If you have seen your doctor recently or know someone who has, then you have most likely been recommended to take a vitamin D supplement. With vitamin D supplement sales predicted, via market analysis, to nearly double to $2.5 billion between the years of 2015-2020, you’re certainly not alone. According to a survey overseen by the Council for Responsible Nutrition, vitamin D was the second most popular dietary supplement among those surveyed. These results are synonymous with larger surveys. This is a huge leap for vitamin D, considering it was not even on the radar of those in the health industry 15 years ago.

Most Popular Supplements Graph
Imaged obtained & altered from crnusa.org

What Is Vitamin D and How Does It Help You?

Vitamin D is a fat-soluble vitamin (you need fat to absorb it) and is found in some foods, but can be obtained as a result of ultraviolet sun rays striking your skin. For this reason, you may hear it being referenced to as the “sunshine vitamin.” Vitamin D can also be obtained through supplements, typically in Vitamin D3 form, which we will discuss below.

Vitamin D is different from many other vitamins because it is converted to a hormone in the body known as calcitriol.

Vitamin D is most well known for its role in bone formation and preservation, along with encouraging calcium absorption in the body. It can help protect against rickets in children, and osteomalacia, osteopenia and osteoporosis in adults. In addition to vitamin D’s well-known bone-related functions, it helps cells regenerate and grow, enhance immunity, aid in neuromuscular function and may reduce levels of systemic inflammation.

Vitamin D has many functions in the human body, which include:

  • Aids in calcium absorption
  • Works in conjunction with calcium (and by blocking parathyroid hormone) to help form bones and preserve bone integrity
  • Plays a role in immune function
  • Plays a role in muscle function
  • Plays a role in brain development
  • Prevention of cardiovascular diseases and related ailments*
  • Prevention of certain types of cancer*
  • Improve mental illness, such as depression*

*Evidence does suggest benefits, but more human clinical research trials are needed.

You could be at risk for vitamin D deficiency if you are obese (due to decreased ability to convert vitamin D2 into vitamin D3), have a dark complexion, take certain medications or have a chronic illness. Vitamin D deficiency can cause the following symptoms:

  • Decreased bone density, leading to osteopenia or osteoporosis (rickets in children)
  • Insulin resistance*
  • Cardiovascular risks*
  • Decreased immunity*
  • Mood disorders*

*Evidence does suggest deficiency-related ailments, but more human clinical research trials are needed.

The Research Behind the Touted Health Benefits of Vitamin D3 Supplementation

Personally, I have seen multiple patients under my care and a physician’s care benefit from the supplementation of vitamin D3 to increase deficient serum vitamin D levels. This observation, of course, was made with patients who needed nutritional guidance and support, so they were not well-nourished to begin with.

Other than the prevention of bone density-related illness, evidenced-based research has provided conflicting information regarding the proposed health benefits of vitamin D3 supplementation. I am going to discuss some of the health benefits that vitamin D3 may provide, as well as conflicting research associated with each benefit.

Cardiovascular Health: Research is conflicting on whether vitamin D3 supplementation can prevent or help symptoms of cardiovascular ailments. Several studies have correlated vitamin D insufficiency and deficiency with an increased risk of cardiovascular disease. Does vitamin D supplementation, however, offer protective benefits against cardiovascular disease?

A study with other 5,000 participants conducted in 2014 found that vitamin D supplementation may offer protective benefits to fight cardiac failure in the older population, but did not show promise towards protection against myocardial infarction or stroke.

Another study conducted in 2016 found that vitamin D3 supplementation of 2,000 IU per day for 14 days could reduce risk factors of cardiovascular disease, as well as improve exercise performance in participants. This study included 15 healthy participants, so larger studies need to continue to be conducted on humans.

Some studies do negate the possibility of vitamin D3 supplementation offering protective benefits against cardiovascular disease, finding no differences between a placebo and vitamin D3 supplementation.

Mental Health: Some studies have shown that vitamin D3 supplementation improves depression. A study published in the 2017 Journal of Diabetes Research, found that vitamin D3 supplementation of 50,000 IU weekly for six months resulted in decreased depressive symptoms among women with type 2 diabetes mellitus. A meta-analysis of 15 randomized controlled trials found that depressive symptoms were reduced among participants taking vitamin D3 supplements, and even declared that the reduction of symptoms experienced was similar to the effects of some psychiatric medications. The correlation of vitamin D3 supplementation and positive mental health outcomes appears to be promising given the results of recent research.

