"Hoodia gordonii is a succulent plant from the botanical family Asclepiadaceae. This plant has a spiny appearance resembling a cactus, and has been used for centuries by the San Bushmen of South Africa as a way of controlling hunger and thirst during hunting expeditions in the Kalahari desert. The folklore use of hoodia as an appetite suppressant and recent research on its benefits have piqued worldwide interest among doctors and scientists engaged in the fight against the global epidemic of obesity. Likewise, the consistent demonstration of the appetite-controlling effects of hoodia has led to massive public interest in the use of this plant as the basis of a dietary supplement for weight control.
Whole hoodia powder contains variable amounts of fiber, organic material, antioxidants and biologically active substances—including steroidal glycosides, which appear to fool the brain into thinking the stomach is “full.”1
Weight control is all about calorie control. Recent scientific studies have confirmed the ability of hoodia to suppress appetite, helping obese people and free-feeding rats lower dietary calorie intake to a degree that promotes weight loss, at least in the short term.2,3 Controlled clinical and laboratory experiments show both animals and humans will restrict the calorie intake in their diet when hoodia is taken orally. Some experiments have involved elaborate studies where obese people have taken hoodia in a controlled metabolic environment; and they have been able to reduce their calorie intake by 1,000 calories per day.4
Being overweight is often associated with high blood pressure, high blood cholesterol, and insulin resistance. This is the metabolic Syndrome X, which affects 70 million Americans and is a common cause of premature death and or disability. Hoodia could be an important nutritional factor to combat Syndrome X, if it fulfills its promise of appetite control and weight loss.
Some researchers believe they have pinpointed the active constituent(s) responsible for hoodia’s appetite-suppressant actions, without much investigation into the plant’s other potential mechanisms of biological action. However, hoodia’s active constituent(s) may have only been partially identified. Government researchers in South Africa have focused attention on the sterol glycosides. Part of a group of naturally occurring substances called cardenolides, glycosides are best known for their effects on cardiac function. However, measurable effects on Na/KATPase, the target of action of cardiac glycosides, are not believed to be associated with the administration of hoodia.
One prevailing hypothesis implies steroidal glycosides act directly upon the hypothalamus, triggering a message that blood glucose is high.5 This is an effect related to the glucostatic mechanism of weight control.6 Animal experiments found intracerebroventricular injection of hoodia extracts (termed “P57AS3” by Phytopharm PLC) resulted in increased ATP content or production in the hypothalamus, which may be a signal for the energysensing of satiety. Specific receptors for the steroidal glycoside (P57) have not been identified in the rat brain, but administration of these compounds into the brain reduces food intake by a factor of up to 60 percent and increases the content of ATP hypothalamic neurons of the rat by up to 150 percent. The sensing of energy input by the hypothalamus may be signaled by increases in intracellular neuronal energy, in the form of ATP.
These animal experiments suggest one potential mechanism of action of hoodia components on brain signals that may regulate appetite, hunger or thirst; but, there are many complex factors that control feeding behaviors operating through many messenger molecules.
Any focus on a single system or unitary mechanism for the control of food intake must be questioned, because these controls are extremely complex. For example, does hoodia alter factors that are involved in the “aminostatic” or “lipostatic” theories of regulation of food intake? The difference in the many regulatory systems for energy balance in the body is well documented. In my new book on hoodia, I discuss the ability of plants to talk to the brain and include examples where actual receptors for the actions of these plant compounds exist in the central nervous system.
Safety and Hoodia Gordonii Sourcing Concerns
The San Bushmen have used hoodia as whole fresh plant or dried whole plant (without flowers or root) for thousands of years in their diet, and at times of famine, they have relied on hoodia as a staple in their diet. This circumstance creates a great precedent for the safety of the hoodia plant, but it does not create precedence for the safety or effectiveness of a drug derived from the hoodia plant.
The effects of hoodia on the central nervous system exhibit powerful potential for weight control, where behavior modification can reduce calorie intake. The San Bushmen report an energizing effect of hoodia, and they have used the plant during their strenuous hunting expeditions.
This implies that hoodia supplements would be safe when combined with aerobic exercise, a major factor in promoting weight loss and health, and in combating insulin resistance (the metabolic Syndrome X). One interesting, but apparently inconsistent, “side effect” of hoodia is its aphrodisiac properties.
In South Africa, the hoodia plant is processed most often by sun-drying the plant to produce powder or concentrates. These substances can be used as dietary supplement ingredients or perhaps as food ingredients.
Unfortunately, there is evidence emerging that bulk suppliers of some material used in hoodia supplements are providing “cactus-like” bulk material imported from Mexico or China. I have been involved in testing some bulk supply labeled hoodia and have found circumstances where steroidal glycoside content is very low, or even negligible, in some samples.
It seems prudent for manufacturers and marketers to use only hoodia from approved South African sources operating as government-approved cultivators. Recent directives from South Africa warn that the supply of hoodia has been outstripped by the demand.The response from the South African government has been to limit export permits to control and conserve hoodia resources. Therefore, purchasers should research their supply channel and test imported material to ensure they are supplying consumers with safe, effective hoodia.
Properly formulated hoodia supplements appear to alter the body function of appetite control in a manner that affords great promise for the “new, healthy diet revolution.” Hoodia may be ideal for use in combination with other supplements that can benefit weight control, such as green tea polyphenols and chromium compounds. While more research may be required to fully understand hoodia’s mechanism of action in weight control, there appears to be mounting open-label experience of its use as a dietary supplement to suppress appetite, control weight and provide minor energizing effects, without any content of stimulant substances.
To have a safe dietary supplement that can help to “switch off” appetite, or at least provide behavioral reinforcement to control appetite, is an outstanding new promise. Hoodia likely will be one of the most popular dietary supplements of 2005, but the pathway forward may be hampered by many negative, emerging commerce issues.
Stephen Holt, M.D., is a New York-based physician and scientific advisor to Natures Benefit Inc. He is the author of Combat Syndrome X, Y and Z... (Wellness Publishing); his book about Hoodia gordonii (The Supreme Promise of Hoodia) is in press. For more information, contact Holt at firstname.lastname@example.org.
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