SADness: Seasonal Affective Disorder & Vitamin D

Being an evolutionary psychologist, I'm interested in how we as a species cope with novel living conditions – large cities, nuclear families, and time spent mostly indoors.

Our relationship with the sun is an interesting one.

On one hand, too much sun exposure gives you skin cancer and wrinkles. On the other – too little puts you at risk for depression, which when confined to the dark days of winter when we tend to stay indoors is called season affective disorder (SAD). Lack of sunlight causes other health problems too.

Exposure to sunlight is necessary for our bodies to produce vitamin D. Too little vitamin D is associated with osteoporosis, rickets, and now - new studies show it's associated with some forms of cancer that happen to be particularly deadly because they are often caught too late.

So what's a person to do to fight seasonal depression and vitamin D deficiency?

Lately, medical doctors have jumped on the bandwagon of having patients take vitamin D supplements, because supposedly for many of us (including indoor sun-phobic me) our bodies don't produce enough of it during the winter. Sunlight helps us produce vitamin D, but getting it from our diet is ineffective, or at least inefficient.

People need 1000 international units (IU) of vitamin D each day, the number experts think is adequate for most people. To put it in perspective, a glass of vitamin D fortified milk or juice provides about 100 IU. A multivitamin usually offers 400 IU.

Other sources of vitamin D include:

• Cod Liver Oil 1 tablespoon = 1360 IU of vitamin D
• Salmon 3 ounces = 425 IU of vitamin D
• Herring 3 ounces = 765 IU of vitamin D
• Sardines Canned, 3 ounces = 255 IU of vitamin D

But who wants to eat enough of that every day to meet the recommendation? Not me.

According to the National Institutes of Heath, just 10 minutes of sunshine a day, 3 times a week is enough for the average person to get all the vitamin D they need.

Sweet. I would much, much rather do that.

But what happens when the sun doesn't come out for months or you're busy working all day?

You become depressed, your sleep-wake cycle gets all goofed up, you become cranky and irritable and you get more headaches.

Why?
Your brain starts producing too much melatonin, a hormone produced by the pineal gland. Melatonin regulates circadian rhythm, i.e. sleep-wake cycle, and is produced at night and while sleeping. Sunlight shuts off its production.

During the winter, when the sun rises later and sets earlier, people are exposed to less sunlight. The pineal gland produces more melatonin and that appears to be a physiologic correlate, maybe even a cause, of depression.

Taking melatonin supplements is stupid if your problem is too much of it. But, when it comes to hormones, our bodies seem to have evolved a mechanism to keep hormone levels optimal. When we produce too much of a hormone, our brain, working through a part called the hypothalamus, sends out signals to produce less. The reverse happens when we produce too little. Tumors and external factors, such as diet and in the case of melatonin, too little sunlight, can wreck that delicate system. The idea behind synthetic melatonin supplements is that you reset an upset system. If you ask me, it's a dumb idea.

Now, drugs can be a wonderful thing, don't get me wrong, but when it comes to fixing problems brought on in part by living a lifestyle we aren't adapted for, such as being cooped up indoors all the time during the winter, I think a natural solution is best.

That means making lifestyle adjustments that are more in line with the lifestyle Homo sapiens lived for millions of years.

A light box that emits UV light like the sun, is one natural way to treat seasonal affective disorder and vitamin D deficiency. It's effective too. Just don't over-do it. The best way to use a light box, when you can't get 15 minutes of sun on your retina first thing in the morning, is to wake up at the same time of day and use your light box for 15 minutes, three times a week. You could do it while reading the newspaper or getting ready in the morning.

Or, you could move to a place that gets sunshine more regularly. This totally awesome, animated map of the US shows where the sunlight is month by month. Good luck with that.