample size, and the publication details list it as a cohort study even though its description identifies it as a review, so readers should treat it as a summary of existing evidence rather than a new trial.
What the Results Show
The review explains that one-carbon metabolism is a network of chemical reactions that uses folate and related vitamins to make building blocks for DNA and to add small chemical tags called methyl groups. These tags help control which genes are active in a cell, which is important for eggs as they grow and mature.
In mouse studies, growing eggs were found to take up a form of folate, and nearby support cells helped deliver a building block called serine. In cattle embryo studies, lowering the amount of the amino acid methionine in the growth liquid changed the methyl tagging of more than 1,600 genes. These results show that the chemistry is sensitive to nutrient levels, but they do not show what this means for women.
The strongest practical clue came from cattle research. A multi-component supplement containing 5-methyltetrahydrofolate, an active form of folate, raised the share of embryos reaching the blastocyst stage from 17.1% to 34.9% during egg maturation. Pig studies also found that high levels of homocysteine, a chemical linked to low folate and B12, harmed mitochondria, the energy centers of cells, and early development.
In human studies, the picture is more mixed. Some retrospective studies linked high homocysteine with fewer live births, and combined folate, B12, and B6 supplements were linked with higher pregnancy and live birth rates than folic acid alone. Because these studies looked back at existing records, they cannot prove that the supplements caused the better outcomes.
The review noted that a large share of women in selected fertility clinic groups carried common versions of the MTHFR gene, which affects how the body processes folate. In one study, more than 40% of women in a group with repeated miscarriages or failed fertility treatments had two copies of these variants. However, the review points out that no comparison group was used to prove this group was unusually likely to carry these variants.
Another study found that only 12% of infertile women had optimal red blood cell folate levels, and 44% had adequate vitamin B12. This suggests that many women may not have ideal levels of these nutrients, though the study did not show whether correcting them would improve fertility.
The review also discussed hydrogen sulfide, a gas made by the body that interacts with this chemical system. Its role in egg aging is still unclear and has not been confirmed in human eggs.
Previous reviews have looked at folate and pregnancy in general, or at early embryo development, but few have focused specifically on how this chemistry works inside growing eggs and how it relates to aging. This review adds that focus. Its conclusions are consistent with broader public health advice that adequate folate is important for pregnancy, while also making clear that the evidence for fertility treatment is still early.
Most of the evidence comes from mice, cattle, and pigs, and animal biology does not always match human biology. Many human studies were observational, meaning they found associations but could not prove cause and effect. Some used small or selected groups of women, such as those already having fertility problems. Blood tests that estimate biological age do not directly measure the age of an egg, which is a key limitation for understanding ovarian aging. The authors also noted that no large randomized trial has yet tested whether these nutrients improve live births or delay ovarian aging in women.
The Bottom Line
Based on current evidence, the most reliable advice is to get enough folate and vitamin B12 through food or standard prenatal supplements, which is already recommended for women planning pregnancy (high confidence). Using specialized multi-vitamin formulas to improve egg quality is not yet supported by human evidence (low confidence). Testing for MTHFR gene variants should not be the sole reason for changing treatment (high confidence, based on the authors’ explicit statement). Women with fertility concerns should discuss personalized options with a doctor.
Women planning a pregnancy, people undergoing fertility treatment, and clinicians who work in reproductive health may find this review useful. Researchers studying egg aging will find the list of knowledge gaps especially helpful. People who are not trying to conceive can still benefit from the general advice to eat folate-rich foods. Women who have already been told they have a gene variant or low vitamin levels should talk with their doctor before starting any new supplement.
Folate and B12 levels can be improved within a few weeks to months of changing diet or taking supplements, and standard prenatal vitamins are recommended for at least one month before conception. However, the review did not find evidence showing how long it takes for these nutrients to change fertility outcomes or egg aging in women. Realistic benefits, if any, are still unknown and will depend on future clinical trials.
Frequently Asked Questions
Does folate help improve egg quality?
Animal and laboratory research suggests folate-related chemistry supports egg development, but human proof is lacking. A 2026 review found no supplement has yet been shown to improve live births or slow ovarian aging in women. Eating folate-rich foods remains a sensible part of fertility planning.
Should I take a 5-MTHF supplement to improve my fertility?
The evidence for 5-MTHF in humans is limited to observational studies that cannot prove cause and effect. A cattle study showed embryo yield rising from 17.1% to 34.9%, but this does not confirm benefits in women. Talk with a doctor before starting any specialized supplement.
Does having an MTHFR gene variant mean I cannot get pregnant?
No. A 2026 review states that common MTHFR variants alone should not determine treatment. Some studies linked these variants with pregnancy problems, but the link was not clearly established. A doctor can assess whether testing or changes in diet and supplements are appropriate for your situation.
How does vitamin B12 affect fertility?
Vitamin B12 works with folate in the body’s one-carbon chemistry system, which helps build DNA and control gene activity. A 2026 review found that 44% of infertile women in one study had adequate B12 levels. Research on whether correcting low B12 improves fertility outcomes is still limited.
Want to Apply This Research?
- Log daily intake of folate-rich foods such as leafy greens, beans, and fortified cereals, and record whether a prenatal or folate supplement was taken each day. Aim for a consistent daily entry for at least 8 weeks so trends are visible. Note the supplement name and dose from the label.
- Add one serving of leafy greens or legumes to at least five meals per week, and set a daily reminder to take a prenatal vitamin if one has been recommended by a doctor. Pair the reminder with an existing habit, such as breakfast, to make it easier to remember.
- Review intake logs monthly and look for patterns in diet and supplement use over time. Encourage users to bring summaries to medical appointments so clinicians can decide whether blood tests for folate or B12 are appropriate. Update the plan after any new test results or changes in medical advice.
This article summarizes a review of animal, laboratory, and observational research and is for general information only. It is not medical advice and does not replace guidance from a doctor, fertility specialist, or registered dietitian. Do not start, stop, or change any supplement or fertility treatment without speaking to a qualified healthcare provider, especially if you are pregnant, planning a pregnancy, or have a known medical condition.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.