The connection between sleep and type 2 diabetes

A good night’s sleep may be one of the greatest gifts on earth. Especially to those who struggle to get it! Poor sleep can lead to an array of health issues – including increased risk for developing type 2 diabetes. But how?

It turns out it may have something to do with a relationship between two hormones – insulin and melatonin.

Hormonal interaction

Insulin is a hormone secreted by the pancreas. Melatonin is a hormone secreted by the pineal gland in the brain.

Insulin acts to shepherd glucose in the blood into cells for use. Melatonin is the master timekeeper of the body, regulating other hormones and maintaining the body’s circadian rhythm over a 24 hour night and day cycle.

Melatonin is a hormone of the night, rising slowly throughout day and in full swing by bedtime, then zapped away by exposure to light.⁵ You can begin to guess what kind of impact our technologically rich world may be having on melatonin production!

But what on earth does melatonin have to do with type 2 diabetes, I hear you cry? Let’s find out.

The study

Researchers from Lund University Sweden wanted to gain further insight into the relationship between melatonin and insulin.⁴

They already understood a very critical point – melatonin actually inhibits the production of insulin. Meaning, the higher the level of melatonin the less insulin is hanging about to deal with the glucose in the blood.

The gene variant of the melatonin reception – MTNR1B – is one of over 100 variants that are connected with a pre-disposition to Type 2 diabetes. The research team had found previously found that receptors in the pancreas of people with this particular gene variant to increases, making them more sensitive to melatonin, therefore causing insulin production to diminish.

It turns out one-third of the population have this variant.

The study assessed the impact of melatonin in human and mouse cells, followed up with a human trial. 45 people, 23 of each carried the gene variant, and 22 that did not, took a melatonin supplement each night before bed for 3 months.

On completion, all participants had an increase in blood glucose levels. Those with the gene had significantly higher blood glucose and those without the gene had 3 times the level of insulin.

Does that mean we should be trying to suppress melatonin production? Heavens no! Here is why.

You need the sleep

Now, what we aren’t saying is lose the sleep and you could stave of type 2 diabetes! In fact it is the opposite. Regardless of whether you sleep, biologically melatonin levels will rise when the day turns dark.

Several studies suggest lack of sleep increases risk of developing type 2 diabetes, due to loss of insulin action.¹ A study of several thousand women showed that those getting less than 6 hours a night were more likely to develop the condition, as with those regularly getting more than 10 hours.³

In fact, short sleep seems to decrease insulin sensitivity by 20%, and due to melatonin levels being up and insulin levels down, eating at night (when biologically we should be sleeping) is correlated with higher blood glucose.²

This may be why night and shift workers have increased risk of developing type 2 diabetes.

However, the increased risk mightn’t be down to the melatonin-insulin relationship alone!

Stress and insulin

Being awake when biologically the body is wired for snooze time can be perceived as a state of stress. In addition, eating at these times often involves stimulants and foods that further encourage increase blood glucose levels and stress hormone release.

The production of cortisol and adrenalin is encouraged when operating at night or in a state of low sleep, in order to keep blood glucose high and you ready for action. Therefore stress hormones are also keen to inhibit insulin production.

Poor insulin cannot seem to catch a break!

What to do?

Regardless if you have the gene variant, everyday diet and lifestyle choices heavily influence whether insulin resistance and high blood glucose can manifest.

Here are a few ideas to help offset a disposition or factors contributing to the developing of type 2 diabetes that will offer a whole heap of additional health benefit at the same time!

1. Get sleep – Consistently you want to aim for 7-8hours of sleep a night, and have a routine of going to bed and getting up at a similar time each day.
2. Manage stress – Life has its challenges, but there are many things you can do to set yourself up to handle whatever is thrown at you.
3. Just eat real food – Eating whole foods rich in fibre, protein and good fats regularly – whether in a day that is 3 meals, 5 smaller meals, or whatever suits you and your belly (just don’t overeat, as you will become sleepy!).

By prioritising sleep, breathing deeply, and avoiding highly processed versions of sugars, grains, oils, meats and the rest, you stand in good stead to stabilise blood glucose and stress hormone release.

By Angela Johnson (BHSc Nut. Med.)

References

1. Broussard, JL, Chapotot, F, Abraham, V, Day, A, Delebecque, F, Whitmore, HR, & Tasali, E 2015, ‘Sleep restriction increases free fatty acids in healthy men’, Diabetologia, vol. 58, no. 4, pp. 791-798.
2. Eckel, RH Depner, CM Perreault, L Markwald, RR Smith, MR McHill, AW Higgins, J Melanson, EL & Wright, KP Jr 2015, ‘Morning Circadian Misalignment during Short Sleep Duration Impacts Insulin Sensitivity’, Current Biology, vol. 16. No. 25.
3. Li, Y Gao, X Winkelman, JW Cespedes, EM Jackson, CL Walters, AS Schernhammer, E Redline, S & Hu, FB 2016, ‘Association between sleeping difficulty and type 2 diabetes in women’, Diabetologia, vol. 59 no.4, pp.719-727.
4. Tuomi, T Nagorny, C Singh, P et al. 2016, ‘Increased melatonin signaling is a risk factor for Type 2 Diabetes’, Cell Metabolism, [Epub ahead of print]
5. University of Maryland Medical Centre, Melatonin, viewed 7 June 2016, <http://umm.edu/health/medical/altmed/supplement/melatonin>.