Vitamin D: Hormone or Vitamin?

Vitamin D is considered not only a fat-soluble vitamin but also a prohormone, meaning it helps amplify the effect of existing hormones.


Strong evidence supports taking Vitamin D above the current recommended dose for bone health. Its job is to help our body absorb calcium and phosphorus, which are mostly obtained from the food we eat, and used in bone and muscle formation. Additionally, there is growing evidence linking higher levels of vitamin D with prevention and improvement in immune function, in cardiovascular and brain health, and in pregnancy.



Also called the “sunshine vitamin,” Vitamin D is produced in our skin in response to exposure to natural sunlight. However, places with little sunlight year round, at-home orders due to COVID, and sunscreen place us at a risk of not obtaining enough Vitamin D. The skin’s ability to produce Vitamin D is reduced by >95% with use of a sunscreen with a SPF >=8.


Other reasons why we might be low on our Vitamin D intake would be:

  • Intolerance to dairy foods (most milk is fortified with Vitamin D to simplify our body’s calcium absorption from the milk)

  • Inability to digest fat (Vitamin D is fat-soluble, and depends on the gut’s ability to absorb dietary fat)

  • Malabsorptions conditions such as celiac, Crohn’s, or cystic fibrosis

  • Experience with gastric bypass surgery (which removes the upper part of the small intestine where Vitamin D is absorbed)

  • Strict vegetarian and vegan diets

  • Genetic variation of the vitamin D receptor (VDR)

  • Infants who are breastfed without supplementation

  • Elderly who are homebound


Vitamin D prolonged deficiencies can lead to rickets in children, a disease where the bones become soft, weak, deformed, and painful. In teens and adults, vitamin D deficiency causes osteomalacia/ osteoporosis.


Which foods are a richer source of Vitamin D?

  • Cod liver oil

  • Salmon

  • Swordfish

  • Tuna fish

  • Sardines

  • Beef liver

  • Egg yolk

  • Orange juice fortified with vitamin D

  • Dairy and plant milks fortified with vitamin D

  • Fortified cereals

*Fish is a source of Vitamin D due to its higher content of healthy fats overall, with Vitamin D’s structure containing some of it


Given the many associated benefits, GLIM recommends taking Vitamin D every day with the goal of optimizing levels to 60-80ng/mL. GLIM believes in monitoring your vitamin D levels through a simple blood test and then personalizing Vit D dosing.


Schedule a free introductory call to work with GLIM on your Vitamin D levels and overall wellbeing!


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