Birçok bitkinin kan şekerini düşürücü etkisi gösterilmiştir. Ancak bu bitkilerin hiçbiri çocuklardaki şeker hastalığında eksik olan insülinin yerini tutmamaktadır. Çocuklarda şeker hastalığının tedavisinde bitki tedavileri denenmesi çocuğun ölümü dahil olmak üzere çok ağır sorunlara yol açabilir. Ancak yetişkinlerde durum farklıdır. Çoğu yetişkinde insulin vardır, bu nedenle dengeli beslenme ve kan şekerini düşürücü bitki çaylarının aşırıya kaçmamak şartıyla alınması önerilebilir. Kan şekerini düşürücü bitkilerin veya bitki çaylarının aşırı miktarda tüketilmesi kan şekerinin aşırı düşmesi ile sonuçlanabilir, bu da bayılma, koma gibi ağır durumlara yol açabilir. Kan şekerini düşürücü etkisi olan bitkiler: nar suyu, zeytin yaprağı çayı, murt çayı, yeşil çay, siyah çay, nane, kekik ve adaçayı. 

Aşağıda iki yazıda kan şekerini düşüren bitkilerle yapılan çalışmalar açıklanmıştır.Plant Foods Hum Nutr. 2008 Mar;63(1):27-33. Epub 2008 Jan 9.Determination of in vitro antidiabetic effects, antioxidant activities and phenol contents of some herbal teas.In this research, some herbal teas and infusions traditionally used in the treatment of diabetes in Turkey, have been studied for their antidiabetic effects on in vitro glucose diffusion and phenolic contents and antioxidant activities. Ten aqueous herbal tea extracts were examined using an in vitro method to determine their effects on glucose movement across the gastrointestinal tract. Total phenol content of herbal teas was analyzed by Folin-Ciocalteu's procedure. Antioxidant activities of herbal teas were evaluated by the effect of extracts on DPPH radical and hydrogen peroxide scavenging. Antioxidant activity was defined as the amount of the sample to decrease the initial DPPH concentration by 50% as efficient concentration, EC50. Antiradical activity [AE] was calculated as 1/EC50. Values were evaluated statistically. Results support the view that none of the herbal teas showed antidiabetic effect on glucose diffusion using in vitro model glucose absorption. Teas were arranged in the order of green tea > peppermint > thyme > black tea > relax tea > absinthium > shrubby blackberry > sage > roselle > olive leaves according to their total phenol contents. Among ten herbal teas, green tea had the highest hydrogen-donating capacity against to DPPH radical. Ranking of the herbal teas with respect to their DPPH radical scavenging activity were green tea > peppermint > black tea > thyme > relax tea > absinthium > roselle > olive leaves > sage > shrubby blackberry. It was determined that adding flavoring substances such as lemon, bergamot, clove and cinnamon, which are commonly used in preparation of black tea in Turkey resulted to have synergistic effect on total antioxidant activities of black and peppermint teas. The highest hydrogen peroxide inhibition value (65.50%) was obtained for green tea at a 250 microl/ml concentration. The H2O2 scavenging activity of herbal teas decreased in the order green tea > peppermint > relax tea > black tea > thyme > olive leaves > sage > absinthium > shrubby blackberry > roselle. In particular, their phenolic compounds and antioxidant activities may be useful for meal planning in type 2 diabetes. They could contribute to sustain plasma antioxidant level because antioxidants present in plants and herbs prevent the development of vascular diseases seen in type 2 diabetes.Nutr Rev. 2009 Nov;67(11):632-8.Olive tree (Olea europaea) leaves: potential beneficial effects on human health.Olive tree (Olea europaea L.) leaves have been widely used in traditional remedies in European and Mediterranean countries such as Greece, Spain, Italy, France, Turkey, Israel, Morocco, and Tunisia. They have been used in the human diet as an extract, an herbal tea, and a powder, and they contain many potentially bioactive compounds that may have antioxidant, antihypertensive, antiatherogenic, anti-inflammatory, hypoglycemic, and hypocholesterolemic properties. One of these potentially bioactive compounds is the secoiridoid oleuropein, which can constitute up to 6-9% of dry matter in the leaves. Other bioactive components found in olive leaves include related secoiridoids, flavonoids, and triterpenes. The evidence supporting the potentially beneficial effects of olive leaves on human health are presented in this brief review.