What does inositol do to the body?

October 30, 2025 •

4 min read

Although commonly referred to as vitamin B8, inositol is not a vitamin but a type of sugar that plays several important roles in the body, primarily as a messenger for cells. This has led many to question, what does inositol do to the body, and why is it so significant?

Quick Summary

Inositol, a naturally occurring sugar, is vital for cellular communication and functions as a secondary messenger for hormones and neurotransmitters. It is often used to support metabolic health, hormonal balance, and mood regulation, especially for conditions like polycystic ovary syndrome (PCOS).

Key Points

Cell Signaling: Inositol acts as a vital messenger within cells, relaying signals for hormones and neurotransmitters.
Metabolic Health: It improves insulin sensitivity and helps manage conditions like PCOS and metabolic syndrome by regulating blood sugar and fats.
Mood Regulation: By influencing neurotransmitters like serotonin and dopamine, inositol offers potential support for mood, anxiety, and OCD.
PCOS Support: A specific combination of myo-inositol and d-chiro-inositol can regulate periods, reduce androgens, and improve fertility in women with PCOS.
Minimal Side Effects: Inositol is generally safe, with mild gastrointestinal issues most common at high doses.
Food Sources: It can be found naturally in many foods, including citrus fruits, beans, and nuts.

What Is Inositol?

Inositol is a carbocyclic sugar molecule that exists in nine stereoisomers, with myo-inositol being the most common and biologically active form. Found naturally in the body and in a variety of foods, it is often called a 'pseudovitamin' or 'vitamin B8,' although it is not officially a vitamin because the body can synthesize it from glucose. A typical diet can provide about 1 gram of inositol per day, sourced from fruits, nuts, grains, and legumes, but therapeutic doses are often much higher, necessitating supplementation.

How Inositol Works in the Body

Inositol's primary function is its role in cell signaling and membrane structure. It is a key component of membrane phospholipids, specifically phosphatidylinositol (PI), and its phosphorylated derivatives, known as phosphoinositides, act as critical 'second messengers'.

Cellular Communication

These second messengers are responsible for relaying signals from the cell's exterior to its interior, triggering various biological processes. This includes signal transmission from hormones like insulin and neurotransmitters such as serotonin and dopamine. This signaling cascade is central to how inositol influences metabolic and mental health.

Insulin Sensitivity

Inositol is directly involved in the insulin signaling pathway, particularly through its two most studied forms: myo-inositol (MI) and D-chiro-inositol (DCI).

Myo-inositol works primarily by activating glucose transporters to improve the body's use of glucose.
D-chiro-inositol is involved in the synthesis and storage of glycogen.

This complementary action improves insulin sensitivity, making cells more responsive to insulin and helping to regulate blood sugar levels.

Key Functions and Benefits of Inositol

Metabolic Syndrome Management

Clinical studies have shown that inositol supplementation can be beneficial for individuals with metabolic syndrome. This syndrome is characterized by a cluster of conditions that increase the risk of heart disease, stroke, and type 2 diabetes. Inositol has been shown to:

Improve insulin resistance
Reduce blood triglyceride and cholesterol levels
Lower blood pressure
Aid in weight management, particularly in cases linked to insulin resistance

Polycystic Ovary Syndrome (PCOS)

PCOS is a hormonal disorder characterized by irregular periods, excess androgen levels, and insulin resistance. Inositol, especially in a specific MI to DCI ratio, offers significant benefits for women with PCOS.

Restores Ovulation and Menstrual Regularity: Inositol can help restore regular menstrual cycles and improve the frequency of ovulation.
Lowers Androgen Levels: By improving insulin sensitivity, inositol helps to reduce elevated androgen levels, which can decrease symptoms like hirsutism and acne.
Enhances Fertility: Research indicates that inositol can improve egg quality and increase pregnancy rates for women with PCOS undergoing fertility treatments.

Mental Health Support

Inositol's influence on brain chemistry has led to its use in supporting mental health.

Neurotransmitter Modulation: Inositol assists in regulating neurotransmitters like serotonin and dopamine, which are key for mood control. Lower levels of inositol have been observed in the brains of individuals with certain mood disorders.
Panic Disorder and OCD: Some studies suggest that high doses of myo-inositol may help reduce the frequency of panic attacks and alleviate symptoms of obsessive-compulsive disorder (OCD).

