Archive for the 'vitamin d' Category

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Vitamin D and Athletic Performance

Published on May 15, 2010 in Dr. Cannell, healthy aging spotlight and vitamin d. 0 Comments

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Vitamin D – Run Faster, Jump Higher!

A little-appreciated consequence of too little vitamin D is muscle soreness that can often result in sore legs and increased discomfort while walking or even standing up. Research findings presented at a June 2006 conference on bone health indicate that vitamin D is a powerful promoter of muscle health and function in older adults and the elderly. In this study, daily dietary supplementation with 3,000 IU of vitamin D for 6 months increased lower limb muscle strength in previously vitamin D deficient elderly men and women by an average of 20% – enough to restore mobility and improve their quality of life substantially.27 We do not know if this would be increased even further if they took 5,000 IU/day. In addition, none of the supplemented subjects exhibited any signs of vitamin D toxicity after the 6 months of vitamin D supplementation and all exhibited minimization of PTH secretion, a proposed measure of vitamin D adequacy.

Keeping with this line of thought, research over several decades points to the ability of vitamin D to influence athletic performance. A recent review highlights the results of numerous studies dating back to the 1950s showing that ultraviolet light exposure improves athletic performance.1 This interesting review also suggests that athletic performance has seasonal variations, peaking at times of the year when vitamin D concentrations are naturally higher and decreasing when vitamin D levels are seasonally lower. Vitamin D administration has also been found to increase muscle strength and the percentage of Type II (fast-twitch) muscle fibers in humans. Studies in the elderly have found that vitamin D can improve balance and reaction time. Given that vitamin D is known to affect the expression of more than 1,000 genes, these findings come as no surprise.

Next Best Kept Secrets to Healthy Aging topic:
Vitamin D’s Helper Nutrients

References:
27. Pedrosa MAC, Moreira LDF, Barros ER, Kunii I, Lazaretti-Castro M. Cholecalciferol supplementation reverts 25-hydroxyvitamin D (25OHD) insufficiency and increases lower limb muscle strength (LLMS) in elderly people living in long-stay geriatric care (LSGC) (abstract P367SA). Proceedings, International Osteoporosis Foundation World Congress on Osteoporosis, Toronto, Canada, June 2-6, 2006, pp. 132-133.
1. Cannell JJ, Hollis BW, Sorenson MB, Taft TN, Anderson JJ. Athletic Performance and Vitamin D. Med Sci Sports Exerc. 2009; 41(5):1102- 1110.

Vitamin D and Immune System Support

Published on May 14, 2010 in healthy aging spotlight and vitamin d. 0 Comments

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Vitamin D – Immune System Support to the Next Level

Activation of the beneficial health-protective activities of white blood cells is a crucial event in the rapid response that is often required of the immune system. Research published in the Journal of Immunology has shown activated vitamin D to be a powerful stimulant to the white blood cells that mount the first line of chemical defense during the initial phases of a heightened immune response.24 This finding has been confirmed more recently by data published in the FASEB Journal and in Science.25,26 Both studies illustrate the effectiveness of vitamin D in maintaining optimal immune responses by targeting the activities of immune components.

Next Best Kept Secrets to Healthy Aging topic:
Vitamin D – Run Faster, Jump Higher!

References:
24. Wang T-T, Nestel FP, Bourdeau V, Nagai Y, Wang Q, Liao J, Tavera- Mendoza L, Lin R, Hanrahan JH, Mader S, White JH. Cutting edge: 1,25-Dihydroxyvitamin D3 is a direct inducer of antimicrobial peptide gene expression. J Immunol 2004;173:2909-2912.
25. Gombart AF, Borregaard N, Koeffler HP. Human cathelicidin antimicrobial peptide (CAMP) gene is a direct target of the vitamin D receptor and is strongly up-regulated in myeloid cells by 1,25-dihydroxyvitamin D3. FASEB J 2005;19:1067-1077.
26. Liu PT, Stenger S, Li H, Wenzel L, Tan BH, Krutzik SR, Ochoa MT, Schauber J, Wu K, Meinken C, Kamen DL, Wagner M, Bals R, Steinmeyer A, Zugel U, Gallo RL, Eisenberg D, Hewison M, Hollis BW, Adams JS, Bloom BR, Modlin RL. Toll-like receptor triggering of a vitamin D-mediated human antimicrobial response. Science 2006;311:1770-1773.

