Inositol is a chemical compound the body creates from glucose found in the kidneys. It functions in the body as a messenger in signaling pathways to support numerous biological processes. Research shows that the biggest role inositol plays in the body is to support the nervous system, neurotransmission in the brain, hormone production, and metabolism.
A healthy body will produce enough inositol to satisfy any immediate biochemical needs. However, research suggests that increasing inositol in the body, through diet or supplementation, may prove useful when conventional or alternative therapies alone fail to provide desired results.
What is Inositol?
Inositol is a chemical compound with a structure represented by a pentagon shape. (1) At the 6 corners of the molecular structure, isomers form a bond and change inositol into one of nine stereoisomers.
The body creates inositol through a multi-step process in the kidneys to yield myo-inositol. This form of inositol is most common in dietary supplements, although the label may only list ‘inositol’ as the ingredient. Supplements may also contain Scyllo-inositol, but it is less common. The other forms of inositol play a minor role in nature.
Inositol was known as vitamin B8. Today it is known as a pseudovitamin. This mean the body makes inositol, and a deficiency will not result in a disease state.
Inositol is naturally present at high levels in citrus fruits and whole grains.(2) Animal tissue also contains inositol but in smaller levels. A pair of healthy human kidneys produces around 2,000 mg of inositol each day. How much inositol is present in the body, or how much the body uses isn't known.
To discover how taking a supplement of inositol might affect inositol concentrations in the body, researchers gave a large dose of inositol to rats each day for 22 days and found that levels of inositol in the brain increased. (3) However, researchers noted that around 3% of inositol crossed the blood brain barrier, signifying that taking inositol in a larger dose on a daily basis may increase the amount of inositol present in the body.
Research has found inositol primarily works in the brain by supporting biochemical functions. This includes support for signaling between neurons and in the central nervous system, hormone regulation, and support for the sexual health of aging women, brain function, blood sugar levels, and metabolism. How inositol interacts with the mechanisms that provide these potential benefits is not entirely clear. Despite this, researchers continue to pursue new research for additional clarity so that physicians and individuals can make better decisions about health and wellness.
Research suggests there may be a link between inositol levels in the brain in people with bipolar disorder and are suicidal. (4) In postmortem cases, one study found that individuals in both situations had “significantly less” inositol levels in the frontal cortex when compared to “normal” individuals. However, in either group, there was no difference in activity of inositol in the frontal cortex, which according to researchers, suggests that insufficient inositol resulted in disruptions to secondary messenger precursors – molecules released in response to hormones or other neurotransmitters such as serotonin that affects how the brain processes information.
A study examining the effect of inositol on depressed individuals suggests that administering 12 grams of inositol daily during a 4 week period helped to improve scores on the Hamilton Depression Rating Scale when compared to a placebo. (5) The researchers note that inositol levels in depressed individuals are found to be lower when compared to people without depression.
In a follow-up to that study, researchers questioned individuals 10 to 12 months later and found that half of the patients that responded well to the inositol “relapsed rapidly” after ceasing use. (6) Nobody in the placebo group that responded well relapsed after stopping the use of inositol. In both groups, Hamilton Depression Scale Scores were similar after the 10 to 12 month period. This suggests that inositol may not provide equivalent results when compared to conventional treatments for depression. A prolonged study with continuous administration of inositol may help researchers to understand the effectiveness of inositol for depression.
To determine the other potential roles that inositol plays in the brain, a group of researchers injected 18 grams of inositol into both arms of 12 patients with bulimia (a disorder characterized by binge eating followed by purging) over a 6 week period. (7) When compared to a placebo, the inositol injection did perform better on the Global Clinical Impression, the Visual Analogue Scale, and the Eating Disorders Inventory, which are all tools to measure outcomes in data collection. Researchers suggest that an increase to inositol supports the function of serotonin in the brain, thus contributing to the positive result. However, the small sample size and short test duration is an important consideration before making a conclusive claim about the results.
Obsessive Compulsive Disorder
To determine if inositol supports other disorders of the mind, researchers administered 18 gram of inositol a day for 6 weeks in 13 patients with obsessive-compulsive disorder (OCD). (8) On the Yale-Brown Obsessive Compulsive Scale, individuals scored better when taking inositol than the placebo group. The researchers believe this results from the effect inositol has on serotonin function in the brain, as noted in other studies.
Plasmalogen is one of the most abundant compounds found in heart tissue, the nervous and immune system. (9) Scientists attribute high plasmalogen levels with HDL cholesterol, the “good” cholesterol. Certain conditions such as hyperlipidemia may result in a decrease in HDL cholesterol levels and an increase to LDL (‘bad’) cholesterol levels. (10) A study looking at the effect on supplementation of myo-inositol on plasmalogens in the cardiovascular system found positive results in individuals with these conditions. A total of 17 individuals participated in the study, with each person receiving 5 grams of inositol daily for 1 week, followed by 10 grams daily for 1 week. Results showed up to a 22% improvement in plasmalogen related parameters and a 23% reduction in LDL levels overall.
