Inositol is a glucose-derived carbocyclic sugar abundant in brain, among other mammalian tissues. It is also a sugar alcohol that is half as sweet as sucrose (or table sugar), and occurs naturally in the human body, with the kidneys producing 4g in total daily.
Of late, inositol has been studied for its supposed abilities to control blood glucose and lipid profiles, and has exhibited insulin-related properties efficient in lowering post-prandial blood glucose levels in metabolic disease patients. However, other studies have produced conflicting results.
Is inositol any use at all?
Researchers at Iran's Shiraz University of Medical Sciences and Kashan University of Medical Sciences, as well as the University of Alberta, reviewed a number of RCTs to summarise the evidence on the impact of inositol supplementation on lipid profiles among metabolic disease patients.
They looked for RCTs up to October 2017 in the Cochrane Library, EMBASE, MEDLINE and Web of Science, ultimately reviewing 14 RCTs altogether.
They then reported that inositol supplementation among metabolic disease patients markedly reduced triglycerides, as well as total and LDL cholesterol levels.
When it came to HDL cholesterol, however, inositol supplementation was found to have no effect, except in polycystic ovary syndrome (PCOS) patients.
One possible factor for this was the duration of the studies reviewed. They lasted between six weeks and 12 months, and sub-group analysis compared studies whose duration was shorter than 14 weeks with studies that lasted 14 weeks or longer.
The researchers observed that the longer the duration of the study, the more beneficial inositol supplementation was on increasing circulating HDL cholesterol levels.
A variety of countermeasures to metabolic syndrome and its associated diseases have been studied, such as a ketogenic diet, increased vitamin D intake, amino acids and even selenium.
Inositol, on the other hand, has only recently been researched as a possible measure against metabolic diseases, with contradictory results across different studies.
The researchers were unable to assess the dose-response link between supplementation and lipid profiles, as the studies reviewed involved different doses and types of inositol administered to the participants.
Additionally, while they noted a high level of heterogeneity across the studies in the meta-analysis, this was lowered following sub-group analysis based on the type of intervention used, leading them to say the results should be "interpreted with caution".
They concluded: "Inositol supplementation may result in reduction in triglycerides, total and LDL cholesterol levels, but did not affect HDL cholesterol levels among patients with metabolic diseases.
"Additional prospective studies regarding the effect of inositol supplementation on lipid profiles in patients with metabolic diseases are necessary."
Source: Lipids in Health and Disease
https://doi.org/10.1186/s12944-018-0779-4
"The effects of inositol supplementation on lipid profiles among patients with metabolic diseases: a systematic review and meta-analysis of randomized controlled trials"
Authors: Reza Tabrizi, et al.