Inositol: Benefits, Uses, and Potential Side Effects

Inositol is a sugar-like compound naturally made by the human body, playing an important role in biological processes such as regulating glucose and fat metabolism. It carries potential health benefits, especially in governing symptoms of PCOS syndrome or regulating insulin resistance. While it can be found in nine different forms, myo-inositol and d-chiro-inositol have been the most studied regarding their potential benefits.

What is inositol?

Inositol is a carbohydrate that naturally occurs in the body. It can be found in large amounts in the kidneys, brain, and other body organs. For a very long time, it has been called vitamin B8, but over time, research has shown that inositol is naturally produced by the human body, which excludes it from the vitamin group.

Inositol occurs in the form of myo-inositol, d-chiro-inositol, l-chiro-inositol, as well as scyllo-, muco-, epi-, neo-, cis- and allo-inositol. Although many of these structural variants are essential in the functioning of the body, myo- and d-chiro-inositol are the ones that studies show the most potential health benefits.

Inositol's role in the body

Inositol is a compound involved in multiple processes in the body, ranging from cell signaling through regulating hormones to governing glucose and lipid metabolism.

One potential role of inositol is regulating thyroid hormones. A small clinical study with patients with Hashimoto disease, a disease where the immune system affects the function of the thyroid, showed that the administration of myo-inositol may help normalize the concentrations of thyroid hormones. Another study showed that myo-inositol could potentially reduce the symptoms associated with thyroid dysfunction.

Inositol potentially enhances the sensitivity of human tissues to insulin and lowers the HOMA IR index (Homeostasis Model Assessment of Insulin Resistance, which estimates insulin resistance in the body). While myo-inositol is involved in insulin signaling, d-chiro-inositol facilitates the action of insulin by helping cells to uptake glucose. A very small yet promising study involving 46 female participants with PCOS has shown that inositol supplements might potentially lower the HOMA IR index.

Specific forms of inositol, such as myo-inositol and d-chiro-inositol, are involved in lipid metabolism. A meta-analysis of 14 studies has shown that inositol supplementation among patients with metabolic diseases may potentially decrease triglyceride and LDL cholesterol levels.

Myo-inositol vs. d-chiro-inositol

Inositol exists in nine different forms, but the most studied ones are myo-inositol and d-chiro-inositol. Myo-inositol is a prevalent form found in tissues, while d-chiro-inositol is derived from the former synthesized by our body when needed.

• Myo-inositol. Myo-inositol is found mainly in tissues with a greater demand for glucose — the heart, brain, and ovaries. The leading roles of myo-inositol include regulating brain neurotransmitters and governing insulin signaling. Taking myo-inositol can be potentially beneficial for individuals with PCOS or PMDD (Premenstrual Dysphoric Disorder).
• D-chiro-inositol. It is present in tissues that store glucose, such as the liver and muscles. Its main roles include regulating glucose or fat metabolism. This compound helps transport glucose to the cells and plays a part in managing triglyceride levels. The d-chiro-inositol supplement might be potentially beneficial in managing PCOS symptoms or excessive weight.

Individuals aiming to incorporate inositol into their daily supplementation might consider using one of the forms or a combination of both, depending on their health goals. While there is no clear indication of what ratio of myo-inositol and d-chiro-inositol is optimal. This will likely depend on the targeted condition. One study reported that consuming these supplements at a ratio of 40-to-1 had a positive impact on metabolic and hormonal profiles in patients with PCOS.

Sources of inositol

Can inositol be found in food? Yes. Inositol foods include whole grains, oats and brans, nuts (e.g., walnuts, almonds, Brazil nuts), or certain fruits. Below, we have included a list of common foods with high myo-inositol content per 100 grams.

Consuming certain foods or beverages, such as refined sugar or caffeine, might potentially increase the bodily intake of myo-inositol. While a balanced diet can provide a good source of inositol, the supplementation of this compound might be beneficial for individuals seeking specific health outcomes. Supplementation may help provide consistent dosing of a particular amount of a selected type of inositol to target particular metabolic pathways.

Potential benefits of inositol

Supplementing your diet with inositol may bring some potential health benefits. Below, we have specified the most investigated.

Inositol for PCOS

One of the potential inositol benefits is related to the management of polycystic ovary syndrome (PCOS). The meta-analysis of 24 trials and experiments has analyzed how the use of inositol could help manage certain symptoms associated with the disease. Several works have reported the potential effect of the supplement on hormone levels, insulin resistance, and fertility. Two studies have reported that inositols play a role in reducing the levels of male hormones (androgens), such as testosterone or androstenedione, which can positively influence the quality of life of individuals living with PCOS. Lowering male hormones in PCOS patients is particularly important, as it's associated with reduced symptoms such as acne or hair loss, provides menstrual regularity, and improves fertility.

One study also showed that combining inositol and folic acid might have an impact on fertility in patients with PCOS, while one clinical trial showed that supplementing with myo and d-chiro-inositol at a ratio of 3.6:1 had a positive effect on irregular menstrual cycles in young women with PCOS. However, while the study describes positive effects, it does not specify how long it takes for myo-inositol to regulate periods.

Some studies have also shown the potential effects of inositol on reducing glucose levels. This could potentially help with the management of insulin resistance, which frequently accompanies PCOS. While some studies indicate the impact of this supplement on cycle regularization and fertility as well as the positive effects of inositol in PCOS, it is challenging to draw unambiguous conclusions as many of the studies evaluated the effect in combination with other treatments and drugs.

Inositol for mental health

The consumption of inositol was also investigated in the context of helping with mental disorders and promoting mental health. The analysis of two studies suggested that myo-inositol can potentially help with the management of Premenstrual Dysphoric Disorder (PMDD).