Natural Sources of Inositol

While supplementation is common, inositol is also found in a variety of foods:

Fruits: Citrus fruits (grapefruit, oranges), cantaloupe, and bananas
Legumes: Beans (lima, navy, adzuki) and peas
Nuts and Grains: Almonds, walnuts, whole-grain products like brown rice and wheat bran, and oats
Vegetables: Leafy greens and cabbage
Meats: Organ meats like liver

Inositol Comparison Table: Myo-inositol vs. D-chiro-inositol


Feature	Myo-Inositol (MI)	D-chiro-Inositol (DCI)
Function	Helps activate glucose transporters and cellular glucose uptake.	Involved in glycogen synthesis and storage.
Role in PCOS	Supports healthy ovarian function and egg quality.	Helps reduce elevated androgen levels and improve insulin signaling.
Optimal Ratio	Often paired with DCI in a 40:1 ratio for maximum effect in conditions like PCOS.	Most effective when combined with MI at a specific ratio, as too much DCI can be detrimental.
Prevalence	The most abundant form of inositol in the body and in supplements.	Produced by the body from MI via an insulin-dependent enzyme.

Safety, Dosage, and Side Effects

Inositol is generally considered safe and well-tolerated at typical supplement doses. However, higher doses, particularly above 12 grams per day, can cause mild gastrointestinal side effects.

Common Side Effects: Mild nausea, stomach pain, diarrhea, and bloating. These can often be mitigated by splitting the daily dose.
Dosage: Optimal dosages vary widely depending on the health condition being targeted. For example, PCOS treatment often uses a 4,000 mg/day dose, while higher doses (12–18 g/day) have been explored for some mental health conditions.
Caution: Individuals on diabetes medication should monitor their blood sugar closely as inositol may enhance the blood sugar-lowering effect. Pregnant and breastfeeding women, and those with underlying health conditions, should consult a healthcare provider before starting supplementation.

Conclusion: Inositol’s Multifaceted Role

Inositol is far more than a simple carbohydrate; it is a critical signaling molecule that profoundly impacts metabolic, reproductive, and neurological functions. By influencing insulin sensitivity and balancing key neurotransmitters, it offers therapeutic potential for a range of conditions, from PCOS and metabolic syndrome to certain mental health disorders. While the body can produce some inositol, strategic supplementation with the correct isomers, like myo- and d-chiro-inositol, can provide targeted support where needed. As research continues to uncover its complex mechanisms, inositol remains a versatile and important compound for overall health. For further information on inositol's role in signaling pathways, the NIH provides detailed research.

Frequently Asked Questions

No, while inositol was once called vitamin B8, it is not a true vitamin because the human body can synthesize it from glucose. It is a sugar-like carbohydrate with key functions in the body.

Inositol acts as a second messenger in the insulin signaling pathway, helping cells become more responsive to insulin. This allows for better glucose uptake and regulation of blood sugar levels.

Some research suggests that inositol may help balance neurotransmitters like serotonin and dopamine, which influence mood and anxiety. Studies have shown potential benefits for panic disorder and OCD, though results for depression are mixed.

Myo-inositol and D-chiro-inositol are two isomers with distinct functions. Myo-inositol helps activate glucose transporters, while D-chiro-inositol is involved in glycogen storage. They work synergistically, with a 40:1 MI to DCI ratio often used for conditions like PCOS.

Good dietary sources of inositol include citrus fruits, cantaloupe, beans, nuts (almonds, walnuts), and whole grains.

Inositol is generally safe, but higher doses (above 12g/day) may cause mild gastrointestinal issues such as nausea, gas, or diarrhea. These effects are rare at standard dosages.

The time frame for noticing effects varies depending on the condition being addressed. For some metabolic issues or PCOS symptoms, it may take several weeks to months of consistent supplementation to see noticeable improvements.

Inositol is considered possibly safe for short-term use during pregnancy, and some studies show it may reduce the risk of gestational diabetes, especially when combined with folic acid. However, it should only be used under medical supervision.