Inositol, sometimes referred to as vitamin B8, naturally occurs in foods such as fruits, beans, grains and nuts ().
Your body can also produce inositol from the carbohydrates you eat.
However, research suggests that additional inositol in the form of supplements may have numerous health benefits.
This article takes a detailed look at the benefits, recommended dosages and potential side effects of inositol supplements.
Though often referred to as vitamin B8, inositol is not a vitamin at all but rather a type of sugar with several important functions.
Inositol plays a structural role in your body as a major component of cell membranes ().
It also influences the action of insulin, a hormone essential for blood sugar control. In addition, it affects chemical messengers in your brain, such as serotonin and dopamine (, ).
It has been estimated that a typical diet in the US contains around 1 gram of inositol per day. Rich sources include grains, beans, nuts and fresh fruits and vegetables ().
However, supplemental doses of inositol are often higher. Researchers have studied the benefits of doses up to 18 grams per day — with promising results and few side effects.
Summary Inositol is a type of sugar that helps provide structure to your cells. It also affects the hormone insulin and the function of chemical messengers in your brain.
Inositol may help balance important chemicals in your brain, including those believed to affect your mood, such as serotonin and dopamine ().
Interestingly, researchers have found that some people with depression, anxiety and compulsive disorders have lower levels of inositol in their brain (, ).
Though more research is needed, several studies suggest that inositol has the potential to be an alternative treatment for mental health conditions. It also seems to have fewer side effects than traditional medications ().
While research is still limited, inositol supplements may be helpful for treating panic disorder, a severe form of anxiety.
Those with panic disorder experience frequent panic attacks, which are sudden feelings of intense fear. Symptoms include rapid heartbeat, shortness of breath, dizziness, sweating and a tingling or numb sensation in the hands (7).
In one study, 20 individuals with panic disorder took either an 18-gram inositol supplement or a common anxiety medication every day for 1 month. Those taking inositol had fewer panic attacks per week, compared to people taking the anxiety medication ().
Similarly, in a 4-week study, individuals experienced fewer and less severe panic attacks when taking 12 grams of inositol per day ().
Inositol may improve symptoms of depression, but research has had mixed results.
For example, an early study demonstrated that taking a 12-gram inositol supplement every day for 4 weeks improved symptoms in people with depression ().
In contrast, subsequent studies were unable to show any significant benefits ().
Overall, there is not enough evidence yet to say whether inositol has a true effect on depression.
As with the other mental health conditions, research on the effects of inositol and bipolar disorder is limited. However, the results of preliminary studies seem promising (, ).
For example, a small study in children with bipolar spectrum disorders showed reduced symptoms of mania and depression when a combination of 3 grams of omega-3 fatty acids and up to 2 grams of inositol were taken daily for 12 weeks ().
In addition, studies suggest that 3–6 grams of inositol taken daily may help reduce symptoms of psoriasis caused by lithium, a common medication used to treat bipolar disorder (, ).
Summary Though more research is needed, inositol shows potential as an alternative treatment option for mental health conditions, including panic disorder, depression and bipolar disorder.
Polycystic ovary syndrome (PCOS) is a condition that causes hormone imbalances in women, which may lead to irregular periods and infertility. Weight gain, high blood sugar and undesirable cholesterol and triglyceride levels are also concerns with PCOS (16).
Inositol supplements may improve PCOS symptoms, particularly when combined with folic acid.
For instance, clinical studies suggest that daily doses of inositol and folic acid may help reduce levels of triglycerides in the blood. They may also improve insulin function and slightly lower blood pressure in those with PCOS (, , ).
What’s more, preliminary research found that the combination of inositol and folic acid may promote ovulation in women with fertility issues from PCOS (, 21).
In one study, 4 grams of inositol and 400 mcg of folic acid taken daily for 3 months induced ovulation in 62% of treated women ().
Summary Inositol may help reduce blood triglyceride levels, improve insulin function, lower blood pressure and promote ovulation in women with polycystic ovary syndrome (PCOS).
Clinical studies suggest inositol supplements may be beneficial for those with metabolic syndrome (, ).
Metabolic syndrome is a group of conditions that raise your risk of chronic disease, including heart disease and type 2 diabetes.