While there is no clear indication of how inositol affects particular diseases, several studies pointed potential involvement of inositol as its level in blood changes in patients struggling with mental diseases. The amount of inositol in the blood was lower in patients with MDD (Major Depressive Disorder), suggesting that the lower levels of this compound might negatively impact mental health.

The effect of inositol on mood and mental health is not fully supported, and many studies are currently in development. Many of these studies were only conducted in laboratory animal models, and hence, the evidence is still evolving. Further clinical trials with patients are needed to confirm potential beneficial effects.

Inositol for weight management and metabolic health

Thanks to their involvement in regulating glucose levels and certain hormones, inositols might potentially affect weight management and metabolic health. One of the main reasons is their influence on glucose levels. A 2022 meta-analysis, including 1,239 subjects, has concluded that inositol may have glucose-lowering effects driven by an improvement in insulin sensitivity independent of weight loss.

These positive effects on glucose homeostasis might suggest incorporating inositol to potentially reduce insulin resistance, but it is always important to consult any new supplementation with healthcare professionals.

Other potential benefits

The potential benefits of different forms of inositol are still being investigated. Aside from using inositol for fertility, PCOS, glucose, or weight management, the compound might have some effects on neurological or respiratory health. One study evaluated the effect of scyllo-inositol on patients with mild to moderate Alzheimer’s disease, showing that administration of this compound may potentially change the levels of specific biomarkers.

Other benefits of inositol include potentially improving skin health or sleep quality and alleviating the cosmetic symptoms of PCOS, such as acne. One study has also suggested that supplementation with inositol in pregnant women may improve sleep quality. While the results of the potential benefits of inositol are promising, the evidence is still limited. Further research with a larger group of participants is needed to fully exploit the benefits of this supplement.

How to use inositol

Before starting to take an inositol supplement, consult with a healthcare professional or dietitian to ensure the dosage is appropriate for your health condition and goals.

Dosage guidelines

There are no clear guidelines regarding the dosage of myo-inositol and d-chiro-inositol in the human diet, and the intake might depend on the disease we target.

Overall, myo-inositol doses of 18 g for 3 months or 4 g for 12 months are considered safe and well tolerated. Many supplements offer daily dosages between 500 mg and 2,000 mg, frequently combining various forms of inositol mixed at different ratios. For example, studies have shown that the dosage of inositol for PCOS between 2,400 mg and 4,000 mg daily brought potential benefits to patients. Therefore, it is important to discuss with healthcare providers for personalized advice and to select the best inositol supplement.

When to take inositol

Inositol can be taken at any time of the day, although some people prefer to use it in the morning or before bed, depending on individual preferences and therapeutic goals. There are no unambiguous studies that would describe the best time to take inositol for weight loss, PCOS management, or mood disorders and how timing can influence its effectiveness.

Different forms of inositol supplements

Inositol supplements are available in different forms, and therefore, they can be adjusted to individual preferences. The most common forms include capsules and powders that contain inositol hexanicotinate, inositol triphosphate, or other inositol complexes.

Inositol capsules might be a preferred choice for individuals who dislike the taste of inositol powder supplements. The less common forms of inositol available on the market include liquids or chewable tablets. Before selecting the suitable form for you, consider convenience, costs, the amount of inositol in the supplement, the presence of additional vitamins or molecules, what inositol is used for, and your health goals.

Inositol side effects and safety

Before start taking inositol, it is good to understand its potential side effects and interactions with other drugs and supplements.

Potential side effects

Inositol side effects are rare. The US Food and Drug Administration (FDA) considers it a safe compound. Potential side effects might occur when this compound is taken at excessively high dosages, such as with other supplements, and this may cause digestive problems such as nausea, vomiting, and abdominal pain.

Interactions and contraindications

While inositol is considered safe and well-tolerated, there are certain situations when inositol supplementation might not be advised. For instance, it might potentially not be recommended for patients with manic and hypomanic episodes in bipolar disorder as increased concentrations of inositol may be found in the brain. However, the role of inositol in bipolar disorder is still under investigation, and some studies suggest that BD results in a decrease in inositol.

Since inositol is involved in insulin and glucose metabolism, it might potentially interact with diabetes medications.

Combining inositol with other supplements

Overall, inositol is safe to take alongside other supplements. However, it is important to be mindful while taking inositol with supplements targeting the same issue or disorder. This could include supplements such as berberine, vitamin D, or folic acid.

Inositol and berberine

Berberine is produced from medicinal herbs. It may have potential effects on insulin sensitivity and glucose levels. There are no scientific studies showing interactions between berberine and inositol, but since they target insulin sensitivity, taking them together might lead to undesired amplified effects.

Inositol and vitamin D

Vitamin D is involved in bone, immune, and cardiovascular health. Similarly to berberine, it might improve insulin sensitivity in patients with PCOS. Therefore, it is advised to check with a healthcare provider if vitamin D and inositol can be taken together. A small study has shown that combining myo-inositol and vitamin D may positively impact the parameters of autoimmune thyroiditis, as taken together, the supplements may potentially have a role in decreasing Thyroid Stimulating Hormone (TSH) levels. However, this shouldn't be used as a treatment.

Inositol and folic acid

While there is limited data available, combining inositol and folic acid might help with fertility in women with PCOS. One study has shown that the administration of both supplements may enhance the fertility ratio in women with PCOS.

Should you use inositol?

While the role of inositol is still under investigation, it's known that this compound is involved in various biological processes such as glucose or lipid metabolism. Incorporating inositol supplements might bring potential benefits in managing symptoms of PCOS. It also may have a positive impact on insulin resistance.

While the compound is generally well-tolerated and can be administered alongside most other medicines or supplements, it is good to consult with a healthcare professional to ensure that the supplementation aligns with our health goals.