For anyone with friends or loved ones battling skin cancer we know how harmful overexposure to the sun can be (also causes premature aging, dark patches or melanin spots, and leathery skin). We are reminded of this fact whenever we see an advertisement for Bullfrog or Coppertone telling us so. Some of us get so afraid or so concerned about the safety of our kids that we do not let them go outside without proper sun screen protection. This is very understandable but the problem with this approach is that it blocks the body’s ability to synthesize vitamin D.
To explain, vitamin D is the “sunshine vitamin” and so whenever sunlight touches our skin, a reaction takes place where vitamin D is actually produced in the form of cholecalciferol or D3 (ergocalciferol is D2). Sunscreen, even at an SPF of 8 prevents this process completely (unless we forget to reapply it of course). In no way is this a recommendation to stop using sunscreen but a little exposure to natural sun which is rich in UVB rays (not tanning beds rich in UVA rays; there is no benefit and they should be eradicated) can go a long way and a total of 5 to 30 minutes twice a week (towards the lower end if skin is very light in complexion such as Caucasian and towards the higher end if darker in complexion such as Mexican American or African American) with at least face, arms, and legs showing is enough (shoot for morning or late afternoon hours if summer and midday hours – 10 am to 3 pm if early spring or autumn). More vitamin D will be produced if we bear body parts that are normally covered in clothes (the thighs, back, chest, and stomach) because the skin of those areas will be lower in the pigment melanin (is what gives us our tan and protects our skin from sun radiation). It is a great idea to perform this as a routine when weather permits (especially if living in a state north of Georgia where UVB rays do not penetrate the atmosphere deep enough in the winter) because considering vitamin D is a fat soluble vitamin, we can build up enough in our bodies to get through the cold months. This is how we make it
The reason all the above is needed to be said is because rickets, caused by vitamin D deficiency, is making a comeback. As a micronutrient, vitamin D assists in the absorption of dietary calcium, (the reason all milk is vitamin D fortified) which is the major mineral constituting our bones. Rickets in children is characterized by bowed legs (looks like they are riding an invisible horse) and fragile bones that break easily. It was a problem in the 19th and early 20th century in countries of colder climate (before vitamin D was added to foods) and it is becoming a problem now in developed nations of warmer climate where populations have been duped into believing that the sun is the absolute “devil” (so kids stay indoors!). Vitamin D is not just important for our bones though because it also assists in cell growth, neuromuscular and immune function, and in the reduction of inflammation.
Besides fortified dairy (yes, includes almond milk and soy milk; I’m not a cow’s milk salesman) vitamin D can be found in other foods but generally speaking it is a scarce micronutrient. However sources include our friend cod liver oil (11.3 mcg in one teaspoon [tsp]), sockeye salmon (13.3 mcg in 3 ounces [oz]), canned sardines (5.8 mcg in 3 oz), canned mackerel (5.3 mcg in 3 oz; higher in mercury), fortified cow’s milk, soy milk, and orange juice (2.5 mcg in 8 fluid oz), and egg yolks (0.6 mcg in one yolk). Irradiated mushrooms are also a good source of vitamin D with UV treated portabella mushrooms containing 11.2 mcg per 100 grams. The Recommended Daily Allowance (RDA) is 15 micrograms (mcg) or 600 International Units (IU) daily for men and women aged 19 to 70 years (increases to 20 mcg daily or 800 IU after 70) and the Upper Tolerable Level Intake is 100 mcg or 4,000 IU daily but toxicity is unlikely unless taken in excess supplementally. The result of toxicity, however, often includes hypercalcemia or the buildup of calcium in the blood which can lead to nausea and vomiting, frequent urination, kidney problems, weakness, and poor appetite. Besides having weak bones, other symptoms of deficiency include bone pain, muscle weakness, increased risk of developing cardiovascular disease, and cognitive impairment.
As a final note, for all our moms who are exclusively breastfeeding (HOORAY!) a liquid multivitamin supplement called polyvisol or trivisol is usually recommended by a pediatrician for the baby (just a few drops in the mouth daily or mixed in with breast milk if bottle feeding). This is because, although human breast milk is the perfect food for a baby up to at least 1 year, it is actually low in vitamin D. Since pediatricians cannot seem to decide on a safe limit of sun exposure for an infant (although it is used to treat jaundice interestingly enough) a liquid vitamin D supplement without iron is often prescribed (with iron if mom is anemic and the breast milk is iron poor) or mommy can take a vitamin D supplement at 600 IU daily to increase its concentration in her milk.
Sources: http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/; http://www.mayoclinic.com/health/vitamin-d/NS_patient-vitamind; http://lpi.oregonstate.edu/infocenter/vitamins/vitaminD/; http://en.wikipedia.org/wiki/Vitamin_d