To "D" or Not To "D"
FEATURE
Bryan Walsh
Vitamin D has emerged as something of a miracle supplement in recent years with hundreds of research studies suggesting that it may be useful in preventing conditions such as osteoporosis, autoimmunity, cardiovascular disease, cancer, and much more. Vitamin D deficiency has even been linked to obesity.1
Recent statistics suggest that between 40 to 50% of healthy adults, infants and toddlers, and pregnant women aie deficient in vitamin D.2 3-4 In fact, there has been a world-wide increase in rickets in recent years, even in industrialized nations5,6 7
With the plethora of research published about vitamin D, there is little doubt that vitamin D has an important emerging role in the human body. However, questions remain about the safety of long-term, high-dose vitamin D supplementation.
Vitamin D’s role in the body
Much of vitam in D’s original known functions were involved with calcium and mineral regulation in the body. Specifically, the active form of vitamin D increases calcium absoiption from food in our digestive tract.
Prior to the recent interest in vitamin D, it was thought that only a few select organs of our body had receptors for vitamin D. However, recent research has suggested that nearly every cell of our body has receptors for vitamin D, suggesting a much more potent role than was previously believed.
This new information has led to advances in the understanding of vitamin D’s newer roles, which include influencing our immune system, blood pressure regulation, insulin secretion, and cell differentiation.
Deficiency
The form of vitamin D largely produced by the liver is 25-hydroxyvitamin D, and it is generally accepted as the most reliable
* Recent * statistics suggest that between 40 to 50% of healthy adults, infants and toddlers, and pregnant women are deficient in vitamin D? Ï
marker to assess one’s vitamin D status. However, that is where the agreement ends. For example, there has been much debate regarding optimal ranges of Vitamin D.22
True vitamin D deficiency is generally indicated at levels below 25 ng/mL in blood.22, 23 The lower end of a more optimal range has been suggested to be anywhere between 50 to 80 ng/mL24,25,26 ,which again, has been the subject of debate.
Should we supplement vitamin D in our patients?
With vitamin D’s role in calcium homeostasis, questions arise as to the long-term safety of vitamin D supplementation in our population. There is little doubt that vitamin D has a number of important roles in the body and that vitamin D deficiency may have negative physiological consequences. In fact, some studies have suggested that the lower one’s vitamin D level, the higher the risk of all-cause mortality.36 However, solid scientific evidence as to the long-term safety of high-dose vitamin D supplementation is currently lacking.
While the practice of supplementing with vitamin D is widely used today, perhaps we need to better evaluate its efficacy.
Let’s explore some important relationships between vitamin D and other key nutrients.
Vitamin D and Calcium
Serum calcium levels are very tightly regulated, and they may remain within normal limits with lab testing despite high levels of calcium elsewhere in the body. One way the body
rids itself of excess calcium is by excreting calcium from the kidneys in urine, called hypercalciuria.
To highlight this relationship, one study demonstrated that nursing home residents taking 5,000 IU of vitamin D for six months had an increase in their urinary calcium/creatinine ratio, suggesting an increase in calcium levels from vitamin D intake.8 Excess calcium that is not effectively excreted can lead to calcium deposition in soft tissues, including arteries. Unfortunately, there are studies suggesting this possibility.
Three particular studies have demonstrated increased arterial calcification in animal models with a range of vitamin D intake.9,1011 Questions on the role of excess vitamin D in human cardiovascular function have been raised as well.12
Vitamin D and Vitamin K
Vitamin K is important in clotting, bone formation, and maintenance, but also helps “direct” where calcium needs to be used. Without vitamin K, the body cannot properly use calcium, which can result in the deposition of calcium hi soft tissues, such as arterial walls. Unfortunately, there aie studies that have shown populations deficient in vitamin K have an increased prevalence of atherosclerosis.34,35 Vitamin D supplementation hi the presence of vitamin K deficiency could therefore lead to excess calcium deposition in soft tissues.
Vitamin D and Magnesium
Another possible relationship exists between vitamin D and
magnesium. Magnesium has been shown to be important in the metabolism and sensitivity of tissues to vitamin D.18 In fact, a number of studies have demonstrated magnesium’s role in proper vitamin D activity and function.19,20,21
Additionally, magnesium also has an intimate connection with the regulation of calcium homeostasis.27 A number of studies have indicated that at least half of the population do not meet the recommended dietary allowance for magnesium.28
Because magnesium is used hi vitamin D metabolism, concerns have been raised regarding vitamin D supplementation causing an even greater magnesium deficiency in an already deficient population. Interestingly, a relatively recent study demonstrated a strong correlation between magnesium and vitamin D deficiency, showing that magnesium supplementation along with vitamin D supplementation was more effective at correcting a vitamin D deficiency than vitamin D supplementation alone.29
But perhaps even more important is the relationship between magnesium and calcium. Specifically, it appeal s the balance between these two minerals is paramount. Not surprisingly, magnesium has been shown to prevent calcification of the arteries.32
Vitamin D and Vitamin A
Vitamin A is another group of compounds that has several roles in the body. It also turns out that vitamin A can prevent vitamin D toxicity, and vice versa. In other words, a high level of vitamin D supplementation has a greater potential for toxicity when there is a vitamin A deficiency.
Speaking specifically to the interaction between vitamin A and vitamin D, though, studies have suggested that vitamin A may antagonize the calcium increase caused by vitamin D protected against the pathological calcification effects of vitamin D supplementation.30 31
Bottom line - It is about balance
In our quest for the magic nutrient, perhaps we should consider and evaluate how these nutrients work together. One study suggested that vitamin D toxicity not only requires réévaluation, but also suggested that vitamin D supplementation contributes to vitamin K deficiency, which is associated with bone loss and the calcification of soft tissues17. The findings of this study prompted researchers to recommend supplementing with vitamins A and K simultaneously.
Summary
The point of this art iele is not to suggest abandoning vitamin D supplementation completely. Rather, we need to consider the possible long-term consequences of high-dose vitamin D supplementation in isolation. While it’s clear that the previous recommendation of200 IUs a day is likely too low, until more conclusive research on long-term, high-dose vitamin D supplementation is completed, doses of 800 to 1,200 IUs per day is likely safe, especially when other key nutrients aie included, such as vitamin K, vitamin A, and magnesium.
There is little question about the importance ofvitamin D, but perhaps we should take a closer look at the reasons for deficiency, as well as the important interaction vitamin D has with other nutrients, and the possible negative repercussions this could have on tlie health of our patients.
an recognized instructor Bryan speaker Walsh at the Maryland is in a the nationally space of University and health internationally of care. Integrative He is Health and the University of Western States. Dr. Walsh has a private practice in Maryland where he attends to patients from all over the world. Dr. Walsh currently senses
as the director of education for Biogenetix, a leading U.S. nutritional company. To learn more about Biogenetix, visitwww.biogenetix.com
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