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An estimated 40% of Americans are vitamin D deficient – not good, since vitamin D is essential for bone health, healthy blood pressure and managing inflammation – and a deficiency in D is linked to mood disorders, diabetes and cancer. And since the sun is one of our key sources of D, the shorter, darker winter days make it even more of a challenge to get our daily dose of D.

Who’s at risk: People with limited little sun exposure (since our skin makes vitamin D from sun)People with dark skin If overweight (body fat stores more fat-soluble D; doesn’t release into bloodstream)People over 50, as well as infants (particularly breastfed infants)   Testing Vitamin D levels | serum 25(OH)D concentrations: Endocrine Society recommends serum 25(OH)D level greater than 75 nmol/L (30 ng/mL) for optimal calcium, bone, and muscle metabolism. Not all experts are aligned: Food and Nutrition Board at the National Academies of Sciences says levels must be <30 nmol/L to qualify as deficient, though ‘inadequacy’ can occur at levels of 30-50 nmol/L.   How much we need: The RDA is just 600 to 800 IU (15-20 mcg) daily, though the Endocrine Society states that adults may benefit from 1500-2000 IU (37.5-50 mcg) daily, and children and teens 1000 IU (25 mcg) daily.   Recent research supports a safe upper limit as high as 10,000 IU daily. For more on doses of vitamin D, check out this National Institutes of Health Vitamin D Fact Sheet.   How to get our daily dose of D: Sunlight is our best source of vitamin D 10 to 15 min in ‘direct’ sunlight (when your shadow is shorter than you) SPF 8+ appears to block the vitamin D-producing raysSun rays that make vitamin D don’t go through glass – so if most of sun exposure is through a window or while driving, you won’t be getting dose of vitamin D   

If you’re not getting enough sunlight or you’re at high risk, take a look at how much vitamin D you’re getting through food and supplements.  But be aware that it’s not easy to get 800-1000 IU through food:

Top food sources of Vitamin D  

  • Milk, vitamin D fortified – 100 IU/cup  (plus it’s vitamin D2, not as well absorbed)
  • Salmon or sardines – 100 IU / ounce (vitamin D3, better absorbed)
  • Cod liver oil provides more than 1,000 IU vitamin D3 per tablespoon
  • Consider supplementing with Vitamin D3 – look for 800-1000 IU of vitamin D3

How to know if you’re getting enough? The only way to know for sure is to check your blood levels of vitamin D; ask your healthcare provider to test your serum 25(OH)D concentrations. 

For more on vitamin D, check out Molly’s article, Vitamin D: Do you need to supplement.


Molly Kimball, RD, CSSD is a registered dietitian + nutrition journalist in New Orleans, and founder of Ochsner Eat Fit nonprofit restaurant initiative. Tune in to her podcast, FUELED | Wellness + Nutrition and follow her on Facebook, Instagram and Twitter at @MollyKimballRD. See more of Molly’s articles + TV segments at, and sign up for Eat Fit Wellness Bites weekly newsletter, here.