Blog Post

Inositol: Is It A Useful Supplement For Those With PCOS?

PCOS and inositol

Inositol is a compound that is abundant in the human body. It plays a major role as a component of cell membranes. It also influences insulin and other chemical messengers in the body.  

Supplementing with inositol has gained traction as a treatment for some of the symptoms and conditions associated with PCOS.

But how useful is inositol supplementation and how do you take it?

What Is PCOS?

PCOS is a condition that affects hormonal levels in women. 

It is categorized by a higher than normal production of male sex hormones which can lead to an inconsistent menstrual cycle, infertility, body and facial hair growth, and cysts on the ovaries.

Around 85% of women with PCOS also experience insulin resistance. Nonetheless, women with PCOS are 35-40% less sensitive to insulin.

This insulin sensitivity may also play a significant role in issues with weight management in people with PCOS.

When PCOS is present it is correlated with a 14-40% lower metabolic rate than what would be expected without PCOS. And it appears that those with more insulin resistance appear to be at the upper end of that range.

Inositol Supplement PCOS

What Is Inositol?

Inositols are a type of carbohydrate that play a role in hormone signaling. With PCOS being a hormonal condition, it makes sense why a compound that can potentially regulate hormonal signaling caught the eye of researchers in this space.

Whilst available in supplement form, inositols are also found naturally occurring in some foods including grains, nuts, and fruit.

There are nine types of inositol in total, however, PCOS research is mainly focused on myo-inositol (MI) and di-chiro-inositol (DI). 

Emerging evidence suggests that inositol supplementation may:

Outside of PCOS, inositol may even reduce the risk of metabolic syndrome, type 2 diabetes & gestational diabetes.

Inositols act as second messengers for insulin. It is the deficiency of MI and DCI that contributes to the various features of PCOS. 

Like many deficiencies, rectifying the deficiency with supplementation tends to alleviate symptoms. 

However, inositol’s role in PCOS does seem to be a little more nuanced than that. 

In PCOS, we observe a myo-inositol deficiency at an ovarian level. This impairs hormonal signaling in the ovaries. 

Furthermore, d-chiro inositol is synthesized from myo-inositol. 

Different tissues in the body have a different ratio of MI to DI and in the absence of a condition like PCOS or diabetes, this ratio is tightly controlled. 

What Is The Best Way To Supplement Inositol?

PCOS, inositol and pregnancy

Evidence For Myo-inositol (MI)

Supplementing myo-inositol has been found to improve the number of good quality oocytes, clinical pregnancies, and delivery rates in overweight women with PCOS. 

In most of these trials, the dosage was 2g daily for 3-6 months. 

One study of 25 women with PCOS trialed 2g of myo-inositol and folic acid, twice daily for six months or until a positive pregnancy test was obtained. Of these women, 22 experienced their first menstrual cycle after ~35 days, 18 continued to have regular menstruation and 10 fell pregnant. 

There was also a significant fall in testosterone amongst participants. 

In another study of fifty women with PCOS, 2g of myo-inositol daily was found to reduce the risk of ovarian hyperstimulation syndrome with ovulation-induction protocols. Overall, insulin sensitivity improved as did pregnancy rate. 

Whilst this supplement appears quite promising in the research, it is important to note that results have been mixed. Systematic reviews and meta-analyses that have collated data on the efficacy of myo-inositol in PCOS suggest the need for further studies.

Evidence For D-chiro Inositol (DI)

Various authors have studied the effect of d-chiro inositol on endocrine, metabolic, and reproductive parameters in PCOS. 

A study published in 2002 found that supplementing with 600mg of di-chiro inositol for 6-8 weeks lead to a reduction in insulin, free testosterone levels, blood pressure, and serum triglyceride levels. There was also a higher ovulation rate noted but it was not statistically significant. 

Furthermore, this study was done in lean women with PCOS that had a BMI between 20 and 24.4kg/m2).

A study in obese PCOS women (BMI >26 kg/m2) also found DI supplementation to improve endocrine parameters including serum testosterone.

It also reduced BMI and improved insulin sensitivity in patients with diabetic relatives, who exhibit a greater response as compared to those with no family history of diabetes.

Combination of Myo Inositol & D-chiro Inositol

The common recommendation for supplementing inositol in 2-4g of myoinositol per day. 

Much of the research up until this point has compared MI to DI to find which is better for the treatment and management of PCOS.

However, more recent studies have found that a ratio of the two may be the most effective option. 

MI and DI have both shown the ability to regulate hormone levels and stabilize insulin response. 

MI on the other hand has demonstrated a greater ability to increase embryo and oocyte quality. Whilst, DCI is recognized to more effectively increase insulin sensitivity.

So being that MI and DI can have different positive impacts on conditions associated with PCOS, a combination of the two makes the most sense.

In a randomized control trial of fifty obese women with PCOS, a combination of 550mg of MI and 14mg of DI was compared to 2g of MI alone. The combination supplement was found to be better at improving metabolic, endocrine, and ovulation parameters, when administered twice daily over 6 months.

An MI:DCI ratio of 40:1 is considered an appropriate strategy to improve the outcomes of inositol supplementation in PCOS.

But it is worth noting that excess of DI may have a detrimental effect on egg health and impact fertility negatively. 

This is likely why many practitioners continue to suggest myoinositol as a stand-alone supplement. At least amongst dietitians in Australia, myo-inositol tends to be the standard recommendation. 

However, one of the most popular inositol supplements in the US, Ovasitol, is a combination of 2000mg of MI and 50mg of DI. 

Another reason why it may not be the go-to recommendation in Australia is that it just isn’t readily available. Although you can purchase it online from websites like Amazon.

Key Take-Away

Based on current evidence supplementing with inositol if you have PCOS seems like a no-brainer. Especially if you are dealing with symptoms such as insulin resistance and infertility. 

If you can get your hands on a combination MI & DI supplement that is in the 40:1 ratio (like this one) that would likely be the most ideal situation.

However, if you are unable to get combination inositol supplements, 2-4g of myo-inositol would be suitable and provide a benefit to those with PCOS. 

If you would like to read more about nutrition for PCOS, you can find that here

By Leah Higl

Leah is an accredited practising dietitian from Brisbane. She also competes as an under 75kg powerlifter with Valhalla Strength Brisbane. As both an athlete and dietitian, she spends much of her time developing her knowledge and skills around sports nutrition, specifically for strength-based sports. Although, she works with a range of athletes from triathletes to combat sports and powerlifting. Leah also follows a plant-based diet and her greatest passion is fuelling vegan/vegetarian athletes and proving that plant-based athletes can be just as competitive as their non-vegan counterparts.​