Capsaicin plays an important role in folk medicine, and in addition to being ingested from chili peppers (Tang Shinzi in Japanese), creams, lotions, and patches containing capsaicin are currently sold in many countries, usually without a prescription, and can be used to treat neurological and musculoskeletal pain.
In empirical medicine, what are the benefits and side effects of capsaicin, which will be detailed below
What is capsaicin?
Chili peppers (Tang spices) are widely used in food as a spicy spice, especially in tropical countries.
Among them, capsaicinoids are a group of alkaloid compounds in peppers, which are the main source of spicy taste and a sharp weapon used by plants to deter herbivores and prevent fungal infections.
These substances include capsaicin, dihydrocapsaicin, nordihydrocapsaicin, and trace amounts of other compounds.
Capsaicin is a major irritant, and about 70% of the spicy sensation is caused by capsaicin.
Pure capsaicin, a hydrophobic, colorless, odorless crystalline compound first isolated in 1876, determined as a structure of capsaicin in 1919, and chemically synthesized in 1930.
The main pharmacological properties of capsaicin
Capsaicin works via transient receptor potential channel type 1 (TRPV1), a transmembrane cation channel that prefers Ca2+ to Na+ with six putative transmembrane domains and a calcium-permeable pore region.
The channel can be activated by a variety of mechanisms, including temperature, low pH, permeation sensing, taste, pressure, tension, vibration, and endogenous and exogenous molecules.
When TRPV1 is activated, depolarization creates action potentials that spread to the spinal cord and brain, which may produce a sensation of heat, burning, tingling, or itching.
What are the proven benefits of capsaicin?
1. Capsaicin is beneficial for blood sugar control
Type 2 diabetes mellitus, a complex metabolic disorder characterized by islet cell failure and insulin resistance, is the most common type of diabetes and is a multifactorial disease in which genetic predisposition, environmental factors, and behavioral changes are involved.
Type 2 diabetes can lead to a range of serious complications, including cardiovascular disease, neuropathy, kidney disease, and a serious threat to health. In recent years, as the number of patients increases and the age of onset decreases, the disease has become a major global public health concern.
A systematic literature review and meta-analysis (14 controlled trials) found no acute or chronic beneficial or harmful effects of capsaicin supplementation on blood glucose and insulin levels. Note 1
*Conclusion: To date, there is no evidence that capsaicin supplementation regulates blood glucose
2. Capsaicin beneficial cannabinoid vomiting syndrome (topical)
Cannabinoid hyperemesis syndrome is a periodic and recurrent form of nausea, vomiting, and abdominal pain associated with high-frequency and prolonged cannabis use, particularly characterized by compulsive hot baths/showers to relieve symptoms.
Onset can be divided into three phases: prodromal, vomiting, and convalescent. The prodromal phase is characterized by nausea and abdominal discomfort. The vomiting phase is characterized by severe nausea, vomiting, and retching and can occur several times within an hour.
Medications used to control symptoms include antiemetics, opioids, benzodiazepines, and dopaminergic antipsychotics
A systematic literature review and meta-analysis (7 controlled trials with 106 patients with cannabinoid vomiting syndrome) suggested that topical capsaicin therapy (topical application) was helpful in improving symptoms and length of stay in the emergency department. Note 1
*Conclusion: For cannabinoid vomiting syndrome, topical treatment with capsaicin may bring positive help, but limited by the small sample size, more studies are needed to support it
3. Capsaicin helps with weight loss
Obesity is now a global problem linked to many chronic diseases, including osteoarthritis, obstructive sleep apnea, gallstones, fatty liver, reproductive and gastrointestinal cancers, dyslipidemia, high blood pressure, type 2 diabetes, heart failure, coronary artery disease and stroke.
It is estimated that more than 3.4 million people worldwide die from obesity-related diseases, which equates to 4% of Years of Life Lost and 4% of Disability-Adjusted Life Years.
A meta-analysis (9 studies with 255 participants) showed that intake of capsaicin or capsinoids promoted energy expenditure and reduced respiratory quotient (indicating increased fat oxidation) for subjects with a body mass index (BMI) of more than 25 kg/m2. Note 1
The mechanism behind it may be related to capsaicin increasing thermogenesis, increasing catecholamine secretion, activating the sympathetic nervous system, activating brown adipose tissue, and regulating the production of conjugated protein.
*Conclusion: For patients with abnormal BMI, oral capsaicin may be a natural new method of weight loss, which can promote negative energy balance (meaning that consumption is greater than intake) and fatty acid metabolism
4. Capsaicin improves cardiovascular disease risk factors
Coronary artery disease, also known as ischemic heart disease, is mainly caused by plaque accumulation in blood vessels, resulting in coronary artery stenosis and hypoxia, angina, acute coronary syndrome, sudden cardiac death and other clinical features.
Key risk factors for coronary heart disease include dyslipidemia, diabetes, arterial hypertension, obesity, smoking, and sedentary lifestyle, as well as stress, age, male sex, and family history of coronary heart disease.
