As infertility rates continue to rise, awareness is growing about polycystic ovary syndrome (PCOS), a leading cause of infertility. While you may already be familiar with the link between PCOS and insulin resistance, specifically how better blood sugar management may improve fertility, one treatment option you may not have heard of is myo-inositol. Myo-inositol is a natural supplement that’s been around since the 1990s but has grown in popularity as a PCOS treatment more recently.
Importantly, while the American Society for Reproductive Medicine’s (ASRM) International Evidence-Based Guideline on PCOS initially listed myo-inositol as an experimental treatment back in 2018, it now reads “Inositol (in any form) could be considered in women with PCOS based on individual preferences and values, noting limited harm, potential for improvement in metabolic measures, yet with limited clinical benefits including in ovulation, hirsutism or weight.”
What is myo-inositol?
Myo-inositol is the most common type of a group of molecules known as inositols. Chemically, the compound is structurally similar to glucose and is classified as a sugar alcohol. In addition to PCOS, it is implicated in many conditions, from Alzheimer’s to Down syndrome, obsessive compulsive disorder, depression, and anxiety [1].
Where does it come from?
Our bodies naturally produce myo-inositol from glucose. It is mostly made by the kidneys, but the liver and brain also make it. We also consume myo-inositol in our food. Nuts, seeds, beans and peas, grains, and some citrus fruits are all relatively high in myo-inositol. Some theorize that inositol deficiency is becoming more common as our modern diets include fewer foods with high concentrations of inositol, such as animal liver. There is no recommended daily intake, but the average diet includes 0.5-1.0 grams per day.
For those (myself included) who aren’t ready to get in touch with their Paleolithic roots and start eating liver on a regular basis, myo-inositol is widely available as an oral supplement.
What does it do?
While scientists still don’t completely understand how myo-inositol works, it is known to play a major role in metabolism and reproduction, as well as in the development and growth of cells, nerves, and bones [2]. The highest concentration of myo-inositol is found in the brain. This makes sense given that it also plays an important role managing the body’s response to signals from neurotransmitters and several hormones, including follicle stimulating hormone (FSH).
Why is it recommended as a treatment for PCOS?
It’s well known that insulin resistance often accompanies PCOS, affecting about 70-80% of women who have PCOS and are overweight and between 15-30% of women with lean PCOS. Myo-inositol, and a similar compound called D-chiro-inositol, are important for insulin regulation because they act as messengers that help control the uptake, use, and storage of glucose in cells [3]. But if those cells have elevated glucose levels (which is common in those with insulin resistance), they will absorb less myo-inositol [3].
Myo-inositol gets converted to D-chiro-inositol naturally within cells, but the process is dependent on insulin. This means that insulin resistant cells reduce the amount of myo-inositol that gets converted to D-chiro-inositol, which in turn can lead to more insulin resistance [2]. With this vicious cycle between inositol deficiency and insulin resistance, it’s hardly surprising that a deficiency in D-chiro-inositol is associated with PCOS and type 2 diabetes.
Unlike hormonal contraceptives, which are often prescribed to treat external symptoms of PCOS like acne and excess hair growth, myo- and D-chiro-inositol are meant to intervene at the root cause of PCOS and improve both metabolic regulation and reproductive health by addressing insulin resistance itself [4].
Unlike hormonal contraceptives, which are often prescribed to treat external symptoms of PCOS like acne and excess hair growth, myo- and D-chiro-inositol are meant to intervene at the root cause of PCOS and improve both metabolic regulation and reproductive health by addressing insulin resistance itself.
Should you take myo-inositol with or without D-chiro-inositol?
Many studies have shown that when taken at the ideal ratio of 40:1, myo-inositol (40 parts) combined with D-chiro-inositol (1 part) has a positive effect on healthy ovulation and fertility as well as insulin sensitivity [5]. Past studies have shown that an excess of D-chiro-inositol could actually be harmful to ovarian function, which is why such a small amount is recommended.
Some women’s health experts, including naturopath Lara Briden, recommend myo-inositol on its own, saying that it’s cheaper and more accessible. (For what it’s worth, I had a harder time finding myo-inositol on its own, but that could be due to the fact that I live in the United States while she is based in New Zealand.)
For women with PCOS with infertility, inositol is still considered experimental
While the ASRM’s 2023 International Evidence-based Guideline for the Assessment and Management of PCOS gave a muted approval to inositol as a potential treatment for PCOS, it still considers inositol in any form an “experimental treatment” in women with PCOS and infertility. The Guideline reads, “Inositol in any form alone, or in combination with other therapies, should be considered experimental therapy in women with PCOS with infertility, with benefits and risks currently too uncertain to recommend the use of these agents as fertility therapies.”
Myo-inositol vs Metformin
If you’ve received a PCOS diagnosis or done research on insulin resistance, you’re probably thinking that myo-inositol sounds pretty similar to metformin–and you’re right! Metformin is one of the most common treatments for insulin-related issues like Type 2 diabetes and PCOS.
Like metformin, myo-inositol and D-chiro-inositol are meant to act as insulin sensitizers, and thanks to their consistent effectiveness and safety in many studies, the supplement has gained a reputation as a treatment for PCOS across the medical community [6].
Inositol even has a couple advantages over metformin: it’s a widely available supplement that you can buy online and in many pharmacies without having to go through insurance or obtain a prescription. It also doesn’t tend to cause any GI issues, which are common side effects with metformin. Despite the higher likelihood of GI side effects, the International Evidence-based Guideline still recommends metformin over myo-inositol for PCOS-related hirsutism and obesity because it has “greater clinical efficacy.”
My experience with myo-inositol
When I visited a doctor with concerns about short cycles and some PCOS-like symptoms, I was surprised when she immediately suspected insulin resistance. I went to the lab for a glucose tolerance test, which measured my blood sugar and insulin levels over the course of two hours, before and after drinking a sugary “glucose solution” to see how my body would react. Sure enough, the results showed clear signs of insulin resistance. My doctor initially recommended Metformin, but when I asked if there were any natural supplements I could try first, she suggested myo-inositol.
My doctor recommended a daily dosage of 4,000 mg, an amount that has been found to improve fasting glucose levels and insulin resistance [3][7]. I was able to find the 40:1 ratio supplement pretty easily on Amazon, and the brand I’m using now costs about $21 for a one-month supply.
In my case, after nearly a year of taking myo-inositol, I haven’t had any negative side effects, but I also haven’t seen any huge improvements, though my cycle and luteal phase did get slightly longer after the first three months or so.
Who can (and should) take myo-inositol
Most women could take a myo-inositol supplement: no major risks are known, and it has consistently been shown to support healthy ovulation and fertility. On her podcast, Dr. Briden notes that myo-inositol is safe to take in combination with other medications, supplements, and hormonal treatments, and can even be taken while pregnant.
In the end, though, myo-inositol is meant to supplement cycle health; it’s not a cure-all and it’s not a requirement. If you’re not experiencing PCOS- or cycle-related symptoms, then it could be just as beneficial (and more cost effective) to try increasing your body’s own inositol levels through the foods you’re eating rather than taking a daily pill.
If you do have PCOS (or think you might) or have struggled with infertility, then myo-inositol might help address the root cause of these issues in a way that hormonal birth control and even many fertility treatments just aren’t designed to do. Seek out a provider trained in restorative reproductive medicine (RRM), via telehealth if necessary, who is likely to be familiar with myo-inositol and can give you the green light or suggest alternatives!
