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Melatonin's four cancer-inhibiting mechanisms

Melatonin's four cancer-inhibiting mechanismsMelatonin is primarily known for its role as a sleep hormone. Nonetheless, studies reveal that melatonin has a variety of anti-cancer properties, and supplementing with the substance may increase the effect of chemotherapy while counteracting its side effects.

Melatonin is both a hormone and a signaling substance that influences all cells in the body. Throughout life, melatonin regulates our 24-hour clock, our sleep, and many general physiological processes. In addition, melatonin is a powerful antioxidant that protects cells and repairs cell damage during our sleep.

Melatonin is primarily produced in the pineal gland of the brain in response to nightfall. Figuratively speaking, the pineal gland is like the body's control tower. As we grow older, it starts to calcify and shrink in size, causing its melatonin production to decrease. The melatonin production of a 60-year old person is around half that of someone in his twenties, and the production of the hormone continues to decrease.

For decades, scientists have pointed to the link between the decreasing melatonin production in older people and the fact that their risk of contracting cancer goes up. Lack of daylight and/or darkness combined with factors such as stimulants, medicine, jetlag, and so-called electro-smog may also cause our melatonin production to drop.

Melatonin increases the lifespan of mice and reduces their risk of cancer

According to studies, feeding melatonin supplements to mice helps them stay youthful, it increases their lifespan by as much as 30 per cent, and it lowers their cancer risk. Researchers assume that melatonin plays a determining role as an antioxidant, it controls our hormonal balance, supports our immune defense, and counteracts undesirable inflammation. Although clinical studies on humans have not been made at this point to demonstrate that melatonin supplements can in fact extend our lifespan and prevent cancer, existing evidence suggests that supplemental melatonin may delay the ageing process and prevent several age-related diseases.

Melatonin improves the effect of chemotherapy while reducing its side effects

Chemotherapy and radiotherapy are standard treatments for cancer. According to a Danish research article published in Ugeskrift for Læger (the journal of the Danish Medical Association), melatonin helps chemotherapy destroy cancer cells while reducing the different side effects that are seen with this type of treatment. By combining chemotherapy and melatonin, doctors can increase the chance of surviving a cancer disease from 28.4 per cent to 52.2 per cent in the course of a whole year. The positive effect of melatonin on cancer patients confirms earlier studies.

Melatonin and its ability to prevent and combat cancer

Melatonin prevents cancer in several different ways and can even combat cancer if the disease occurs, provided the body is well supplied with the hormone. Because many years normally pass, from the first cellular changes occur until a cancer tumor is observed, melatonin's role in prevention and in helping the body fight the disease has a large and often underestimated significance.

Melatonin's anti-cancer properties

  • Functions as a powerful antioxidant that protects cell surfaces and DNA
  • Strengthens the immune system and helps T cells attack cancer cells
  • Counteracts inflammation that exhausts our immune defense and causes damage to cells
  • Counteracts uncontrolled cell growth
  • Helps diseased cells self-destruct (apoptosis)
  • Regulates growth-stimulating hormones like estradiol

It is a dilemma that melatonin cannot be patented

Although more research is required before we can make final conclusions, melatonin already appears to be an inexpensive yet highly effective cancer therapy. Nonetheless, it is difficult to raise money for additional studies of melatonin. The reason is that melatonin, just like any vitamin or mineral, is a natural substance that cannot be patented. Because of that, the pharmaceutical industry has absolutely no incentive to invest in this substance, as the chance of making a profit is marginal or perhaps even non-existent, compared with chemotherapy and other patentable cancer therapies.

Night shifts, breast cancer and prostate cancer

Women who work night shifts have an increased risk of developing breast cancer. This was shown, among other things, in a study by senior researcher, Johnni Hansen, from the Danish Cancer Society. The study was carried out on women in the age group 30-54 years and shows that risk of breast cancer increases by up to 40% in women who work late in the evening and at night.
It is plausible that there is a relation between low melatonin status and breast cancer, as melatonin inhibits the production of estrogens that are involved in the hormone-sensitive forms of breast cancer. There may also be a relation between night shift work, breast cancer and lack of vitamin D, which we primarily synthesize during the summer when we get exposed to sunlight. In terms of shift work, lack of melatonin and vitamin D is generally an unfortunate combination. Now, scientists want to investigate if there is a similar relation between shift work and the risk of prostate cancer in men.

Prostate cancer and deviating melatonin production

During a conference on ageing and cancer, Christian Bartsch, a doctor from Tübingen University in Germany reported that men with prostate cancer not only have elevated testosterone levels but also many other hormonal imbalances. Most striking were the imbalances in their melatonin production. Overall, the men produced too little melatonin, and there deviating fluctuations with higher than normal melatonin production in the afternoon and less melatonin in the evening, which did not fit in with the normal 24-hour rhythm.

Antioxidants are an important shield against cancer

Most carcinogenic substances generate free radicals themselves or cause the body to do so. That is why we depend on powerful antioxidants such as melatonin - which no other antioxidant can replace.


Vinter, Anna Gry, Mogens Helweg Claësson: Melatonins indvirkning på immunsystem og cancer. Ugeskrift for Læger 2015

Christensen, Bo Karl: Melatonins effekt på kræft "næsten for god til at være sand". 2015

Grundy Anne et al. Increased risk of breast cancer associated with long-term shift work in Canada. Occupational & Environmental Medicine 2013

Sanches-Barcelo EJ et al. Melatonin uses in oncology: breast cancer prevention and reduction of the side effects of chemotherapy and radiation. Expert Opin Investig Drugs 2012

Wang YM et al. The efficacy and safety of melatonin in concurrent chemotherapy or radiotherapy for solid tumors: a meta-analysis of randomized controlled trials. Cancer Chemother Pharmacol. 2012
Scrinivasan V et al: Therapeutic actions of melatonin in cancer: possible mechanisms. Integr Cancer Ther 2008

Maestroni GJ, Conti A, Pierpaoli W. Pineal melatonin, its fundamental immunoregulatory role in aging and cancer. Ann N Y Acad Sci 1988

Pierpaoli Walter, Regelson William. The Melatonin Miracle. Simon and Schuster 1996

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