Sage Advice Blog

Melatonin, Chemotherapy, and Cancer Survival

December 1, 2017

Alex Speers ND, MS


In an earlier blog post, we discussed a study where nighttime exposure to dim light completely shut down melatonin production in mice with breast tumors and was associated with increased resistance to the breast cancer drug tamoxifen. Today, we continue our discussion of melatonin, but this time with humans! Specifically, we’ll discuss the safety and effectiveness of using melatonin alongside chemotherapy in cases of advanced cancer. But first, a quick review of melatonin.


Melatonin is a hormone produced by our pineal gland, which is roughly located in the center of our brain. Melatonin production follows a circadian rhythm, with the highest levels being produced at night while we sleep. As discussed previously, nighttime exposure to light can significantly decrease melatonin production and multiple observational studies have linked night shift work to the development of breast cancer. As an interesting aside, women with breast cancer in Denmark can now receive financial compensation if, without any other risk factors, they had worked at least 1 night shift per week for the 20 years prior. One hypothesis to explain the association between night shift work and breast cancer is that lower levels of melatonin production at night lead to increases in estrogen and breast stem cell turnover, resulting in an increased risk of malignant transformation.


While the potential benefits of melatonin for patients with breast cancer are exciting, recent human trials suggest that the beneficial effects of melatonin extend far beyond breast cancer. Recently, a meta-analysis was conducted to evaluate the effects of melatonin when combined with conventional cancer treatments. A meta-analysis is a type of study that combines the data from multiple studies.


In this meta-analysis, the authors found 21 human trials published between 1992 and 2010 where melatonin was studied as a supplement for patients with cancer. In total, the 21 trials included over 3,500 patients with advanced cancer receiving chemotherapy, radiation therapy, or supportive care. A variety of cancer types were represented, including breast, colon, lung, kidney, liver, and brain cancers.


After combining the data from all 21 trials, the researchers found that melatonin supplementation reduced the risk of death at 1 year by 37%. Researchers also found that when melatonin was taken alongside chemotherapy, a greater number of patients responded to chemotherapy, suggesting a possible synergistic relationship between melatonin and some chemotherapy drugs.  In addition, using melatonin alongside chemotherapy reduced the occurrence of hair loss, anemia, fatigue, and low platelets.


There are a few important things to note about this meta-analysis. First, none of the studies found any serious side effects from taking melatonin. Second, the doses of melatonin used in these studies (10-50 mg/day, with 20 mg being the most common dose) are significantly higher than the doses commonly used for insomnia (0.3-5 mg/day). Third, most of the studies included were conducted by the same group of researchers in Italy. While this doesn’t necessarily discount the findings, it does highlight the need for additional studies on melatonin from other research groups. Fourth, none of the studies were blinded, which means that every patient knew if they were receiving melatonin. This could potentially bias the results as there could be a beneficial placebo effect from knowing that you are taking a supplement. While additional, more robust studies are warranted, melatonin appears to be a safe and potentially beneficial supplement for patients with advanced cancer based on the available evidence.


Seely D, Wu P, Fritz H, et al. Melatonin as adjuvant cancer care with and without chemotherapy: a systematic review and meta-analysis of randomized trials. Integr Cancer Ther. 2012;11(4):293-303.


DISCLAIMER: These statements have not been evaluated by the Food and Drug Administration. There are no financial ties to any supplement companies, pharmaceutical companies, or to any of the products mentioned in this post. This post is not meant to treat, cure, prevent, or diagnose conditions or diseases and is meant for educational purposes. As always, please consult your doctor before trying any new treatments or supplements.

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