by Melissa Hudec
It’s a beautiful (but chilly!) sunny mid-November day in Boston, and my friend and I decide to soak up the sun and go for a walk in the park. Sometimes having nutrition students for friends leads to interesting conversations. All my friend had to do was ask how much Vitamin D we were getting on our walk, for me to say “well actually…” And the rest is history!
Vitamin D’s Superhero Profile
Who is Vitamin D?
Vitamin D always seems to push its way into the spotlight every year as the days get shorter.
Discovered in 1922, Vitamin D had been shown to boost calcium absorption, thereby playing a major role in bone health. It was added to milk in the 1930s to ensure Americans were getting enough their diets, resulting in an almost total elimination of rickets, a serious bone disease, from the U.S. population. Scientists have also found a correlation between adequate D levels and fighting against diseases like breast cancer, multiple sclerosis, and many mood disorders. A study in the Archives of Internal Medicine found that Vitamin D deficiency is also associated with a twofold risk of death overall and from cardiovascular causes in older men and women (the study population averaged age 62). Studies show that D can reduce the impact of colds, and fight seasonal affective disorder (SAD), two issues that always seem to rear their ugly heads in the winter months
Beyond fending off the villains of disease, Vitamin D (which, oddly, is not a vitamin, but a hormone), plays a role in over 300 different metabolic processes in many types of tissues and cells.
Where can D be found?
My walking buddy accurately recognized that we can get Vitamin D from sun exposure. (It is, in fact, the best — and cheapest! — way to get D.) It’s synthesized in the skin after exposure to UVB light, and typically your skin can make enough with as little as 20 minutes of sun exposure.
Unfortunately, this is not as simple as a “walk in the park.” D production doesn’t fare well above the 37th parallel in the U.S. Living in the North greatly reduces your chances of synthesizing this super-vitamin, as does seasonality, having darker skin, covering up when going outside (including sunscreen), the time of day of exposure, and increasing age. So sadly, wintertime in Boston reduces the potential for “free D.”
To make matter trickier, there are few food sources of Vitamin D. It naturally occurs only in animal sources, such as fatty fish and eggs. Many milk, orange juice, and cereal products have also been fortified with the vitamin, allowing for more adequate consumption in the population.
Another option for many people is Vitamin D supplements. The vitamin is fat soluble, meaning it is absorbed best with a meal containing fat, and is also easily stored in body fat. This is great news because it means you can take larger doses of D less often. In other words, your body can store extra D for a “rainy day.”
The Dietary Reference Intake (DRI) for D is 600 International Units (IU) per day for most people, and 800 IU for people 70 years old or older. Some supplements contain as much as 5,000 IU and are meant to be taken only once a week. Though Vitamin D toxicity is not a large concern, be careful if you’re taking a multivitamin with D and getting plenty from food and the sun.
Are you seeing enough of this superhero in your neighborhood?
More likely than not, many Americans could do with more D. A Nutrition Journal study from 2010 found that almost 42% of Americans were deficient, with the highest rates among Hispanic and African American populations. Studies show those who are overweight or obese also tend to be deficient in D. However, the CDC distributed a press release in 2013 saying that, “overall, the U.S. population has good levels of Vitamin D in the body, but some groups still need to increase their levels of [the] vitamin.”
It’s not always easy to tell if you’re deficient. According to the Vitamin D Council, deficiency symptoms can be very vague, such as tiredness or general aches and pains, and some people who are deficient have no symptoms at all. Severe deficiency symptoms can manifest as weakness and pain in your bones, as well as a resulting difficulty of movement. But again, not everyone will experience these symptoms.
The best way to determine if you’re deficient is to ask your doctor for a 25(OH) D level test. It accurately measures the amount of D in your body via a simple blood test. Normal levels range from 30.0 to 74.0 nanograms per milliliter (ng/ml). It could be worth your while to get this simple test done to see where you stand, even if you don’t think you’re deficient. Remembering that symptoms can be vague, the test could motivate you to make changes to your diet and lifestyle, to ensure that D makes a regular appearance.
Ultimately, this super vitamin is on the rise in the U.S. population, but we still need to prioritize getting proper sunlight, eating fatty fish, and supplementing with D for optimal bone, immune, and mood health.
I bet my friend didn’t think her simple question about Vitamin D would take our walk in the park to a whole different level!
Melissa Hudec is a first year FPAN student who hails from Colorado. She enjoys the outdoors and travelling. And after learning that fatty fish is a great source of D, you can bet she’ll take any opportunity to enjoy good smoked salmon.