In recent years Nopal (scientifically a member of the Opuntia Cactaceae family) been subjected to increasing study by hospital-based medical practitioners, health scientists in private practice and researchers at such institutions as the USDA Agricultural Research Service-Food and Nutrition Laboratory at Beltsville Maryland, and a number of University based Health Science and Nutrition Centers.

Hospital-based clinical studies have consistently found that Nopal has a clear hypoglycemic effect on obese, insulin-resistant Type 2 Diabetic patients. Nopal is rich in pectin (a soluble fiber), but in addition to fiber-related inhibition of glucose absorption, fasting glucose is also significantly lowered; indicating that Nopal also has the effect of increasing the body's sensitivity to insulin. Focused studies corroborate this finding, showing that small amounts of a active fraction isolated from nopal can partially reverse Diabetes. Similar effects on reduced serum levels of low-density cholesterols and triglycerides not explained by fiber absorption were found, indicating a beneficial effect on hepatic function.



Scientific Studies of NOPAL

Abstract

The Nopal has been used as a medicinal plant and is a hallmark vegetable in the Latin American diet. Various studies have demonstrated Nopal’s ability to affect blood glucose and hypercholesterolemia. The intake of Nopal decreases plasma LDL levels, increases expression of apolipoprotein receptor expression, increases hepatic LDL turnover, and affects cholesterol homeostasis. The Nopal demonstrates the ability to decrease blood glucose levels as well the hyperglycemic peak during glucose tolerance testing. In addition, Nopal has demonstrated the ability to control experimentally induced diabetes. Similar studies, along with domestic surveys have prompted international evaluation of the Nopal cactus to determine its ability to regulate glucose utilization. Currently, homeopathic industries have begun to incorporate Nopal into supplements intended to help regulate plasma glucose levels.


Nopal On Diabetes

Study 1

In 1995, the anti-hyperglycemic affect of 12 edible plants was studied by Roman-Ramos et al, on 27 healthy rabbits. The fasting animals were given subcutaneous glucose tolerance tests after gastric administration of water for control group, tolbutamide suspension for reference control group, or a traditional preparation of the plant for experimental group2. Blood glucose levels were measured in fasting, and at 60, 120, 180, 240, and 300 minutes. Among the twelve edible plants studied was, of coarse, Opuntia Streptacantha, also known as nopal. Opuntia demonstrated a significant decrease in blood glucose values as demonstrated as a decrease of 17.8% (p<0.05) in the area under the glucose tolerance curve and a decrease of 18% (p<0.05) in the hyperglycemic peak as compared to controls. The interest of controlling diabetes mellitus with edible plants is simple, food and medication become one. Possiblities include diabetic patients reducing dosage of current hypoglycemic agents by incorporating these plants into their diet. Also, patients with mild Type 2 diabetes could possibly avoid the use of these agents and control blood glucose via diet alone.

Study 2

In 1996, a study by Trejo-Gonzales et al, demonstrated the ability to control experimentally induced diabetes in rats by utilizing purified extract from Opuntia, the prickly pear cactus. Diabetes was induced by intraperitoneal injection of streptozotocin (STZ). A suspension of prickly pear powder was administered daily through a gastric catheter. Throughout the experiment, the glucose levels of the nondiabetic control groups remained similar to initial levels. Insulin treated diabetic rats showed high glucose levels after 1 week, decreasing by week 2 and then stabilizing at moderately high levels. Diabetic rats receiving only Opuntia extract had glucose levels similar to those of insulin treated rats. Diabetic rats receiving both insulin and Opuntia extract were the only diseased animals with normalized glucose levels. Within 2 weeks, glucose levels in this group had declined to values found in the nondiabetic group. Insulin treatment was suspended due to hypoglycemia after week 8, and normal glucose levels were maintained during the subsequent 7 weeks with administration of Opuntia extract alone6. The important conclusion expressed in this study is that the control of diabetes by purified extract of Opuntia can be attained with daily oral doses in the range of 1mg/kg body weight. This appears to be a promising result which could possibly one day replace the numerous high doses of insulin injection required for similar hypoglycemic effects.


Nopal On Cholesterol

Study 1

In 1992, a study by Fernandez et. al, demonstrated that the intake of prickly pear pectin decreased plasma LDL concentrations by increasing the hepatic apolipoprotein B/E receptor expression and increasing receptor mediated LDL turnover in guinea pigs that were fed a high cholesterol diet. The guinea pigs were given a diet containing lard and cholesterol (LC Diet) or a diet in which cellulose was partially replaced by prickly pear pectin (LC-P diet). The guinea pigs on the LC-P diet demonstrated a decrease in plasma LDL cholesterol concentrations by 33% (p<0.001), whereas plasma VLDL and HDL cholesterol levels were unchanged. This resulted in an overall decrease of 28% (p<0.01) in total cholesterol for the LC-P diet group. Hepatic apolipoprotein B/E receptor expression was 60% higher in guinea pigs on the LC-P diet (p<0.01) whereas the affinity constant Kd was equal in both groups. The size of the Apolopoprotein LDL pool and total LDL fractional catabolic rate exhibited a significant negative correlation (r = -0.52, p<0.01).

