7 Things to Know Before Taking A Vitamin D Supplement
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Vitamin D (also known as calciferol) is an important micronutrient for the body—it plays an important role in bone health, supports the absorption of calcium and phosphorus, helps reduce inflammation, and supports the immune system, metabolism, and cell growth (1)(2).
Extremely low vitamin D can have some serious consequences. Vitamin D deficiencies can lead to things like rickets (deformed bones) in children and osteomalacia (soft bones) in adults (1). Sadly, studies show a significant number of people in the U.S. are deficient in vitamin D (3).
Whether you’re currently taking a vitamin D supplement, considering taking one, or need to take one, we’ve outlined seven things you need to know!
7 Things to Consider Before Taking Vitamin D Supplements
First and foremost, it’s important to know, recommending supplements and nutrient amounts (aside from directing clients to the Dietary Guidelines) is outside the scope of practice for a personal trainer. It is, however, important for you to be well-educated in nutrition and supplementation so you can educate your clients, help them ask better questions to their medical provider, and guide them toward credible resources so they can make the right decisions for themselves.
That being said, the following list includes seven pieces of info you should know about vitamin D.
1. Certain Populations Have an Increased Risk of Vitamin D Deficiency
There are several risk factors that can increase the chances of a client having a vitamin D deficiency. The following list includes a few of the higher-risk populations:
- Those with darker skin
- Breastfed infants
- People with limited sun exposure (1)
2. Vitamin D is a Fat-Soluble Vitamin
There are a few fat-soluble vitamins and vitamin D is one of them. Because it’s fat-soluble, the absorption of vitamin D is improved when it’s consumed with fat (2)(4). So, clients need to discuss with their doctor whether they need to eat fat with their vitamin D supplementation.
3. Supplements Aren’t the Only Source of Vitamin D
Humans can get vitamin D from certain foods and the body can synthesize it from sun exposure.
Vitamin D from Dietary Sources
There are only a handful of foods that contain vitamin D. Here are a few examples:
- Liver oil
- Egg yolks
- The flesh of fatty fish like salmon or trout
- Vitamin D fortified foods
Vitamin D from Sun Exposure
The body can use rays from the sun and convert them into vitamin D. But things like cloudy days and sunscreen can impact sun exposure (which ultimately can impact vitamin D levels).
Interesting tip: The UVB radiation (from sun exposure) needed to synthesize vitamin D in the body does not penetrate glass. So, your clients aren’t getting their vitamin D just by sitting near the sunshine, inside a window (1).
4. There is a Recommended Dietary Allowance (RDA) for Vitamin D
The National Academies Press defines RDAs as:
“The levels of intake of essential nutrients that, on the basis of scientific knowledge, are judged by the Food and Nutrition Board to be adequate to meet the known nutrient needs of practically all healthy persons.”
In other words, experts created them to provide a nutritional reference to help “serve as a goal for good nutrition.” (5)
Many people in America only consume about a third of the current recommended amount of vitamin D. The National Institutes of Health recommends 15 micrograms (mcg) for males and females between the ages of 1 and 70. However, it’s important to keep in mind, each client can vary in their individual needs (1).
5. Taking Too Much Can Lead to Vitamin D Toxicity
As with most foods and supplements, more is not always better. Taking too much vitamin D can be problematic. Excessive amounts of vitamin D can cause nausea, dehydration, muscle weakness, etc. In extreme cases, too much vitamin D can cause heart problems, renal failure, and even death (1).
There Are Two Main Forms of Vitamin D
The two forms of vitamin D are:
There isn’t much difference between the two when observing how they work within the human body. However, research shows vitamin D3 might have a little better impact on vitamin D blood levels and may last for a longer period of time (1).
6. Some Medications Have an Influence on Vitamin D in the Body
There are several different drugs known to interfere with vitamin D in the body. The following list includes a few examples:
So, it’s incredibly important to have clients speak with their doctor to understand if any of their medications may cause a vitamin D deficiency or discuss making any modifications to their supplement intake (1)(6).
Want more info on choosing the right dietary supplement, check out this site!
If you’re interested in learning more about nutrition and supplementation, check out ISSA’s Nutritionist Course! You’ll learn more about micronutrients, food and supplement labels and claims, nutrient needs, and so much more!
- U.S Dept of Health & Human Service. “Office of Dietary Supplements - Vitamin D.” NIH Office of Dietary Supplements, U.S. Department of Health and Human Services, 9 Oct. 2020.
- National Research Council (US) Committee on Diet and Health. “Diet and Health: Implications for Reducing Chronic Disease Risk.” Washington (DC): National Academies Press (US); 1989. 11, Fat-Soluble Vitamins.
- Parva, N. R., Tadepalli, S., Singh, P., et. al. (2018). “Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011-2012).”Cureus, 10(6).
- Dawson-Hughes, B., Harris, S.S., Lichtenstein, A.H., et. al., “Dietary fat increases vitamin D-3 absorption.” J Acad Nutr Diet. 2015 Feb;115(2):225-30.
- National Research Council (US) Subcommittee on the Tenth Edition of the Recommended Dietary Allowances. “Recommended Dietary Allowances: 10th Edition.” Washington (DC): National Academies Press (US); 1989. 2, Definition and Applications.
Gröber, U., & Kisters, K. (2012). “Influence of drugs on vitamin D and calcium metabolism.” Dermato-endocrinology, 4(2), 158–166.
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