I’ve discussed Vitamin D before and how important it is to your overall health. It has been shown to help with heart disease, cholesterol, cancer and high blood pressure.

Vitamin D also plays a crucial role in activating your Immune System to fight off sickness. T cells are immune cells that are involved in your first line of defense. T cells must have Vitamin D to be mobilized and activated against foreign bacteria and viruses. (1)

Vitamin D also helps your Immune System produce over 200 different types of antimicrobial peptides that protect you against colds and flu’s. These natural peptide are much more effective and than synthetic antibiotics or antivirals.

The higher your blood serum Vitamin D levels, the lower your risk is for contracting colds, flu’s and other respiratory tract infections.

Many research studies have proven that people with lowered Vitamin D levels are more vulnerable to respiratory tract infections. (2-6) One study showed that school age children that were given Vitamin D supplements from December 2008 to March 2009 were 50% less likely to get sick compared to children who got a placebo. (7) Incidentally, these children’s asthma rates went down too.

What Are Optimal Vitamin D Levels?

To be truly healthy, your Vitamin D levels should test in the 50-70ng/mL range. Less than 50ng/mL is too low and studies show that the majority of people today are deficient in Vitamin D. (8)

“But I spend plenty of time in the sun!” you say.

It is true that your body can make all the Vitamin D it needs from exposure to sunlight. That is why it is often called “the Sunshine Vitamin”. But you need to spend at least 20 minutes in bright midday sunlight with most of your skin uncovered (think bathing suit exposure) everyday. And that’s skin without UVB blocking sunscreen, makeup, etc.

When was the last time you spent 20 minutes per day sunbathing to make your daily Vitamin D requirements?

It should make sense that the “cold and flu season” is in the wintertime when there is less sunlight. Because of the colder temperatures, you spend less time outdoors. Your body isn’t able to produce as much Vitamin D so your Immune System is then weakened and you are more likely to get sick.

Thankfully, you can take a supplement to get all the Vitamin D that your body optimally needs. But there are some important facts you must know before you take any Vitamin D supplement.

1) Not all Vitamin D supplements are created equal.

Most medically prescribed Vitamin D supplements are in the Vitamin D2 or ergocalciferol form. This synthetic form is also what is used to fortify processed foods and milk. The D2 form is cheaper but it does not get absorbed well in your body and has a shorter shelf life.

Vitamin D3, or cholecalciferol, is the naturally found form found in fish oils, eggs and animal fats. It is equivalent to the Vitamin D formed in your skin from UVB sunlight. It is converted in your body 500% faster than the D2 form and it is 4 times more potent.

2) Vitamin D is a fat-soluble vitamin.

Excess fat-soluble vitamins (such as Vitamins A, D, E and K) are stored in your body so it’s important you get your blood tested to be sure you’re not taking too much.

It is highly unlikely that you will ever reach toxic levels. Published cases of Vitamin D toxicity occurred in people taking 40,000 IU per day, which are far higher than the dosages I recommend you take. (9)

But the only way to be sure is to have you blood levels tested by your physician on a regular basis (Be sure your doctor orders the 25(OH)D or 25-Hydroxyvitamin D blood test, NOT the 1,25(OH)D test. It is not as accurate).

Recommended Vitamin D3 dosages are:

• 5,000 IU/day for adults
• 2,500 IU/day for children 5-10 years old
• 35 IU/pound of body weight for children under 5 years old.

* There is no evidence of adverse effects in adults with taking 10,000 IU/day. (10)

Vitamin D is a prohormone and a neurosteriod. It has been shown to be an epigenetic influencer of over 2,000 genes in your DNA. Since your whole genome is made up of only 30,000 genes, Vitamin D has a great influence on so many aspects of your health.

That is why Vitamin D supplementation has been demonstrated to significantly reduce risk of ALL causes of mortality. A 2008 meta-analysis of 18 Vitamin D studies revealed that it plays an important role in preventing heart disease, cancer, multiple sclerosis, Alzheimer’s disease, diabetes and even autism. (11)

Think of bacteria or viruses as seeds that are spread around via coughing, sneezing or contaminating surfaces your touch with your hands. Seeds can only sprout and take root in fertile soil that will allow it to grow. If you have a weakened Immune System, then your body becomes an ideal place for a bacteria or virus to plant itself, grow and flourish.

Strengthen your Immune System by practicing the healthy lifestyle habits described earlier and by optimizing your Vitamin D levels. This will insure that your body is an inhospitable environment for those foreign invaders and you won’t get sick.

References

1. Nat Immunol Apr 2010; 11(4): 344-349
2. Arch Intern Med Feb 2009; 169(4): 384-90
3. Am J Clin Nutr Sept 2007; 86(3): 714-717
4. Eur J Clin Nutr Apr 2004; 58(4): 563-567
5. Eur J Clin Nutr Apr 2009; 63(4): 473-477
6. Pediatr Res May 2009; 65(5 Pt 2): 106R-113R
7. Am J Clin Nutr May 2010; 91(5): 1255-1260
8. Clin Lab Med Sept 2000; 20(3): 569-590
9. Am J Clin Nutr May 1999; 69(5): 842-856
10. Am J Clin Nutr May 1999; 69(5): 842-856
11. Altern Med Rev 2008; 13(1): 6-20