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Vitamin D: Part III

Quick Hit Summary

Vitamin D plays an integral role in maintaining bone health. Without vitamin D, absorption of dietary calcium, the main mineral required for bone formation, is extremely inefficient. However, when vitamin D is present in sufficient amounts, it increases calcium absorption increases by ~30% (10% —> 40%). Thus, degenerative conditions such osteoporosis and osteomalacia can be slowed down. Additionally, vitamin D may also play a role in idiopathic pain conditions and autoimmune problems such as Crohn’s disease. To receive the protective benefits of vitamin D, I recommend taking 2000 IU/day.

Vitamin D

Figure 1 The molecular Structure of Vitamin D319

In the first 2 parts of this series, we covered the following topics:

In Part III of this series, we’re going to examine the relationship between vitamin D and its role in bone health and pain management. In addition, we’ll discuss the optimal amount that one should receive to optimize serum blood levels.

Bone Health

Maintenance of normal, healthy bone metabolism is the most common role associated with vitamin D. Within the human body, bone is continuously reforming in order to meet the demands of one’s lifestyle. The primary minerals associated with bone structure are calcium, phosphorus and magnesium. Of the three, calcium is the “major player” with respect to bone structure and strength1. Although present in many dietary sources, many individuals may lack enough calcium to maintain proper bone metabolism. In the United States alone, approximately 1.5 million cases of osteoporosis, develop annually2. Often the development of this disease is directly related to low calcium levels in the blood. The lack of calcium is primarily caused by age and/or low vitamin D levels.

As one ages, decreases in reproductive hormones, specifically estrogen, reduces the ability of the GI tract to efficiently absorb dietary calcium3. Additionally, the aging process compromises the body’s ability to naturally produce vitamin D in response to UV-B exposure (from the sun or artificial sources)4. Along with other hormones, vitamin D acts within the gut to increase calcium absorption. Without vitamin D, only a modest 10-15% of all dietary calcium can be absorbed. However this escalates to 30-40% when one’s vitamin D status is optimal5. Once absorbed into the blood stream, calcium can be used to increase bone density. Preserving serum calcium levels is also essential for the regulation of parathyroid hormone. When serum calcium dips below its normal range, parathyroid hormone is released, causing one’s bone to dissolve, thus restoring blood-calcium levels6. Why would the body want to dissolve bone just to increase serum calcium levels? Well, calcium is essential for muscle contraction. Thus, without a continuous supply of calcium, both skeletal muscles as well as the heart would fail to properly contract, resulting in death.

Figure 1. Maintenance of Blood Calcium Levels. When blood calcium levels drop, parathyroid hormone is released, converting pro-vitamin D into its active form. This acts to increase blood calcium levels by increasing it’s absorption from the gut and decreasing urinary excretion of it. Additionally, vitamin D causes it to reabsorbed from the bone back into the bloodstream.

Due to the high prevalence of osteoporosis in society, many researchers have examined the combined effects of calcium and vitamin D supplements on reducing bone fractures. Using a population consisting of >3000 elderly French women, it was found that a vitamin D & calcium supplementation (800 IU vitamin D, 1200 mg calcium) reduced hip fractures by 43% and nonvetebral fractures by 32%7. In a study conducted by Dawson-Hughes et al., 318 individuals (consisting of men & women > 65 yrs of age) were randomly assigned to receive either 700 IU vitamin D and 500 mg calcium or a placebo8. At the end of 3 years, changes in bone mineral density were examined. Compared to those who received a placebo, both men and women receiving the supplement were better able to maintain their bone strength. Additionally, they found that supplementation significantly decreased nonvetebral fractures. It must be noted that other randomized clinical control trials, notably the Women’s Health Initiative study, have not found vitamin D and calcium to have a protective effect. However, their experimental supplement (consisting of 400 IU vitamin D and 1000 mg) used ~ ½ the amount of vitamin D as seen in the aforementioned trials5.

Pain Management

Outside of losing a loved one, I’m not for sure if anything can be as difficult to live with as pain. I’m not talking about the acute pain you feel upon pulling a hamstring or whacking your head on a partially open cabinet door. I’m referring to the type that stays with you on day by day, month by month type of basis. Often, chronic pain leaves you not only physically exhausted, but mentally as well.

Mounting evidence seems to indicate that vitamin D inadequacy may play a significant role in various types of chronic musculoskeletal pain syndromes4. As explained in the above section on bone health, one of vitamin D’s roles is maintaining serum calcium levels. When calcium levels drop, resulting in increased parathyroid hormone release, a condition known as secondary hyperparathyroidism develops. Besides osteoporosis, this may cause osteomalacia to develop. Osteomalacia is characterized by the loss of both calcium and phosphorus from the bone. In response to this bone demineralization, the body lays down a spongy collagen matrix just underneath the surface of the bone5. However, due to the spongy nature of this matrix, it swells up against the bone’s outer surface (periosteum), triggering the densely packed pain sensing nerves to fire9. Furthermore, a common symptom of osteomalacia is muscle weakness and fatigue10. Therefore, individuals with this condition have a higher risk of falling and breaking their already mineral depleted bones.

