As the population of diabetics continues to grow, and as obesity burdens a greater number of people than ever before, consumers will turn increasingly to drugs and nutritional supplements to mitigate these conditions. Chris Kilham explores six promising botanicals on the horizon
A number of herbs have been used traditionally to stabilise blood sugar and address excess weight gain by appetite suppression or other means. Additionally, scientific inquiry into these botanicals yields increasing knowledge about how they work. While dietary intake and exercise play the most significant roles in noninsulin-dependent (type 2) diabetes control, the herbs fenugreek, gymnema, banaba and bitter melon can help regulate blood glucose.
Fenugreek (Trigonella foenum-graecum) is a tall annual herb that is native to the Mediterranean, Ukraine, India and China. The plant bears pods filled with numerous light brown, diamond-shaped seeds that possess a sweet maple aroma and are commonly used in cookery and flavouring.1 Studies reveal that fenugreek helps regulate blood glucose.2 The glucose-regulating, antidiabetic properties of fenugreek seed are linked to a novel free amino acid, 4-hydroxyisoleucine.3 This compound stimulates insulin secretion, thereby limiting the extent to which blood glucose is elevated; by promoting insulin secretion and inhibiting the rise of blood glucose, it helps stabilise blood sugar and reduces body fat production.4 In one human study, 15g/day fenugreek significantly reduced glucose levels after meals. Today fenugreek shows value as an antidiabetic agent with potential for weight control due to its 4-hydroxyisoleucine content.5 Some supplements are capsules of powdered seed, while others are more concentrated extracts standardised to 4-hydroxyisoleucine.6
Gymnema (Gymnema sylvestre) originates from India, where it was apparently taken up in Ayurveda centuries ago. The leaves are used primarily to treat blood-sugar disorders, notably diabetes.7
Gymnema sylvestre is known as gur-mar, or ?sugar destroyer.? When gymnema leaf is placed directly on the tongue, it eliminates the sensation of sweetness, even if sugar is put in the mouth immediately following.8 When taken internally, it helps to control blood-sugar levels in diabetes.9
In the 1920s, preliminary scientific studies found some evidence that gymnema leaves can reduce blood-sugar levels. The active constituents in Gymnema sylvestre have been identified as a group of novel compounds collectively known as gymnemic acids.10 The leaves of Gymnema sylvestre perform two significant functions relative to diabetes. First, they suppress blood glucose, especially after eating. Secondly, they are insulinotropic and promote insulin secretion. By this two-pronged approach, Gymnema sylvestre proves a valuable aid in diabetes control.11 Banaba (Lagerstroemin spp) is a tree found in the Philippines, Thailand, Indonesia, Malaysia and Taiwan. Growing as tall as 50 feet, it possesses pink or lavender flowers. For its shade and its beauty, banaba is planted as an ornamental. The tree is also known as queen?s crape myrtle.12
Banaba leaf and its extracts have been used as folk medicines in the Philippines to control diabetes.13 Phytochemical analysis of banaba leaf has revealed the presence of corosolic acid, as well as other compounds that act as natural insulinlike compounds.14,15 In unusually small amounts, these compounds appear to modify blood glucose.
In animal studies, administration of banaba leaf extract resulted in a significant decrease of blood glucose. The same studies suggest that corosolic acid may stimulate glucose transport into tissue. In other animal studies, administration of banaba leaf extract resulted in reduced weight gain, reduced triglyceride accumulation and reduced adipose tissue, with no changes in diet. In noninsulin-dependent animals, administration of banaba leaf extract resulted in suppressed blood plasma glucose, lower serum insulin and lower urinary excretion of glucose.16,17,18
In clinical studies conducted by Dr William Judy and associates at the Southeastern Institute of Biomedical Research in Bradenton, Florida, a one per cent corosolic acid extract of banaba leaf reportedly reduced serum glucose in people with type 2 diabetes, but did not reduce serum glucose in healthy individuals.19 Human studies on banaba extract used doses ranging from 16-48mg of corosolic acid daily, with best results at the highest dose.
