Vitamin D is so important for healthy bodies that it is often referred to now as a pro-hormone — more than just a vitamin.  

Vitamin D is made in the skin in response to ultraviolet (UV) rays in sunshine and has a role in strong bones, healthy blood vessels, robust immune systems, and optimal brain and nervous system function.

But since most of us work inside, the chance to get prolonged sun exposure to produce vitamin D is inadequate.

The availability of inexpensive blood tests to measure the level of vitamin D has identified many people who are far below acceptable levels not only during the winter but year-round. In my clinic, I would estimate that over 75% of persons not taking vitamin supplements are low in D and some are rock bottom.

On the other hand, I am also starting to see some patients that were advised to take extremely high doses of vitamin D and they are coming in poisoned by overdosing.  

Below I review a few questions and answers about vitamin D that might help you make good decisions for your health, particularly when sun exposure is limited by the season or your lifestyle.

 

1. Can artificial lights produce vitamin D?

 

Sunlight causes our skin to produce vitamin D by emitting UV rays. Light therapy, which has a role in seasonal depression, has UV rays filtered out and therefore has no role in producing vitamin D. Tanning beds tend to emit UVA rays while it is UVB rays from the sunshine is what stimulates vitamin D production. Tanning beds are not recommended for a wintertime boost of vitamin D.

 

2. How much vitamin D do I need?

 

The conventional answer is about 800 IU a day or less. This is the usual dose in most multivitamins.  

The availability of blood testing has shown that this dose is rarely adequate to achieve blood levels over 30 ng/ml due to absorption issues.

 

3. What foods contain vitamin D?

 

While vitamin D is found in fatty fish, eggs, cheese, and beef liver, the cholesterol and saturated content is so high and adverse for heart health that I do not recommend these sources.  

Mushrooms are high in vitamin D2 (1 cup of diced mushrooms has about 400 IU of vitamin D) and mushroom capsules with about 2,000 IU per serving have been shown to boost blood levels adequately.  

However, studies comparing D2 to D3 generally show that vitamin D3 is more biologically active and easier to convert in the body to the active vitamin and is the preferred form. Most non-dairy milks like almond and soy milk are fortified with about 200 IU of vitamin D per serving.

 

4. What are the 2 kinds of vitamin D?

 

Vitamin D2 is the form found in mushrooms. Vitamin D3 is often found in animal sources such as lanolin, although vegan sources from lichen are now available. Vitamin D3 is more active and generally the preferred form for supplementation.

 

5. Are certain groups prone to low vitamin D levels?

 

Darker-skinned people and older people produce less vitamin D from sun exposure. Persons with bowel disease like Crohn’s or celiac disease often absorb fat poorly and vitamin D is a fat-soluble vitamin. Obese individuals may bind vitamin D in fat and it will not be available in the blood for testing or to supply vital tissues.

 

6. What happens if my levels are low?

 

Extreme deficiencies of vitamin D weaken bones and are called rickets. Lesser deficiencies have been linked to diabetes, hypertension, dementia, autoimmune diseases, and multiple sclerosis. Vitamin D supports healthy immune systems, so being deficient can result in a weaker immune system.

 

7. Can I get too much vitamin D?

 

Yes, and I have seen several cases this year of persons taking over 10,000 IU daily for long periods of time producing illness and blood levels over 150 ng/ml.

 

8. When should I take a vitamin D supplement?  

 

Vitamin D is a fat-soluble vitamin and may be absorbed more completely if taken with meals. Most meals contain some fat so there is no need to add fat to the diet to boost absorption. Pairing vitamin D with vitamin K2 can also help with absorption and improve bone and blood vessel health.

 

Vitamin D shouldn't be ignored.

 

At my clinic, all my patients get their vitamin D level checked, with the optimal blood level is around 50-60 ng/ml.  

For most people, I recommend adding at least 2,000 IU of vitamin D3 through a supplement, and making it a habit to eat extra mushrooms during the winter.