by Mark J. Tallon, Ph.D.
Chili peppers are well known for their ability to produce a sensation of heat when eaten. In the past few years, the nutrition industry has focused on the fruit of the chili plant, or capsicum, and one of its active components, capsaicin. Capsaicin's potential to enhance weight loss has made its entrance into the dietary supplements market highly successful, and now it's being studied and used for other applications, including treatment for high cholesterol, pre-diabetes, hair loss, pain and immune-system enhancement.
According to the U.S. Pharmacopeia, capsicum is the dried fruit of Capsicum frutescens1 or a tincture of Tabasco pepper.2 The capsicum fruit has many active components, including capsaicinoids, flavanoids, vitamins and minerals. The five naturally occurring capsaicinoids include capsaicin, dihydrocapsaicin, nordihydrocapsaicin, homocapsaicin and monohydrocapsaicin.3 Capsaicinoids are responsible for chili peppers' mouth-burning sensations; they make up more than 95 percent of the total content of capsicum,4 and capsaicin (8-methyl-N-vanillyl-6-nonenamide) accounts for 69 percent of the total capsainoids.3
Capsaicin is available as a dietary supplement, in topical form and in peppers. Eating peppers may create the same benefits as the supplemental form, so long as the same dose of capsaicin is delivered. In one study, which examined how ingesting hot red peppers affected energy metabolism in long-distance male runners (ages 18 to 23), this dose was 10 g,5 or about a quarter of an average red chile pepper.
Turn up the heat Capsaicin has received much attention of late for its anti-obesity effect. Its mechanisms include lipid mobilization (the release of fats from fat cells and the release of intramuscular triglycerides into the bloodstream),6 alteration in appetite-controlling neuropeptides,7 thermogenesis (expending calories as heat)8 and decreased adipogenesis (the growth and proliferation of fat cells).9
Capsaicin’s anti-obesity effects have been studied mainly in rodents;10,11,12 however, in 2007, researchers from Kyoto University in Japan conducted a human study, assessing the impact of capsaicin on the use of energy sources (protein, carbohydrates and fat) and whether capsaicin’s sympathetic thermogenic activity (using the sympathetic nervous system to produce heat by burning body fat) influences cardiac function.13 Ten males were recruited to take either 150 mg of capsaicin or a placebo one hour prior to exercise, with electrocardiogram and fuel-use measures recorded at rest and during 30 minutes of exercise at 50 percent of maximal ventilatory threshold. The results of the study showed that capsaicin supplements significantly increased the oxidation of fat as an energy source compared with the placebo. This data suggests that capsaicin enhances the use of fats as a fuel source during rest and exercise and may increase weight loss during a controlled diet or exercise plan. Furthermore, the study demonstrated that supplementation did not cause any adverse effects on cardiac function despite significantly improving lipolysis (the breakdown of stored fat into the bloodstream, where it can be used more effectively as an energy source).13 More research on humans is needed to improve the certainly of these results.
Lipids and cholesterol
The American Heart Association estimates the direct and indirect costs of cardiovascular disease treatment in 2006 at $403.1 billion.14 There are 315 million cases of hypercholesterolemia (high cholesterol) alone at any given time in the world’s seven largest health care markets, including more than 50 percent of the population in the U.S., Germany, France and the United Kingdom. This makes the search for cost-effective and natural solutions enticing.14
A study published in October 2007 from the Central Food Technological Research Institute in India assessed the impact of dietary intake of the curry spice curcumin (0.2 percent of total dietary intake), capsaicin (0.015 percent) or their combination for eight weeks on hypercholestrolemic or non-hypercholestrolemic rats. Eight groups of eight Wister rats were used in the study, and those in the hypercholestrolemic groups were fed diets known to cause hypercholesterolemia while those in the nonhypercholestrolemic groups were fed a diet known to not change blood-cholesterol levels. Capsaicin lowered liver cholesterol and triglyceride levels in both normal (liver cholesterol, 26 percent decrease; liver triglycerides, 57 percent decrease) and hypercholesterolemic (liver cholesterol, 15 percent decrease; liver triglycerides, 27 percent decrease) rats. Curcumin and capsaicin also lowered liver and blood lipid peroxides (a marker of excessive oxidative stress) in hypercholesterolemic rats; and in combination, their effect was stronger than either one alone. Curcumin, capsaicin and their combination significantly reduced hypercholesterolemia by lowering total blood cholesterol by 20 percent, 22 percent and 21.5 percent, respectively.15
This data supports work carried out in the 1980s showing that rabbits supplemented with capsaicin over a five-week period showed a decrease in plasma total cholesterol, triglycerides and the total cholesterol to “good cholesterol” ratio.16 These effects are believed to be a result of changes in intestinal lipid absorption. Clearly, more human work is needed in this area, but early data using animal models show great promise.
The fight against pre-diabetes
Pre-diabetes (also known as insulin resistance or metabolic syndrome) is now classified as a disease state, and the American Diabetes Association estimates 54 million Americans are pre-diabetic, primarily from the obese and overweight demographic.17 It is not surprising, then, that products that effectively control insulin and/or glucose levels have a fantastic potential in sales volume.
