Myo-inositol is a carbocyclic sugar that the body produces from glucose. While sometimes called vitamin B8, it is not a vitamin because the body can synthesize it. This compound is a structural component of every cell membrane. Its presence is part of the basic processes that allow cells to function, grow, and communicate.
Myo-Inositol’s Role in Cellular Communication
Myo-inositol is a participant in signal transduction, where it functions as a secondary messenger. Think of a primary messenger, like insulin, as a doorbell on the outside of a cell. Myo-inositol acts as an internal signal that tells the cell what to do after the doorbell has been rung. This system allows hormones and neurotransmitters to communicate their instructions from outside the cell to the machinery inside.
Specifically, myo-inositol is a precursor to molecules called inositol phosphoglycans (IPGs). When insulin binds to its receptor on a cell’s surface, it triggers the release of these IPGs. These IPGs then act as secondary messengers within the cell, activating various enzymes involved in glucose metabolism. This process ensures that cells respond appropriately to insulin, for example by taking up glucose from the blood.
This signaling cascade is particularly active in tissues that use a lot of glucose, such as the brain and ovaries. Problems in this pathway can arise when high glucose levels interfere with the cell’s ability to take up and use myo-inositol. This interference can disrupt insulin signaling and contribute to a state of insulin resistance, where cells become less responsive to insulin’s effects.
Impact on Hormonal and Metabolic Health
Myo-inositol’s function in insulin signaling makes it relevant for conditions like Polycystic Ovary Syndrome (PCOS), which often involves insulin resistance. In PCOS, impaired insulin signaling can lead to higher blood insulin levels, stimulating the ovaries to produce excess androgens and causing symptoms like irregular cycles. By improving insulin sensitivity, myo-inositol supplementation helps lower both insulin and androgen levels. Studies show this can lead to more regular ovulation and menstrual cycles, a benefit for those with infertility associated with the condition.
Beyond PCOS, myo-inositol’s influence on insulin sensitivity extends to broader metabolic health. It has been studied for its role in managing metabolic syndrome, a cluster of conditions that increase the risk of heart disease and type 2 diabetes. Research suggests myo-inositol can improve several markers of metabolic syndrome, including blood sugar control, triglyceride levels, and HDL (good) cholesterol. It has also shown potential in helping to manage gestational diabetes by supporting healthy insulin function.
Supplementation, Dosage, and Safety
For therapeutic purposes, especially for PCOS and metabolic health, myo-inositol is taken as a dietary supplement. Dosages used in clinical studies for PCOS range from 2 to 4 grams per day, often divided into two doses. This amount is much higher than what can be obtained through diet, making supplementation necessary to achieve these levels.
Myo-inositol is frequently combined with another isomer, D-chiro-inositol, often in a 40:1 ratio. This formulation is thought to mimic the natural plasma ratio in healthy individuals. Myo-inositol improves insulin signaling and glucose uptake, while D-chiro-inositol is involved in glycogen synthesis. This specific ratio is believed to support both metabolic and ovarian function.
Myo-inositol is considered safe, and side effects are uncommon at standard therapeutic doses. When they do occur, they are mild and related to the digestive system, such as gas, bloating, or diarrhea. These effects are more likely at very high doses exceeding 12 grams per day.
Natural Food Sources
Myo-inositol is naturally present in a variety of foods. Fresh foods provide higher levels of myo-inositol compared to canned, frozen, or processed versions. Rich sources include:
- Fresh fruits, particularly cantaloupe, grapefruit, and oranges
- Beans and legumes, such as great northern beans and lima beans
- Whole grains like brown rice and oats
- Nuts and seeds, including almonds and walnuts