Herbs and diabetes

Copyright © 2019 John Wiley & Sons PRACTICAL DIABETES Vol. 36 No. 5 159 M has used herbal remedies for millennia. Humans are not the only species to use herbs. Many animals appear to do so, for example monkeys, pigs, and elephants. Ethiopian baboons exposed to schistosomiasis eat Balanites fruits, which are rich in diosgenin, a potent antischistosome, while those living in other areas do not.1 Some birds add greenery to their nests. European starlings choose yarrow (Achillea millefolium). When yarrow was added to the nests of tree swallows (which do not use greenery), fewer fleas were found after fledging compared with non-yarrow nests.2 Hundreds of herbal remedies have been claimed to have benefit in diabetes care (Box 1). A Google search for ‘herbs + diabetes’ found about 58,900,000 results including claims that herbal treatment can cure diabetes. People want to believe this. The Times of India recently described fenugreek as ‘A magical kitchen ingredient that can cure diabetes’.3 Fenugreek (Trigonella foenum graecum) is used widely in cooking and herbal medicine in India, Africa and the Mediterranean. In the 10th century Avicenna treated diabetes with powders of fenugreek, lupin, and wormseed.4 Clinical trials of fenugreek are small; most are uncontrolled. They suggest that fenugreek lowers blood glucose, possibly by increasing dietary fibre. Rat studies showed changes in exocrine pancreatic function.5 Fenugreek seed powder also reduced lipids in people with type 2 diabetes.6 TimesNow describes ‘How to cure diabetes with using bitter gourd leaves’.7 Momordica charantia (bitter gourd, bitter melon, bitter apple, bitter squash, balsam-pear, or karela) has a warty cucumber-like fruit. It grows in Asia where it is often used in cooking. Small studies in animals and humans have shown improved glucose tolerance, and reduced blood glucose. The mechanism is unclear but it does not increase insulin secretion. An aqueous extract of the fruit appears most effective.5,8,9 The round bitter melon (Citrullus lanatus) of Australia and South Africa is a different plant. ‘In this video you will come to know about a magical herb which is highly beneficial for treating Diabetes the natural / Herbal way.’ The ‘magical herb’ was banaba.10 Lagerstroemia speciosa (banaba, giant crepe-myrtle, Queen’s crepe-myrtle, or pride of India) grows in India, the Philippines and South East Asia. Banaba leaf extract lowers glucose and improves lipids and weight. The hypoglycaemic effect is attributed to corosolic acid and ellagitannins.11 Lactic acidosis associated with acute kidney injury followed banaba use by one patient.12 Galega officinalis is an old herbal remedy. Common names are goat’s rue, French lilac, Italian fitch, Spanish sainfoin, and professor weed. In 1772 John Hill advocated it for treating thirst and frequent urination. Later G. officinalis was found to contain guanidine and similar compounds. In the early 20th century guanidine derivatives were found to lower glucose but usage lapsed because of toxicity and the introduction of insulin. A French physician, Jean Sterne, re-started research into guanidine-related products. After much effort he discovered that the biguanides were effective and safer. He established clinical use of metformin in people Herbs and diabetes