The recipe for Vitamin D
The recipe for Vitamin D
If you’re like me, you may have gone to your doctor for a routine checkup, only to be told that you’re Vitamin D deficient. You may have been urged to get out more and to bask in the sun so that your skin can make Vitamin D!
But doesn’t that sound odd? How can sitting in the sun produce vitamins and eliminate a nutritional deficiency? Aren’t plants the only organisms who can use the sun’s light?
Well, unlike plants, we can’t manufacture our own food. But we can make some vitamins, including Vitamin D, when we expose our skin to sunlight.
I thought I’d try my hand at explaining Vitamin D synthesis for you, but in an easy to read way. Since I’ve been watching a lot of cooking shows recently, let’s “boil it down” and look at the recipe for Vitamin D!
- Ultraviolet (UV) sunlight
Necessary cooking utensils
- Your skin, liver, and kidneys
Step 1: Shine UV light onto your skin.
Every skin cell contains cholesterol in its cell membrane. Yes, that cholesterol, the kind we eat in eggs and meat. While it’s true that cholesterol can be unhealthy in large amounts, like most nutrients, it’s an integral part of every cell of our body.
Light contains energy, and the normal type we see ranges in color from violet to red, just like a rainbow. Violet light has higher energy than red light, and light with even more energy than violet light is invisible to us. However, it’s just as real and potentially far more damaging. It is this type of light that we call ultraviolet, or UV light.
When UV light hits your skin, it contains just the right kind of energy that converts cholesterol into a chemical called cholecalciferol. So, technically, the skin doesn’t make Vitamin D; the sun does! UV light can also break apart DNA, which is why you shouldn’t spend more time in the sun than necessary to get your Vitamin D fill (about 5-30 minutes from 10 AM to 3 PM, twice a week).
Step 2: Transport cholecalciferol through the blood stream to the liver.
Once sunlight produces cholecalciferol, it gets transported to the liver where it gets converted to yet another awkwardly named chemical, calcidiol. Interestingly, because Vitamin D travels through the blood to act on a different part of the body, it fits the technical definition of a hormone.
Step 3: Transport calcidiol through the blood stream to the kidneys.
In the kidneys, calcidiol is converted into the final, active, and protective form of Vitamin D called calcitriol.
Step 4: Work together with other hormones to regulate bone health.
Once Vitamin D is in its active form, it protects us by working together with a number of other chemicals in our body. Along with parathyroid hormone (PTH) from the parathyroid glands, and calcitonin from the thyroid gland, Vitamin D regulates blood calcium levels. Bone formation and growth relies on adequate amounts of calcium in the blood stream, so Vitamin D plays a critical role in providing our skeletons the resources it needs.
Next time you’re at your doctor’s office and he or she tells you that you either need to hit the beach or take more Vitamin D supplements, you might want to take note. It could mean the difference between a strong, healthy body or a trip to the ER for a bone fracture.
Bischoff-Ferrari HA, Dawson-Hughes B, Willett WC, et al. Effect of vitamin D on falls: a meta-analysis. JAMA. 20004;291:1999-2006.
Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr. 2004;80 (suppl):1678S-1688S.
Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Flouride. Washington, DC: National Academies Press; 1997.