Study 2

In 1994, a study by Fernandez et. al, investigated the effects of prickly pear pectin on the rate of absorption of cholesterol and on HMG-CoA reductase and acyl CoA: cholesterol acyltransferase (ACAT), the enzymes responsible for hepatic cholesterol homeostasis. The guinea pigs were fed one of the following three diets. 1) a lard-basal diet with no added cholesterol or prickly pear pectin (LB diet). 2) the LB diet with cholesterol (LC diet). 3) the LC diet with prickly pear pectin added at the expense of cellulose (LC-P diet). Total plasma cholesterol was significantly lower in the LC-P than the LC group. The cholesterol lowering was specific to LDL because VLDL and HDL cholesterol plasma concentrations were unaffected. It was determined that this hypocholesterolemic effect of prickly pear pectin on total plasma cholesterol and LDL levels does not result from a reduction in cholesterol absorption, but may be due to its affects on LDL receptor expression and LDL turnover. This lowers hepatic ACAT activity while not affecting hepatic HMG-CoA reductase activity, therefore having a major effect on hepatic cholesterol homeostasis.


Analysis on Nopal

Based on a survey of South Texas residents that revealed a significant use of herbal remedies, including Opuntia, Aguilar et al. have been reviewing and systematically quantifying a relationship between the prickly pear cactus and the metabolic control of people with Type 2 Diabetes Mellitus. Analysis of six medical studies from Mexico has provided sufficient evidence that ingestion of prickly pear cactus reduces serum glucose levels among diabetics between 10 to 30 mg/dl at 30 to 180 minutes post-ingestion when measured from baseline. Complete full-scale review, however, is incomplete because published control group data was determined to be insufficient. The primary investigators have agreed to provide the complete data on control groups to assist completion of international review. Definite conclusions cannot be made as of yet, however, preliminary findings strongly suggest that ingestion of prickly pear cactus has a true metabolic effect for diabetic patients.


Conclusion

In Latin American folk medicine, curanderos have continued to utilize herbs and medicinal plants to maintain the well-being of their community. These traditions have endured many generations, and have been incorporated into daily life and beliefs. As we progress in this age of technology, we are continuously reminded about our history and the reasons why beliefs and traditions have remained throughout the ages. We continue to validate traditions that were once well established, but now via scientific and research methodology. The nopal has not only become a food staple, but has been utilized as a mode of controlling disease, such as, diabetes and hypercholesterimia. The interest with alternative treatments stems from the limitations of current diabetic treatments. Management of Diabetes Mellitus consists of controlling glucose intake in the diet and utilizing pharmacological therapies which attempt to stabilize the glucose levels. The use of oral drugs is restricted due to side affects and interactions with other medications or due to the fact that they become less effective with prolonged use. The problem with insulin injection is that while it does lower blood glucose, it does not maintain physiological normal levels. The prickly pear cactus (Opuntia) appears to be one of the most promising sources of "plant-derived Diabetes Mellitus-active suppressants". The results of these studies indicates the importance and the need to advance into the investigation of Opuntia into human clinical trials. In addition, the nopal has demonstrated its use in altering and managing cholesterol levels. With the widespread incidence of heart disease, the importance of continued investigation into this mechanism of action will provide insight on how to combat and overcome this major cause of the death. 

REFERENCES

1. Ibanez-Camacho, R. and Roman-Ramos, R. Efecto hipoglucemiante del nopal. Archivos de Investigacion Medica (MEX). 10 (1979). 223-230.

2. Roman-Ramos, R., Flores-Saenz, J.L., Alarcon-Aguilar, F.J. Anti-hyperglycemic effect of some edible plants. Journal of Ethnopharmacology. 48 (1995) 25-32.

3. Fernandez, M.L., Lin, E.C.K., Trejo, A., McNamara, D.J. Prickly pear (Opuntia sp.) pectin reverses low density lipoprotein receptor suppression induced by a hyper-cholesterolemic diet in guinea pigs. Journal of Nutrition. v122. n12. (Dec, 1992): 2230.

4. Fernandez, M.L., Lin, E.C.K., Trejo, A., McNamara, D.J. Prickly Pear (Opuntia sp.) pectin alters hepatic cholesterol metabolism without affecting cholesterol absorption in guinea pigs fed a hypercholesterolemic diet.(Biochemical and Molecular Roles of Nutrients). Journal of Nutrition. v124, n6 (June, 1994):817-823.

5. Ciesla, Bill. Opuntia: points about the prickly pear. Americas (English Edition). v40, n4 (July-Aug,1988):10.

6. Trejo-Gonzalez, A. Gabriel-Ortiz, G., Puebla-Perez, A.M., Huizar-Contrera, M.D., Munguia-Mazariegos, M., Mejia-Arreguin, S., Calva, E. A purified extract from prickly pear cactus (Opuntia fuliginosa) controls experimentally induced diabetes in rats. Journal of Ethnopharmacology. 55 (1996) 27-33

7. Aguilar, C., Ramirez, C., Castededa-Andrade, I., Frati-Munari, A.C., Medina, R., Mulrow, C., Pugh, J. Opuntia (prickly pear cactus) and metabolic control among patients with diabetes mellitus (abstract). Annu Meet Int Soc Technol Assess Health Care, 1996, 12:14.

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