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PCOS and inositol – does the form matter?

Inositol is one of those supplements that every woman with PCOS ought to try.  As with most things, it may work wonders for some, and do absolutely nothing for another person.  

To give inositol it’s best chance of working for you, or if you’ve tried it and not found it effective, it’s worth looking at the finer details such as the form and dose.  

One of the characteristics of PCOS is hyperandrogenism (high testosterone) and chronic anovulatory cycles. PCOS is also associated with insulin resistance and dysfunction in the cells in the pancreas which make insulin, which increases the likelihood of getting diabetes.  The result of insulin resistance (IR) is insulin levels which are much higher than normal, and this has a major role to play in the high testosterone levels in women with PCOS.  Furthermore, insulin also decreases SBHG (sex hormone binding globulin), which increases the bioavailability of androgens.  

The relationship between hyperandrogenism and IR is a chicken and egg problem.  On the one side androgens have a direct role in how insulin works, causing cells to become resistant to insulin.  And on the other side insulin has a direct role in controlling ovulation, and insulin also stimulates the ovaries to make more androgens.  It therefore makes sense to try to decrease insulin resistance and insulin levels – this is where alongside dietary modification, supplements like inositol or medications like Metformin come into the picture. 

There are two types of inositol in supplement form: D-chiro-inositol (DCI) and myo-inositol (MI).  They have slightly different effects in the body.  DCI can decrease insulin resistance throughout the body, which causes cells to be more sensitive to insulin and leads to lower insulin levels.  While MI improves insulin signalling inside the ovaries, which can lead to normal ovulation.  DCI is known as an aromatase inhibitor and in the wrong balance can increase androgens which will not be beneficial for most women with PCOS.  

According to research studies the most effective inositol formula is a combined supplement of myo-inositol and c-chiro-inositol in 40:1 ratio, which is similar to the body’s normal ratio.  The standard dose is 4000 mg a day. Being a high dose, we recommend taking it in powder form.  Our preference is to use a supplement without additional nutrients such as folic acid for the reason that you may not require additional folic acid if there is folate in a multivitamin, also folic acid is not a natural form of folate.  Lastly, it is advisable to inform your health care team if you are supplementing with inositol.