Download Symposium: Optimizing Vitamin D Intake for Populations with

Symposium: Optimizing Vitamin D Intake for Populations
with Special Needs: Barriers to Effective Food
Fortification and Supplementation
Public Health Strategies to Overcome Barriers to Optimal Vitamin D
Status in Populations with Special Needs1
Mona S. Calvo*2 and Susan J. Whitingy
*Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD and yCollege
of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada
KEY WORDS: vitamin D fortification supplementation
Importance of optimal vitamin D status to health. Recent
studies have revealed the importance of adequate levels of
circulating 25-hydroxyvitamin D [25(OH)D]3 in preventing
chronic diseases associated with significant morbidity and
mortality in the U.S. and Canadian populations (1). In the
general population of North America, the majority of circulating
25(OH)D originates from cutaneous synthesis upon exposure to
sunlight; however, seasonal changes, living at high latitudes or
low-pollution altitudes, dark skin pigmentation, and aging are
among the many factors that can impede this process, requiring
periodic reliance on dietary sources to supply the precursor to
25(OH)D (2,3). Prevalence of low circulating levels of 25(OH)D
are higher than anticipated in North America, despite the
required fortification of milk (4,5); further, this prevalence is
much higher than previously thought, year around, in darkskinned young and old adults (6). The groups at greatest risk for
vitamin D insufficiency and deficiency include African
American men, women, and children living in northern
latitudes, but all race or ethnic groups with darker skin face
some risk during all seasons. Moreover, African Americans
and Mexican Americans have a much higher incidence and
mortality of specific types of cancers and autoimmune diseases,
including diabetes, that cannot be attributed entirely to
socioeconomic differences or disparities in health care (4,7).
These populations at risk for low-circulating 25(OH)D or
vitamin D insufficiency or deficiency also face unique barriers to
1
Presented as part of the symposium ‘‘Optimizing Vitamin D Intake for
Populations with Special Needs: Barriers to Effective Mechanisms of Food
Fortification and Supplementation’’ given at the 2005 Experimental Biology
meeting on April 4, 2005, San Diego, CA. The symposium was sponsored by
the American Society for Nutrition and supported, in part, by educational grants
from the Centrum Foundation of Canada, the Coca-Cola Company, and the
Natural Ovens Bakery, Inc. The proceedings are published as a supplement to The
Journal of Nutrition. This supplement is the responsibility of the guest editors to
whom the Editor of The Journal of Nutrition has delegated supervision of both
technical conformity to the published regulations of The Journal of Nutrition and
general oversight of the scientific merit of each article. The opinions expressed in
this publication are those of the authors and are not attributable to the sponsors or
the publishers, editor, or editorial board of The Journal of Nutrition, and do not
necessarily reflect those of the Food and Drug Administration. The guest editors for
this symposium publication are Susan J. Whiting, College of Pharmacy and
Nutrition, University of Saskatchewan, SK, Canada and Mona S. Calvo, Center for
Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD,
USA.
2
To whom correspondence should be addressed. E-mail: mona.calvo@
cfsan.fda.gov.
3
Abbreviations used: NHANES, National Health and Nutrition Examination
Surveys; 25(OH)D, 25-hydroxyvitamin D.
0022-3166/05 $8.00 Ó 2006 American Society for Nutrition.
1135
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ABSTRACT In North America, there is increasing public health awareness of the importance of adequate vitamin D
intake to the maintenance of optimal vitamin D status and overall health. Experts now define this as circulating levels
of 25-hydroxyvitamin D of 75–80 nmol/L. This serum level and high levels of dietary intake have been associated with
significantly reduced risk of chronic diseases, such as osteoporosis, cardiovascular disease, diabetes, and some
cancers. All of these diseases are more prevalent in the elderly of all races, and some are more prevalent and of
greater severity among blacks than whites. Our objective is to review recent actions to increase public awareness of
the health importance of maintaining optimal circulating 25(OH)D and potential strategies to increase vitamin D
intake. Clinicians and educators are encouraged to promote improved vitamin D intake and status, particularly
among the elderly and blacks. This will largely depend on combined efforts to judiciously fortify our food supply and to
develop individual supplementation protocols for supplements or controlled use of UV light exposure to maintain
optimal serum 25(OH)D, especially in high-risk groups. Growing evidence supports a low risk of toxicity with vitamin
D use in fortification or supplementation, despite its past reputation of potential toxicity in excess. The cost to fortify
food or supplements with vitamin D is relatively inexpensive compared with developing drugs used to treat or prevent
chronic diseases; moreover, there is significant potential for broad health benefits in the reduced risk and prevention
of multiple chronic diseases. J. Nutr. 136: 1135–1139, 2006.