Vitamin D: Defender of Self-Recognition

Published on May 13, 2010 in healthy aging spotlight and vitamin d. 0 Comments

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Vitamin D – Defender of Self-Recognition

The importance of vitamin D’s contribution to a healthy immune system cannot be overstated. According to research published recently in the Journal of Immunology 1,25-dihydroxyvitamin D3 acts within the immune system to reduce the activity of the subpopulation of lymphocytes (a type of white blood cell) that are the most prone to accidentally mistake one of your cells for an outside invader.23 In other words, vitamin D focuses cells on performing their designated tasks and prevents them from overdoing it – truly a nutrient that works as an immune modulator. It promotes enhanced immune activity when necessary but protects the immune system from becoming overactive.

At the same time, locally produced 1,25-dihydroxyvitamin D3 also stimulates the activity of the subpopulation of lymphocytes responsible for correcting any “mistakes” that have already occurred. Thanks to vitamin D, your immune system is able to distinguish friend from foe and take the appropriate actions by fixing what’s needed to get your immune system to function at its best.

Next Best Kept Secrets to Healthy Aging topic:
Vitamin D – Immune System Support to the Next Level

References:
23. Chen L, Cencioni MT, Angelini DF, Borsellino G, Battistini L, Brosnan CF. Transcriptional profiling of T cells identifies a role for vitamin D in the immunoregulation of the V.9V.2 response to phosphate-containing ligands. J Immunol 2005;174:6144-6152.

Vitamin D and Mature Behavior in Young Cells

Published on May 12, 2010 in healthy aging spotlight and vitamin d. 0 Comments

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Vitamin D – Promoter of Mature Behavior in Young Cells

One of the most important functions of 1,25-dihydroxyvitamin D3 throughout the body is its ability to force young cells to “grow up,” called cellular differentiation. Because nature has decided that a cell can either reproduce itself or mature into its full function, all young cells face a choice: reproduce or go to work. Activated vitamin D (1,25-dihydroxyvitamin D3) forces a cell to choose maturity and function instead of immaturity and continued replication. This tutelage by vitamin D ensures that there are enough working cells to keep any organ or tissue healthy.

Vitamin D keeps cells healthy and in a working state, allowing them to keep functioning at a high level and doing their designated job. The results of the Health Professionals Follow-Up Study that was published recently have shown that routine daily consumption of about 1500 IU of vitamin D enhances the ability to maintain digestive tract, and particularly colon, health.20 These results also predict that routine daily consumption of only 400 IU of vitamin D doesn’t have the same effect and likely will not support a healthy digestive tract, confirming the results of earlier research and results obtained again in the Women’s Health Initiative Study published recently in the New England Journal of Medicine.21,22

Next Best Kept Secrets to Healthy Aging topic:
Vitamin D – Defender of Self-Recognition

