The winter light is here. I met up with a friend for lunch at Angelica Kitchen today (which had a John Lennon-themed specials menu) and enjoyed some chili and cornbread at a seat by the window. After having been stuck inside at my volunteer site all morning, it was nice to see the sun.

Speaking of the sun, it makes me a bit uncomfortable that this one (from a Biochem lecture on Vitamin D) has a mustache.

As you may be aware, we need some sun (most doctors recommend 10-15 minutes) to synthesize vitamin D. Sunlight converts 7-dehydrocholesterol in the skin to previtamin D3, which is then converted to vitamin D3 and enters the blood.  This fat-soluble vitamin plays a big role in the regulation and absorption of calcium and phosphorous, making it an important factor in bone health. Research is also being done on vitamin D’s effect on blood pressure, multiple sclerosis, and some forms of cancer.

For those of us in northern states, most people get a lot less sun (and a lot less vitamin D) in the winter months and fall short of the recommended 600 IU a day. Unfortunately (or fortunately, depending on your point of view), fortified foods like milk and juice are the most common sources, but you can also get vitamin D from certain fatty fish like salmon and mackerel and from fish oil. Supplements are also an option, but you have to be careful not to in take too much, as fat-soluble vitamins are more easy to overdo it on because they can be stored in the body, allowing levels to build up to a point of toxicity.

After finding out I was deficient in D (and suffering an injury—awesome), my doctor recommended I take a calcium supplement with vitamin D in it. While I don’t think supplements are for everyone, I feel like it’s the right decision for me right now, and I do think it’s a good conversation to have with your doctor if you’re concerned.