1136
SYMPOSIUM
FIGURE 1 Mean intake of vitamin D from foods for 1-d as
measured by NHANES, where 1 represents NHANES III, 1988–1994
(data provided by M. Calvo and C. Barton, FDA) and 2 represents
ongoing NHANES 1999–2000 (10). Two adult groups are provided for
each survey but the age range differs in each survey. In NHANES
III,1988–1994, the term Younger is 20–49 y and the term Older is .50 y,
whereas in the ongoing NHANES 1999–2000, Younger is 19–50 y and
Older is .51 y. NHW, non-Hispanic white; NHB, non-Hispanic black;
Mex, Mexican Americans. Groups are listed in descending order of their
initial (survey 1) vitamin D intake.
FIGURE 2 Mean intake of vitamin D from foods and supplements as
measured by NHANES where 1 represents NHANES III, 1988–1994, and
2 represents ongoing NHANES 1999–2000. Survey-1 data are usual
mean intake from food and supplements (2) and survey 2 uses 24-h or
1-d vitamin D intake from food and supplements. Two adult groups are
provided for each survey but the age range differs in each survey. In
NHANES III,1988–1994, the term Younger is 20–49 y and the term Older
is .50 y, whereas in the ongoing NHANES 1999–2000, Younger is 19–
50 y and Older is .51 y. NHW, non-Hispanic white; NHB, non-Hispanic
black; Mex, Mexican Americans. Groups are listed in descending order of
their initial (survey 1) vitamin D intake.
more important questions: what public health strategies are in
place or are proposed to help optimize vitamin D status in
North America, and what are the inherent problems that we
face with each?
Strategies to correct low dietary vitamin D intake. There
are 3 different dietary approaches that could enable most of us
to improve our vitamin D status without consulting a physician
or participating in a new drug trial. All 3 approaches require
educating the public and food manufacturers as to the needed
adjustments in labeling or level of fortification. Consumers can
improve and maintain vitamin D status through increased
consumption of natural or fortified food sources or vitamin
D-containing dietary supplements. Planned exposure to sunlight is an alternative approach but beyond the scope of this
article. Each approach by itself, or in any combination, could be
effective in maintaining 25(OH)D levels. Below, we discuss
strategies to overcome the barriers to optimal vitamin D intake
associated with natural food sources, fortification of foods, and
dietary supplement use.
Natural food sources. There are very few foods that are
naturally rich in vitamin D, and most of these are not frequently consumed and are subject to large seasonal variation in
vitamin D content (14). Fatty fish, such as salmon, are the
richest natural source of vitamin D that is frequently consumed
in North America. Frequent fish consumption can be a very effective way to maintain desirable circulating levels of 25(OH)D,
as observed in elderly Japanese women (15). Nakamura et al.
(15) reported significantly higher mean serum 25(OH)D levels
in older women consuming fish more than 4 times/wk relative
to those who ate fish less frequently or not at all. Frequent fish
eaters were able to maintain desired serum 25(OH)D levels
even during the winter.
Other natural vitamin D–rich foods include organ meats,
such as liver, but many people do not consume these sources
because of the high cholesterol content. A largely unrecognized
food source of vitamin D includes all the edible mushrooms,
wild and domestic. Wild mushrooms naturally contain small
amounts of vitamin D2, but all edible mushrooms make
abundant amounts of ergosterol, which, when irradiated with
sunlight or UVB light, is converted to vitamin D2 (16–21).
