The study was conducted by researchers associated with several universities and institutions in Iran. It was published in the International Journal of Preventive Medicine and was supported by public research grants.
Little research using essential oil
The researchers noted that there is some evidence for the effects of fermented soy milk and the essential oil of Cuminum cyminum (the cumin spice plant) on diabetes markers when used separately. They said their study was the first to use them in combination.
Research interest in fermented soy foods has been modest over the years. The PubMed database maintained by the US National Institutes of Health recorded a high of 23 studies in published in 2012, with the number declining gradually to 16 last year. Interest in C. cyminum essential oil has been even more modest. In 2011 eight studies were published, falling to six last year.
The present study used Wistar rats in which diabetes had been induced with the use of streptozotocin-nicotinamide. This is the most common rat model of diabetes, another being the use of African Grass Rats which develop a diabetes like metabolic syndrome when fed a standard test diet.
The researchers used 50 test rats divided into five groups. One was a control fed a standard diet. The others received an addition of standard soy milk, soy milk fermented with Lactobacillus plantarum A7 (KC 355240), the standard soy milk with C. cyminum essential oil added, or the final group which received the fermented soy milk along with the C. cyminum essential oil.
Concentration raises toxicity concerns
Essential oils, unlike most herbal extracts, capture large quantities of the volatile portions of the herbs from which they are sourced. For highly fragrant species like cumin, rosemary and others, an essential oil contains much of what makes the herbs aromatic and thus incorporates some of the fractions that make these herbs prized in traditional medicine systems as well as in ethnic cuisines.
But essential oils do concentrate these fractions to orders of magnitude more than what a user might be exposed to when using an extract or using the botanical as a spice ingredient. Toxicity concerns have been raised about the ingestion of essential oils as opposed to using them in topical formulations or as aromatherapy ingredients. In the case of C. cyminum essential oil, these concerns were investigated in a toxicity study done in Iran in 2013. And there has been increasing interest in using the oils in ingestible applications in the US.
Fermented soy plus essential oil worked best
The rats in the present study were gavaged with saline solution or with the test materials at the rate of 1 ml per day. Blood was drawn on the first, tenth, twentieth and final day of the 30-day study. The rats were also weighed at 10-day intervals.
The researchers found that soy milk had beneficial effects on fasting blood glucose, triglyceride levels and total cholesterol compared to the control group. They postulated this was associated with the flavones, genistein, protein and polysaccharides in soy milk. These effects were more pronounced with fermented soy milk. Similarly, the addition of the C. cyminum essential oil also enhanced these effects.
“Probiotic soy milk using LA7 added with essential oil of C. cyminum create a more significant reduction in FBS, TG and TC levels. . . . It seems the combination of probiotics and essential oils is a robust functional supplement for diabetes management in an animal model,” they concluded.
Effects of probiotic soy milk fermented by lactobacillus plantarum A7 (KC 355240) added with Cuminum Cyminum essential oil on fasting blood glucose levels, serum lipid profile and body weight in diabetic Wistar rats
Authors: Babashahi M, et al.