Dietary Aloe vera supplementation & glycemic control in diabetes

Townsend Letter for Doctors and Patients,  May, 2007  by Ken Jones

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Diabetes is a deficiency or absence of the hormone insulin, which is the main hormone responsible for the control of sugar in the blood. According to the National Health Interview Survey, (1) conducted by the Center for Health Statistics at the Center for Disease Control (CDC) in 2005, nearly 20.8 million adults and children in the United States, or about seven percent of the population, suffered from diabetes. Of this group, only about 15.6 million have been formally diagnosed with diabetes; another 6.2 million people remain unaware that they have the disease. Diabetes is currently the fifth-leading cause of death in the United States, but health policy experts believe that mortality attributed to diabetes is vastly under-reported. Diabetes is associated with a number of serious complications that increase the risk of death, including heart disease and stroke, obesity, cancer, high blood pressure, kidney failure, neurological diseases, traumatic amputations, and metabolic imbalances.

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Only 35% to 40% of decedents with diabetes have it listed anywhere on the death certificate, and only about ten percent to 15% have diabetes listed as the underlying cause of death. The overall risk of death for diabetics is about twice that for non-diabetics of comparable age. Heart disease and stroke account for about 65% of deaths for people with diabetes. Adult diabetics' risk factors for stroke and death from heart disease are two to four times that of non-diabetic adults. Additionally, diabetes is associated with a number of co-morbid conditions that adversely affect quality of life, including blindness and other vision problems, mouth and gum diseases, loss of extremities due to amputation, impaired circulation, loss of mobility, and osteoporosis. (2)

Diabetes has been linked to factors associated with a Western lifestyle, but the reality is that diabetes is one of the leading causes of death worldwide. There are two main types of diabetes. Type 1 is caused by an absolute deficiency of insulin, and because it usually manifests before the age of 25, type 1 is sometimes called insulin-dependent or juvenile-onset diabetes. Management of the disease requires insulin supplementation, usually administered by injection or via metered infusion pumps. Type 2, or non-insulin-dependent, diabetes usually manifests after age 40 and is due to a combination of relative deficiency of insulin (insufficient quantities are made in the body) and insulin resistance, meaning that the body is unable to efficiently utilize the reduced amount of insulin it does produce. Type 2 diabetes sometimes requires supplementary insulin, but, more commonly, it can be managed through diet and exercise, often in combination with oral hypoglycemic medications. There is a strong correlation between being overweight or obese and the development of type 2 diabetes. (3) The American Diabetes Association website (http://www.diabetes.org/home.jsp) offers information on weight loss and a brochure titled "Weight Loss Matters" to provide advice on how to start losing weight and become more active. (4)

Although the management of type 1 diabetes requires insulin supplementation, type 2 diabetes can often be managed solely by getting sufficient exercise and eating a healthy diet. In some cases, oral medications can be added to the treatment regimen to stimulate the pancreas to produce more insulin, decrease the amount of glucose made by the liver, slow the absorption of starches in the diet, or control blood sugar. But the management of diabetes without any side effects is still a challenge and has increased the demand for research on natural products with antidiabetic activity.

An abundance of evidence has implicated oxidative stress in the pathogenesis of diabetes (see Kaneto et al. (5) for a recent review). Infiltration of pancreatic tissues by various immune cells triggers inflammatory processes that lead to destruction of [beta]-cells. In type 2 diabetes, [beta]-cell dysfunction results in hyperglycemia and insulin resistance, a process known as "glucose toxicity." Under these conditions, oxidative stress is provoked, and the JNK kinase pathway* is activated. JNK activation together with oxidative stress is involved in the progression of atherosclerosis, which is often associated with diabetes. It is likely that activation of the JNK pathway and oxidative stress are involved in the pathogenesis of both type 1 and type 2 diabetes. (6)

A growing body of preclinical and clinical research shows that the gel** of the Aloe vera plant, administered as a juice or in dried form, has significant antidiabetic activity. Not surprisingly, studies using animal models outnumber clinical trials, but animal studies provide supporting evidence and often provide insights into mechanisms of action.

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The control of blood sugar is critical in the management of diabetes. Research has shown that elevated blood sugar leads to increased oxidative stress and risk of cardiovascular disease, and evidence of oxidative damage has been demonstrated in arterial samples from human diabetic subjects. (7) Patients with diabetes have decreased antioxidant defenses with lower levels of antioxidants such as vitamins C and E, or reduced activities of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx). Singh et al. conducted an extensive study, (8) showing that oral dosing with aloe induced the Phase II enzyme system (including SOD, catalase, and glutathione peroxidase) of mice and significantly reduced lipid peroxidation. Supplementation with Aloe vera gel has also been found to markedly enhance the bioavailability and half-life of the antioxidant vitamins, ascorbate (vitamin C), and tocopherol (vitamin E). (9)