UVB irradiation of cultivated mushrooms produces significant vitamin D2 content that is bioavailable, efficiently
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achieving adequate intakes of vitamin D, as addressed by Drs.
Harris (7) and Heaney (8) in this issue. Our goals in this article
are to review the current guidelines and health policies
demonstrating awareness of the importance of maintaining
optimal levels of circulating 25(OH)D and adequate levels of
vitamin D intake, and to evaluate the specific public health
strategies currently in place or proposed that individuals may
use to help optimize vitamin D status, especially in the high-risk
groups.
Cross-sectional and local studies in North America reveal
a significant disparity between amount of vitamin D actually
consumed and the amount needed to maintain healthy circulating levels of 25(OH)D. We know, from the nationally
representative National Health and Nutrition Examination
Surveys (NHANES) conducted in 1988–1994 and 1999–2000
(6,7,9,10), that there has been little change in vitamin D intake
over the last decade in the U.S., and that few age, race, and
gender groups meet the dietary intake guidelines (Figs. 1 and
2). Moreover, based on median usual intake estimates from
NHANES III, even fewer older men and women of all racial
and ethnic groups meet the dietary needs demonstrated by
Heaney in this symposium (8) that are necessary to maintain
serum 25(OH)D at optimal levels (2). In Canada, longitudinal
studies in young and primarily white women revealed that
consumption of vitamin D at the dietary guideline (5mg) was
not effective in maintaining vitamin D status at the 80 nmol
level in winter, when cutaneous synthesis of vitamin D is reduced even in younger women (11).
This growing awareness of the need for greater consumption
of vitamin D, particularly in the elderly, was conveyed to the
public as a key recommendation in the 2005 Dietary Guidelines
for Americans (12), which is aimed at older adults, people with
dark skin, and people exposed to insufficient ultraviolet band
radiation (i.e., sunlight) who are advised to consume extra
vitamin D from D-fortified foods and/or supplements. In
Canada, the main effort to increase public awareness about
the need for vitamin D is through the Osteoporosis Health
Claim appearing on eligible food products. This health claim
recognizes the importance of both calcium and vitamin D to
osteoporosis prevention: ‘‘A healthy diet with adequate calcium
and vitamin D, and regular physical activity, help to achieve
strong bones and may reduce the risk of osteoporosis’’ (13; p.
306). These initiatives will hopefully draw attention and action
to this important dietary need, but such guidelines beg even
STRATEGIES TO OPTIMIZE VITAMIN D STATUS
differences in vitamin D intake from these 2 fortified food
sources are shown in Table 1 of the introduction to this issue
(23). Because of a higher prevalence of lactose intolerance and
low milk consumption in African-Americans, there are marked
differences in food consumption patterns between whites and
blacks that affect vitamin D intake. Selective fortification of
these 2 staples is a major barrier to optimal vitamin D status in
African Americans who are at greatest risk of poor vitamin D
status.
Unlike Canada, where vitamin D fortification is mandatory
for milk and margarine, the addition of vitamin D to eligible
foods in the U.S. is optional, with the exception of fortified milk
(14). If the label declares that the milk is fortified, then it must
contain added vitamin D. Although many categories of foods
are eligible for controlled levels of vitamin D fortification in the
U.S., there is a large discrepancy between the number of eligible
foods and the number and variety of vitamin D–fortified foods
currently observed in the U.S. marketplace (14).
By encouraging manufacturers to utilize these fortification
options, the vitamin D intake of groups at risk could be significantly improved. To illustrate this point, we used the recommended daily amount of food from each of 6 food categories in
the 2005 USDA My Pyramid food intake patterns guidelines
(http://www. MyPyramid.gov). We used the 2000 calories/
d level as the basis for estimating potential contributions to
vitamin D intake if foods in this category were fortified to the
maximum optional fortification levels (14). Under current U.S.
