Melatonin, A Sleep Hormone with Many Uses: Part 2

Melatonin has a surprising number of benefits beyond its use as a sleep aid. Previously, in part 1 we mentioned documented benefits for Alzheimer’s disease, irritable bowel syndrome, migraines and tinnitus. In the second part of this article we’ll touch on benefits for:

  • Diabetes and blood sugar problems
  • Cancer
  • Heart disease
  • Fibromyalgia

Diabetes and Blood Sugar Problems

It’s worth commenting that the data on melatonin for blood sugar control is a little mixed, although it leans towards the beneficial side. A recent meta-analysis showed that melatonin generally helps lower fasting glucose and improves insulin sensitivity (Doosti-Irani 2018). However, there are some small studies on younger, healthy individuals that showed worsening glucose tolerance with melatonin (Rubio-Sastre 2014). These results are likely due to taking melatonin at the same time as a high carb meal. In the studies that showed problems, they used glucose tolerance testing which involves taking a large dose of sugar water at the same time as the melatonin. The combination appears to have negative effects on blood sugar. Another study showed worsening glucose tolerance when individuals took melatonin with a large quantity of sugar as well (Garaulet 2015). The authors conclude that individuals should be cautious with food consumption at the same time as melatonin dosing. To get the benefits of melatonin for blood sugar problems, it may be best to take it before bed on an empty stomach.   


I’m definitely not saying that melatonin is a cure for cancer, but the data on melatonin and cancer is impressive. Per a recent review, “There is highly credible evidence that melatonin mitigates cancer at the initiation, progression and metastasis phases (Reiter 2017).” 

Cancer is seen to have three stages in its development (Pitot 1993):

  • Damage to a cell’s DNA that starts the process (initiation)
  • Growth of the damaged cells (promotion)
  • Transformation from benign to malignant, encouraging further growth and spread of the now cancerous cells (progression) 

Some standard anti-cancer agents only work at a single stage, and some may have problematic effects at other stages, like chemotherapy and radiation, which attack the growth of cancer and its spread but at the cost of causing additional DNA damage that could seed new cancers ( 2019).

Not only has melatonin been shown to help at all stages of cancer development, it makes standard chemotherapy more effective with fewer side effects (Reiter 2002). The number of benefits and complexity of how melatonin affects cancer really begs for a separate blog entry covering this one topic in more detail. 

Heart Disease

There is a strong relationship between lower levels of naturally produced melatonin and increased heart disease suggesting a connection between the two (Dominguez-Rodriguez 2010). Melatonin administered at night to men and women with hypertension reduced their blood pressure (Grossman 2006, Cagnacci 2005). In addition, melatonin decreases platelet/blood clotting activity, acting as a blood thinner (Zhou 2017). Animal studies appear to indicate significant beneficial effects in heart failure and the results appear well-regarded in the published literature (Jiki 2018). However, human studies for heart failure are few and far between, most likely due to melatonin being unpatentable. Melatonin has well known anti-oxidant and anti-inflammatory benefits which also likely protect the heart as well (Reiter 2016). 


“Fibromyalgia is a disorder characterized by widespread musculoskeletal pain accompanied by fatigue, sleep, memory and mood issues ( 2019)”. Treatment is often difficult, with conventional treatments having only modest benefits if any (Moore 2012). 

Melatonin appears to have pain relieving properties along with its other benefits (Danilov 2016). Trials with melatonin have shown improvements in fibromyalgia symptoms with minimal side effects (Hussain 2011). While the first line standard drug therapy for fibromyalgia is amitriptyline, a clinical trial showed that melatonin outperformed the drug in individuals struggling with fibromyalgia (Zanette 2014). At its core, fibromyalgia has gastrointestinal problems (Pimentel 2004), free radicals, sleep dysregulation and pain, all of which melatonin appears to help address. 


Melatonin is a fascinating hormone with a multitude of effects that we are only beginning to understand. It’s something I’ve often prescribed in my practice for patients for a myriad of conditions. 

It’s worth noting that I have observed that different brands may have different efficacies. Occasionally, cheap “grocery store” melatonin doesn’t seem to work as well as other brands. If a certain product isn’t providing the desired results, it may be worth trying a different brand. 

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