Many of you are enjoying the reliable benefits of inositol. Specifically, supplemental Myo-inositol has a proven track record for enhancing egg quality, normalizing ovulation, supporting weight management and inflammation by reducing insulin resistance and testosterone levels, as well as enhancing your heart health. Our knowledge of the benefits of D-chiro-inositol, on the other hand, is a bit more sketchy. Myo-inositol breaks down to D-chiro-inositol and in that form it has functions slightly different from its parent molecule. Some research suggests women with PCOS do not convert as much myo-inositol into D-chiro-inositol. It’s logical to wonder if adding D-chiro-inositol as a supplement will help. A series of research studies have been done looking at this combination. All are unfortunately flawed.
Someone, some where, at some time decided to state that the normal, physiologic ratio of myo- to d-chiro- inositol in human plasma is 40:1, and this is the ratio tested in at least 3 studies.[i],[ii]. [iii] All 3 studies concluded that both inositols demonstrate significant benefit, but note there should be a specific selection for clinical application. In essence, there are no contraindications at all to using myo-inositol. It significantly improves reproductive function by positively effecting blood sugar and insulin as well as testosterone levels, while enhancing ovulation and increasing the quality of women’s oocytes (eggs). D-chiro inositol adds additional benefit to cardiovascular health, but it will also damage a woman’s oocytes. There are claims made by suppliers of supplement products that the tiny amount of d-chiro-inositol available in products with the 40:1 ratio is not dangerous. However, one study noted that d-chiro-inositol by itself “negatively effects oocyte quality.”[iv]
Unfortunately, no one seems to be able to identify the research that determined the validity of the claim that the 40:1 ratio actually represents a human norm. The authors have been contacted and asked to produce their original source; they have apparently not replied to the request. In my communication with colleague Dr. Michael Jurgelewicz, I am intrigued by points he makes regarding the rationale for the 40:1 ratio. Specifically, presuming 40:1 is the desirable ratio in all humans, women with PCOS would have higher plasma levels than other people, since we don’t convert it as efficiently. Therefore it makes more sense to supplement with a ratio LOWER than 40:1 in order to compensate for a high MI/DCI ratio occurring in PCOS patients.
Because we don’t have actually reliable data on 1. the validity of a 40:1 ratio or 2. the clinical risks involved in lowering that ratio, effectively increasing the d-chiro component, in my practice, I am not recommending the use of d-chiro-inositol products to my patients and clients who want to have children. We need definitive studies that identify at what dose of D-chiro-inositol we start seeing a decline in oocyte quality. There is so far a single study that examines that question; the authors conclude “The number of immature oocytes was significantly increased in the three groups that received the higher doses of DCI. Concurrently, the number of MII oocytes was significantly lower in the D group compared to placebo group. Noteworthy, the number of grade I embryos was significantly reduced by DCI supplementation. Indeed, increasing DCI dosage progressively worsens oocyte quality and ovarian response.”[v]
Considering the current state of our understanding, I consider it irresponsible to use D-chiro-inositol with a woman struggling with fertility issues until that data is clear. Theoretically I would be comfortable using it with a woman who will not be trying to get pregnant but does have some cardiovascular disease risk. However, since there are so many other reliable, proven ways to protect cardiovascular health, d-chiro-inositol is just not that interesting to me as a clinical tool.
Take good care of yourselves, UnCommon Women! Be alert to “new, new, new!” things to buy. Too new may mean someone is jumping the gun to produce profit, without sufficient respect for your well being.
Resources:
[i] Dinicola S, et al. The rationale of myo-inositol and D-chiro-inositol combined treatment for polycystic ovary syndrome. J Clin Pharmacol. 2014 Oct;54(10):1079-92. doi: 10.1002/jcph.362. Epub 2014 Jul 18.
[ii] Unfer V, Porcaro G. Updates on the myo-inositol plus d-chiro-inositol combined therapy in polycystic ovary syndrome. Expert Rev Clin Pharmacol. 2014 Sep;7(5):623-31. doi: 10.1586/17512433.2014.925795. Epub 2014 Jun 5.
[iii] Nordio M, Proietti E. The combined therapy with myo-inositol and D-chiro-inositol reduces the risk of metabolic disease in PCOS overweight patients compared to myo-inositol supplementation alone. Eur Rev Med Pharmacol Sci. 2012 May;16(5):575-81.
[iv] Dinicola S, et al. The rationale of myo-inositol and D-chiro-inositol combined treatment for polycystic ovary syndrome. J Clin Pharmacol. 2014 Oct;54(10):1079-92. doi: 10.1002/jcph.362. Epub 2014 Jul 18.
[v] Isabella R, Raffone E. Does ovary need D-chiro-inositol? J Ovarian Res. 2012 May 15;5(1):14. PubMed PMID: 22587479; PubMed Central PMCID: PMC3447676.
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