References:
20. Giovannucci E, Liu Y, Rimm EB, Hollis BW, Fuchs CS, Stampfer MJ, Willett WC. Prospective study of predictors of vitamin D status and cancer incidence and mortality in men. J Natl Cancer Inst 2006;98:451-459.
21. Grau MV, Baron JA, Sandler RS, Haile RW, Beach ML, Church TR, Heber D. Vitamin D, calcium supplementation, and colorectal adenomas: Results of a randomized trial. J Natl Cancer Inst 2003;95:1765-1771.
22. Wactawski-Wende J, Kotchen JM, Anderson GL, Assaf AR, Brunner RL, O’Sullivan MJ, Margolis KL, Ockene JK, Phillips L, Pottern L, Prentice RL, Robbins J, Rohan TE, Sarto GE, Sharma S, Stefanick ML, Van Horn L, Wallace RB, Whitlock E, Bassford T, Beresford SA, Black HR, Bonds DE, Brzyski RG, Caan B, Chlebowski RT, Cochrane B, Garland C, Gass M, Hays J, Heiss G, Hendrix SL, Howard BV, Hsia J, Hubbell FA, Jackson RD, Johnson KC, Judd H, Kooperberg CL, Kuller LH, LaCroix AZ, Lane DS, Langer RD, Lasser NL, Lewis CE, Limacher MC, Manson JE; Women’s Health Initiative Investigators. Calcium plus vitamin D supplementation and the risk of colorectal cancer. N Engl J Med 2006;354:684-696.

Vitamin D is not just for bones

Published on May 10, 2010 in healthy aging spotlight and vitamin d. 0 Comments

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Vitamin D – Not Just for Good-Looking Bones

Although you and your doctor may not know this, very reliable hard-core research (most funded by the US government) has demonstrated that without a doubt, failing to consume enough vitamin D will increase your chances of developing several chronic conditions.6

As important as it is to consume enough vitamin D to maximize intestinal calcium absorption and minimize PTH secretion, much more vitamin D is necessary to supply enough 25-hydroxyvitamin D3 to the brain, heart, small intestine, colon, prostate, breast, lung, stomach, pancreas, skin, testes, ovaries, parathyroid gland, macrophages, lymphocytes, bone marrow and other organs and tissues to allow them to perform their own local conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3.6 In fact, locally-produced 1,25-dihydroxyvitamin D3 is now known to support many physiologic functions in these organs and tissues that are not related to bone health, including regulation of normal blood glucose metabolism, regulation of lymphocyte function, stabilization of heart muscle contractions, normalization of inflammatory responses, production of naturally occurring antibiotics called antimicrobial peptides, promotion of healthy thyroid function, and hundreds of other functions. For example, a 20-year study of 83,779 female nurses (the Nurses’ Health Study) found that women who consumed the RDA for calcium plus at least 800 IU of vitamin D daily were very much more likely to have healthy blood sugar levels when these nutrients were consumed as a part of their diet.19

Next Best Kept Secrets to Healthy Aging topic:
Vitamin D – Promoter of Mature Behavior in Young Cells

References:
6. Holick MF. Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. Am J Clin Nutr 2004;79:362-371.
19. Pittas AG, Dawson-Hughes B, Li T, Van Dam RM, Willett WC, Manson JE, Hu FB. Vitamin D and calcium intake in relation to type 2 diabetes in women. Diabetes Care 2006;29:650-656.

How Much Vitamin D Do I Need?

Published on May 7, 2010 in Dr. Cannell, healthy aging spotlight and vitamin d. 0 Comments

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
How Much Vitamin D Do I Need?

A steadily growing body of scientific research demonstrates that daily intakes of vitamin D much greater than the current RDA of 400 IU are required to minimize PTH secretion, optimize skeletal health, and perform the myriad of other functions inside the cell. For example, the results of an elaborate analysis of published research in the Journal of the American Medical Association (JAMA), indicate a clear improvement in bone health among men and women over 60 years of age who routinely consumed double the RDA (about 800 IU of vitamin D daily) compared to those who stuck to the RDA.15 In fact, the results of the Women’s Health Initiative Study published recently in the New England Journal of Medicine proved that the RDA for vitamin D was no better than vitamin D deficient diets in protecting the skeleton.16 The results of another study published recently in the British Medical Journal indicate that even 800 IU daily is not enough vitamin D for every elderly person to help prevent falling and fractures.17

