You’ve likely heard of Vitamin D. You may have even heard of the disease that is caused by a Vitamin D deficiency – rickets. This is a disease characterized by soft bones due to insufficient calcium in the bones because Vitamin D increases calcium absorption in the gut. Increasing Vitamin D resolves rickets. In fact, the Recommended Daily Intake set by the US Government is set at an intake 10% over the amount needed to prevent rickets.

But the amount of Vitamin D required to prevent rickets is NOT the optimal intake of Vitamin D for optimal function!

The active form of Vitamin D is 1,25-dihydroxycholecalciferol. It is responsible for the regulation of Calcium & Phosphorus levels but has also been suggested to have a role in hypertension, diabetes, insulin resistance, multiple sclerosis, and cardiovascular disease as well as some cancers.

The ‘normal’ range of Vitamin D is 30-74 ng/mL.

I prefer that my patients have levels between 70 and 100.

I have yet to see a patient who is not supplementing with Vitamin D have a level above 40 and most of them range between 20-35. This is horrible!

Sun Exposure

The BEST way to improve Vitamin D levels is through sun exposure. If you get enough sun exposure to produce a light pink coloration to the skin (1 minimum erythemal dose) produces 10,000-25,000 IU of Vitamin D. Additionally, the Vitamin D that is produced through sun exposure seems to last longer (longer 1/2 life).

The problem is that most of us, especially my patients since we live in Tulsa, Oklahoma, live well north of the equator and do not have year round sun exposure. Even during the summer we aren’t getting enough sun exposure. There are a few reasons for this. We live and work primarily indoors and so we don’t get adequate sun exposure. Even when we do work or play outside we often use sunscreen which prevents 97% of Vitamin D conversion.

I recommend putting sunscreen on 10-15 minutes AFTER going out into the sun. Yes, I know what the dermatologists are saying and that probably is the best advice for the SKIN. However, I don’t treat skin. I treat patients and patients need Vitamin D!


The other way to get Vitamin D is through dietary sources or supplementation. You can eat food sources that are high in Vitamin D or take a supplement. There are 2 forms of Vitamin D available for supplementation: D2 & D3.

D2 (ergocalciferol) is the plant form and D3 (cholecalciferol) comes from animal sources. D3 seems to be a better source for supplementation. Your doctor may prescribe a Vitamin D supplement (Ergocalciferol) at 50,000 IU. This form does not seem to be as effective as the D3 form. Some sources say that D3 is 3x more potent.

Here is an article  from the Journal of Clinical Endocrinology & Metabolism entitled Vitamin D2 is Much Less Effective Than Vitamin D3 in Humans. And an article from the American Journal of Clinical Nutrition – The Case Against Ergocalciferol As a Vitamin Supplement.

If you are currently taking a prescription of Ergocalciferol then you should consider stopping it and taking Vitamin D3 (Cholecalciferol) instead. If you are one of my patients and I have prescribed Ergocalciferol in the past, switch to Vitamin D3 30,000 IU per day for a total of 8 weeks and then we will re-check your labs at that time.

If your Vitamin D level is:

  • <20 – take 30,000 IU of Vitamin D3 daily for 8 weeks and then we will repeat a Vitamin D level
  • 20-30 – take 20,000 IU of Vitamin D3 daily for 8 weeks and then we will repeat a Vitamin D level
  • 30-50 – take 10,000 IU of Vitamin D3 daily for 8 weeks and then we will repeat a Vitamin D level
  • 50-100 – take 5,000 IU of Vitamin D3 daily
  • >100 – consult your physician for recommendations

You can get Vitamin D3 from Sam’s Club for pretty cheap. The picture above is the one I recommend. You can also use the 5,000 IU version and just take more of them to make the correct dose.

Also, remember that Vitamin D is a fat-soluble vitamin meaning that it is distributed throughout your fat tissues. If you are obese then you are at higher risk for Vitamin D deficiency because you have a bigger ‘tank’ to fill. This also means that you need to take your Vitamin D with some form of fat in a meal to ensure optimal absorption.

Bear in mind that a healthy gut is essential to ensuring appropriate absorption of all nutrients. See the Paleo Diet for more information on how to heal your gut!

Good food sources of Vitamin D are:

  • Fish liver oils, such as cod liver oil. 1 TBSP (15 ml) = 1,360 IU of vitamin D
  • Cooked wild salmon. 3.5 oz = 360 IU of vitamin D
  • Cooked mackerel. 3.5 oz = 345 IU of vitamin D
  • Sardines, canned in oil, drained. 1.75 oz = 250 IU of vitamin D
  • One whole egg = 20 IU of vitamin D
  • Porcini mushrooms 4 ounces = 400 IU of vitamin D

You can read more about the structure, function, and synthesis of Vitamin D on the Vitamins page.