If you fly into DIA (Denver International Airport), you’ll be greeted by a terminal that matches our mountains and seven and a half acres of solar photovoltaic panels. Yes, we’re a cutting-edge, groovy city with a totally hip and charmingly dorky mayor* who’s putting us on the map as the greenest city in the country. Solar energy isn’t hard to come by around here considering we average 300 days of sunshine per year. That’s even more than Miami Beach or San Diego. You didn’t know that, did you? Now, forget I ever said it unless you already live here.
Back to my point.
Solar cells use sunlight to produce electricity.
What does this have to do with nutrition or food, you ask? Actually, nothing, but I thought it would be a good segue into the weirdness of vitamin D.
Skin cells use sunlight to produce vitamin D.
See, all you are is a bikini-clad solar panel. Or, if you’re a guy, a speedo-clad solar panel (guys — hopefully you’re not really wearing a speedo unless you’re under 12 and on swim team).
But I digress, which is an ongoing pattern with me. Because vitamin D is the hot new nutrient these days and there’s lots of confusing information about it, I thought I’d dedicate an entire post to it.
I haven’t even started and we’re already in murky territory — vitamin D isn’t even a vitamin, it’s a hormone, one we can synthesize on our own. We do this with the help of sunlight and a precursor the body makes from cholesterol.
*Hormones are chemical messengers, substances made in one part of the body that cause a response in another part of the body. Vitamins are essential nutrients found in food and needed in small amounts to prevent disease and support health. Two different things.
How do we make vitamin D (which is not a vitamin)?
The liver produces the precursor to vitamin D from cholesterol. Ultraviolet light from the sun hits this precursor (7-dehydrocholesterol, in case you’re interested), which is in the skin, and converts it to previtamin D3. Over the next day or so, this substance works its way into the body and is eventually converted to its active form — that of a functioning hormone. Two things must occur for it to become fully active, one change takes place in the liver and one in the kidneys. Conditions impacting liver or kidney function can interfere with the activation of vitamin D, resulting in deficiencies.
Important roles of vitamin D
It’s a convoluted process, but vitamin D helps maintain blood concentrations of calcium and phosphorus, which in turn helps bones grow strong and dense. If there is a deficiency or a problem along the pathway, growing bones may not calcify, become weak, and skeletal abnormalities result (rickets in children). In adults, a deficiency in vitamin D, a failure to adequately synthesize it, or malabsorption can lead to osteoporosis.
In addition to being mandatory for bone growth and strength, research also suggests that vitamin D plays a role in brain and nervous system health; immunity; insulin secretion (type 2 diabetes) and other autoimmune conditions; skin, muscle, and cartilage health; reproductive health; cardiovascular health, and may be beneficial against many types of cancer.
Vitamin D and celiac disease
Osteoporosis is often seen in people with celiac disease. In fact, it is one of the most common adult presentations. The reasons are complex and different for each individual, but intestinal damage resulting in the malabsorption of calcium and vitamin D can play a key role. If you aren’t synthesizing and absorbing vitamin D, then calcium absorption is compromised. If you’re not able to utilize these nutrients, your bones will pay the price.
Vitamin D sources and possible toxicity
Not many foods contain vitamin D — at least in a natural state. Some foods such as milk, infant formula, orange juice, and some breads and cereals have been fortified with vitamin D. Some fish (wild-caught salmon, mackerel, sardines), fish liver oil, and eggs from hens that have been fed vitamin D are good sources, but that’s about it as far as food goes.
But, remember, our skin is made up of little solar panels, so we can easily produce our own vitamin D. No need to worry if you live in a sunny climate and don’t wear a burka or sunscreen with a higher number than 8. All you need is 15 minutes of sunshine a few times a week. You don’t have to bake in the sun and risk skin cancer — plus, the sun poses no risk of vitamin D toxicity. You can’t overdose on vitamin D from the sun.
You can on synthetic vitamin D though. My Understanding Normal and Clinical Nutrition book states, “Vitamin D is the most likely of the vitamins to have toxic effects when consumed in excessive amounts. The amounts in foods are within safe limits, but supplements…should be kept out of the reach of children and used cautiously, if at all, by adults.”
Excessive vitamin D raises blood calcium levels, which in turn, can cause kidney stones. The kidneys make an effort to to excrete concentrated calcium.
Here’s where it gets dicey. Some research suggests many of us aren’t getting enough vitamin D and that the current RDA (recommended daily allowance) is too low. The RDA measurements are the average daily amounts considered adequate to meet the needs of most healthy people. Advocates suggest we need far more than the UL (tolerable upper intake levels) to be healthy. But then again, what if we’re taking too much and it’s toxic?
The RDA for infants up to 1 year old is 1,000 IU per day. For children and adults, it’s 2,000 IU per day. That 15 minutes of sun I suggested can produce up to 20,000 IU depending on where you are, how direct and cloud-free the sun is, what your skin color is (darker skinned people need longer exposure), and how much of your body is exposed. That’s way more than you need for one day, so your body saves it for a rainy day. Literally.
Vitamin D is one of the trendy nutrients right now and there are many reasons to take this one seriously. People who live in northern climates or those who don’t get any sun, older people, people with digestive disorders resulting in malabsorption, post menopausal women, and those who get no vitamin D in the diet might want to consider supplementation. Talk with your health care provider if you think you may be at risk of a deficiency.
I can’t end this without saying how important it is to not only make sure you get enough of the right nutrients (vitamin D, calcium, magnesium, phosphorus) for strong bones, but also to do some weight bearing exercise every day. Stand on your hands! Your bones will thank you.
Go forth and sing — here comes the sun doo-be-doo-be — here comes the sun and I say, it’s all right.
* With limited name recognition, no political experience and a reputation for having an offbeat and weathered wardrobe, mayoral candidate John Hickenlooper turned those challenges into opportunities with his quirky ads (and now famous) mode of transportation. (Courtesy of YouTube)