regulations, food components of 4 of these general food
categories are eligible for optional fortification: fruits (calciumfortified 100% fruit juice), grains, milk, and oils (margarine)
(14,24). The maximum allowed fortification of each food in
common household units and 100-g equivalents, and the total
amount of vitamin D that would be available if the eligible food
was fortified to the maximum allowable level, is shown in Table
1. This hypothetical exercise illustrates that considerable
amounts of vitamin D could be obtained through mandatory
fortification of staples, such as grain products, at levels not to
exceed what is currently allowed (14). Cereal grain products
include pasta, bread, and other baked goods that are frequently
consumed by the general population and could reach specific
target populations, such as the elderly. Consideration should be
TABLE 1
Hypothetical contributions to vitamin D intake in the United
States through universal fortification of eligible foods at the
maximum level currently allowed
Food
category
Maximum
Potential amount
Daily suggested allowed addition of vitamin D
amount consumed1 of vitamin D2 from fortification
Serving size, g
Fruits
Grains
Milk
Oils (margarine)
FIGURE 3 Vitamin D intake (mg/d) by different gender, age, and
race/ethnic groups. Vitamin D intakes from fortified foods and natural food
sources were estimated from the ongoing NHANES (1999–2000) and the
figure was drawn from data presented in reference 10.
2
6
3
6
cups (474)
oz (168)
cups (711)
tsp (30)
IU
mg, IU
100 (RACC)3
90 (100 g)
42 (100 g)
331 (100 g)
5.0 (200)
3.7 (153)
7.5 (302)
2.5 (99.3)
1 Food patterns obtained from the USDA MyPyramid guidelines for
the amount of food in each category recommended to be consumed as
a healthy eating pattern for a 2000 kcal daily intake.
2 Maximal level of vitamin D that can be added in accordance with
the Code of Federal Regulations governing the addition of vitamin D
21 CFR 184.1 (b) (2) for this category of food.
3 RACC, reference amount customarily consumed, or the USFDA
regulatory serving size.
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metabolized to 25-hydroxyvitamin D2, and functional in
promoting bone mineralization in rodent models (20,21).
Depending on the type of mushroom and the duration of
UVB exposure, vitamin D2 content may reach as high as 25 mg/g
of dried shitake (19); thus, irradiated cultivated mushrooms are
a potential important alternative for fatty fish or other natural
food sources of vitamin D and is of particular importance to
vegans and vegetarians whose diet is otherwise extremely
limited in vitamin D (6).
One common barrier to improving vitamin D intake that is
characteristic of all natural food sources, whether of animal or
plant origin, is the lack of vitamin D content information on
the label. Examination of many different frozen or canned fish
products in our respective local marketplace revealed that
only the Canadian products were labeled with the vitamin D
content, and this important labeling information was highly
variable, with its presence being the exception rather than the
rule. Similarly, none of the Nutrition Facts panels of any of the
mushroom products contained vitamin D content information.
The addition of vitamin D content information to the labels is
a relatively easy barrier to overcome and would facilitate
educating the public about natural sources of vitamin D.
Fortification. U.S. and Canadian populations are most
reliant on fortified foods to meet their vitamin D needs during
the winter months (Fig. 3). Fortified foods constitute the
largest contributor (65–87%) to dietary vitamin D intake as
calculated from the ongoing NHANES (1999–2000) (10).
Although vitamin D fortification is clearly effective in reaching
the general population and is the greatest source of vitamin D
for all age, gender, and racial groups, it is apparent that the
current level of fortification in the U.S. (4,6) and in Canada
(11) is not effective in reaching the needed levels for vitamin
D intake. Consideration needs to be given to the level of
fortification, especially in countries like Canada, where only 2
food staples, milk and margarine, are required to be fortified,
while fortifying other staples with vitamin D is not allowed
(2,14). Milk is the major fortified staple in the U.S. and
Canada, but as shown by Vieth et al. (11), the amount of
vitamin D added to milk (1 mg/100g fluid milk) is not adequate
to produce the desired increase or maintenance of circulating
25(OH)D, while fortification at higher levels (10 mg/50g
powdered milk) has been shown to be effective in improving
vitamin D status and bone mineralization in older women (22).
