Which Factors Affect Your Vitamin D3 Level?
Skin Color - The Fitzpatrick Scale was developed by Harvard dermatologist, Dr. Thomas Fitzpatrick, to measure skin sensitivity to sunlight exposure [1].
Darker skin types may need 50X more exposure to the same amount of sunshine as light skin types, to make the same amount of D3 [2]. Darker skinned people are more at risk for D3 deficiency, particularly when living a typical urban lifestyle, above 35° latitude. See Effects of Location, below.
Age - as the skin ages, it gradually loses the ability to manufacture cholecalciferol, vitamin D3, from sunlight. At age 70, your skin is only 30% to 50% as efficient at converting cholesterol into D3 as it was when you were 20 years old [2]. So, increased age is a risk factor for D3 deficiency.
Genetics – scientists found that the highest risk for dementia and stroke were seen in those with the lowest D3 levels. [3]. Many daily lifestyle choices regulate health and wellness - diet, exercise, and quality sleep are the most noticeable.
Medications and medical conditions – These common medications have been found to lower D3 levels: https://www.grassrootshealth.net/blog/medications-may-affect-vitamin-d/
Body Weight and BMI – when your body mass is larger, more D3 is needed to reach all the cells. The larger your body mass, the more risk for D3 deficiency [2].
Sun Exposure – The skin, your body’s largest organ, is designed to metabolize cholecalciferol (D3) from sunlight. Up to 10,000 IUs (International Units) may be produced by Type 2 skin in 15 minutes, with 25% of the body exposed, at noon on a summer day [2].
Effects of Location on Sunlight Absorption - Sunlight strikes the Earth directly at a 900 angle, year-round, only at the equator. As the Earth tilts towards the sun in the summer months, UV light becomes more available (and less available when tilted away in the winter). So, you are more at risk for D3 deficiency if you live farther from the equator simply because the UV part of sunlight is not available all year around.
Food and Supplements – D3 is found in fatty fish, mushrooms, or fortified milk. The optimal supplement range is between 40 – 60ng/ml, shown to be preventative for cancers, diabetes and fractures [4]. Have your D3 levels tested and aim for optimal levels to reduce your risk.
Co-nutrient Intake – Vitamin K2 (found in fermented foods like sauerkraut) is an essential co-nutrient for D3 absorption. Other essential micronutrients, like magnesium, boron, calcium, zinc, and B vitamins are supplied by a high-nutrient density diet and lots of plant variety.
Digestion – In order for D3 supplements to be usable by the body, your stomach acid must be strong enough. Sometimes this is an added risk factor with age.
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References: 1. Fitzpatrick Skin Type Classification system, 1975, by Thomas Fitzpatrick, MD, PhD. 2. Holick, MF, (2003) The UV Advantage, New York, NY, iBooks. 3. American Journal of Clinical Nutrition April 2022. 4. www.grassrootshealth.net
