Nopal has traditionally been used as a medicinal plant and vegetable food 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. 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 in animals. Similar studies, along with domestic surveys have prompted international evaluation of the Nopal cactus to determine its ability to regulate glucose utilization.
Nopal On Diabetes
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 1 diabetes could possibly avoid the use of these agents and control blood glucose via diet alone.
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 alone. 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
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).
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.
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 drugs, however, has a "downside" due to side effects 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. Nopal appears to be one of the most promising sources of "plant-derived Diabetes Mellitus-active suppressants".
The results of the studies referred to above indicate the importance and the need to advance the investigation of Nopal in human clinical trials. In addition, 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 of Nopal is obvious and will provide insight on how to combat and overcome this major cause of death.