Vitamin D

Vitamin D is a fat-soluble nutrient essential for bone growth and general health.

Vitamin D is a micronutrient that our bodies depend on for a variety of functions. Besides being important to keeping bones strong and healthy, vitamin D supports your healthy muscles, heart, lungs, and brain function. And it helps your immune system too.

It has a unique property that it functions very much like a hormone. Its target tissues include the kidneys, intestines, and bones, where it helps regulate calcium and phosphorus homeostasis. Its specific activity in the intestines involves stimulating the synthesis of active transport proteins that mediate absorption of calcium. In bone tissue, vitamin D plays a role in regulating calcium deposition (bone mineralization) and mobilization.

View from AsktheScientists:
Vitamin D


The current recommendation of 400 IU of vitamin D per day may not be enough to prevent vitamin D deficiency. USANA’S supplement has 2000 IU of vitamin D per tablet.

  • Necessary for normal bone mineralization and growth
  • Helps in the development and maintenance of bones and teeth
  • Helps in the absorption and use of calcium and phosphorus
  • Helps to prevent vitamin D deficiency

*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.


It is acquired through diet and exposure to sunlight. Light-induced synthesis occurs in the skin when ultraviolet light reacts with a form of cholesterol, converting it to vitamin D. Do we get enough exposure to sunlight or eat good diet to get the Vitamin D that our body needs?

As doctors continue to discover the benefits of healthy vitamin D levels, more and more research indicates that a lack of vitamin D may lead to other health issues. Visit the Vitamin D council's website to see what their research has uncovered.


The truth is that the only surefire way to know if you’re dealing with vitamin D deficiency is to have your blood tested by a physician. But that doesn’t mean you can’t keep an eye out for symptoms associated with vitamin D deficiency. Below are the symptoms and signs:

  • Feeling down and out: This is because our brains produce serotonin—a hormone that affects our moods—at a higher rate when we’re exposed to sunshine or bright light.
  • Skin Color: Some research suggests that those with darker skin may need up to 10 times more sun exposure than those with lighter skin to produce a comparable amount of vitamin D.
  • Age: The skin loses its ability to absorb as much vitamin D as we get older.
  • Sweat: Excessive sweating (specifically, on your forehead) is a very common symptom of those facing vitamin D deficiency.
  • Achy Bones: Many people who are unknowingly deficient in vitamin D will complain of bones and joints that are achy or painful.
  • Excessive Weight: If you’re overweight, the excessive amount of fat in your body needs a comparable amount of vitamin D to absorb.
  • Gut Problems: Certain gut conditions that cause a lower absorption of fat can also lower your absorption of vitamin D.


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These recommendations do not replace medical advice. Always follow the recommendations of your physicians.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.