Overview
Chili peppers are well known and usually strongly liked or disliked by people in their foods. The hotness of chili peppers comes from a group of compounds called the capsaicinoids, of which capsaisin is the most well studied due to its higher prevalence and potency. Chili peppers have a long traditional use in many cultures for several dysfunctions, and for aiding and protecting in normal processes, such as digestion. There are both internal and topical uses of capsaicin or chili peppers of a wide variety, including gastrointestinal health, headache, pain (both rheumatoid and osteoarthritis) and psoriasis and dermatitis. Capsaisin is theorized to wok on pain because it is a substance P depletor, and substance P has been implicated in the development of pain and inflammation.
Comments
Cayenne or chili peppers are a good example of a botanical medicine and food that is so prevalent in so many cultures—and often for similar uses—that the good clinical results seem inevitable. It is not surprising then, that most of the clinical work on capsaicin and cayenne peppers have revealed beneficial results in a wide variety of disorders.
Scientific Support
Gastrointestinal Health
In order to demonstrate in humans the early results of animal studies that showed gastroprotection of capsaicin against gastric mucosal injury, 18 healthy volunteers were recruited for two different studies, two weeks apart. The subjects were administered 20 g of chili orally with 200 ml of water, and just water in another study. Each group followed the initial treatment with 600 mg aspirin BP with 200 ml water. The gastric injury in the treatment group as determined by endoscopy was 1.5 compared to 4 in the control group, indicating a significant gastroprotective effect of the chili in humans (Yeoh et al. 1995).
Gonzalez et al. (1989) performed a controlled trial in order to investigate whether or not a capsaicin-containing red pepper sauce (Tabasco) could activate the afferent nerves in the regulation of gastrointestinal motility. After baseline recordings , red pepper or saline solution was administered intraesophageally in 7 healthy volunteers. Red pepper was found to have significant effects on gastrointestinal motility: prolonging gastric emptying, decreasing the perception and discomfort threshold of intraesophageal balloon distension, and reducing the % normal electrical activity of the EGG. The authors theorized that these profound changes in gastrointestinal motility could be the result of retaining the pepper irritant in the stomach and then faster intestinal transit (as found in the study) in order to improve clearance and protection of the esophagus.
Skin Health
In order to determine the role of substance P (undecapeptide neurotransmitter) in the development of psoriasis and pruritus, a double-blind, placebo-controlled study was conducted on the effect of capsaicin (a substance P depletor) in patients with pruritic psoriasis. The patients were instructed to apply capsaicin (0.025%) cream or placebo cream four times daily for six weeks. The capsaicin cream resulted in significant improvements of global evaluation and pruritus relief, and in psoriasis severity scores. The most frequent but transient side effect that was reported was a burning sensation when the cream was applied. The authors concluded that these results also supported a role for substance P in psoriasis and pruritis (Ellis et al., 1993).
Bernstein et al. (1989) performed a double-blind study on the effect of capsaisin in psoriasis. The 44 participants with psoriasis applied capsaicin topically on lesions on one side of their body, and a placebo cream to the other for 6 weeks. The capsaisin application produced significant improvements throughout the study in the psoriasis. There were reported side effects of burning, stinging, itching and redness in almost half of the patients on initial application, but this diminished or was absent for the rest of the study upon further applications.
Exercise and Metabolism
Yoshioka et al. (1999) conducted two studies to investigate the effect of red pepper (capsaicin) on feeding behavior and energy intake. In the first study, the capsaicin was added to a high-fat (HF) and high-carbohydrate (HC) diets, and the subsequent effect on energy and macronutrient intake was studied. The capsaisin was found to significantly reduce the desire to eat and hunger after breakfast when added to a HC diet, and this effect was found for the HC breakfast alone. The capsaisin-added diets were found to significantly decrease protein and fat intakes during lunch. In the second study, an appetizer with capsaicin was studied in 10 males. The red-pepper significantly reduced the energy and carbohydrate intakes in the meals following a few hours later. A power spectral analysis was performed and indicated that these results were related to an increase in the ratio of sympathetic to parasympathetic nervous system activity.
