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 are inositol supplements and how do you take them?

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. This can lead to:

  • An inconsistent menstrual cycle
  • Reduced fertility
  • Body and facial hair growth
  • 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.

There is research indicating that there could be 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.

While other research has not found this, if it is relevant, theoretically would make weight-loss noticeably more difficult.

Inositol Supplement PCOS

What Is Inositol?

Inositols are a type of carbohydrate that plays a role in hormone signalling. It makes sense why a compound that can regulate hormonal signalling interests 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 mainly focuses on myo-inositol (MI) and di-chiro-inositol (DI). 

Emerging evidence suggests that inositol supplements 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 supplements tends to alleviate symptoms. 

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

In PCOS, we observe a MI deficiency at an ovarian level. This impairs hormonal signalling in the ovaries. 

Furthermore, d-chiro inositol is synthesized from MI. 

Different tissues in the body have a different ratio of MI to DI. 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)

In overweight women with PCOS, supplementing MI has been found to improve:

  • The number of good quality eggs
  • Likelihood of pregnancy
  • Delivery rates.

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

One study of 25 women with PCOS trialled 2g of MI and folic acid for 6 months. Or until a positive pregnancy test was obtained. The supplements were split over 2 doses a day. Of these women:

  • 22 experienced their first menstrual cycle after ~35 days
  • 18 continued to have regular menstruation
  • 10 fell pregnant. 

There was also a significant fall in testosterone amongst participants. 

In another study of 50 women with PCOS of 2g MI per day:

  • There was a reduced risk of issues with protocols designed to induce ovulation.
  • Overall insulin sensitivity improved.
  • Pregnancy rates improved. 

Whilst this supplement appears quite promising in the research, it is important to note that results have been mixed. Systematic reviews on the efficacy of MI 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 600mg of di-chiro inositol for 6-8 weeks lead to a reduction in:

  • Insulin
  • Free testosterone levels
  • Blood pressure
  • Serum triglyceride levels.

There was also a higher ovulation rate noted but it was not significant. 

Furthermore, this study was done in lean women with PCOS that had a BMI between 20 and 24.4kg/m^2.

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

It also reduced BMI and improved insulin sensitivity in patients with diabetic relatives. These individuals 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. The aim was 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.

Since MI and DI have different positive impacts on conditions associated with PCOS, a combination of the two makes sense.

In a randomized control trial, 50 women with PCOS took a combination of 550mg of MI and 14mg of DI. This was compared to 2g of MI alone. The combination supplement was administered twice daily for 6 months. It was found to be better at improving metabolic, endocrine, and ovulation parameters.

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

But it is worth noting that excess 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, MI tends to be the standard recommendation. 

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

Another reason it may not be the go-to recommendation in Australia is that it 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. 

A combined MI & DI supplement that is in the 40:1 ratio would be the ideal situation. An example could be this one.

However, if you are unable to get combination inositol supplements, 2-4g of MI would be suitable. It will still 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.​