Best inositol supplement for PCOS

Inositol’s are a type of supplement that is on the market that can support fertility in women with PCOS. But what best inositol supplement for PCOS and what dose do you take? We are here to give you the low down and the answers you need.

What are inositol’s?

Firstly, you may be wondering what inositol’s actually are. Well, they are vitamin-like, naturally occurring substances. Fibre rich foods such as legumes and beans, fruit, nuts and seeds, meat, eggs and wholegrains contain inositols. When it comes to them in supplement form there are different types which is why you may be wondering what the best inositol supplement is for PCOS. Myo-inositol is the most bioavailable form. The other main form is D-chiro-inositol.

Reduction of PCOS symptoms with myoinositol 

For women with PCOS, having a irregular periods and difficulty conceiving can be one of the main symptoms. This can be due to insulin resistance and hormonal abnormalities.

A drug called metformin can lower insulin and blood sugar levels and used to treat Type 2 diabetes. Resistance to the hormone insulin is common in PCOS. Metformin is often used to control insulin levels in these women and promote fertility.

Myoinositol is naturally involved in controlling our blood sugar levels. Studies have found that in women with PCOS, supplementation with myoinositol can be as effective, if not more effective than metformin alone. Myoinositol can be the best supplemental option for restoring normal menstrual cycles and ovulation in patients with PCOS (1,2).

The improvements observed in menstrual and ovarian function with a myoinositol supplement have the potential to;

  • restore spontaneous ovulation
  • improve menstrual cycle irregularities
  • improve fertility
  • improve clinical pregnancy rates

Supplementation with Myoinositol can also decrease PCOS associated excessive hair growth and acne through reducing androgen levels (3,4).

Myoinositol in women with PCOS undergoing fertility treatment 

Myoinositol works to reduce the effects of insulin resistance. Alongside this, it is also involved in follicle stimulating hormone (FSH) signalling. The levels of myoinositol in the follicular fluid also positively correlate with embryo quality. For women with PCOS undergoing fertility treatment, myoinositol supplementation can help reduce the dose of FSH required and decrease the number of days required for ovarian stimulation, contributing to a reduced risk of ovarian hyperstimulation, and beneficial effects on ovarian function and egg development.

Multiple studies have analysed the research looking at the effects of myoinositol in women with PCOS undergoing fertility treatment. Some have found that myoinositol supplements were not able to improve egg quality, embryo quality or pregnancy rate (5), and were not able to improve ovarian reserve (6). Others were uncertain of its effects on live birth rates or clinical pregnancy rate compared to the standard treatment (7).

In contrast however, there is research that supports the role of myoinositol in women with PCOS undergoing IVF. Studies have found it can

  • have positive effects by reducing the need for gonadotropins, and efficiently reducing ovarian hyperstimulation (8).
  • it can increase clinical pregnancy rate in infertile women undergoing ovulation induction for ICSI or IVF and embryo transfer (9).

Myoinositol’s positive effects on women with PCOS were corroborated in a recent review of all the available evidence. The conclusion was that (10) at a dose of 4 g per day (generally taken as 2g twice a day), three months prior to ovarian stimulation, myoinosiol is effective at

  • normalizing ovarian function,
  • improving egg quality
  • improving embryo quality

Ratios of myoinositol and d-chiro inositol

Myoinositol and d-chiro inositol are the two most common inositols. In the ovary we see conversion of myoinositol into d-chiro inositol. The normal levels of these two inositols occur in a 40:1 ratio.

Although women with PCOS have insulin resistance, compared with other tissues in the body, the ovary actually maintains normal sensitivity to insulin (11). This means that there could be high levels of insulin in the ovary. High ovarian insulin levels can result in overproduction of d-chiro inositol and reduced levels of myoinositol. The resulting deficiency in myoinositol could be what leads to poor egg quality and impairment of follicle stimulating hormone signalling in women with PCOS.

Low doses of d-chiro inositol alone in women with PCOS can;

  • improve insulin sensitivity,
  • reduce circulating free testosterone levels
  • increase frequency of ovulation.

A higher dose of d-chiro inositol however did not confer the same benefits.

The combination of myoinositol and d-chiro inositol in a 40:1 ratio does however seem to be beneficial (12). The combination can be the best option to restore ovulation in women with PCOS compared with using myoinositol alone.

Take care when shopping for your inositol supplement. Supplements that contain myoinositol and d-chiro inositol at ratios other than those at 40:1 are found on the market. There isn’t any evidence for a therapeutic effect of these so make sure you are buying the 40;1 ratio. this along with the knowledge that higher doses of DCI can lead to negative effects, supplement formulations with ratios other than 40:1 are not recommended (12). However, as above, there is significant evidence of the effects of myo-inositol independent of the combination with d-chiro inositol.

The bottom line 

Myo-inositol or a myo-inositol and DCI combination in a 40:1 ratio is the best inositol supplement for PCOS. It is a secure and cost-effective alternative in the treatment of PCOS, with no side effects observed in the standard dosage. An inositol supplement can be beneficial for women with PCOS whether trying to conceive naturally or undergoing fertility treatment alongside making PCOS specific changes to your diet. Speak to your fertility specialist or a Specialist Fertility Dietitian or Nutritionist for individualised advice.

With the right support and dietary management, you can manage your PCOS symptoms and enhance fertility. Check out our specialist PCOS guides – PCOS weight loss meal plan & guide and Lean PCOS meal plan & guide for further guidance.