The best estimates available suggest that an intake of 2,000 IU of vitamin D per day is the bare minimum that should be consumed by adults who also expose themselves to full-body sun on the weekends, just to ensure that the body’s daily needs are met. A pioneer of vitamin D research, Dr. Hector F. DeLuca of the University of Wisconsin, has advised all adults to consume 2000 IU of vitamin D daily.15 However, remember studies suggest that an intake of between 3,800 IU and 5,000 IU of vitamin D3 are needed on a daily basis to achieve levels of 25(OH)D3 of 30 ng/ mL in 97.5% of people.4 Many researchers, including Dr. John J. Cannell, Director of the Vitamin D Council, have suggested that optimal levels of 25(OH)D3 for health and wellness are 50 to 80 ng/ml.2 In order to obtain these levels, most adults require a daily intake of 5,000 IU of vitamin D3. Certain individuals (those with dark skin, obese, or older) may require even more. Taking 5,000 IU of vitamin D3 on a daily basis is very safe with little, if any, risk of toxicity. It has been suggested that everyone should be periodically tested for blood levels of twenty-five-hydroxy-Vitamin D [25(OH)D] to ensure that adequate concentrations are being sustained. The first test can be performed after 2 or 3 months on a daily dose of 5,000 IU, and then periodically thereafter. This is in fact the only way to ensure that you are getting the amount of vitamin D that your body needs to function optimally. Check with your nutritionally-oriented physician or naturopathic doctor in order to assure that your 25(OH)D levels are between 50 and 80 ng/ml, the midpoint on the reference range.

Next  Best Kept Secrets to Healthy Aging topic:
Vitamin D – Not Just for Good-Looking Bones

References:
2. Cannell JJ, Hollis BW. Use of vitamin D in clinical practice. Altern Med Rev 2008 Mar;13(1):6-20.
4. Aloia JF, Patel M, Dimaano R, Li-Ng M, Talwar SA, Mikhail M, Pollack S, Yeh JK. Vitamin D intake to attain a desired serum 25-hydroxyvitamin D concentration. Am J Clin Nutr. 2008 Jun;87(6):1952-8.
15. Bischoff-Ferrari HA, Willett WC, Wong JB, Giovannucci E, Dietrich T, Dawson-Hughes B. Fracture prevention with vitamin D supplementation: A meta-analysis of randomized controlled trials. JAMA 2005;293:2257-2264.
16. Jackson RD, LaCroix AZ, Gass M, Wallace RB, Robbins J, Lewis CE, Bassford T, Beresford SA, Black HR, Blanchette P, Bonds DE, Brunner RL, Brzyski RG, Caan B, Cauley JA, Chlebowski RT, Cummings SR, Granek I, Hays J, Heiss G, Hendrix SL, Howard BV, Hsia J, Hubbell FA, Johnson KC, Judd H, Kotchen JM, Kuller LH, Langer RD, Lasser NL, Limacher MC, Ludlam S, Manson JE, Margolis KL, McGowan J, Ockene JK, O’Sullivan MJ, Phillips L, Prentice RL, Sarto GE, Stefanick ML, Van Horn L, Wactawski-Wende J, Whitlock E, Anderson GL, Assaf AR, Barad D; Women’s Health Initiative Investigators. Calcium plus vitamin D supplementation and the risk of fractures. N Engl J Med 2006;354:669-683.
17. Porthouse J, Cockayne S, King C, Saxon L, Steele E, Aspray T, Baverstock M, Birks Y, Dumville J, Francis R, Iglesias C, Puffer S, Sutcliffe A, Watt I, Torgerson DJ. Randomised controlled trial of calcium and supplementation with cholecalciferol (vitamin D3) for prevention of fractures in primary care. BMJ 2005;330:1003 (6 pages). doi:10.1136/bmj.330.7498.1003
(http://bmj.com/cgi/content/full/330/7498/1003).