Bitter melon is the common name for Momordica charantia, also known as African cucumber, balsam pear and bitter gourd.20 The plant is aptly named, as all parts of the plant, including the fruit, taste bitter.21
Widely sold in Asian groceries as a vegetable, bitter melon is employed as a folk remedy primarily for regulating blood sugar in cases of diabetes, as well as for colitis and dysentery, intestinal worms, jaundice and fevers.22 Current understanding of the phytochemicals in bitter melon suggests that these multiple uses may be well founded.23
Among the constituents in bitter melon, charantin is identified as a primary agent for blood-sugar regulation. Charantin demonstrates hypoglycaemic (blood sugar lowering) or other actions of potential benefit in diabetes mellitus. The fruits also contain insulinlike peptides, including one known as polypeptide P, and alkaloids.23 It is likely that several substances in bitter melon contribute to its blood sugar-modifying effects.24,25 In human studies, bitter melon demonstrates significant blood-sugar control after food intake and overall blood sugar-lowering effects.26
While there is absolutely no dietary supplement that will affect weight loss without significant dietary or exercise modification, some herbs can help to assist weight control.
Yerba mate? (Ilex paraguariensis) originates from South America and is a tree cultivated in Paraguay, Brazil and northern Argentina.27 The leaves of yerba mate? are made into a tonic and stimulating beverage, due to the presence of both caffeine and theobromine.6 Decoction of yerba mate? is drunk both hot and cold, to alleviate fatigue, suppress appetite, stimulate body and mind, and boost metabolism. Current science on yerba mate? shows that a decoction of the leaves enhances bile flow and speeds intestinal transit time.
Analytical studies show that dried yerba mate? naturally contains approximately 0.56 per cent caffeine. But perhaps more significant is the theobromine value of yerba mate?.6 Like caffeine, theobromine is a central nervous system stimulant alkaloid, though it is appreciably weaker than caffeine. But theobromine is a stronger cardiac stimulant, smooth muscle relaxant and diuretic.23 Yerba mate? naturally contains approximately 0.03 per cent theobromine.
The easiest way to derive benefit from yerba mate? is to drink the tea before meals, although supplements are also made. The appetite-suppressing, diuretic properties will curb eating and enhance elimination of excess water weight.
Guarana (Paullinia cupana) has long been known by the native people of Brazil?s upper Amazon rainforest, who have used the plant to boost energy, curb appetite and infuse extra drive into any physical endeavour.27
Guarana is used primarily in the same manner as coffee or tea, as a safe and convenient stimulant due to its caffeine content. In South America, guarana is used ubiquitously in beverages, in the same way that kola nut is employed in the United States.28 Dried guarana seed paste has a history of other uses as well. In traditional Amazonian folk medicine, guarana is often employed by natives as a stimulant, to relieve fatigue, boost energy, aid concentration and brighten mood.29 At this point in time, the stimulant, thermogenic, appetite-suppressing and diuretic properties of guarana have been well substantiated.30 This makes guarana an ideal supplement for supporting heal-thy weight control. By weight, guarana naturally contains between 2.5-7 per cent caffeine. It also contains modest amounts of related compounds theophylline and theobromine.23
Guarana appears in dietary supplements in the US as a stimulant, a thermogenic (to boost metabolism for purposes of weight loss) and as an appetite suppressant. Guarana is sold in tablets, capsules, and various fluid and dried extracts.
Guarana is a caffeine-based stimulant, and as such, people have varying levels of tolerance. About 15 per cent of adults are sensitive to caffeine. Otherwise, studies show that up to 300mg/day caffeine is generally safe and beneficial for most adults.
Chris Kilham is an ethnobotanist and adjunct professor in the medicinal plant program at the University of Massachusetts at Amherst.
Respond: firstname.lastname@example.org All correspondence will be forwarded to the author.
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