Tuesday, October 23, 2007

Sleep, Darkness, Fitness, Health

Last year I read a very interesting book Lights Out: Sleep Sugar and Survival:

In some ways it is a fairly standard paleo / low-carb diet book, but it takes this idea a little further with the proposal that one of the key problems we face in the world today is that we do not get enough sleep nor - importantly - enough darkness. It looks at how various hormones in the body are promoted by sleep and darkness and how others are released in response to light. The premise is that today we live in an environment where we are almost always in the light. Our bodies and their hormones think we are living in a perpetual summer. A review on Amazon explains:

Our internal clocks are governed by seasonal variations in light and dark; extending daylight artificially leads to a craving for sugar, especially concentrated, refined carbohydrates that, in turn, cause obesity. More seriously, lack of sleep inhibits the production of prolactin and melatonin--deranging our immune systems and causing depression, diabetes, heart disease, and cancer. The authors prescribe sleeping at least nine and a half hours in total darkness in the fall and winter and switching to a diet low in carbohydrates and high in protein, vegetables, and healthy fats.

This makes a lot of sense. Too much light, too little sleep - stress. It is back to stress and the HPA axis again!

Anyway I was reminded of all this by a study I saw today:

Effects of a single dose of N-Acetyl-5-methoxytryptamine (Melatonin) and resistance exercise on the growth hormone/IGF-1 axis in young males and females

Full article here

It says that a single dose of melatonin and heavy resistance exercise had a positive impact on Growth Hormome (GH) in the blood. Now the study was looking at using a melatonin supplement, but melatonin is a natural hormone. The wikipedia entry says:

Normally, the production of melatonin by the pineal gland is inhibited by light and permitted by darkness. For this reason melatonin has been called "the hormone of darkness." The secretion of melatonin peaks in the middle of the night, and gradually falls during the second half of the night. Until recent history, humans in temperate climates were exposed to up to eighteen hours of darkness in the winter. In this modern world, artificial lighting typically reduces this to eight hours or less per day all year round. Even low light levels inhibit melatonin production to some extent, but over-illumination can create significant reduction in melatonin production. Reduced melatonin production has been proposed as a likely factor in the significantly higher cancer rates in night workers,[12] and the effect of modern lighting practice on endogenous melatonin has been proposed as a contributory factor to the larger overall incidence of some cancers in the developed world.[13] As inadequate as blood concentrations may be in brightly-lit environments, some scientists now believe that people's overnight output of melatonin can be further jeopardized each time they interrupt their sleep and turn on a bright light (suggesting that the lower brightness level of a nightlight would be safer). Others suggest that such short exposures do no harm.[14]

GH is a very important hormone for lots of reasons - it is anti-ageing and it promotes fat burning and muscle growth.

Now as I've said before I'm not a scientist - I may be simplifying thins too much - but putting 2 and 2 together (and hopefully making 4 not 5)this study might add support to the argument in Lights Out that we actually need more sleep and more darkness.

If melatonin has benefits in terms of promoting GH release, rather than taking it as a supplement, maybe we just need more sleep and more darkness?

I'm going to bed!

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