Vitamin D Recommendations and Assumptions

Published on May 6, 2010 in healthy aging spotlight and vitamin d. 0 Comments

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Vitamin D Recommendations and Assumptions

Many scientists now think that one way to ensure that someone’s vitamin D health is optimized is to recommend that the person consume enough vitamin D to prevent more than a trickle of parathyroid hormone (PTH) from being released by the parathyroid glands. PTH is selected as the biomarker for vitamin D adequacy because the parathyroid glands secrete PTH when they sense that the concentration of calcium in the blood is getting too low to be able to support brain and heart muscle function. PTH is the hormone that 1) triggers renal conversion of 25(OH)D3 to 1,25(OH)2D3 in order to increase the efficiency of absorption of dietary calcium (usually only 20% to 40% of ingested calcium is absorbed so there’s plenty of room for improvement) and 2) itself causes bone tissue within existing bones to dissolve in order to add to the circulating supply of calcium. If vitamin D keeps the plasma calcium level high enough, the parathyroid glands sense that there is no need for them to secrete PTH – and less bone is destroyed in order to release its calcium. However, other biomarkers like PTH exist, and scientists are discovering that other biomarkers, such as the amount required so that breast milk has enough Vitamin D for the infant, require even high vitamin D blood levels to be satisfied, 7,000 IU/day in the case of breast feeding women.

Findings published recently in the Journal of Nutrition have shown conclusively that the density of skeletal bone begins to decline just when vitamin D intake becomes too low to prevent an increase in PTH secretion.11 On the other hand, recent findings published in the Journal of Bone and Mineral Metabolism demonstrate that the first measurable indicator of early vitamin D deficiency in adult human’s blood is an increase in PTH secretion.12 As confirmed by the results of studies published recently in the Journal of the American Medical Association and the Journal of Clinical Endocrinology and Metabolism, minimizing parathyroid secretion of PTH by optimizing vitamin D intake achieves a true healthful balance between the diet, vitamin D, calcium and the skeleton.13,14

Next  Best Kept Secrets to Healthy Aging topic:
So How Much Vitamin D Do I Need?

References:
11. Hollis BW. Circulating 25-hydroxyvitamin D levels indicative of vitamin D sufficiency: Implications for establishing a new effective dietary intake recommendation for vitamin D. J Nutr 2005;135:317- 322.
12. Hashemipour S, Larijani B, Adibi H, Sedaghat M, Pajouhi M, Bastan- Hagh MH, Soltani A, Javadi E, Shafaei AR, Baradar-Jalili R, Hossein- Nezhad A. The status of biochemical parameters in varying degrees of vitamin D deficiency. J Bone Miner Metab 2006;24:213-218.
13. Steingrimsdottir L, Gunnarsson O, Indridason OS, Franzson L, Sigurdsson G. Relationship between serum parathyroid hormone levels, vitamin D sufficiency, and calcium intake. JAMA 2005;294:2336-2341.

14. Snijder MB, van Schoor NM, Pluijm SM, van Dam RM, Visser M, Lips P. Vitamin D status in relation to one-year risk of recurrent falling in older men and women. J Clin Endocrinol Metab 2006;91:2980-2985.

Vitamin D Levels and Normal Aging

Published on May 5, 2010 in healthy aging spotlight and vitamin d. 0 Comments

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Vitamin D Levels and Normal Aging

While the consumption of lower levels in youth may allow one to achieve better blood concentrations of vitamin D, the requirement increases in middle age and thus the dose required to achieve optimal levels also increases. For one thing, the ability of your skin to make vitamin D in response to sunlight becomes much less efficient – skin loses 50% to 75% of its ability to make Vitamin D in response to exposure to sunlight by age 60 – increasing the need for dietary vitamin D to narrow the ever-expanding gap between vitamin D requirement and supply. For another, older people tend to spend less time exposed to the sun – partly out of fear of skin cancer, partly out of reduced mobility. In addition, the ability of the kidneys and tissues to perform the final step in the activation of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3 declines with age, meaning that even more vitamin D must be available in the blood in order to satisfy the physiological needs of the calcium economy for the older adult. Finally, overweight individuals need to consume more vitamin D than they needed when they were lean and trim because fat deposits soak up and store vitamin D – the more fat, the greater the percentage of ingested vitamin D that ends up in storage rather than use.

