Inositol for PCOS: the complete guide
Inositol is a safe and effective way of treating PCOS, backed by plenty of quality scientific research. Inositol supplements for women with PCOS have been shown to reduce insulin resistance, reduce testosterone, improve menstruation, improve ovulation, and improve fertility. Inositol is cheap, easy to use, and has no side effects. In this article, we look at why inositol is important, how it helps PCOS, which kind of inositol is best, and how much you should take. This is the complete guide to inositol for PCOS.
Contents
What is Inositol?
Inositol is a naturally occurring sugar. It is chemically identical to glucose, but has a different structure. There are 9 different types of inositol but two are specifically related to the human body and PCOS: Myo-inositol and D-Chiro Inositol. Myo-inositol is the most abundant form of Inositol [source]
Humans get almost all of their inositol from their diet in the form of myo-inositol, mostly from fruits, seeds and nuts. The human body converts myo-inositol to d-chiro-inositol using an enzyme called epimerase, which is controlled by insulin. In healthy individuals, myo-inositol and d-chiro-inositol are found in different ratios throughout the body. In the ovaries, the myo-:d-chiral ratio is 100:1, whereas everywhere else (muscles, liver), it is more like 40:1 [source].
Why is Inositol important?
“Inositol is responsible for healthy ovulation and fertility”
Inositol is an essential chemical inside the body because it is the intermediate step that converts insulin signals to metabolic and hormonal changes. Both myo- and d-chiro-inositol respond to insulin, but they have different effects.
When insulin binds to its receptors on the surface of a cell, it sends signals into the cell that activate myo- and d-chiro-inositol. Myo-inositol is responsible for helping the cell to absorb glucose from the blood [source], so it is very high in organs that use a lot of energy, like the brain and the heart [source].
On the other hand, d-chiro-inositol is involved in storing glucose in the form of glycogen, an important energy store for the body. For this reason, DCI is higher in organs that need immediate access to energy, like the liver and muscles [source].
In the ovaries, things are very different. The ovaries are so metabolically different from the rest of the body that they can be considered a completely different world. In the ovaries, insulin signalling causes d-chiro-inositol to increase testosterone levels in response to insulin [source]. On the other hand, myo-inositol in the ovaries responds to Follicle Stimulating Hormone (FSH), a hormonal signal that is absolutely essential for proper egg development and release, and therefore fertility. FSH causes myo-inositol to improve the growth and maturation of the cells that become mature follicles (eggs). Myo-inositol also helps to regulate a hormone called AMH, which further improves egg maturation [source]. For this reason, myo-inositol levels are much higher in the ovaries, compared to DCI. In fact, healthy women have 100x more myo-inositol than d-chiro-inositol in their ovaries [source].
In essence, both myo-inositol and d-chiro-inositol are important for the regular function of the human body. Throughout the body, both are responsible for the body’s response to insulin. In the ovaries, myo-inositol is responsible for healthy ovulation and fertility.
Does Inositol help PCOS?
The short answer is yes. Many studies have shown that both myo-inositol and d-chiro-inositol can act as insulin sensitisers and there is a very large body of evidence showing that this is highly beneficial for treating and managing PCOS.
“no matter how severe the insulin resistance, the ovaries always remain sensitive to insulin”
But how exactly does inositol treat PCOS? Inositol helps PCOS symptoms in several ways. PCOS is very heavily associated with insulin resistance, and for most sufferers of PCOS, insulin resistance is the root cause of their symptoms. Insulin resistance causes cells to become desensitised to insulin, stimulating the body to release more and more insulin (hyperinsulinemia) in an effort to receive a response. However, no matter how severe the insulin resistance is, the ovaries always remain sensitive to insulin (because they are so different from the rest of the body). This means that the ovaries are being hyper-stimulated by all the excess insulin in the body, which causes the unwanted effects of PCOS (high testosterone, anovulation, infertility).
The reason that excess insulin causes this response in the ovaries is that insulin activates the epimerase enzyme, which converts myo-inositol to d-chiro-inositol. As we mentioned above, high levels of myo-inositol are required for healthy ovulation, but an over-active epimerase enzyme converts all the myo-inositol to d-chiro-inositol, which stimulates the ovaries to produce testosterone [source]. A healthy ovary will have a myo- to d-chiro- ratio of 100:1, but in women with PCOS this can be as low as 0.2:1 [source]!
Unfortunately, the excess testosterone produced makes the symptoms of PCOS even worse, which makes insulin resistance even worse, which causes the body to produce more insulin, creating an even stronger negative response in the ovaries. This is a vicious negative cycle that has to be constantly managed to prevent it from spiralling out of control.
A large number of studies have been published in recent years that show that supplementation with Inositol causes a significant drop in insulin resistance and testosterone levels, reducing symptoms of PCOS, such as acne and hair growth, and restoring menstrual regularity and fertility [source]. By taking inositol as a dietary supplement, the normal, healthy ratios of myo-inositol and d-chiro-inositol are restored in the body, which improves insulin sensitivity, reducing the amount of excess insulin present, and prevents the ovaries from producing too much testosterone.
Will Inositol help fertility for PCOS?
“Restoring correct levels of Inositol can restore normal ovary function”
As we mentioned above, high levels of myo-inositol in the ovaries are required for healthy ovulation by improving signalling from Follicle Stimulating Hormone, allowing healthy egg maturation and therefore ovulation, menstruation and fertility. Ovarian myo-inositol levels are depleted in women with PCOS, causing anovulation and infertility. Restoring the correct levels using inositol supplementation can restore normal ovary function.