Another drawback to limiting fortification to only a few
staples is the inability to reach vulnerable populations with
different dietary preferences or aversions to specific foods such
as milk. In the U.S., the 2 major contributors to vitamin D
intake observed in both NHANES were from fluid milk
products and ready-to-eat cereals (10,14). Significant racial
1137
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SYMPOSIUM
FIGURE 4 Serum 25(OH)D concentration (nmol/L) by intake
category for African American (dark bars) and white (gray bars) women.
Intake categories: none ¼ reference (lowest response in any reference
category); milk ¼ .3 servings/wk; cereal ¼ .3 servings of fortified cereal/
wk; supple. ¼ daily intake of supplement containing ¼ .400 IU/d (10 mg/d).
Data is adapted from reference (26).
the marketplace in the U.S. and Canada that are food-like in
many respects, but are clearly identified as dietary or vitamin
supplements. In Canada, there are a number of fruit drinks that
are fortified with a variety of nutrients, but the vitamin D
content is only ;70 IU or ,2 mg. The Nutrition Facts panel of
a recent FDA-approved dietary supplement, now available in
the U.S., is shown in Figure 5. This chocolate candy, or dietary
supplement, contains 2000 IU (50 mg) of vitamin D and represents the most potent supplement source of vitamin D sold
over the counter in the U.S. The introduction of this novel
dietary supplement product lowers the barrier to obtaining
adequate vitamin D intake for many individuals and suggests
a new approach to providing products that are custom designed
to the tastes and needs of a specific target population.
Conclusion. With each of the 3 public health strategies
discussed here, there is a need for both safety- and efficacytesting of any changes introduced, such as a shift from optional
to mandatory fortification of cereal grain products. At
minimum, this would entail monitoring the circulating levels
of 25(OH)D, parathyroid hormone, and other select endpoints
that would reflect improved vitamin D status or potential
toxicity. In this issue, Vieth (33) discusses the growing
evidence that supports a low risk of toxicity from vitamin D
use in fortification or supplementation. The development of
natural food sources with higher vitamin D content, the shift to
mandatory fortification of cereal grain staples, or the development of high-potency–food-based vitamin D supplements
FIGURE 5 The Nutrition Facts panel from a new type of dietary supplement showing the highest vitamin D content of a dietary supplement to
date.
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given to a proposed shift from optional to mandatory
fortification for eligible food staples frequently consumed by
the entire population as a potentially viable and effective
strategy to meet vitamin D needs of target groups. The safety
and efficacy of the recently proposed mandatory fortification of
cereal and grain products (25) clearly merits further study.
Supplementation. Dietary supplement use is another option
for improving vitamin D status. The NHANES (2,10,26) show
that supplement use can significantly increase vitamin D intake
across all age, race, ethnic, and gender groups. However, as
observed in NHANES III, the benefit of supplement use was
gained more in persons whose intakes were already above the
median intake and less gain was observed in individuals with
low vitamin D intake from food (2). Supplement use varies
among race or ethnic groups, with African Americans consuming the lowest amount from supplements. Furthermore,
there are significant racial differences in the effect of daily
intake of supplements containing .400 IU (10 mg) vitamin D
(Fig. 4). Nesby-O’Dell et al. (26) showed that the prevalence of
vitamin D insufficiency is markedly higher in African
Americans compared with Caucasian women, even when
both consume .10 mg/d (400 IU/d). Harris et al. (27,28) show
similar differences in older African American and Caucasian
women consuming vitamin D supplements at or above the
recommended intake guidelines. In a recent study, African
American women (15–49 y) were given daily vitamin D
supplements (400 IU, 10 mg) in addition to their usual food
sources of vitamin D, but 11% of these subjects had serum
25(OH)D levels #37.5 nmol/L, a conservative cutoff point for
vitamin D insufficiency (29). These findings suggest the need
for race- or age-specific dietary supplements with higher
vitamin D content that reflects the specific needs of the group.
As discussed by Heaney in this symposium (8), many experts
now believe that intakes of 25–65 mg/d (1000–2600 IU/d) are
needed for many people to achieve 75–80 nmol/L circulating
concentrations of 25(OH)D (30,31). For the elderly and dark
skinned, this suggests the need for dietary supplements with
higher vitamin D levels than what is currently available without
prescription.