Although many animal studies show capsaicin's effect on insulin/glucose metabolism—for instance, capsaicin has been shown to decrease blood glucose levels in dogs18 and rodents19—little research on humans is available.
The first significant human study investigating the effects of capsaicin on insulin metabolism was conducted in 2006. Researchers from the University of Pecs, Hungary, carried out a glucose-loading test. Fourteen people ingested 75 g of glucose either with or without supplemental capsaicin (a one-time oral dose of 400 µg), and their blood glucose and insulin levels were subsequently monitored. Results demonstrated that capsaicin increased glucose absorption from the gastrointestinal tract and also increased glucagon release. Insulin secretion increased in people taking capsaicin, but was not significant when compared with the control group.20 This evidence suggests that in those not able to maintain a relatively stable blood-glucose level, capsaicin may provide a valuable and valid natural intervention.
Capsaicin accelerates hair growth
Natural therapies that can effectively enhance hair growth are few and far between. However, researchers from Nagoya City University in Japan recently identified a link between insulin-like growth factor-1, capsaicin and hair growth.21
IGF-1 stimulates hair growth, so it may be useful for those with male-pattern alopecia (hair loss). Phytoestrogens, in the form of isoflavones, and capsaicin can enhance IGF-1 levels.21 The study examined supplementation with capsaicin (6 mg per day) and isoflavones (75 mg per day) during a five-month period in 31 patients with alopecia.21 In an adjunct study on mice, capsaicin and isoflavones were given as separate treatments, and dermal IGF-1 was assessed.21, 22
Results demonstrated that in people with alopecia, hair regrowth, which was assessed visually using before-and-after photographs, was significantly higher in those taking both capsaicin and isoflavone (64.5 percent) compared with a placebo (11.8 percent).21 This beneficial effect was directly linked to the elevations in participants’ dermal IGF-1 levels following supplementation. In the mice study, capsaicin significantly elevated IGF-1 when given alone.21 Further human studies on capsaicin taken alone as an adjunct therapy for hair regrowth would be of great interest.
Global awareness of immune-system attack has increased because of issues such as chemical and biological attack (e.g., sarin, anthrax and ebola), severe acute respiratory syndrome and hospital-based infections such as methicillin-resistant Staphylococcus aureus. Consumers in densely packed populations, such as those found in parts of India and China, now rate enhancing immunity among their top five concerns.23
Researchers from the Department of Food and Nutrition, University of Ulsan, Korea, studied capsaicin and its effects on immune status. During a three-week period, mice were fed one of five different doses of capsaicin or a placebo, while researchers recorded indicators of immune status (e.g., mitogen-induced proliferation, plaque-forming cell numbers and total serum immunoglobulin levels).24
The results suggested that dietary capsaicin significantly enhances immune status (the balance of biological measures such as T cells and lymphocytes) as well as select immune function (immune activity in response to bacterial challenge).24 This study actually raises more questions than it answers. For example, is elevated immune response a beneficial effect that helps defend against infection, or is it a response that identifies capsaicin as a biological threat, which the immune response tried to destroy? Furthermore, if mice were exposed to bacteria or viruses after capsaicin supplementation, would related symptoms or incidences of infection decrease? More work in this area is on the horizon.
The power of pain protection
Sensory neuropathies are associated with many diseases, including herpes zoster (shingles) and celiac disease. Pain from these disorders can produce greater disability than the primary disease and, unfortunately, there aren’t many nonpharmacological therapies available. U.S. researchers administered capsaicin at topical doses of 5 percent to 10 percent (10 times the 1 percent dose sold in stores) to 10 individuals with neuropathic pain disorders. In previous studies with larger-dose, topical concentrations of capsaicin, participants reported intense burning sensations. To enable patients to tolerate the high concentrations in this study, every participant was given regional anesthesia, which lasted no longer than 2.5 hours.25
People chosen to receive capsaicin were selected from 25 patients with chest or foot pain who were unresponsive to conventional analgesia; 15 participants dropped out of the study for various reasons, such as the resolution of the underlying disease, death from the underlying disease (HIV and chronic myelogenous leukemia), failure to respond and cerebrovascular accident (stroke). Nine of the 10 people who completed the study reported substantial pain relief that lasted from one to 18 weeks. The authors suggest that the study demonstrates that intermittent application of large-dose topical capsaicin may provide significant pain relief, decrease chronic analgesic dependence and reduce health care costs.
The above research highlights capsaicin’s potential as more than a weight-loss aid by offering applications that penetrate health and disease markets. Recent studies also show many other applications may exist for capsaicin, from sports performance to blood-pressure regulation and its impact on cardiovascular disease.26 In light of this research, the future of capsaicin as a dietary supplement and food fortification is clearly hot in more ways than one.
Mark Tallon, Ph.D., is chief science officer of NutriSciences, a London-based consultancy firm specializing in health-claim substantiation, product development and technical writing. He is also co-founder of Cr-Technologies, a raw-ingredients supplier.
Natural Foods Merchandiser volume XXVIII/number 7/p. 38,40