Another 6-week single blind controlled trial in 40 patients with type 2 diabetes evaluated the addition of 1 tablespoonful aloe gel or placebo twice daily to the sulfonylurea glibenclamide, 5 mg twice daily.110 Fasting glucose declined significantly from 288 mg/dl (16.0 mmol/l) to 148 mg/dl (8.2 mmol/l; P = 0.01 vs. control) in the aloe vera group. Total cholesterol remained the same: 230 mg/dl (5.95 mmol/l) at baseline and 226 mg/dl (5.80 mmol/l) after 6 weeks. However, triglycerides declined significantly from 265 mg/dl (3.0 mmol/l) to 128 mg/dl (1.5 mmol/l; P = 0.01 vs. control).
Summary
Aloe is a tropical plant used to treat type 2 diabetes. The active ingredients are thought to work as fiber to help stimulate cell glucose uptake. No adverse effects have been reported. However, there is concern that additive hypoglycemia may occur if aloe is combined with diabetes drugs. Also, there is a potential for prolonged bleeding with the anesthetic agent sevoflurane during surgery; thus aloe use should be discontinued 2 weeks before surgery. Three small studies have indicated that aloe may decrease fasting glucose and triglycerides, but not total cholesterol. No long-term information regarding aloe use is available, and the effect on A1C was reported in only one very small trial. The dose used has been 1 tablespoonful (15 ml) twice daily of aloe leaf gel.109,110 Use of this supplement is not recommended because of the possibility of inadvertent contamination with some of the cathartic ingredients.
BANABA (Lagerstroemia speciosa L.)
Banaba is a type of crape myrtle that grows in the Philippines, India, Malaysia, and Australia.113 Banaba is also known as queen’s crape myrtle, queen’s flower, and pride of India.75 The tree is deciduous and has leathery leaves that turn red-orange in the fall. The tree has flowers that are a bright pink to purple and give way to nut-like fruits.75 It has been used as a folk medicine in the Philippines, and a tea made from the leaves is used to treat diabetes.113 Other uses include purgative and diuretic actions from the leaf; and root constituents are used for stomach upset.75 Recently, banaba has become popular in the U.S. It has been used for diabetes and weight loss, although information regarding long-term human use is not available. Information on weight loss is theorized from animal research because of effects on adipocyte differentiation.75
Chemical Constituents and Mechanism of Action
Active ingredients include corsolic acid and tannins, including the ellagitannin lagerstroemin. Besides ellagitannins and lagerstroemin, flosin B and reginin A are thought to be glucose-transport enhancers.114 The ellagitannins are plant polyphenols, which reportedly bind to several polypeptides such as the regulatory subunit of protein kinase A. The active ingredients are thought to stimulate glucose uptake and have insulin-like activity. The latter activity is thought to be secondary to activation of insulin receptor tyrosine kinase or the inhibition of tyrosine phosphatase. Activation of tyrosine kinase causes tyrosine phosphorylation of several proteins, which then induce the functional change of signaling molecules such as phosphatidylinositol 3-kinase.115 Animal research has shown that banaba may inhibit alpha-amylase and alpha-glucosidases and thus potentially lower elevated postprandial glucose.75
Adverse Effects and Drug Interactions
No adverse effects have been reported. Theoretically, banaba may cause blood glucose to be excessively lowered when combined with drugs that can cause hypoglycemia, such as sulfonylureas, or with CAM supplements that have hypoglycemic activity (Gymnema sylvestre, American ginseng, etc.). Doses of these medications or CAM supplements may have to be adjusted to prevent excessive lowering of blood glucose.
Clinical Studies
A 15-day randomized control trial was done in 10 patients with type 2 diabetes and fasting glucose levels between 140 mg/dl (7.8 mmol/l) and 250 mg/dl (13.9 mmol/l).113 Diabetes medications were stopped for 45 days prior to the study. The authors used a 1% corsolic acid extract called Glucosol. Three different doses of banaba—16, 32, or 48 mg—in either a soft gel or hard gel formulation were used. Five subjects in each group received the three different doses for 15 days, with a 10-day washout between doses. Basal glucose was determined by a fasting blood sample 7 days before starting treatment. During the study, three samples were taken, and an average of the three readings was compared to the basal value. The 32- and 48-mg soft gel formulations showed 11% and 30% decrease, respectively, from basal blood glucose values after 15 days of treatment P ≤ 0.01 and P ≤ 0.002, respectively). Only the 48-mg hard gel formulation showed a significant decrease of 20% (P ≤ 0.001), but the effect was still less than that of the soft gel formulation.
Summary
Banaba is a tropical plant that shows potential benefit to treat type 2 diabetes. It is also being used in multi-ingredient products for weight loss. The active ingredients are thought to stimulate cell glucose uptake by insulin-like activity. In one small study there were no adverse effects or drug interactions reported. This study indicated that banaba may be helpful in lowering blood glucose in patients with type 2 diabetes. However, the authors only reported percentage lowering of blood glucose and did not report the actual values. There is no long-term information available, and the effect on A1C has not been reported. The usual dose is 48 mg/day of the 1% corsolic acid extract, using the soft gel formulation.113
CAIAPO (Ipomoea batatas)
Caiapo is a form of white sweet potato cultivated in a mountainous region of Kagawa Prefecture, Japan. An extract of the skin of the root has been used as a nutraceutical for type 2 diabetes in Japan.116 Caiapo has been eaten raw because of the belief that it may help diabetes, hypertension, and anemia. Caiapo also grows in the mountains of South America, and it has also been used by Native Americans to decrease “thirst and weight loss,” possible symptoms of diabetes.117
Chemical Constituents and Mechanism of Action
An acidic glycoprotein has been isolated from caiapo and is thought to be the active ingredient.117,118 The mechanism of action is thought to be improved insulin sensitivity and decreased insulin resistance.
Adverse Effects and Drug Interactions
Adverse effects noted in human studies are mostly gastrointestinal in nature and include constipation, gastrointestinal pain, and meteorism.116 In theory, caiapo may cause additive hypoglycemia if used with secretagogues or CAM supplements that lower blood glucose.
Clinical Studies
A 6-week pilot study of 18 patients with type 2 diabetes compared 2 g and 4 g caiapo to placebo.119 Fasting glucose decreased from 158 mg/dl (8.8 mmol/l) to 151 mg/dl (8.4 mmol/l) with low-dose caiapo and from 149 mg/dl (8.3 mmol/l) to 130 mg/dl (7.2 mmol/l) with the higher dose (P < 0.05 vs. baseline for the higher dose). The lower dose resulted in unchanged A1C, but A1C decreased from 7.1% to 6.8% with the higher dose (P value not significant). Total and LDL cholesterol also decreased in patients on the higher dose (from 192 mg/dl [5.0 mmol/l] to 172 mg/dl [4.4 mmol/l], P < 0.05; and 120 mg/dl [3.1 mmol/l] to 105 mg/dl [2.7 mmol/l], P < 0.05, respectively).
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