Individuals suffering from musculoskeletal pain generated from an unknown source (ie- ideopathic pain) may be early signs of osteomalacia or another syndrome related to vitamin D deficiency. Plotnikoff & Quigley looked at 150 patients suffering from generalized low back and other ideopathic musculoskeletal pain syndromes. Upon taking blood samples, it was found that 93% were vitamin D deficient11. Taken alone, this study only shows a correlation between low vitamin D and nonspecific musculoskeletal pain conditions. However, Al Faraj & Al Mutairi, examined 360 patients who had been diagnosed with idiopathic low back pain12. X-Rays, MRI’s, and various blood tests were completed to rule out conditions such as herniated disks, compression fractures, fibromyalgia or rheumatoid arthritis. Although none of the film test (X-rays, MRI’s) showed signs of any specific condition, blood tests revealed that 299 of these patients had deficient levels of circulating vitamin D. After 3 months of supplementation, symptomatic improvement was seen in all 299 individuals.

Vitamin D may also play a role in painful TH-1 driven autoimmune diseases such as Crohn’s disease. As mentioned in my earlier discussion on type 1 diabetes, vitamin D appears to have a modulating effect on inflammatory/auto-immune responses. Substantial evidence indicates that vitamin D down-regulates (decreases) TH-1 cytokines that promote inflammation13. Its been observed that Crohn’s disease is more prevalent in northern latitutudes where individuals do not receive as much vitamin D stimulating UV-B radiation14. Peyrin-Biroulet et al. hypothesized that supplementing with vitamin D could be effective at treating those suffering from this condition. However, randomized clinical control trials are still needed to determine if supplementation would be an effective treatment for those suffering from this Crohn’s Disease.

Although I’ve mentioned various chronic pain conditions that appear to be related to inadequate vitamin D, there are some limitations in the studies on this subject matter. First, there have not been many large scale randomized clinical control trials investigating vitamin D’s impact on these diseases. Second, just because one is vitamin D deficient, it doesn’t necessarily mean that they will develop these diseases. The research just seems to indicate that those who have these conditions are more likely to be vitamin D deficient vs. healthy individuals of the same population. Despite these limitations, I think that in chronic pain syndromes, especially those which are idiopathic, the possibility of vitamin D deficiency should be examined.

Optimal vitamin D intake

In an ideal situation, one would not have to worry about dietary intake of vitamin-D since ample amounts are produced naturally within the skin (assuming adequate exposure to UV-B sunlight). However, due to heightened awareness of skin cancer, working 9:00am-5:00pm indoor desk jobs, and living in northern geographic regions, many individuals lack sufficient exposure to UV-B radiation.

Currently, the National Institute of Health (NIH) states that an adequate intake (AI) of vitamin D is around 200-600 IU per day1. They’ve also put an upper limit (UL) intake of 2000 IU/day. These figures were established in 1997. However, due to the large body of research that has been conducted during the past 12 years, the Institute of Medicine is currently convening to see if dietary vitamin D recommendations should be increased15. It’s expected that in May of 2010, a new consensus statement regarding vitamin D intake will be put out.

Of all the studies that I reviewed in writing this report, it appears that many conditions responded with intakes between 700-3000 IU/day. Various experts in the field recommend getting between 1-4000 IU/day. Until the Institute of Medicine finishes reviewing the current research and possibly establishes new intake levels, I’d recommend dietary vitamin D around 1,000-2,000 IU/day. Beyond this amount, the risk of toxicity may become an issue (being a fat soluble vitamin, vitamin D is stored in the body). My gut feeling is that the current recommendations for vitamin D will be increased. However, being that the new results will be published in less than a year, I don’t recommend >2000 IU/day UNLESS you’re periodically getting blood levels measured. If you’re getting blood levels tested for vitamin D, I have no problem advising individuals to increase their intake greater than this amount.

Additionally, one should consider their exposure to UV-B sunlight when deciding how much vitamin D they need. For instance, if one spends a lot of time outside during times of peak exposure to UV-B radiation (10am-2pm during warm sunny time periods), large amounts of dietary vitamin D are probably not warranted. On the other hand, if you only have limited exposure to UV-B radiation due to your job and/or geographic location, you may want to consider increasing your dietary intake during late fall, winter and spring months.

There are not many foods that contain significant amounts of vitamin D. Please see Table 1.As you may assume, many individuals, especially those who are lactose intolerant, getting enough vitamin D through food sources may be difficult. If you believe that this applies to your situation, I would recommend obtaining vitamin D supplement. As a tip, be sure to take the supplement along with a small meal/snack that contains fat. Being a fat soluble vitamin, this enhances vitamin D absorption. Also, if you obtain vitamin D from cod liver oil, be careful as these may have significant levels of vitamin A.

Table 1 Food sources of vitamin D. Information obtained from the NIH’s Office of Dietary Supplements17.

