Hey Team,

Vitamin D is unique among vitamins because it is a steroid hormone produced from cholesterol when your skin is exposed to the sun. However, sun exposure alone does not always provide enough vitamin D, so it's essential to obtain it from supplements or your diet.

There are two primary dietary forms of vitamin D: D3 (cholecalciferol) and D2 (ergocalciferol). D3 is found in animal foods like fatty fish and egg yolks, while D2 is found in some plants, mushrooms, and yeasts. D3 is more effective at increasing blood levels of vitamin D than D2. Vitamin D must undergo two conversion steps to become active in the body. First, it is converted to calcidiol in the liver, which is the vitamin's storage form. Then, it is converted to calcitriol, the active steroid-hormone form, mostly in the kidneys.

Vitamin D, particularly D3, is not just about bone health. It also plays a significant role in immune function and protection against cancer. It interacts with the vitamin D receptor (VDR) found in almost every cell in your body, turning genes on or off and leading to changes in your cells. It is important to take vitamin K2 alongside vitamin D3 supplements, as vitamin D3 alone can lead to arterial calcification if not balanced by K2, which helps direct calcium to the bones rather than the arteries.

Sunshine is an effective way to get vitamin D, as your skin produces it when exposed to UVB rays from the sun. However, if you live in an area with limited sunlight, obtaining vitamin D from foods or supplements is essential, especially during the winter. Some good food sources of vitamin D3 include fatty fish like salmon and sardines, and fish liver oil, such as cod liver oil, is an excellent source. Additionally, fortified foods like dairy products and cereals, rare mushrooms, and egg yolks also contain small to moderate amounts of vitamin D.

Vitamin D deficiency is more common than you might think, with around 41.6% of the U.S. population being deficient. If you have limited exposure to sunlight, you're not alone. It's important to obtain vitamin D from your diet or supplements to maintain adequate levels in your body.

Symptoms of Vitamin D deficiency can take years to show. The most well-known symptom is Rickets, a bone disease common in children in developing countries. Rickets has been mostly eliminated from Western countries because of the fortification of some foods with vitamin D. Deficiency is also linked to Osteoporosis, reduced mineral density, and an increased risk of falls and fractures in older adults. Additionally, studies indicate that people with low vitamin D levels have a much greater risk of heart disease, diabetes, cancer, dementia, and autoimmune diseases like Multiple Sclerosis. Finally, vitamin D deficiency is linked to reduced life expectancy. However, it's unclear whether deficiency directly causes these diseases or if people with low levels are more likely to get them.

Remember to get your vitamin D levels checked by a healthcare provider to find out if you need to take supplements. The vitamin D storage form, calciferol (D3), will be measured in your blood. If your levels are under 12 ng/ml, you are deficient; if they are above 20 ng/ml, you have enough vitamin D.

The recommended daily intake of vitamin D is:

- 400 IU (10 mcg) for infants aged 0–12 months

- 600 IU (15 mcg) for children and adults aged 1–70 years

- 800 IU (20 mcg) for older adults and pregnant or breastfeeding women

While adequacy is measured at 20 ng/ml, many health experts suggest that aiming for levels higher than 30 ng/ml is better for overall health and preventing diseases.

The U.S. National Academy of Medicine states that 4,000 IU (100 mcg) per day is the safe upper limit for vitamin D intake. Vitamin D3 supplements are more effective than D2 supplements in raising vitamin D levels. They are available in most supermarkets, health food stores, and online.

• The author, Rob Sumner, is a Doctor of Physical Therapy, Athletic Trainer, owner of Specialized Strength Fitness, Specialized Massage and Specialized Physical Therapy in Colville. He's happy to answer any questions about this article, wellness, fitness, or your health overall by phone at (509) 684-5621 or by email at Rob@SumnerPT.com