A randomized, double-blind, controlled clinical trial (3 months, 42 dyslipidemic patients) noted that oral capsaicin capsules helped increase serum high-density lipoprotein cholesterol (HDL-C) levels, but also reduced triglycerides, C-reactive protein, and phospholipid transfer protein) activity. Note 2
*Conclusion: Capsaicin can help improve the risk factors related to coronary heart disease, which may be of positive help to prevent the disease, but limited by the small sample size, more large trials are still needed to support it
5. Capsaicin improves athletic performance
Maximizing athletic performance is a common goal for athletes, coaches, athlete support professionals and sports scientists.
Sports supplements, on the other hand, are dietary aids designed to improve athletic performance, which can help athletes gain an edge in weight loss, increased energy during exercise, recovery from fatigue, muscle growth, and more.
A randomized, double-blind trial (of 10 physically active men) showed that capsaicin supplementation reduced running test time and rate of perceived exertion compared with placebo, but there was no significant difference in blood lactate content. Note 3
*Conclusion: Capsaicin supplementation may improve mid-distance running performance and reduce exercise consciousness intensity
6. Capsaicin improves osteoarthritis (topical)
Osteoarthritis is the main cause of reduced mobility in the elderly, mainly manifested as obvious joint structural damage, dysfunction and pain, about 10% of Americans over the age of 60 are disabled by it, and the annual economic impact exceeds $60 billion.
To date, there are no known treatments that can alter the disease progression of osteoarthritis in the long term. Current treatments are largely pain-based regulation, including nonsteroidal anti-inflammatory drugs (NSAIDs), opioids (opiates), and more recently concentrated action medications to avoid pain.
A systematic literature review and meta-analysis (28 randomised controlled trials, 7372 people with osteoarthritis) found that at permissible doses, either topical nonsteroidal anti-inflammatory drugs or capsaicin, were superior to placebo for pain relief (although non-steroidal anti-inflammatory drugs or capsaicin were not directly compared, but there was no significant difference in analgesic efficacy). Note 4
The mechanism behind it may be related to capsaicin, which acts as a TRPV1 receptor agonist, which can produce anti-inflammatory and analgesic effects.
*Conclusion: For patients with osteoarthritis, topical capsaicin and nonsteroidal anti-inflammatory drugs can confer a similar degree of pain relief, but more large trials are needed to support this due to possible bias
7. Capsaicin improves diabetic peripheral neuropathy (topical)
Diabetic peripheral neuropathy is a common complication of type 1 and type 2 diabetes, characterized by nerve damage. When painful symptoms occur, the condition is known as pain-diabetic peripheral neuropathy, and the overall prevalence is estimated to be 15% in people with diabetes.
Pain tends to be bilateral, although it extends mainly to the lower extremities, especially the feet, and in some cases, may involve the upper extremities, including the fingertips and palms, and is usually worse at night, especially under stress and fatigue.
A literature review and meta-analysis (25 RCTs) noted that capsaicin patch (8%) had the same efficacy as oral drugs for diabetic painful peripheral neuropathy, but oral drugs significantly increased drowsiness, dizziness, fatigue, and risk of discontinuation related tolerant effects. Note 5
*Conclusion: Topical capsaicin patch (8%) is helpful in relieving pain associated with diabetic peripheral neuropathy with no less effective than drugs
Are there any side effects of capsaicin?
Short-term oral capsaicin is probably safe for most adults at appropriate recommended doses, but reported side effects include stomach upset, gastroesophageal reflux, sweating, flushing, nausea, diarrhea, and runny nose.
In rare cases, large doses or prolonged consumption may cause liver or kidney damage.
Safety precautions (8 contraindications for use)
1. Do not use if you are pregnant, lactating or child or have any physical discomfort (whether by oral administration or dermal application), as the relevant safety is unknown
2. Capsaicin should not be used on open wounds, which may cause erythema, burning, tingling or itching.
3. Inhalation of capsaicin can cause nasopharyngeal or breathing irritation, sneezing and tearing.
4. May have anticoagulant effect, so stop taking it two weeks before surgery
5. Do not use in combination with anticoagulant/antiplatelet drugs, because capsaicin has anticoagulant effect, and may increase the chance of bruising or bleeding, related drugs such as: aspirin, clopidogrel, diclofenac, ibuprofen, naproxen, dalteparin (dalteparin sodium), enoxaparin, Heparin, Warfarin
6. Do not combine with theophylline (a bronchodilator), which may affect the efficacy of the drug or enhance side effects
7. Do not use in combination with hypertension drugs: ACE inhibitors, because some drugs to treat hypertension may cause cough, and there has been a case of cough aggravation after combined use (but whether this phenomenon is harmful is still unknown), related drugs such as: captopril, enalapril, lisinopril, Ramipril
8. Do not use if you have been allergic to chili peppers, it may cause allergic reactions, symptoms include tightening of the throat, difficulty breathing or swallowing, severe swelling of the throat, lips, tongue or face, rash on the skin etc.