Now that we have covered the basics of supplementing safely, let’s take a closer look at a few common deficiencies and some good ways to address them. We’ll begin this series with a vitamin that is currently trending in health circles: vitamin D.
What are vitamins?
Vitamins are micronutrients essential for normal physiological function that are not synthesized by the body in sufficient amounts to maintain homeostasis. Deficiency of these essential micronutrients causes a known disease state. The most well-known micronutrient deficiency is likely that of vitamin C, which results in scurvy. Humans are unable to synthesize vitamin C and must obtain it from supplemental sources. When dietary intake of vitamin C is insufficient, a disease state expressed in swollen, bleeding gums, painful limbs, and lethargy is the result. When vitamin C intake is adequate, the symptoms resolve.
We now know that specific, predictable syndromes that result from vitamin deficiencies are only part of the picture. Micronutrients play an important role in prevention of chronic disease as well. Vitamin D is an excellent example of this; not only is adequate vitamin D status linked to prevention of a deficiency disease like rickets, but it plays an important role in protecting against autoimmune disorders, multiple sclerosis (MS), cardiovascular disease, hypertension, certain cancers, diabetes, and possibly even erectile dysfunction1 2 3 4. Vitamin D research has increased dramatically over the past decade, and scientists are discovering more and more physiological functions that depend on vitamin D for a healthy outcome.
What is vitamin D?
Vitamin D3 is a fat-soluble precursor to vitamin D that can be synthesized from cholesterol in the skin and external ultraviolet light. Vitamin D3 can also be absorbed in the small intestine with dietary lipids, though most dietary sources contain rather small amounts of this micronutrient. Hydroxylation of vitamin D3 in the liver and then again in the kidneys yields the active form of vitamin D: 1,25(OH)2D3. Vitamin D usually functions as a steroid hormone and excess is stored mainly in adipose tissue. Vitamin D is known to modulate over 50 genes but is best known for maintaining calcium/phosphorus balance in the body.
You may be wondering why vitamin D is classified as a vitamin since it can be synthesized by the body in sufficient amounts to maintain homeostasis. The key word here is “can”; vitamin D can be synthesized in adequate amounts for normal physiological function but it often is not. Factors such as climate (northern/southern latitudes, air pollution, etc), working indoors during daylight hours, use of sunscreen, dark skin pigmentation, and aged skin can all reduce vitamin D production significantly. Crohn’s disease, cystic fibrosis, celiac disease, and pancreatic insufficiency can limit dietary absorption of this micronutrient as well.
How much vitamin D3 does my body need?
Serum levels of 25(OH)D (25-hydroxy vitamin D) are the most common indicator of vitamin D status. 25(OH)D levels lower than 30ng/ml are considered to be insufficient. If a deficiency is present, additional exposure to sunlight or increased dietary intake is recommended.
The US Institute of Medicine (IOM) has published Dietary Reference Intakes for vitamin D that indicate adequate intake and tolerable upper level intake.5 Adequate intake (AI) is considered to be the minimum amount required to prevent bone malformation and ranges from 100 IU of D3 daily for infants to 600 IU of D3 daily for adults over the age of 70. The tolerable upper level intake (UL) is set at the level presumed to cause no adverse effects for healthy individuals in a given population and ranges from 1,000 IU of D3 daily for infants up to 12 months old to 2,000 IU of D3 daily for everyone over 12 months old. Recent studies show that the recommended AI may be insufficient; daily vitamin D3 intake of between 1,800 and 4,000 IU has been shown to be effective at maintaining serum 25(OH)D levels of 30-44ng/ml with no increased risk to health.6 Some researchers suggest that a daily vitamin D3 intake of 4,000 IU may be too low and that the AI should be re-evaluated.1
Should I consider taking a vitamin D3 supplement?
IOM claims that a significant portion of the population does not meet the current daily AI requirements for vitamin D3. Evaluating your lifestyle and your diet can help answer whether or not your vitamin D status is adequate. If you regularly spend time outdoors in a sunny climate and eat foods containing vitamin D3 (e.g. fatty fish, eggs, butter, liver, and fortified foods), your vitamin D status may be adequate.
If you do not have access to at least 20 minutes of direct sunlight per day and do not regularly consume foods that contain vitamin D3, you may be not be getting an adequate amount of vitamin D. If your skin is deeply pigmented or aged, you may not be able to synthesize enough vitamin D even if you do spend at least 20 minutes daily exposed to sunlight. If you cover your skin with sunscreen or clothing, you are likely not able to synthesize enough vitamin D3 to maintain an adequate vitamin D status. Malabsorption and diseases of the digestive system can impair absorption of dietary vitamin D3 and can cause a reduction in 25(OH)D serum levels.
