Vitamin D: Why We Need It & How to Get It

by Laurel Sterling, MA, RD, CDN

Vitamin D3 has been a “hot” topic of discussion for the past few years, and the scientific research continues increasing regarding the crucial role it plays in our health and wellbeing. Vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) are the two vitamin Ds referred to in research and are found in both food and supplements. Vitamin D3 is known as nature’s sunshine vitamin, and is a vitamin we can actually make in our body under proper conditions. Because of this, many believe we receive enough D3, but large-scale studies find deficiency is widespread in adults and children.
 
Vitamin D3 Benefits
Vitamin D is important for our entire body. Vitamin D receptors are found everywhere from immune cells to the brain. Vitamin D3 promotes healthy growth and development; teeth, bone, and muscle health; healthy immune and cardiovascular systems; and mood health. 
 
Making Vitamin D from the Sun
Our skin contains a precursor to D3, called 7-dehydrocholesterol. When the sun’s UV rays shine on our skin, 7-dehydrocholesterol synthesizes D3, though conditions need to be perfect. Many of us don’t get enough time in the sun to make and maintain adequate 25(OH)D levels (the form made after D3 is converted in the liver and the best indicator of vitamin D status). And if we are in the sun, our body often doesn’t synthesize adequate amounts of vitamin D due to sunscreen, latitude, time of year, color of skin, etc.
 
Getting Vitamin D through our Diet
There aren’t many naturally occurring dietary sources of vitamin D, which is why many turn to vitamin D supplements to keep their levels up. It can be found in the flesh of fatty fish like salmon (approximately 500 IU (12.5 mcg) in 3 ounces), mackerel, and tuna and in fish liver oil. Some mushrooms provide vitamin D2, which our body still needs to convert to the bioavailable D3 form. Most of the dietary vitamin D comes from fortified foods such as orange juice, non-dairy beverages, egg yolks (from D3 supplemented hens), and some dairy (milk, yogurt, and cheese).
 
Supplementing with Vitamin D3
The recommended daily intake of vitamin D3 varies widely across organizations. The Institute of Medicine (IOM) Food and Nutrition Board RDA’s are the official recommendations for the US. Their latest recommendations are 400 IU (10 mcg) per day of vitamin D3 for infants, 600 IU (15 mcg) per day for children over 1 years old, and 600 to 800 IU (15 to 20 mcg) per day for adults.
 
The Vitamin D Council, Endocrine Society, and many physicians feel these recommendations are too low and are requesting they be increased. The IOM states adult sufficiency of vitamin D3 levels is 20 ng/ml, the Endocrine Society says 30 to 100 ng/ml and the Vitamin D Council says 40 to 80 ng/ml.
 
The amount necessary to increase and maintain our D levels is different from everyone and varies throughout the seasons. Make sure to get your levels tested regularly and adjust supplementation accordingly. Research has found that vitamin D3 is the preferred form to supplement with in order to increase levels effectively.

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​Laurel Sterling, MA, RD, CDN
​Laurel is a registered dietitian nutritionist and certified nutritionist and has worked in the natural products industry since 2000. Laurel has counseled hundreds of individuals, lectured at various corporations and events, written numerous articles and blogs on health and nutrition, and appeared on local TV and radio shows.