Food Source, serving size Amount/Serving (IU’s)
Cod Liver Oil, 1 tablespoon 1360 IU
Salmon (sockeye), 3 oz 794 IU
Tuna Fish (canned in water & drained), 3 oz 154 IU
Milk (vitamin D fortified), 1 cup 120 IU
Orange Juice (vitamin D fortified), 1 cup 100 IU

On a final note, if you suffer from hypercalcemia (too much calcium in your blood) or have a history of kidney stones, I would recommend against taking large amounts of dietary vitamin D as this could worsen your condition16.

Bottom Line

In conclusion, I feel that vitamin D is the “next” big nutrient/supplement with respect to human health. It appears to play a large role in a variety of health conditions such as cancer (notably colon, breast & prostrate), cardiovascular disease, diabetes, osteoporosis/osteomalacia, and pain management. To take advantage of the benefits try to get ~2000 IU/day via diet and/or supplementation.


1 Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. Washington, DC: National Academy Press, 1997.

2 Riggs BL, Melton L. The worldwide problem of osteoporosis: insights afforded by epidemiology. Bone 1995;17:505S-11S.

3 Heaney RP, Recker RR, Stegman MR, Moy AJ. Calcium absorption in women: relationships to calcium intake, estrogen status, and age. J Bone Miner Res 1989;4:469-75.

4 Leavitt,SB. Vitamin D – A Neglected ‘Analgesic’ for Chronic Musculoskeletal Pain. June 2008, .Obtained September 23, 2009 from: http://Pain-Topics.org/VitaminD.

5 Holick MF. Vitamin D deficiency. N Engl J Med 2007;357:266-81.

6 Brown, E.M., et al. 1993. Cloning and characterization of an extracellular Ca2+ -sensing receptor from bovine parathyroid. Nature. 366:575-580.

7 Chapuy MC, Arlot ME, Duboeuf Fetal. Vitamin D3 and calcium to prevent hip fractures in elderly women. N Engl J Med 1992; 327:1637-42

8 Dawson-Hughes B, Harris SS, Krall EA, Dallal GE. Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older. N Engl J Med 1997;337:670-6.

9 Lerner UH. Neuropeptidergic regulation of bone resorption and bone formation. J MusculoskeletNeuronal Interact 2002;2:440–7.

10 Pfeifer M, Begerow B., Minne HW. Vitamin D and Muscle Function. Osteoporos Int (2002) 13:187–194.

11 Plotnikoff GA, Quigley JM. Prevalence of severe hypovitaminosis D in patients with persistent, nonspecific musculoskeletal pain. Mayo Clin Proc. 2003 Dec;78(12):1463-70.

12 Al Faraj S, Al Mutairi K. Vitamin D deficiency and chronic low back pain in Saudi Arabia. Spine 2003;28:177-179.

13 Baeke F, Etten E, Gysemans C, Overbergh L, Mathieu C. Vitamin D signaling in immune-mediated disorders: evolving insights and therapeutic opportunities. Mol Aspects Med 2008;29:376–87.

14 Peyrin-Biroulet L, Oussalah A, Bigard MA. Crohn’s disease: the hot hypothesis. Med Hypotheses. 2009 Jul;73(1):94-6. Epub 2009 Mar 6.

15 Yetley EA, Brulé D, Cheney MC, Davis CD, Esslinger KA, Fischer PWF, et al. Dietary Reference Intakes for vitamin D: justification for a review of the 1997 values. Am J Clin Nutr 2009;89:719-27.

16 Jackson RD, LaCroix AZ, Gass M, Wallace RB, Robbins J, Lewis CE, et al. Calcium plus vitamin D supplementation and the risk of fractures. N Engl J Med 2006;354:669-83.

17 Dietary Supplement Fact Sheet: Vitamin D-Health Professional Fact Sheet. National Institutes of Health. Office of Dietary Supplements. Accessed May 12, 2010 from: http://ods.od.nih.gov/factsheets/vitamind.asp#h10

18 Accessed May 31, 2010 from: http://en.wikipedia.org/wiki/File:Calcium_regulation.png/wiki/File:Calcium_regulation.png

19 fn12(ref). Accessed May 31, 2010 from: http://en.wikipedia.org/wiki/File:Cholecalciferol-3d.png

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Written on October 04, 2009 by Sean Casey
Last Updated: December 19, 2011

This information is not intended to take the place of medical advice.Please check with your health care providers prior to starting any new dietary or exercise program. CasePerformance is not responsible for the outcome of any decision made based off the information presented in this article.

About the Author: Sean Casey is a graduate of the University of Wisconsin-Madison with degrees in both Nutritional Science-Dietetics and Kinesiology-Exercise Physiology. Sean graduated academically as one of the top students in both the Nutritional Science and Kinesiology departments.
Field Experience: During college, Sean was active with the UW-Badgers Strength and Conditioning Department. He has also spent time as an intern physical preparation coach at the International Performance Institute in Bradenton, FL. He also spent time as an intern and later worked at Athletes Performance in Tempe, AZ. While at these locations he had the opportunity to train football, soccer, baseball, golf and tennis athletes. Sean is also active in the field of sports nutrition where he has consulted with a wide variety of organizations including both elite (NFL’s Jacksonville Jaguars) and amateur athletic teams. His nutrition consultation services are avalable by clicking on the Nutrition Consultation tab.