The vitamin D content of dietary supplements for daily use
in the U.S. ranges from 200 to 400 IU/tablet (5–10 mg/tablet),
while those in Canada contain 400–1000 IU (10–25 mg/tablet).
Dietary supplements are allowed to contain up to the tolerable
upper limit (2000 IU or 50mg) as designated by the 1997 Dietary
Reference Intakes (32). Although manufacturers of daily use,
multiple, or single-nutrient supplements in the U.S. have not
yet responded to the growing public demand for greater vitamin
D potency, others have. Several novel products have entered
STRATEGIES TO OPTIMIZE VITAMIN D STATUS
are all potentially safe and effective mechanisms for overcoming
the barriers to optimal vitamin D status, and they each merit
further study. The cost to fortify food with vitamin D or to
increase supplement potency is relatively inexpensive compared with the cost of developing drug treatments for the many
chronic diseases strongly associated with vitamin D insufficiency. In the case of maintaining optimal vitamin D status, an
ounce of prevention may very well be worth a pound of cure.
LITERATURE CITED
17. Mau JL, Chen PR, Young JH. Ultraviolet irradiation increased vitamin D2
content in edible mushrooms. J Agric Food Chem. 1998;46:5269–72.
18. Perera CO, Jasinghe VJ, Ng FL, Mujunedar AS. The effect of moisture
content on the conversion of ergosterol to vitamin D in shitake mushrooms. Drying
Technol. 2003;21:1093–101.
19. Jasinghe VJ, Perera CO. Distribution of ergosterol in different tissues of
mushrooms and its effect on the conversion of ergosterol to vitamin D2 by UV
irradiation. Food Chem. 2005;2:541–6.
20. Outila TA, Mattila PH, Piironen VI, Lamberg-Allardt CJE. Bioavailability of
vitamin D from wild edible mushrooms (Cantharellus tubaeformis) as measured
with human bioassay. Am J Clin Nutr. 1999;69:95–8.
21. Jasinghe VJ, Perera CO, Barlow PJ. Bioavailability of vitamin D2 from
irradiated mushrooms: an in vivo study. Br J Nutr. 2005;93:951–5.
22. Chee WS, Suriah AR, Chan SP, Zaitan Y, Chan YM. The effect of milk
supplementation on bone mineral density in postmenopausal Chinese women in
Malaysia. Osteoporos Int. 2003;14:828–34.
23. Whiting SJ, Calvo MS. Overview of the proceedings from experimental
biology 2005 symposium: optimizing vitamin D intake for populations with special
needs: barriers to effective food fortification and supplementation. J Nutr. 2006;
136:1114–6.
24. Fda.gov [home page on the Internet] Rockville: U.S. Food and Drug
Administration Code of Federal Regulations Online; c2000-01 [updated 2005
April 1; cited 2006 Feb 17] Available from http://www.accessdata.fda.gov/
scripts/cdrh/cfdocs//cfcfr/CFRSearch.cfm?fr=184.1950
25. Newmark HL, Heaney RP, Lachance PA. Should calcium and vitamin D
be added to the current enrichment program for cereal-grain products? Am J Clin
Nutr. 2004;80:264–70.
26. Nesby-O’Dell S, Scanlon KS, Cogswell ME, Gillespie C, Hollis BW,
Looker AC, Allen C, Doughertly C, Gunter EW, Bowman BA. Hypovitaminosis D
prevalence and determinants among African American and white women of
reproductive age: third national health and nutrition examination survey, 1988–1994.
Am J Clin Nutr. 2002;76:187–92.
27. Harris SS, Soteriades E, Dawson-Hughes B. Secondary hyperparathyroidism and bone turnover in elderly blacks and whites. J Clin Endocrinol Metab.
2001;86:3801–4.
28. Harris SS, Stoeriades E, Coolidge JA, Mudgal S, Dawson-Hughes B.
Vitamin D insufficiency and hyperparathyroidism in a low income, multiracial,
elderly population. J Clin Endocrinol Metab. 2000;85:4125–30.
29. Aloia JF, Talwar SA, Pollack S, Yeh J. A randomized controlled trial of
vitamin D3 supplementation in African American women. Arch Intern Med. 2005;
165:1618–23.