Many studies have confirmed that inositol supplementation improves regularity of ovulation and menstrual cycles in women with PCOS. Similarly, studies have proven that myo-inositol improves egg maturation, egg quality and embryo quality, leading to higher pregnancy rates and higher birth rates [source].
Which type of Inositol is best for PCOS? Myo-inositol vs D-chiro-inositol
“Never take D-chiro-inositol on its own!”
There have been many studies carried out to investigate which type of inositol is most effective at treating PCOS. In short, the best inositol to take is myo-inositol, or a combination of myo- and d-chiro-inositol, as these seem to have the most positive effects. D-chiro-inositol should never be used on its own, as this seems to have negative effects and can actually make the situation in the ovaries worse.
This is a very complicated topic due to the complexity of insulin signalling and the metabolic differences between the ovaries and the rest of the body. Studies were first performed in mice, and later in humans, that compared the effects of supplementation with different ratios of myo-inositol and d-chiro-inositol. The results showed that a ratio of 40:1 myo- + d-chiro was the most effective, actually curing the mice of the PCOS symptoms completely, with similar positive effects in humans. As the levels of d-chiro-inositol were increased, researchers found that PCOS symptoms got worse in both mice and humans. This may be due to the increased levels of d-chiro-inositol in the ovaries increasing testosterone production even further. For that reason, d-chiro-inositol should never be taken on its own as a supplement.
A recent set of 12 different studies compared the use of myo-inositol on its own, vs a combination of myo- and d-chiro-inositol in the optimum 40:1 ratio. The studies found that both strategies had strong benefits, both causing significant reductions in insulin resistance and testosterone levels [source]. The studies concluded that the combination of myo-inositol and d-chiro-inositol may be better than myo-inositol on its own, however the results were very similar.
For these reasons, supplementation with myo-inositol, and possibly a combination of myo- and d-chiro-inositol in a 40:1 ratio are strongly suggested in order to help treat PCOS [source]. Just remember to avoid d-chiro-inositol on its own!
How much Inositol should I take?
Researchers have investigated a wide range of doses of inositol, including myo-inositol and a combination of both inositols together. The evidence shows that limiting daily intake to approximately 4 g per day, split into two doses of 2 g, has the best effects. Taking more will not improve the benefits and may have unwanted side effects, as well as just wasting money [source].
If you're taking myo-inositol on its own, research has shown that taking it in combination with folic acid seems to improve the positive effects, creating higher rates of successful ovulation and better regularisation of the menstrual cycle. You should have two doses per day of 2 grams of myo-inositol and 200 micrograms of folic acid. The best way to do this is buy an inositol product that already includes the folic acid [source].
How to take Inositol
Inositol is very easy to take, regardless of whether you are taking myo-inositol and folic acid, or a myo- and d-chiro-inositol combination. It can be bought either as a loose white powder, which has a neutral taste and is slightly sweet, or it can be bought in capsules that contain a pre-measured dosage of the same powder. The powder can be stirred into water, tea, coffee, or even sprinkled over food.
You should divide your daily inositol intake into two doses, one in the morning and one in the evening. For the best effects, try to take your inositol when you are fasted (e.g. before you eat anything in the morning), or a few hours after eating (e.g. right before you go to sleep). This is because high blood sugar, which is the case after eating, seems to prevent the inositol from being absorbed properly. However, don’t worry if you miss this window, taking your inositol after eating will be better than not taking any at all!
As with all PCOS management strategies, the benefits are not overnight. It is recommended to take inositol for 3-6 months before significant changes will be seen, so keep that in mind and don’t be discouraged!
Inositol side effects: is Inositol safe?
There have been many studies investigating the safety of inositol. At the recommended daily dosage of 4 grams, there are no side effects reported. The U.S. Food and Drug Association (FDA) has specifically listed myo-inositol as a safe compound [source]. Recent studies have confirmed that inositol is also safe during pregnancy [source]. However, it is always best to consult your doctor before starting any new supplement, especially while pregnant! Researchers have found that when the daily dose reaches approximately 12 grams per day, people start to experience unwanted side effects like flatulence and nausea. As we mentioned above, for the best effects you shouldn’t take more than 4 grams per day anyway, so that shouldn’t ever be a problem.
Can I take Inositol with metformin?
Metformin is one of the most commonly used treatments for PCOS, and is considered a first line treatment and preventative. Like inositol, metformin is also used to increase insulin sensitivity, however metformin also has some unpleasant side effects and many people find themselves intolerant to it. Many studies have compared the use of inositol and metformin for treating PCOS and found that metformin and inositol have very similar effects on insulin, testosterone and BMI. Importantly though, inositol has no side effects, suggesting it may be able to replace metformin in the future, but much more work is needed before that [source].
You can take metformin and inositol in combination. Studies have shown that when taken together, less metformin is required to achieve the same effect. This could be very beneficial for people who are intolerant to the standard doses of metformin due to the unwanted side effects [source]. As always, check with your doctor before changing your prescribed medication program.
Does Inositol work for everyone with PCOS?
Inositol is a very promising treatment strategy for women with PCOS, however it is unfortunately not suitable for everybody. As inositol helps by increasing insulin sensitivity, it does not have the same benefits for sufferers of PCOS who do not exhibit high insulin resistance. About 30% of women with PCOS will not experience significant benefits from taking inositol. With that being said, inositol is a very cheap and easy to implement strategy, so it is recommended that everybody try it for at least 6 months to see if it can help.
