This blog post was co-written by University of New Hampshire dietetic intern Kalelys L. Calero and NEDFC Nutrition Specialist Becca Story, MS, RD, LD.
Cold New England winters with their shorter days make it easy to cozy up with a blanket and stay inside all day. Trouble is, inadequate sunlight exposure can put you at risk for low vitamin D levels, even if you make it outside during daylight. So why is that a big deal and what can be done about it? Find out by reading on!
The deal with vitamin D
Vitamin D a.k.a the “sunshine vitamin”, comes in two forms naturally:
- D2 (ergocalciferol): Can be found in plant-based foods, especially fungi. Fun fact: Mushrooms are the only vegetable that naturally produce vitamin D from exposure to sunlight (like we humans do!)
- D3 (cholecalciferol): Naturally produced in skin of humans with exposure to sunlight and likewise can be found in animal sources like salmon, swordfish, tuna, egg yolks cod liver oil and Swiss cheese.
Both forms can be made synthetically and added to foods, or made into supplements. Both forms are metabolized in the body the same way and thus the term “vitamin D” may be used to describe either.
Which type is better?
Hard to say. According to National Institute of Health there isn’t enough information available to determine definitively what type of vitamin D is better, though some studies suggest D3 may have an edge over D2 in some respects. The good news is that both can be converted in the body to the active form (calcitriol) that is needed for function, so whether it’s coming through dietary sources or sunlight, you’re getting the vitamin D your body needs.
What does it do for me?
- Helps you to absorb calcium and phosphorous from the foods you eat…
- … and therefore, helps to strengthen bones preventing debilitating diseases like oseteomalacia, osteoporosis and rickets in children. Something to think about: The incidence of rickets was dramatically reduced in the U.S. since the introduction of vitamin D fortified milk in the 1930’s.
- May reduce risk of chronic diseases like type 2 diabetes.
- We talk more about dairy & type 2 diabetes in this blog post.
- Involved in brain development and contributes to mental health.
- It may also have a a role in several other functions, but more research is needed.
How much do I need?
The RDAs (recommended intake levels to meet nutrient needs) for vitamin D for much of our life is 600 IU (International Units) or 15 mcg (micrograms). The exception being for infants (0-12 months old) who need 400 IU (10mcg), and older adults (over 70 years old) who need 800 IU (20mcg).
What are vitamin D sources?
The sun, when you can get it. This also depends on other factors, including UV index, your geographical location, time of day you are outside, and whether you use SPF protection.
Supplementation is an option, but a more delicious way would be to plan your menu to include your favorite dairy foods paired with other vitamin D -containing foods (natural or fortified) like fish (especially the skin), eggs, and orange juice, just to name a few.
Check out some of the top vitamin D food sources according to the USDA Food Composition Database:
|Food and Serving Size||IU per serving|
|Cod liver oil, 1 tablespoon||1360|
|Halibut (raw), 3 oz||1097|
|Mackerel (raw), 3 oz||1006|
|Salmon, canned with skin and bones 3 oz||859|
|Swordfish (raw), 3 oz||558|
|Tuna (canned in water), 3oz||269|
|Orange juice (fortified, check labels), 8 oz||101|
|Yogurt (fortified, check labels), 8 oz||99|
|Egg (1 large)||40|
|Mushrooms (raw), 1 cup (can vary by type and exposure to UV light)||12-1135|
|Swiss Cheese, 1 oz||20|
|Other full fat cheese, 1 oz (can vary by type and fortification)||10-32|