Let's talk about inositol. Many people take it for PCOS and insulin resistance, and some recommend it for sleep and mental health. But is there any evidence to support its use?
In this article, I'll go over some genuine benefits of inositol that are supported by scientific literature. On the flip side, I'll also cover some commonly reported benefits of inositol that aren't well supported by strong evidence. At the end, I'll go over important safety information and potential side effects to be aware of before taking the supplement.
What Is Inositol?
Inositol is a sugar-like compound often referred to as vitamin B8, although it's not actually a vitamin. It's essential in many biochemical pathways, and our bodies naturally synthesize it, primarily in the kidneys. Inositol is also found in fiber-rich foods like beans, brown rice, and citrus fruits.
Inositol for PCOS
Perhaps the most studied use of inositol is in the treatment of PCOS (polycystic ovary syndrome). A recent meta-analysis of 26 randomized controlled trials, including almost 1,700 patients, showed that inositol was a safe and effective treatment for PCOS and was found to be non-inferior compared to the gold-standard treatment, metformin. More specifically, it affected BMI, free and total testosterone, and glucose and insulin levels.
Another meta-analysis of six randomized controlled trials, published in Gynecological Endocrinology, showed that inositol treatment was better tolerated and associated with fewer adverse events than metformin.
Since there are several types of inositol, it's worth highlighting a 2019 randomized controlled trial that found that a 40:1 ratio of myo-inositol to D-chiro-inositol, at 2 grams twice a day for three months, was the most effective for restoring ovulation in women with PCOS.
Inositol for Gestational Diabetes
Inositol has also been studied for gestational diabetes. A recent systematic review and meta-analysis of seven randomized controlled trials showed that 4 grams of myo-inositol per day significantly decreased the incidence of gestational diabetes, significantly decreased plasma glucose levels, and reduced the need for insulin treatment. It also reduced the incidence of preterm delivery and neonatal hypoglycemia (low blood sugar in newborns).
Inositol for Metabolic Health
There's also solid evidence supporting the use of inositol in metabolic health. A 2018 systematic review and meta-analysis of 14 randomized controlled trials showed that inositol supplementation significantly decreased triglycerides and LDL cholesterol levels.
Another randomized controlled study evaluated postmenopausal women with metabolic syndrome and found that treatment with myo-inositol at 2 grams twice daily for 12 months led to significant improvements in glucose and insulin levels, as well as a decrease in markers of insulin resistance.
Inositol also seems to affect blood pressure. A recent meta-analysis of seven randomized controlled trials showed that supplementation with inositol significantly decreased both systolic and diastolic blood pressure. However, the analysis showed substantial heterogeneity, so much larger randomized controlled trials are needed to validate these findings.
Inositol for Sleep and Mental Health: Where the Evidence Is Weak
Many people take inositol for sleep or to help with mental health, but this is an area where the supporting evidence gets pretty weak.
Some earlier studies noted low levels of inositol in the brain and cerebrospinal fluid of people suffering from depression and bipolar disorder. However, subsequent studies looking at inositol supplementation did not show any benefit in treating depression compared to placebo.
Some small studies are pointing to a possible use of inositol in treating anxiety or panic disorders. One such study, a very small randomized controlled trial with only 21 patients, showed comparable efficacy between inositol and fluvoxamine in reducing anxiety. Still, much larger studies are needed to evaluate its effectiveness in this area properly. In fact, a recent review paper, published in February of this year, noted that the use of inositol in treating psychiatric disorders remains controversial, and there isn't enough evidence to recommend its use until more robust studies are conducted.
Safety and Side Effects
When it comes to safety, the usual side effects of inositol include nausea, headaches, and GI upset. Still, these typically occur at higher doses, around 12 grams per day, which is much higher than the typical doses used for PCOS or metabolic syndrome, about 2 to 4 grams per day.
It's also worth noting that inositol is sold as a supplement and is not regulated by the FDA, so I recommend talking to your doctor before starting this or any other supplement.
Conclusion
Inositol has some of the most solid evidence among popular supplements, particularly for PCOS, gestational diabetes, and aspects of metabolic health such as cholesterol, insulin resistance, and blood pressure. Its use for sleep and mental health, however, is much less supported, with current evidence too limited or inconsistent to recommend it for those purposes. Overall, inositol appears to be a well-tolerated supplement at typical doses. Still, as with any supplement, it's best to talk with your doctor first, especially since it isn't FDA-regulated and individual needs can vary.
FAQ
What is inositol used for?
Inositol is most commonly used for PCOS (polycystic ovary syndrome), gestational diabetes, and aspects of metabolic health like cholesterol and blood pressure. It's also sometimes used, with much weaker evidence, for sleep and mental health.
Does inositol really help with PCOS?
Yes, this is its most well-studied use. Multiple meta-analyses show inositol is safe and effective for PCOS, with effects on BMI, testosterone levels, and glucose and insulin control comparable to metformin, and generally better tolerated.
Is inositol effective for gestational diabetes?
Research suggests yes. Studies show myo-inositol supplementation can reduce the incidence of gestational diabetes, lower plasma glucose, and reduce the need for insulin treatment, as well as reduce preterm delivery and neonatal hypoglycemia.
Can inositol help with depression, anxiety, or sleep?
The evidence here is weak. While some early studies noted low inositol levels in people with depression, later placebo-controlled studies found no clear benefit for depression. Some very small studies suggest possible benefits for anxiety, but larger trials are needed before it can be recommended for psychiatric use.
What are the side effects of inositol?
Inositol is generally well tolerated at typical doses (2 to 4 grams per day). Side effects like nausea, headaches, and GI upset are more commonly seen at much higher doses, around 12 grams per day.
Does the FDA regulate inositol?
No. Inositol is sold as a dietary supplement and is not FDA-regulated, so it's a good idea to talk to your doctor before starting it, as with any supplement.