Cancer: Many encouraging studies have shown a possible connection between cancer prevention and adequate vitamin D status (plus vitamin D3 supplementation) in in-vitro and clinical animal trials. However, more human clinical trails need to be conducted in order to establish a concrete relationship between vitamin D3 supplementation and reduced cancer risk. Some studies have shown that a higher blood level of vitamin D correlated with a reduced risk of colorectal cancer, but other studies show conflicting information. According to the National Institutes of Health, ongoing or recently completed large cohort human clinical studies have been initiated.

Muscle Function: Several studies have found that vitamin D3 supplementation in athletes who are vitamin D insufficient or deficient improves muscle function. This study found that correction of low serum vitamin D levels with vitamin D3 supplementation (for serum vitamin D levels to reach 40 ng/mL) improved muscle function in athlete participants.

Although popular among health professionals and the dietary supplement industry, vitamin D needs more conclusive, human-based research to allow most of its touted health benefits to nestle into a concrete position within health recommendations.

How Much Vitamin D Do You Need & How Do You Get It?

The established Recommended Dietary Allowances (RDAs) for Vitamin D vary depending upon life stage.

RDA for Vitamin D
* Adequate Intake (AI) *This image was obtained from https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/#h3.

Circulating blood levels of vitamin D as 25(OH)D lower than 12 nanograms/milliliter defines vitamin D deficiency; blood levels of 25(OH)D between 12 nanograms/milliliter and 20 nanograms/milliliter defines insufficiency; blood levels of 25(OH)D greater than 20 nanograms/milliliter is usually considered adequate. Research suggests that 25(OH)D levels greater than 50 nanograms/milliliter could result in toxicity.

Vitamin D is not known for its abundance in foods. For this reason, you will see vitamin D2 and vitamin D3 fortification in foods like milk, soy milk, orange juice, cereals and yogurt. The information below has been obtained from the National Institutes of Health (NIH).

Food (serving size)Vitamin D per serving
Cod Liver Oil (1 tbsp)1,360 IU
Salmon, Sockeye, cooked (3 ounces)566 IU
Tuna fish, canned in water (3 ounces)154 IU
Milk, non-fat, reduced fat, whole, fortified with vitamin D (8 ounces)115-124 IU
Orange, fortified with vitamin D (amount of vitamin D varies) (8 ounces)100-137 IU
Egg, large, yolk included (1 egg)41 IU

Your primary sources of vitamin D are supplements and the sunlight.

Vitamin D2 vs. Vitamin D3

If you were in the market for or just curious about vitamin D supplements five years ago, you would have only seen vitamin D2 on the shelves. Suddenly, a few years later, you now see only vitamin D3 on the shelves. What’s the difference?

Vitamin D2: Also known as ergocalciferol, vitamin D2 is synthesized by plants upon UV exposure.

Vitamin D3: Vitamin D3 is synthesized upon exposure to UV rays by the skin of animals, including humans. It is also known as cholecalciferol.

Fairly recent research has shown that there are differences in the efficiency and efficacy of the absorption and utilization between vitamin D2 and vitamin D3, contrary to prior belief.  According to one of the meta-analysis studies mentioned before, no matter what type of dose was provided to participants (bolus or daily, small and intermittent), vitamin D3 showed significant favorability, compared to vitamin D2, with effectively increasing serum vitamin D levels (25(OH)D, the type of vitamin D that is usable in the blood) in the participants. There are many complicated reasons behind why vitamin D3 has shown to be more effective with raising serum levels of vitamin D, like the affinity to vitamin D receptors and enhanced processing by the liver and kidneys.

The Great Debate Among Scientists

Many scientists attribure the contradictory evidence of vitamin D to the fact that many different organizations disagree on an adequate vitamin D blood level, as well as a how much vitamin D you need daily. These discrepancies can result in variable interpretation of research involving vitamin D. Until more research is completed, it is best to refer to the Institute of Medicine of The National Academies Recommended Dietary Allowance reference points, and ask your physician and/or dietitian about your blood levels of vitamin D.

If you are interested to hear more and receive personalized nutrition, check out STYR’s app, fitness tracker and suite of connected smart devices. Through the platform, you can track and log activity, food, hydration, sleep, nutrition, mood and more to personalize your nutrition needs based on data, science and access to registered dietitians, nutritionists and personal trainers.

Please note that this information is not intended to be a substitute for professional medical advice, diagnosis or treatment. We insist that you always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical/health condition or treatment and before initiating a new health care regime. Do not disregard professional medical advice or delay in seeking it because of something you have read on the STYR app or on www.MyNutritioniQ.com.

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