In order to determine the effect of hot red pepper on energy metabolism, a clinical study was performed involving long distance runners (18-23 yrs old). A breakfast meal with or without 10 g of hot red pepper was consumed, and the expired gasses and venous blood were collected both during rest (2.5 hrs after the meal) and during exercise. The hot red pepper was found to significantly elevate the respiratory quotient and blood lactate both at rest and during exercise. There was a nonsignificant increase in oxygen consumption at rest (30 min after the meal), and there was a significant increase 30 min after the meal in plasma epinephrine and norepinephrine levels. The authors concluded that the hot red pepper stimulates carbohydrate oxidation both at rest and during exercise (Lim et al., 1997).
Headache
The acute effects of capsaicin (300 micrograms/100 microliters) on human nasal mucosa of cluster headache sufferers was studied by Sicuteri et al. (1989). The application of the capsaicin was performed on both healthy and cluster headache sufferers, and found to produce desensitization to the initial painful sensations to treatment (pain, sneezing and nasal secretion) in both groups after 5 days of treatment. After capsaicin treatment, the number of cluster headache attacks was significantly decreased for 60 days following treatment. Sicuteri et al (1990) performed a subsequent study to determine the features of pain transmission in cluster headache sufferers.
Pain (Osteo- and Rheumatoid Arthritis, postherpetic neuralgia, headache)
Capsaicin is theorized to be effective on pain relief due to its substance P depleting ability. Capsaicin was reported above for pain relief due to cluster headaches (Sicuteri et al., 1989; Sicuteri et al., 1990).
Keitel et al. (2001) performed a randomized, double-blind, parallel group study on the effect of capsaicin cream (CAS 404-86-4) on patients with nonspecific back pain. The 154 patients were administered the cream or placebo for 3 weeks. Three different pain scales were used as primary outcome assessments, and secondary assessments included tests of motility, a disability index and global assessments by patients and physicians. The capsicum group produced significant decreases in the sums of all pain scores compared to placebo. Efficacy ratings by both physicians and patients were significantly higher for capsicum treatment. The tolerance ratings for the capsicum cream was higher than placebo, and adverse effects that were reported in this study were mostly mild and transient.
McCarthy and McCarty (1992) performed a randomized, double-blind, clinical trial on the effect of topical capsaicin 0.075% on the painful joints of rheumatoid arthritis and osteoarthritis sufferers. The 21 patients were instructed to apply the capsaicin cream 4 times daily for 4 weeks or placebo. Capsaicin was found to reduce tenderness and pain significantly in those with osteoarthritis, but not for rheumatoid arthritis. A local burning sensation was experienced was the only minor side effect noted.
Deal et al. (1991) performed a randomized, double-blind, placebo controlled study on the effect of capsaicin cream on 70 patients with either osteo- or rheumatoid arthritis. The patients were instructed to apply the 0.025% capsaicin cream or placebo to painful knees four times daily for 2 weeks. Both pain scales and global evaluations were used as primary outcome assessments. Significantly more pain relief was experienced by the capsaicin-treated patients than the placebo throughout and at the end of the study. Both rheumatoid (57%) and osteoarthritis (33%) patients reported significant improvements from the treatment. There was transient burning sensations reported from the application of the cream as a side-effect.
Bernstein et al. (1989) performed a double-blind, placebo controlled study on postherpetic neuralgia after uncontrolled studies had reported success with capsaicin treatment on this disorder. The 32 elderly patients with chronic postherpetic neuralgia were treated with either capsaicin cream or placebo for 6-weeks. Pain scales and global evaluation were used for outcome assessments. In all efficacy variables capsaicin cream proved to be significantly better than placebo. Additionally, after the 6 weeks of treatment approximately 80% of the participants using capsaicin experience some pain relief. The authors recommended capsaicin treatment for postherpetic neuralgia as an initial management therapy due to the low possibility of drug interaction or systemic toxicity.
Incontinence
Cruz (1998) reviewed the recent findings of a category of unmyelinated type C bladder afferent fibers in the pelvic nerves that were extremely sensitive to capsaicin. Capsaicin was able to desensitize these fibers by intravesical administration, and reduce involuntary micturition and increase urinary capacity in patients, and to reduce intensity of pain in patients with bladder pain.