Blood Sugar Support
A study found that myo--inositol and D-chiro-inositol may help to play a role in the reduction of insulin levels in children after the consumption of glucose. (11) This study examined the effect of inositol on insulin-resistant obese male children with high basal insulin levels. Researchers compared the values obtained with an oral glucose tolerance test against values that did not receive inositol. The study concludes that the “results confirm that myo-inositol and D-chiro inositol acutely reduce insulin increase after glucose intake mainly in children with high basal insulin level.”
Another study found that when administering 1 g/kg of inositol orally to mice before an oral injection of 2 g/kg glucose resulted in a faster intake of glucose into skeletal muscle, thus lowering glucose and insulin levels in the blood. (12)
A similar study examining 80 postmenopausal women with a metabolic syndrome found that diet and 2 grams of an inositol supplements over a 6 month period showed “improved systolic and diastolic blood pressure, HOMA index, cholesterol, and triglyceride serum levels with highly significant differences, compared with the groups treated only with diet and placebo.” (13) In the same study after 12 months, eight women in the inositol and diet group no longer had a metabolic syndrome. (14)
Other human and animal studies show a similar effect of inositol on insulin, as well as changes to glucose uptake and insulin production. (15)(16)(17)(18)(19) These do not, however, indicate a sole alternative to disorders related to blood sugar levels, or insulin production or resistance. Future studies would be necessary to further clarify the role of different variants of inositol on the body.
Women’s Reproductive Health
Polycystic Ovarian Syndrome
Polycystic ovary syndrome (PCOS) is a condition that results in ovarian dysfunction, consecutive anovulation, irregular menstrual cycles, and infertility problems. (20) Scientists suggest that lifestyle, gestational environment, and insulin influences the development of PCOS. Around 15% of women will experience PCOS during the reproductive period of their life. Researchers note that insulin resistances often precedes PCOS, with elevated androgen production that results in a reduction of sex hormones found in the blood.
Treatments for this condition can include insulin sensitizing drugs, but this has been found to reduce inositol levels, which is believed to help return sex hormone levels to normal concentrations. To determine the efficacy of inositol in PCOS, researchers evaluated 3602 women with PCOS and provided a supplement comprising 4,000 mg myo-inositol and 400 micrograms of folic acid each day for 8 to 12 months. Researchers sought to show that women would experience restoration to ovulatory function and pregnancy rate after treatment. The results show that “2,520 women experienced an improvement of their menstrual cyclicity towards ovulatory cycles. Among this group, a total number of 545 women became pregnant. The pregnancies occurred after the intake of two to three months of myo-inositol and folic acid.
Other studies have administered similar doses and yielded positive results in women. (21) Studies that administered less than 200 mg of inositol found no significant change in women's hormones.
Inositol Dosage, Interactions, and Warnings
There is no established safe dosage of inositol. Supplements are commonly available with inositol doses ranging from under 500 mg to around 4,000 mg. For a psychological effect, a supplement may contain more than 10,000 mg, although these supplements may not be as readily available. An inositol supplement should never be used to address mental health concerns without first consulting a primary care physician. Inositol is considered to be well tolerated for healthy individuals.
Taking a higher dose of inositol may cause discomfort in the gastrointestinal tract. Individuals taking lithium, oral contraceptives, melatonin, who use a nicotine patch, or take medication for diabetes, blood clotting, cholesterol or any other prescription drugs should consult a physician before taking inositol. (22) Users should stop taking inositol if they experience an allergic reaction, jaundice, or stomach pain. There is insufficient research on the effects of inositol on the health of pregnant women.
Natural Sources of Inositol
Inositol is naturally present in many foods, but in comparatively smaller quantities than in supplements. In a 1,800 calorie diet, food will provide about 225 to 1,500 mg of inositol.
Wheat and grain products provide the highest quantity of inositol per gram eaten. Vegetables such as beans, rutabaga, green beans, artichoke, and okra also contain the highest amount of inositol. Milk products, fruits, meats, and seafood also provide inositol, but in lower amounts.
Start Using Inositol Supplements
Inositol is available in capsules, tablets, powders, and liquid extracts. No matter how each person uses the supplement, there are a range of potential health benefits that may support the body in a multitude of ways. While research is inconclusive, studies continue to help provide insight into how inositol may work in the body.
Experience inositol for yourself and see if it makes a difference to your health!