Vitamin D is a fat soluble vitamin meaning that it is stored in body fat and in the liver once consumed. Inactive Vitamin D is synthesized from dermal exposure to UV light as well as from dietary intake. Once synthesized the inactive form goes through a process first in the liver, followed by the kidney where it becomes the active form. Food sources of vitamin D are limited, making dermal synthesis the most important way to obtain adequate Vitamin D. Studies have shown that many Americans do not consume enough Vitamin D through their diet nor do they have enough exposure to the sun. This has resulted in increased incidence of Vitamin D insufficiency, or subclinical Vitamin D Deficiency, in the United States.
Vitamin D is critical in the body for:
- Proper calcium balances
- Bone metabolism
- Blood sugar regulation
- Cell growth and development
- Immune system function
- Metabolism
Recommend Dietary Allowance for Vitamin D is 600IU (15mcg) for adults 18-70 and 800IU (20mcg) for adults over 70 daily.
Severe vitamin D deficiency can lead to Rickets and Osteomalcia.
Rickets is seen in children and is associated with improper bone formation that leads to soft bones, skeletal deformities and if severe, can also cause seizures, spasms, failure to thrive, delays in development, bone pain, heart complications and dental complications.
Osteomalacia is seen in both children and adults and is characterized by improper bone formation resulting in weak bones. Osteomalacia can also cause bone pain, seizures, spasms as well as dental complications.
Vitamin D Deficiency is most common in:
- Infants who are exclusively breast fed for prolonged periods
- Populations with very low sun exposure
- Those with lack of vitamin D fortified foods in their diets such as vegans, lactose intolerant
- Malabsorptive syndromes
- Those who have undergone gastric bypass surgery
- Those with impaired liver function
- Those with impaired kidney function
- The elderly
- Those with darker skin tones
- Those who are obese
Being a fat soluble vitamin, vitamin D Intoxication can occur from high dose supplementation. There is no evidence that vitamin D intoxication can occur from sun exposure. The dose at which it occurs has not yet been established. The Institute of Medicine defines the “tolerable upper intake level” for vitamin D to be 4000 IU or 100 micrograms daily for non pregnant, non breast feeding adults.
Symptoms of Acute Vitamin D Intoxication include:
- Confusion
- Increased urination
- Increased thirst
- Anorexia
- Nausea/Vomiting
- Muscle weakness
Research is being conducted in regards to the role of Vitamin D and chronic diseases such as cardiovascular disease, diabetes, multiple sclerosis and certain cancers but to date findings are conflicting and further research is needed.
Conclusive findings have determined an association between low vitamin D as a cause of osteoporosis as well as cause for increased cancer mortality.
Given the known cancer risk with UV light exposure, it is important to focus on ways to obtain Vitamin D through dietary sources.
Food sources of Vitamin D include:
- Egg yolks
- Mushrooms exposed to UV light
- Fortified Cows Milk
- Fortified Non-Dairy Milk
- Fortified yogurt
- Fortified cereals
- Beef liver
- Salmon
- Tuna
- Sardines
- Trout
- Mackerel
- Cheese
- Red Meat
- Fortified orange juice
As mentioned above, Vitamin D through dietary sources alone can be difficult and making sure to add these foods to your diet plays a crucial role in maintaining adequate levels.
This article is for information purposes only and is not medical advice. Consult with your medical provider prior to any lab testing, diet changes or new supplement/medication.
Wondering what your vitamin status is? Check out ROOTINE.
References:
Institute of Functional Medicine Fact Sheet. Micronutrients: Vitamins. Accessed 2020
National Institutes of Health- Office of Dietary Supplements. Vitamin D. Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
Uptodate.com. Pazirandeh et al. Overview of Vitamin D. October 2019.
Vitamin D Deficiency. Sizar et al. https://www.ncbi.nlm.nih.gov/books/NBK532266/. July 2020.
All photos used with permission from Snappa.com
