Before IVF:
What Nutrition Can and Can’t Do

The grades in this post: Strong means good randomised trials agree. Mixed means the trials are few, small, short, unblinded or conflicting. Mechanistic means the biology makes sense but hasn’t been shown to change outcomes in people. None means there’s no usable evidence. Practice means expert, guideline or coaching practice, not trial-tested. Observational studies are labelled as such: they show a link, not proof of cause.

The short version

If you’re about to start IVF, the supplement market will offer you a long list. I’ve been through the trials. Most of the list rests on small, low-quality studies. Some of the best-run trials found nothing at all.

The basics the NHS recommends still stand. Beyond those, nothing I can point to reliably raises your chance of a baby. If anything on this page makes you want to change your treatment, take that to your fertility clinic first.

What the success numbers actually are

The Human Fertilisation and Embryology Authority (HFEA) publishes UK figures. Its key facts page (published 4 March 2024, using 2022 data) gives IVF birth rates per embryo transferred, using fresh embryos:

• age 18–34: 35% (preliminary)
• age 40–42: 10%
• age 43–44: 5%

These figures are per embryo transferred, not per cycle and not per couple. Your clinic can give you its own figures for someone of your age and history. Ask for them.

Age is the factor that moves these numbers most. None of the trials below found a supplement that comes anywhere near that effect.

Vitamin D: the link is real, but topping up hasn’t helped

What’s seen. A 2018 review of 11 cohort studies (2,700 women) found that women with good vitamin D levels had more live births after IVF than women with low levels (odds ratio 1.33). They also had more clinical pregnancies (OR 1.46). There was no difference in miscarriage (Chu 2018). That is an association. Women with good vitamin D may differ in other ways too. Observational.

What happened when it was tested. Two good randomised trials have now asked whether giving vitamin D before IVF helps:

• SUNDRO (Italy, 630 normal-weight women with vitamin D below 30 ng/mL, 75 nmol/L) tested a single large dose before the cycle. Clinical pregnancy was 37% with vitamin D and 40% with placebo, so no benefit (Somigliana 2021).
• A 24-centre Chinese trial (876 women with PCOS, average starting level about 16 ng/mL, 40 nmol/L) tested daily vitamin D for up to 90 days before trigger. Blood levels roughly doubled. Live births were 52.0% vs 50.2%, so no benefit (Hu 2026, BMJ).

Strong for no benefit on IVF success in the groups tested. A third population might respond differently, but nobody has shown that yet.

What I’d still say. Vitamin D matters for bone and general health, and the NHS advises it in pregnancy anyway. NHS advice is 10 micrograms a day from early October to late March, and all year for some groups, and not more than 100 micrograms a day (nhs.uk pregnancy vitamins page, last reviewed 3 June 2026). Those are the NHS’s public-health amounts, not doses I’m recommending. UK deficiency is below 25 nmol/L (10 ng/mL) (SACN 2016). My own working range is 75–125 nmol/L (30–50 ng/mL). That’s a clinical target, not official guidance, and the trials above tell us that reaching it is not a fertility treatment.

Folic acid: follow the NHS advice

NHS advice is 400 micrograms of folic acid a day while trying to get pregnant (ideally starting 3 months before) and for the first 12 weeks of pregnancy. Some women are advised to take a higher 5 mg dose, prescribed by a GP. This applies if you or the baby’s father has a neural tube defect or a relative with one, if you’ve had a previous pregnancy affected by a neural tube defect, or if you have diabetes, sickle cell anaemia or thalassaemia, or take medicine for epilepsy or HIV (nhs.uk pregnancy vitamins page, last reviewed 3 June 2026). These are NHS amounts, quoted as NHS advice. Practice NHS public-health advice, built on prevention of neural tube defects.

Earlier versions of this page said that people with MTHFR gene variants “need” methylfolate instead of folic acid. I’ve withdrawn that. The figures I gave weren’t sourced. Gene-variant studies on miscarriage are inconsistent: one meta-analysis found a link with recurrent pregnancy loss in developing countries but not in developed ones (Zhang 2018). A large genetic study in European women found no link between genetically raised homocysteine and pregnancy loss once all the variants were included (Kjaergaard 2021). If you have a reason to take something other than standard folic acid, discuss it with your GP or clinic. None for “methylfolate instead of folic acid for MTHFR carriers improves fertility”.

CoQ10: some signal, not the breakthrough it’s sold as

The idea. Eggs rely heavily on mitochondria. In older mice, CoQ10 restored egg mitochondrial function (Ben-Meir 2015). Mechanistic

The trials.

• The often-quoted Bentov trial (women aged 35–43) was stopped early, over safety concerns about the egg-biopsy technique, not about CoQ10. Only 24 women completed a cycle. It found no significant difference in egg chromosome errors or pregnancy (Bentov 2014). Earlier versions of this page described it wrongly.
• In 169 young women with low ovarian reserve, CoQ10 for 60 days before IVF gave more eggs and more good embryos. Pregnancy and live birth were not significantly different (Xu 2018).
• A meta-analysis of 5 small trials (449 women) found more clinical pregnancies (28.8% vs 14.1%) but no difference in live birth (Florou 2020).

Mixed Lab measures improve in some trials, but live birth, the outcome that matters, hasn’t been shown to.

Inositol for PCOS: uncertain, not “among the strongest”

I used to say the evidence for inositol was among the strongest of any nutritional intervention. It isn’t. The Cochrane review (13 trials, 1,472 women with PCOS) rated the evidence low to very low. It was uncertain whether myo-inositol improved live birth or clinical pregnancy before IVF. An apparent drop in miscarriage depended on one trial with an unusually high miscarriage rate in the control group, and it vanished when that trial was removed (Showell 2018). A later meta-analysis also found no clear difference in clinical pregnancy against no treatment (Unanyan 2022). Mixed very low certainty. If you have PCOS, ask your clinic about it alongside the treatments they use.