Safety / Dosage
The usual dosage for internal use of capsicum is 60 mg or in the range between 30-120 mg. Caution is advised not to bite or chew on the capsules. For topical applications for pain or skin irritation, the content of creams in clinical studies has ranged between 0.025-0.075% capsaicin, with the application being 4-5 times daily.
For the topical use of the capsaicin cream, frequent and transient, but not serious side effects of a burning sensation is reported with use. Capsaicin and the capsaicinoids are strong irritants to the mucous membranes, and it can produce dermatitis.
References
1.Bernstein JE, Korman NJ, Bickers DR, Dahl MV, Millikan LE. Topical capsaicin treatment of chronic postherpetic neuralgia. J Am Acad Dermatol. 1989 Aug;21(2 Pt 1):265-70.
2.Bernstein JE, Parish LC, Rapaport M, Rosenbaum MM, Roenigk HH Jr. Effects of topically applied capsaicin on moderate and severe psoriasis vulgaris. J Am Acad Dermatol. 1986 Sep;15(3):504-7.
3.Cruz F. Desensitization of bladder sensory fibers by intravesical capsaicin or capsaicin analogs. A new strategy for treatment of urge incontinence in patients with spinal detrusor hyperreflexia or bladder hypersensitivity disorders. Int Urogynecol J Pelvic Floor Dysfunct. 1998;9(4):214-20.
4.Deal CL, Schnitzer TJ, Lipstein E, Seibold JR, Stevens RM, Levy MD, Albert D, Renold F. Treatment of arthritis with topical capsaicin: a double-blind trial. Clin Ther. 1991 May-Jun;13(3):383-95.
5.Ellis CN, Berberian B, Sulica VI, Dodd WA, Jarratt MT, Katz HI, Prawer S, Krueger G, Rex IH Jr, Wolf JE. A double-blind evaluation of topical capsaicin in pruritic psoriasis. J Am Acad Dermatol. 1993 Sep;29(3):438-42.
6.Gonzalez R, Dunkel R, Koletzko B, Schusdziarra V, Allescher HD. Effect of capsaicin-containing red pepper sauce suspension on upper gastrointestinal motility in healthy volunteers. Dig Dis Sci. 1998 Jun;43(6):1165-71.
7.Keitel W, Frerick H, Kuhn U, Schmidt U, Kuhlmann M, Bredehorst A. Capsicum pain plaster in chronic non-specific low back pain. Arzneimittelforschung. 2001 Nov;51(11):896-903.
8.Lim K, Yoshioka M, Kikuzato S, Kiyonaga A, Tanaka H, Shindo M, Suzuki M. Dietary red pepper ingestion increases carbohydrate oxidation at rest and during exercise in runners. Med Sci Sports Exerc. 1997 Mar;29(3):355-61.
9.McCarthy GM, McCarty DJ. Effect of topical capsaicin in the therapy of painful osteoarthritis of the hands. J Rheumatol. 1992 Apr;19(4):604-7.
10.Sicuteri F, Fanciullacci M, Nicolodi M, Geppetti P, Fusco BM, Marabini S, Alessandri M, Campagnolo V. Substance P theory: a unique focus on the painful and painless phenomena of cluster headache. Headache. 1990 Jan;30(2):69-79.
11.Sicuteri F, Fusco BM, Marabini S, Campagnolo V, Maggi CA, Geppetti P, Fanciullacci M. Beneficial effect of capsaicin application to the nasal mucosa in cluster headache. Clin J Pain. 1989;5(1):49-53.
12.Yeoh KG, Kang JY, Yap I, Guan R, Tan CC, Wee A, Teng CH. Chili protects against aspirin-induced gastroduodenal mucosal injury in humans. Dig Dis Sci. 1995 Mar;40(3):580-3.
13.Yoshioka M, St-Pierre S, Drapeau V, Dionne I, Doucet E, Suzuki M, Tremblay A. Effects of red pepper on appetite and energy intake. Br J Nutr. 1999 Aug;82(2):115-23.
EDITOR'S NOTE: This monograph can be found in The Health Professional's Guide to Dietary Supplements (Lippincott, Williams & Wilkins) by Shawn M. Talbott, PhD and Kerry Hughes, MS.
