Inositol--sometimes called Vitamin B8 (even though it is not a vitamin)--is a natural sugar that is probably already in your diet.
You may have seen it advertised as an over the counter supplement that can help with conditions such as polycystic ovarian syndrome, hormonal imbalances in women, metabolic disorders, and mental health conditions including depression and anxiety.
But what is inositol, can it really help, and is it safe to take?
Inositol is a type of sugar found in many foods such as grains, beans, nuts, and fruits (Clements & Darnell, 1980).
There are different types of inositol; the most common one found in food is myo-inositol, but in supplements you’ll often see it paired with D-chiro-inositol. When paired, these two inositols help the body process insulin, and have effects for other hormones associated with mood disorders and metabolic conditions.
Inositol is being recommended more frequently for the management of certain illnesses including PCOS, metabolic disorders, and mood disorders.
Polycystic ovarian syndrome (PCOS) is a lifelong condition in women (or other people with ovaries) that impacts the levels of male and female hormones in the body.
This comes with many side effects, which can include:
Birth control pills are often prescribed to help with some of the hormonal problems associated with PCOS. However, there are several ways to relieve PCOS symptoms naturally, including diet, exercise, and supplements like myo-inositol.
Many of the side effects of PCOS patients come from an excess of androgens (male sex hormones). One study found that myo-inositol, D-chiro-inositol, or both taken together can help manage androgens in PCOS patients, leading to better results for menstruation, fertility, facial hair, and acne (Wojciechowska et al, 2019).
Another study examined overweight PCOS patients taking a supplement with a 40:1 ratio of myo-inositol and D-chiro-inositol, and found some evidence that the supplement might help reduce the risk of developing a metabolic disorder such as diabetes (Nordio & Proietti, 2012).
Inositol can mimic the effects of insulin, which means they can help process glucose and therefore lower blood sugar. In addition to helping PCOS patients manage their insulin and reduce their risk of developing a metabolic disorder, this effect can help manage disorders such as gestational diabetes and metabolic syndrome.
Gestational diabetes is diabetes, generally type 2, which occurs at the onset of pregnancy (i.e. the person did not have diabetes before pregnancy). Those who develop gestational diabetes have up to a 14% chance of their diabetes lasting beyond pregnancy, increases the risk of the pregnant person developing diabetes later in life, and increases the risk of diabetes for the child born out of that pregnancy (American Diabetes Association, 2004).
One review of existing research on prevention of gestational diabetes looked at 71 trials including 23,000 women and found evidence that myo-inositol can help, though more research is needed.
The review also suggested that pregnancy-appropriate exercise and nutrition, the anti-diabetic medication Metformin, and Vitamin D (found in sunlight) might all help prevent gestational diabetes (Griffith et al, 2020).
Little is known about the relationship between inositol and type 1 or type 2 diabetes. One small study in Italy looked at the role of myo- and D-chiro-inositol supplements on 20 patients with type 2 diabetes.
The supplements did not reduce BMI or blood pressure, but patients did show a significant decrease in the level of sugar in their blood (Pintaudi, Di Vieste, & Bonomo, 2016).
While this study alone is not enough to recommend inositol for managing diabetes, it is promising, and we can hope more studies will be done to investigate this link in the future.
Metabolic syndrome is not a disorder on its own, but rather a combination of disorders and symptoms--such as elevated blood sugar, blood pressure, and cholesterol--that increase your risk for developing complications such as heart disease and diabetes.
As with diabetes types 1 and 2, we have very limited research on the link between inositol and metabolic syndrome. One study of 80 postmenopausal women with metabolic syndrome found several beneficial effects of myo-inositol supplementation, including improved blood pressure and insulin resistance (Giordano et al, 2011).
Again, while this research is not enough, it is promising evidence to support inositol’s benefits in treating metabolic disorders.
Inositol shares a relationship with the hormones serotonin and dopamine--both associated with mental health conditions including depression, anxiety, PTSD, OCD, and ADHD. A 1997 review of inositol used as treatment for a variety of psychiatric disorders found that “inositol has therapeutic effects in the spectrum of illness responsive to serotonin selective re-uptake inhibitors, including depression, panic and OCD” (Levine). More research is needed to confirm the benefits for inositol and mood disorders.
The U.S. Food and Drug Administration classifies Inositol as “GRAS” - generally regarded as safe (FDA, 2020). Research has shown very little risk for either humans or animals upon taking inositol, even during pregnancy--though you may have some side effects at higher doses.
For most conditions, the recommended dosage of inositol is 4 grams per day. When supplementation has exceeded 12 grams per day, side effects have included headaches, fatigue, dizziness, nausea, and other mild gastrointestinal problems (Formoso et al, 2019).
The naturally occurring sugar inositol has a number of potential benefits for your physical and mental health--especially for those with PCOS or mental health conditions, or who are at risk of developing a metabolic condition including gestational diabetes. Studies suggest that doses under 18 grams are very safe (even during pregnancy) and have virtually no side effects.
However, if you do have any side effects such as headaches, dizziness, fatigue, or nausea, talk to your doctor. And you should always consult with your doctor before trying any new supplements.