Next Best Kept Secrets to Healthy Aging topic:
Vitamin D Recommendations and Assumptions

Vitamin D deficiency is more prevalent than we think

Published on May 4, 2010 in healthy aging spotlight and vitamin d. 0 Comments

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Vitamin D Deficiency – More Prevalent than we think

Five years ago, in his 2003 Robert H. Herman Memorial Award in Clinical Nutrition, Dr. Michael F. Holick argued convincingly that there is an unrecognized epidemic of vitamin D deficiency among children and adults in the US.6 In children and adults, vitamin D deficiency results in bone issues – issues that are on the rise in 21st century America. In fact, Dr. Holick’s research published in the Journal of Clinical Endocrinology and Metabolism discovered that at least half of all adult women in the US do not consume even 400 IU of vitamin D daily.7

Other scientists who have published their research results more recently in the Journal of Nutrition have made the same discovery: about 25% of all adult men and over half of all adult women in the US do not consume even 400 IU of vitamin D daily.8,9,10 These percentages are doubled among black and Hispanic men and women. Even more adults are vitamin D “insufficient” – a fancy way of saying that they haven’t reached the low levels associated with clinical deficiency but have lower than optimal levels, nonetheless.

Tomorrow’s topic: Vitamin D Levels and Normal Aging

References:
6. Holick MF. Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. Am J Clin Nutr 2004;79:362-371.
7. Holick MF, Siris ES, Binkley N, Beard MK, Khan A, Katzer JT, Petruschke RA, Chen E, de Papp AE. Prevalence of Vitamin D inadequacy among postmenopausal North American women receiving osteoporosis therapy. J Clin Endocrinol Metab 2005;90:3215-3224.
8. Hanley DA, Davison KS. Vitamin D insufficiency in North America. J Nutr 2005;135:332-337.
9. Moore CE, Murphy MM, Holick MF. Vitamin D intakes by children and adults in the United States differ among ethnic groups. J Nutr 2005;135:2478-2485.
10. Harris SS. Vitamin D and African Americans. J Nutr 2006;136:1126-1129.

How Much Vitamin D Do I Need?

Published on May 3, 2010 in Dr. Cannell, healthy aging spotlight and vitamin d. 0 Comments

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
How Much Vitamin D Do I Need?

While the amount of vitamin D needed by any individual on a daily basis varies, it is clear that current reference amounts are woefully inadequate. Two recent studies published in the American Journal of Clinical Nutrition serve to highlight this point rather dramatically. The first study looked at the relationship between serum levels of vitamin D3 and blood levels of 25(OH)D, the functional status indicator of vitamin D and its principal storage form in the body.3 What the researchers found was that a 25OHD3 blood level of 40 ng/ml was needed in order for the liver enzymes that are responsible for the conversion of vitamin D to become saturated in 50% of people. This means that, up to this blood level, the body’s needs for vitamin D are not adequately met in 50% of people, as all of the vitamin D available is quickly being converted and utilized by the body and those people are no longer suffering from “substrate starvation.” When one achieves levels of 50 ng/ml, more than 90% of people are no longer “substrate starved.” According to these researchers, the point at which the liver enzymes are saturated can be defined as the low end of “normal” vitamin D status. However, at this low level, the body is not storing any vitamin D for future use and is unable to adequately satisfy the burden of need for vitamin D by all organs and systems.