If you suspect your vitamin D status is insufficient, talk to your health care practitioner. Your doctor can order a blood test that will indicate your vitamin D status, or you can order a test kit from the Vitamin D Council if you’d like to check your levels before you see your doctor. A note of caution: because vitamin D is stored in adipose tissue, it can accumulate to toxic levels if large supplemental doses are taken regularly. The use of multiple supplements, e.g. taking a multivitamin with an extra D3 supplement, can result in excessive serum levels. In addition, conditions such as sarcoidosis, lymphoma, tuberculosis, primary hyperparathyroidism, kidney failure, and liver failure can affect metabolism of vitamin D and cause an increased risk of adverse effects. Monitoring vitamin D status can help reduce the likelihood of adverse health events, so please discuss supplementation with your doctor before you begin.
What are some ways to ensure proper vitamin D status?
Many doctors recommend a combination of sun exposure and supplementation to correct vitamin D deficiency.7 Sun exposure is the safest means of acquiring vitamin D, since excessive exposure degrades the precursor to vitamin D3 and eliminates the risk of toxicity. However, excessive sun exposure can also damage skin. Increased dietary intake of vitamin D3 or supplementation may help reduce the risk associated with exposure.
Increasing dietary intake of vitamin D3 is a way to support a healthy vitamin D status; however, the vitamin D3 levels of most foods are very low.8 Relying on diet alone to provide adequate amounts of vitamin D would require a greater intake of these foods than is practical for most people, particularly those consuming a primarily vegetarian diet. Here are a few examples of foods containing vitamin D3 and the approximate amount per serving:
- salmon, three-ounce portion: 420 IU
- fortified milk, eight ounces: 100 IU
- sardines, one-ounce portion: 84 IU
- chicken liver, three-ounce portion: 44 IU
- egg yolk: 24 IU
- beef liver, three-ounce portion: 16 IU
Cod liver oil is one of the richest dietary sources of vitamin D. Most cod liver oil supplements contain between 400 IU and 1,000 IU per dose. Cod liver oil contains other fat-soluble vitamins and cofactors besides vitamin D3 that may provide a protective synergy to reduce the likelihood of toxicity.9 Vitamin A to vitamin D ratios of between 5:1 and 8:1 are considered by most practitioners to be safe for consumption by healthy adults, and a recent study examining the effects of cod liver oil supplementation on 47 young children showed that supplementation at those ratios resulted in a clinically significant reduction in pediatric care requirements during the study.10
The safest way for most people to achieve adequate vitamin D status is through regular exposure to sunlight on the skin. While there is evidence that a significant portion of the population does not have adequate vitamin D status to maintain good health, there is not enough conclusive data to support daily supplementation above the safe UL of 2,000 IU for healthy adults and 1,000 IU for healthy infants up to 12 months of age.11 If you suspect that your vitamin D status is less than ideal, talk to your health care practitioner. Regular blood testing can show deficiencies or excessive serum levels and prevent adverse health events.
1Grant, William B. and Tangpricha, Vin (2012). Vitamin D; Its Role in Disease Prevention. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427203/
2Van Amerongen, Barbara M. and Feron, Francois (2012). Effect of High-Dose Vitamin D3 Intake on Ambulation, Muscular Pain and Bone Mineral Density in a Woman with Multiple Sclerosis: A 10-Year Longitudinal Case Report. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3497336/
3Sorenson, Marc and Grant, William B. (2012). Does Vitamin D Deficiency Contribute to Erectile Dysfunction? Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427191/
4Sane, David C. Vitamin D and Cardiovascular Disease – New Frontiers for Prevention. Video lecture retrieved from http://youtu.be/m-sXcvDTO68
5 Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine (1997). Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Retrieved from http://www.nap.edu/catalog.php?record_id=5776#description
6Bischoff-Ferrari, Heike A.; Shao, Andrew; Dawson-Hughes, Bess; et al (2011). Benefit-Risk Assessment of Vitamin D Supplementation. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3062161/
7Reinhold, Uwe; Dirschka, Thomas; Hartgens, Klaus; et al (2012). Vitamin D supply: from sun or pill? – Attitudes and recommendation on vitamin D and impact on sun protection practices among German general practitioners evaluated by the network of dermato-oncologists, Onkoderm e.V. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3506811/
8Mahan, L. Kathleen and Escott-Stump, Sylvia (2008). Krause’s Food & Nutrition Therapy.
9Masterjohn, Chris (2010). Update on Vitamins A and D. Retrieved from http://www.westonaprice.org/cod-liver-oil/update-on-vitamins-a-and-d
10Linday, Linda A. (2010). Cod Liver Oil, Young Children, and Upper Respiratory Tract Infections. Retrieved from http://www.jacn.org/content/29/6/559.long
11Masterjohn, Chris (2006). From Seafood to Sunshine: A New Understanding of Vitamin D Safety. Retrieved from http://www.westonaprice.org/fat-soluble-activators/seafood-to-sunshine#adults