The Vitamin D Deficiency Dilemma

Written by: Ella Kenney


In the nutrition world, vitamin D is currently all the rage.  Even folks removed from nutrition science and academia may be familiar with the quandary at hand: it appears that many, maybe even a majority, of Americans are vitamin D deficient.  Perhaps this “D dilemma” has touched people close to you, as it has affected my loved ones.  Seven months ago, my mother’s doctor informed her that she was D deficient.  She began taking weekly megadoses (50,000 units) of Ergocalciferol, a form of D.  After two months, her D levels had increased, but were still considered “insufficient.”

Additionally, my fellow dietetics/nutrition classmate was told by her doctor that she was vitamin D deficient.  A lifelong resident of the Northeast, she has very limited exposure to sunlight and therefore likely has little D synthesis going on in her body (more on that later).

And finally, a good friend of mine gave birth to her first child, an adorable little girl named Sierra.  Since breastmilk does not contain adequate D, Sierra and other exclusively breastfed babies must be given supplements to meet nutritional requirements.  However, Sierra doesn’t like their taste and spits them out.  Her mother, a nurse practitioner who is well informed about nutrition, is vexed. “Can she get enough vitamin D sitting beside a closed window on a sunny day?” she asked me recently.

What is vitamin D, anyway, and why is it so important? It’s an essential vitamin for human life that acts as a hormone, regulating calcium and phosphate in the body to ensure healthy bones, as well as influencing neuromuscular function and reducing inflammation.  Vitamin D is found naturally in relatively few foods, but often products (milk, margarine) have vitamin D added to them in a process called “fortification.”  The body synthesizes D when exposed to the UV rays in direct sunlight.  (Sorry, Kimmie, the necessary rays can’t penetrate glass – Sierra has to take those yucky supplements.)  Vitamin D deficiency can lead to diseases such as rickets (soft bones and skeletal deformity) and osteomalacia (weak muscles and bones).

So… if it’s in some foods and even in the sun, for goodness sake, then what is causing a potentially widespread vitamin D deficiency?

  • Location.  In the northern half of the United States, it is nearly impossible to get enough sunlight to synthesize adequate D in late fall/winter months.  Only Los Angeles (or on the east coast, Columbia, SC) and their southern neighbors receive enough sunlight for adequate year-round D synthesis.
  • Indoor mania.  Many Americans spend the vast majority of their waking hours indoors, hidden like vampires from the sun.  How many people do you know who wake up in the morning, get in their car, drive to work, step into the office for the day, drive home, and then stay inside all evening?  That makes for barely a moment outdoors, let alone at the peak 10 am – 3 pm sunlight hours.  Children do not fare much better: a new study from the Kaiser Family Foundation shows that youth ages 8-18 spend 7.5 hours each day watching TV, playing on the computer or using a smart phone – and presumably little of that occurs outdoors.
  • Sunscreen.  Given the correlation between UV rays and skin cancer, it is not uncommon for Americans to use sunscreen at all times when in direct sunlight.  This severely inhibits D synthesis.  The National Institute of Health recommends 5-30 minutes of sun exposure without sunscreen between 10 am and 3 pm at least twice a week to the face, arms, legs or back to lead to sufficient vitamin D synthesis.
  • Diet.  Vitamin D is found naturally in many fish (salmon, mackerel, tuna, sardines, catfish), egg yolks, and beef liver; foods that are often D fortified include milk, orange juice, yogurt, margarine and cereals.
  • Skin tone.  Darker skinned individuals have more melanin (pigment), reducing the skin’s ability to produce vitamin D from sunlight exposure.  African American women are 10 times more likely than Caucasian women to be D deficient.
  • Obesity.  People with a BMI greater than 30 often have low D levels due to excessive body fat, which stores vitamin D and keeps it from circulation in the blood.

Although you can’t change your skin tone, you can control certain lifestyle factors to attain adequate vitamin D intake: eat D-rich foods (whether naturally or via fortification), get enough direct sunlight, and maintain a healthy body weight.  And if it comes down to it, move to San Diego or Florida.  All in the name of health, right?

What have you heard about Vitamin D in the news or from friends?  Do you know if you’re deficient?


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One Response

  1. This is a great post. Thanks for the info!

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