30. Dawson-Hughes, B., Heaney, R.P., Holick, M.F., Lips, P., Meunier, P.J. &
Vieth, R. (2005) Estimates of optimal vitamin D status. Osteoporos Int (in press)
(Epub ahead of print 3/18/05)
31. Hollis BW. Circulating 25-hydroxyvitamin D levels indicative of vitamin D
sufficiency: implications for establishing a new effective dietary intake recommendations for vitamin D. J Nutr. 2005;135:317–22.
32. Institute of Medicine. Dietary reference intakes for calcium, phosphorus,
magnesium, vitamin D and fluoride. Washington DC: National Academy Press,
1997. p. 250–87.
33. Vieth R. Critique of the considerations for establishing the tolerable upper
intake level for vitamin D: critical need for change upwards. J Nutr. 2006;
136:1117–22.
Downloaded from jn.nutrition.org by guest on February 9, 2013
1. Grant WB, Holick MF. Benefits and requirements of vitamin D for optimal
health: a review. Altern Med Rev. 2005;10:94–111.
2. Whiting SJ, Calvo MS. Dietary recommendations to meet both endocrine
and autocrine needs of vitamin D. J Steroid Biochem Mol Biol. 2005;97:7–12.
3. Calvo MS, Whiting SJ. Overview from the proceedings from Experimental
Biology 2004 symposium: vitamin D insufficiency: a significant risk factor in chronic
diseases and potential disease-specific biomarkers of vitamin D sufficiency. J Nutr.
2005;135:301–3.
4. Calvo MS, Whiting SJ. Prevalence of vitamin D insufficiency in Canada
and the United States: importance to health status and efficacy of current food
fortification and dietary supplement use. Nutr Rev. 2003;61:107–13.
5. Hanley D, Davison KS. Vitamin D ‘‘insufficiency’’ in North America. J Nutr.
2005;135:332–7.
6. Calvo MS, Whiting SJ, Barton CN. Vitamin D intake: a global perspective
of current status. J Nutr. 2005;135:310–6.
7. Harris SS. Vitamin D and African Americans. J Nutr. 2006;136:1126–9.
8. Heaney RP. Barriers to optimizing vitamin D3 intake for the elderly. J Nutr.
2006;136:1123–5.
9. Looker AC, Dawson-Hughes B, Calvo MS, Gunther EW, Sahyoun NR.
Serum 25-hydroxyvitamin D status of adolescents and adults in two seasonal
subpopulations from NHANES III. Bone. 2002;30:771–7.
10. Moore CE, Murphy MM, Holick MF. Vitamin D intakes by children and
adults in the United States differ among ethnic groups. J Nutr. 2005;135:2478–85.
11. Vieth R, Cole DE, Hawker GA, Trang HM, Rubin LA. Wintertime vitamin D
insufficiency is common in young Canadian women and their vitamin D intake does
not prevent it. Eur J Clin Nutr. 2001;55:1091–7.
12. Department of Human Health Services and Department of Agriculture
Dietary Guidelines for Americans. [monograph on the internet]. Washington DC:
U.S. Government Printing office; 2005. Available from: http://www.health.gov/
dietaryguidelines/dga2005/document/.
13. L’Abbe MR, Whiting SJ, Hanley DA. The Canadian health claims for
calcium vitamin D and osteoporosis. J Am Coll Nutr. 2004;23:303–8.
14. Calvo MS, Whiting SJ, Barton CN. Vitamin D fortification in the US and
Canada: current status and data needs. Am J Clin Nutr. 2004;80:1710S–6S.
15. Nakamura K, Nashimoto M, Hori Y, Yamamoto M. Serum 25-hydroxyvitamin D concentrations and related dietary factors in peri- and postmenopausal
Japanese women. Am J Clin Nutr. 2000;71:1161–5.
16. Attila PH, Lampi AM, Ronkainen R, Toivo J, Piironen V. Sterol and vitamin
D2 contents in some wild and cultivated mushrooms. Food Chem. 2002;76:293–8.
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