A second study looked at the amount of vitamin D needed on a daily basis by adults to raise the concentration of 25(OH) D to the minimum level of 30 ng/mL (which is considered to be sub-optimal). Based on the findings of this six-month randomized double-blind, placebo-controlled study, the researchers concluded that adults needed to take between 3,800 and 5,000 IU daily for 97.5% of people to obtain this minimum concentration.4 An earlier study of 208 African American women by the same research team found that a daily dose of 2,000 IU of vitamin D3 failed to raise levels of 25(OH)D to above 30 ng/ mL in 40% of the participants. These findings formed the basis for conducting the new study in African American and white men and women. While the higher dosages administered in the new study successfully brought the majority of study subjects up to the minimum threshold 25(OH)D level of 30 ng/mL, researchers found that many African American subjects required a daily dose that was 50% higher than the white study subjects in order to achieve this goal. This indicates that certain individuals and groups require much higher intakes of vitamin D to optimize health.

These studies also illustrate the fact that the current Recommended Daily Allowance (or “RDA”) of 400 IU for all adults fails to even come close to meeting daily vitamin D requirements. Regardless of age, ethnicity and other factors, this amount just doesn’t cut it given the evidence and recent data concerning widespread deficiencies. Children are also at risk for being low in vitamin D. Vitamin D deficiency in children is usually seen when blood levels are tested, and many are severely deficient.

It had earlier been thought that excessive supplemental doses of vitamin D may lead to signs of toxicity. There have been scattered reports of toxicity to vitamin D in the literature but these all are either dosing errors, rare industrial manufacturing errors, or from the administration of high doses of Vitamin D2 by physicians. However, most of these reports have been affiliated with vitamin D2 supplements taken at high doses. Vitamin D2 is produced synthetically and is the form that occurs in plants. Vitamin D2 is generally safe at normal doses; however, it is considerably less efficient at being converted to the active form of vitamin D in the body. Vitamin D2 is also not human vitamin D as it does not occur naturally in the body, and its metabolism may result in byproducts that are not normally found in humans.2 The consensus now is that vitamin D3 (the form found in humans and other mammals) is the optimal form of vitamin D for supplementation and is extremely safe even at higher doses. Vitamin D3 is more effective than vitamin D2 at raising levels of 25(OH)D, the standard laboratory measure of vitamin D sufficiency.

Most scientists agree that the existing recommendation for daily vitamin D intake is flawed because it is based on survey data that were interpreted with the assumption that vitamin D deficiency is virtually nonexistent in the United States. As mentioned above, vitamin D deficiency is highly prevalent worldwide, including in the US. Therefore, this assumption is blatantly incorrect. In her summary of the Experimental Biology 2004 Symposium on Vitamin D Insufficiency that was published recently in the Journal of Nutrition, the US Food and Drug Administration’s Mona S. Calvo described “the pressing need to define a new dietary requirement for vitamin D” in light of “the widespread prevalence of vitamin D insufficiency in North America.”5

Tomorrow’s topic: Vitamin D Deficiency

References:
2. Cannell JJ, Hollis BW. Use of vitamin D in clinical practice. Altern Med Rev 2008 Mar;13(1):6-20
3. Heaney RP, Armas LA, Shary JR, Bell NH, Binkley N, Hollis BW. 25-Hydroxylation of vitamin D3: relation to circulating vitamin D3 under various input conditions. Am J Clin Nutr. 2008; 87(6):1738- 42.
4. Aloia JF, Patel M, Dimaano R, Li-Ng M, Talwar SA, Mikhail M, Pollack S, Yeh JK. Vitamin D intake to attain a desired serum 25-hydroxyvitamin D concentration. Am J Clin Nutr. 2008 Jun;87(6):1952-8.
5. Calvo MS, Whiting SJ. Overview of the proceedings from Experimental Biology 2004 symposium: Vitamin D insufficiency: A significant risk factor in chronic diseases and potential diseasespecific biomarkers of vitamin D sufficiency. J Nutr 2005;135:301-303.