NAC

A meta-analysis of 15 trials found no statistically significant improvement in clinical pregnancy (OR 1.55, 95% CI 0.98–2.47), with high variation between trials (Devi 2020). I found no trial showing it improves pregnancy in endometriosis. Mixed

Antioxidants for women, taken together

The Cochrane review of antioxidants for subfertile women (63 trials, 7,760 women) found the evidence low to very low quality. The authors were uncertain whether antioxidants improve live birth, and found no difference in miscarriage (Showell 2020). In March 2026, Cochrane added an editorial note: seven of the included trials have since been retracted and two carry expressions of concern. The editors say removing them doesn’t meaningfully change the conclusions. That retraction rate tells you something about this field. Mixed

Omega-3, selenium and zinc

• Omega-3. In 100 women at a US fertility clinic, higher blood omega-3 went with a higher chance of live birth (Chiu 2018). A 2018 review found the cohort studies conflict, with no good trial of giving omega-3 before IVF (Lass 2018). Observational.
• Selenium. In 103 Chinese couples, selenium in the egg’s follicular fluid went with better early embryos but worse blastocyst development (Wu 2020). That’s conflicting and small. Observational, conflicting.
• Zinc. When a human egg is activated, it releases a burst of zinc, the “zinc spark” (Duncan 2016). It’s real and striking biology. It doesn’t show that eating or supplementing more zinc helps you conceive. Mechanistic

The male side

A male factor is estimated to contribute to up to half of couples’ fertility problems (Cochrane review background, de Ligny 2022). So it’s worth asking: does treating the man with supplements help?

• The Cochrane review (90 trials, 10,303 men) found very low-certainty evidence that antioxidants might raise live birth. When the trials at high risk of bias were removed, the benefit disappeared (de Ligny 2022, updating Smits 2019).
• FAZST (2,370 men, US) tested folic acid plus zinc for 6 months against placebo. Live birth was 34% vs 35%, and most measures of semen quality didn’t change. Sperm DNA fragmentation was slightly higher with the supplement (29.7% vs 27.2%), and stomach upsets were more common (Schisterman 2020, JAMA).
• MOXI (174 men with abnormal semen or high DNA fragmentation) tested a multi-antioxidant formula. Semen measures and DNA fragmentation didn’t improve. Live birth was 15% vs 24% with placebo, so no benefit (Steiner 2020).
• Some smaller trials show CoQ10 or L-carnitine improving sperm counts or movement, but with very little live-birth data (Omar 2019).

Mixed for semen numbers. The largest, best-run trials found no benefit for live birth.

Sperm DNA damage. One large meta-analysis linked high DNA damage to lower implantation and pregnancy rates in conventional IVF, but not to significantly lower live birth, and the pregnancy link weakened after correcting for publication bias (Ribas-Maynou 2021). Another found no significant link at all (Chen 2022). Observational, inconsistent. Whether to test it is a question for your clinic.

Thyroid

I used to say TSH should be below 2.5 mIU/L before and during IVF. I’ve withdrawn that.

• The American Society for Reproductive Medicine’s 2024 guideline found moderate evidence that TSH between 2.5 and 4 mIU/L (the same numbers in µIU/mL) is not associated with miscarriage. It does not recommend levothyroxine for subclinical hypothyroidism in women wanting to become pregnant (ASRM 2024).
• For women with normal thyroid function but positive TPO antibodies, two large trials tested levothyroxine. In the UK TABLET trial (952 women), live birth was 37.4% vs 37.9% (Dhillon-Smith 2019). In a Chinese IVF trial (600 women), live birth was 31.7% vs 32.3% and miscarriage 10.3% vs 10.6% (Wang 2017, JAMA).
• ASRM does not recommend routine thyroid antibody screening in infertile women without symptoms (a weak recommendation). It says targeted screening may be considered after recurrent miscarriage.

Strong (null) for treating thyroid antibodies with levothyroxine to improve IVF results; ASRM’s guideline says the same for mild TSH rises. Your TSH should be read against your lab’s reference range. Thyroid disease that needs treatment is your GP’s or clinic’s call. Never start, stop or change thyroid medicine without your prescriber.

Gut and the uterine microbiome

A small study (35 IVF patients) found that a uterine lining not dominated by Lactobacillus bacteria went with much lower live birth (Moreno 2016). It’s an interesting early finding. Nobody has shown that testing or treating the gut changes the uterine microbiome or IVF results. Observational (tiny); None for gut treatment as an IVF tool.

Endometriosis

The WHO estimates endometriosis affects about 10% of women of reproductive age (190 million), and that as many as 25–50% of women with infertility have it (WHO fact sheet, 15 October 2025). It needs specialist care. I found no trial showing that supplements improve fertility outcomes in endometriosis. Mechanistic at most.

What I’d do

If I were about to start IVF, this is what I’d do:

• Follow the NHS folic acid and vitamin D advice, and ask my GP whether I’m in a group that needs the higher folic acid dose.
• Tell my fertility clinic about every supplement I take, and ask before adding anything. That applies to the man too.
• Not spend money that could go on treatment on a pre-IVF “protocol”. The trials don’t support one. For the male partner, the two largest trials found nothing.
• Test only where a result would change a decision. A vitamin D level if I’m at risk of deficiency is reasonable. Anything to do with thyroid, ovarian reserve or sperm DNA belongs with the clinic.
• Remember that age moves the numbers most. Ask the clinic for its own figures for someone of my age.

Don’t start, stop or change any fertility medicine or prescribed treatment because of anything here. Talk to your fertility clinic.

How strong is the evidence?

Sources

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