Vitamin D—Strong Bones and Beyond

Vitamin D is a fat-soluble vitamin obtained from sun exposure, certain foods, and supplements. When most people think of this vitamin, they think of bone health, and for good reason. Vitamin D is important for building and maintaining strong bones and teeth, as well as support a healthy immune system and cellular function.

Many people are concerned about obtaining enough of this vitamin, especially in the past few years. Few fail to realize, however, that most people can quite easily get enough from being in the sun for 10-15 minutes a day.

Learning more about Vitamin D, what it does, and who may be at risk of deficiency can help you understand the vitamin and make the best choice regarding adding more to your diet.

What Does Vitamin D Do?

It has multiple roles in the human body, including the promotion of calcium absorption in the gut. This is why you often see food packages flaunting their vitamin D and calcium content together, and why both come to mind when thinking about bone health.

This vitamin is essential or bone growth and remodeling, and working together with calcium and phosphate, it helps maintain normal bone mineralization. Your bones are constantly breaking down and rebuilding at a microscopic level, and these micronutrients are what keep the process flowing seamlessly. Without enough, bones can get brittle.

But it has many functions in the body besides maintaining bone health. It’s important for immune function, cell growth, proliferation (when one cell splitting into two daughter cells), and differentiation (cells deciding what specific function to have in the human body), and the reduction of inflammation. It also plays a role in regulating blood pressure and diminishing risks of heart disease.

The Different Forms of Vitamin D and Why It Matters

Many people do not realize that there are multiple forms of many vitamins, including vitamin D.

For vitamin D specifically, there are two forms. First and most potent, there’s dietary vitamin D, also known as D3 or cholecalciferol. Vitamin D3 is biologically active, and found in animal sources. It’s also the form made when sunlight is converted into vitamin D in our bodies.

There’s also vitamin D2, also known as ergocalciferol. Plants produce vitamin D2 when they are exposed to UV light. Calciferol is a form of vitamin D that is not naturally made by the human body, and is therefore less easily used in the body.

Most supplements contain the D2 form.

While both forms of the vitamin are important, Vitamin D3 is more effective for maintaining health and blood levels of vitamin D, even in the winter months.

How much Vitamin D do I need?

The recommended daily intake of Vitamin D varies by country, and there are a lot of differing opinions about how much you really need.

In the United States, the recommended daily allowance for healthy adults is 600 IU/day, with the upper safety limit set at 4,000 IU. However, as mentioned above, your body’s ability to use the different forms of the vitamin varies, so the amount you need may depend on your source.

In other countries, the recommended daily allowance for vitamin D falls between 400-800 IU/day. For adults with a low blood level of vitamin D who may need more, supplementation of 1,000-2,000 IU/day may be appropriate.

Lately, it seems many health care professionals push large vitamin D supplements on patients. Most supplements contain the D2 form of the vitamin, and therefore, more is required to raise blood levels of the vitamin. Whether these mega-doses of D2 are effective at raising blood levels of this important vitamin, however, is a subject of debate.

Vitamin D Deficiency

A deficiency can lead to thinning, brittle bones and osteoporosis. Children who do not get enough of this vitamin risk developing rickets, a disease that leads to soft, weak, brittle bone formation, bone pain, and stunted growth. Adults who do not get enough may develop osteomalacia, or bone softening.

Certain populations are more at risk than others when it comes to a deficiency.

Older individuals, those who do not get sufficient sun exposure, and people with certain absorption conditions (such as Irritable Bowel Disease or Crohn's disease) are most at risk.

Vegans and vegetarians may also be at risk if they don’t consume vitamin D fortified foods, and/or don’t spend any time in the sun.

So, if you don’t spend a lot of time outside, have a condition that prevents you from absorbing vitamins and minerals (especially fat-malabsorption disorders) and/or follow a strict dietary pattern, a supplement may help you reach your needs.

Sources of Vitamin D

Vitamin D3 is naturally found in larger amounts in fatty fish, fish oil, and fish liver, and in smaller amounts in beef liver, egg yolks, and certain cheeses. Vitamin D2 (the less biologically available source) is naturally found in mushrooms.

Many foods are also fortified with vitamin D. Milk, yogurts, cereal, orange juices, almond and other non-dairy milks, and margarine are among foods commonly fortified with vitamin D2. A majority of these foods and most dietary supplements use the D2 form of the vitamin, which is far less potent.

Vitamin D and You

This vitamin is important for healthy bone, immunity, and cellular function. If you have concerns about your intake, try spending more time in the sun (using sunscreen, of course), and increasing your intake from foods.