PCOS and inositol: what does the science really say?

The polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age. International estimates place its prevalence between 6 and 13%, according to the diagnostic criteria used. It is a complex hormonal and metabolic disorder, not just a fertility problem.

Among the options studied to improve certain symptoms,inositol (in particular myo-inositol and D-chiro-inositol) is the subject of much research. Here is a comprehensive summary, based solely on established scientific data.

Understanding PCOS

The diagnosis is based on Rotterdam criteria (international recommendations), which require at least two of the following three criteria :

• Ovulation disorders (irregular or absent cycles)
• Clinical or biological hyperandrogenism (acne, hirsutism, alopecia, high testosterone)
• Polycystic ovarian morphology on ultrasound

PCOS is also associated with metabolic disorders. A significant proportion of affected women present with insulin resistance, regardless of weight. This resistance promotes the increase of androgens and contributes to ovulatory disorders.

PCOS is recognized as The number one cause of infertility due to anovulation.

What is inositol?

Inositol is a molecule that is naturally present in the body. It exists in several forms (isomers), of which the two main ones studied in PCOS are:

• Myoinositol (MI)
• D-chiro-inositol (DCI)

These molecules are involved in insulin signaling and in the mechanisms involved in ovarian function.

Inositol and PCOS: What the studies show

Several randomized clinical trials and meta-analyses have evaluated inositol in women with PCOS. These are the clinical trials that many brands use to sell their expensive supplements! Before buying dietary supplements, we recommend that you make sure that they are suitable for your situation by looking our series dedicated to PCOS. No one should take supplements without understanding if they are really good for you and what their effects are on your health.

Effects on ovulation and cycles

The data studied show that myo-inositol:

• May improve menstrual regularity
• may increase the frequency of ovulation in some women
• may improve ovulation rates compared to placebo

Recent international recommendations indicate that myo-inositol can be considered to improve cycles and ovulation, although the level of evidence is considered to be moderate. This means that it does not work every time, and especially that it is ideal to take care of your health in a global way, as explained in our series dedicated to PCOS.

The metabolic effects of inositol

Meta-analyses indicate that inositol can:

• reduce insulin on an empty stomach;
• improving the HOMA-IR index (insulin resistance marker);
• have a modest effect on certain lipid parameters;

However, the effects observed remain variables according to studies and do not replace health and dietary measures. In any case, insulin resistance must be understood and especially validated or not by a doctor before going further on the intake of dietary supplements. You can also impact your insulin by changing your diet first and this is what is recommended first and foremost.

Other impacts of inositol on PCOS

Some studies show that the improvement of visible symptoms (acne, hirsutism) is possible, but generally gradual and variable. As well as the probable impact of inositol on fertility. However, it is not a miracle cure and it is recommended to be accompanied and to understand why and how you are taking supplements when you have PCOS.

The 40:1 ratio: what does that mean in concrete terms?

There are several forms of inositol. The two main ones studied in PCOS are:

• the myo-inositol
• the D-chiro-inositol

In the body, these two forms are naturally present. And when we measure their proportion in the blood or in the ovaries, we find approximately 40 parts myo-inositol for 1 part D-chiro-inositol.

That's where the famous 40:1 ratio.

Some studies suggest that respecting this ratio as a dietary supplement could be interesting in PCOS.
But it's important to understand one thing:

‍
👉 there is currently no scientific consensus affirming that this ratio is essential or superior in all cases.

The international recommendations mainly talk about myo-inositol, used alone or in combination.

What dose is used in the studies?

In the majority of clinical studies, we find:

• 4 grams of myo-inositol per day
  (in general 2 g in the morning + 2 g in the evening)
• sometimes associated withfolate
• over a period of at least 3 to 6 months

Why several months?
Because the ovarian cycle and metabolic parameters take time to change. It is not a supplement that works in a few weeks.

⚠️ Any supplementation should be discussed with a health professional, especially if you are already taking treatment. You can watch our series dedicated to PCOS to understand which exams to take, which supplements are right for you and how to move forward at each stage.

What the international recommendations really say

Based on the available data, inositol is generally well tolerated. The side effects reported are rare and most often mild, mainly transient digestive disorders such as bloating or slight nausea at the start of taking. It is still a dietary supplement, not a drug treatment. It should therefore not replace a treatment prescribed (such as metformin or an ovulation induction treatment) without medical advice. Any supplementation should be discussed with a health professional in order to be adapted to your situation.

International recommendations updated in 2023 indicate that myo-inositol may be proposed to improve the regularity of menstrual cycles and that it may be considered in case of poor metformin tolerance. However, the level of scientific evidence is considered moderate and the results may vary according to the profiles (presence or absence of insulin resistance, type of PCOS, metabolic context). Inositol is therefore not presented as a universal first-line treatment, but as a possible complementary option in personalized care.

‍

In other words:

👉 Inositol is not touted as a miracle cure.
👉 It is also not a mandatory treatment.
👉 It's a additional option possible, to be discussed on a case-by-case basis.

‍

A comprehensive approach to PCOS is key

In any case, the international recommendations, studies and professionals in the Reflet community are unanimous: lifestyle is the first lever that helps to live better with PCOS. And in particular:

1. Regular physical activity
2. A diet adapted to the metabolic profile
3. Weight management if necessary
4. Individualized medical follow-up

Supplementation, if chosen, is part of this overall approach.

To remember

• PCOS is common and multifactorial
• Inositol (especially myo-inositol) shows moderate positive effects on ovulation and insulin resistance
• The data is encouraging but variable and does not guarantee a positive impact.
• You have to pay attention to the marketing discourse of dietary supplement companies
• It is not a miracle treatment, but a possible complementary option.
• Any intake should be discussed with a health professional.

We look forward to seeing you join the Reflet community to help you better understand SPOTand know how to take your supplements!

‍