Specifically, five conditions are associated with metabolic syndrome ():
- Excess fat in the stomach area
- High levels of triglycerides in the blood
- Low “good” HDL cholesterol levels
- High blood pressure
- High blood sugar
In a year-long clinical study in 80 women with metabolic syndrome, 2 grams of inositol taken twice daily reduced blood triglyceride levels by an average 34% and total cholesterol by 22%. Improvements in blood pressure and blood sugar were also seen ().
Amazingly, 20% of the women taking inositol supplements no longer met the criteria for metabolic syndrome by the end of the study ().
Summary Inositol may help control metabolic risk factors by helping lower blood triglyceride levels, blood pressure and blood sugar. It may also improve cholesterol levels.
In animal studies, inositol has been directly related to the function of insulin, a hormone that regulates blood sugar levels (, ).
Only a limited number of studies are available on the supplement and GDM in humans. However, some suggest that a combination of 4 grams of myo-inositol and 400 mcg of folic acid may be helpful in preventing GDM when taken daily throughout pregnancy (, , ).
However, more research is needed, as other studies have not shown the same effects ().
Summary Inositol may help prevent high blood sugar levels during pregnancy when taken in combination with folic acid, but more studies are needed to confirm this effect.
Inositol has been studied as a potential treatment option for many conditions.
Besides those already mentioned, research suggests inositol may be helpful in the following conditions:
- Respiratory distress syndrome: In preterm infants, inositol appears to be helpful for treating breathing issues from underdeveloped lungs ().
- Type 2 diabetes: A preliminary study suggests that inositol and folic acid taken daily for 6 months may aid blood sugar control in people with type 2 diabetes ().
- Obsessive-compulsive disorder (OCD): A small study suggests that 18 grams of inositol taken daily for 6 weeks may reduce symptoms of OCD ().
Summary Inositol is a potential treatment option for preterm infants with respiratory distress syndrome. It may also aid blood sugar control in people with type 2 diabetes and may reduce symptoms of obsessive-compulsive disorder.
Inositol supplements seem to be well-tolerated by most people.
However, mild side effects have been reported with doses of 12 grams per day or higher. These include nausea, gas, difficulty sleeping, headache, dizziness and tiredness ().
Up to 4 grams of inositol daily has been taken by pregnant women in studies without adverse effects, though more research is needed in this population (, ).
There are also not enough studies to determine the safety of the supplements while breastfeeding. However, breast milk seems to be naturally rich in inositol ().
In addition, it’s unclear whether inositol supplements are safe for long-term use. In most studies, inositol supplements were only taken for a year or less.
As with any supplement, talk to your doctor before taking inositol.
Summary Inositol supplements are associated with very few and only mild adverse effects. More research is needed to determine its safety in pregnant and breastfeeding women as well as in long-term use.
There are two main forms of inositol used in supplements, namely myo-inositol (MYO) and D-chiro-inositol (DCI).
Though there is no official consensus on the most effective type and dosage, the following have appeared to be effective in research studies:
- For mental health conditions: 12–18 grams of MYO once daily for 4–6 weeks (, , , ).
- For polycystic ovary syndrome: 1.2 grams of DCI once daily, or 2 grams of MYO and 200 mcg of folic acid twice daily for 6 months (, ).
- For metabolic syndrome: 2 grams of MYO twice daily for one year ().
- For blood sugar control in gestational diabetes: 2 grams of MYO and 400 mcg of folic acid twice daily during pregnancy (, , ).
- For blood sugar control in type 2 diabetes: 1 gram of DCI and 400 mcg folic acid once daily for 6 months ().
While these inositol doses appear to be helpful for certain conditions in the short-term, more research is needed to determine if they’re safe and effective over longer periods.
Summary There is no official consensus for recommended doses of inositol. Dosage and type of inositol supplement vary depending on the condition.
Research suggests that inositol may aid people with mental health and metabolic conditions, such as panic disorder, depression, bipolar disorder, polycystic ovary syndrome, metabolic syndrome and diabetes.
It appears to be safe for most people and cause only mild if any side effects in daily doses up to 18 grams.
While your diet likely contains small amounts of inositol, taking a supplement may prove beneficial for some.
Always discuss the use of supplements with your healthcare provider first.