A-Z tentang Tulang, Vitamin D, dan Calcium
- Referensi :
- Vitamin D
- Mild Vitamin D Deficiency and Health Problems
- Dietary Sources of Vitamin D
- Can Sunshine During the Summer Months Provide Enough Vitamin D?
- Vitamin D3 vs. Vitamin D2
- Vitamin D in Fortified Foods
- Older People
- Bones, Calcium, and Vegan Diets: Why All the fuss?
- What Causes Osteoporosis?
- Calcium and Vitamin D
- Research on Vegans
- Conclusion on Calcium and Vegan Diets
- Calcium Tips
- Vitamin D RDA
While not found in many foods, vitamin D can be made by the action of sunlight (UV rays) on skin. If you get exposed to 10 to 15 minutes (20 minutes if dark-skinned, 30 minutes if elderly23, 24, 25) of midday sun (10 am to 2 pm), without sunscreen, on a day when sunburn is possible (i.e., not winter or cloudy), then you do not need any dietary vitamin D that day. On all other days, you should take 25 mcg (1,000 IU) of vitamin D2. This amount can only be obtained through vitamin D2-only supplements. Country Life makes one that is commonly available in natural foods stores in the U.S. and is fairly inexpensive. Deva makes one that can be ordered by mail.
These recommendations are higher than in the past. This is because of three things: recent research linking mild vitamin D deficiency with a host of health problems and showing that a high percentage of people have mild deficiency (a 2008 research paper called vitamin D deficiency “pandemic”), my encountering three vegans with some of these problems who were helped by vitamin D, and research indicating that the vegan version of vitamin D does not stay in your system for much longer than three days.
For people who are already somewhat deficient, 95 mcg (3,800 IU) to 125 mcg (5,000 IU) for 9 weeks has been shown to be required to get vitamin D levels back to ideal levels.28
Based on research showing that vegans who consumed less than 525 mg per day of calcium had higher bone fracture rates than people who consumed more than 525 mg per day, vegans should make sure they get a minimum of 525 mg of calcium per day. It would be best to get 700 mg per day for adults, and at least 1,000 mg for people age 13 to 18 when bones are developing. This can most easily be satisfied for most vegans by eating high-calcium greens on a daily basis and drinking a nondairy milk that is fortified with calcium.
For a quick summary on vitamin D compiled from an interview from leading vitamin D researcher Dr. Michael Holick, click here. But don’t forget to return to this page to read about calcium below!
Traditionally, vitamin D recommendations have been based on how much was required to prevent the most obvious diseases of vitamin D deficiency: rickets and osteomalacia. Recently, it has become evident that the amount of vitamin D required for optimal health is much greater. Sub-optimal vitamin D levels have been linked with fibromyalgia, rheumatoid arthritis, multiple sclerosis, upper respiratory tract infections, premenstrual syndrome, polycystic ovary disease, psoriasis, muscle weakness, lower back pain, diabetes, high blood pressure, and cancer.16 Bone pain is another symptom that sometimes clears up upon vitamin D supplementation. One study reported that the only side effect of vitamin D supplements was “improved mood,”16 indicating that perhaps vitamin D is linked to depression. This make sense given that many people often become depressed when they are deprived of sunshine for long periods.
The recent research described above indicates that the ideal level of vitamin D in the blood is 80 to 100 nmol/l of 25(OH)D.16 Most healthy people not getting sun require at least 1,000 IU of vitamin D to maintain such levels.16
It should be noted that some researchers do not believe 25(OH)D is the best marker of vitamin D status, and have argued that 1,25(OH)D (aka calcitriol) is better.31 Not all agree, and since most research has used 25(OH)D as the vitamin D measurement, it is what I’ll have to base recommendations on until that changes. It should also be noted that not all researchers agree that vitamin D intakes need to be significantly increased. In mid-August of 2009, an Institute of Medicine committee was to convene in order to discuss whether the recommended daily intake of vitamin D should be increased.
Most Americans get vitamin D through sunshine, fortified milk, and fortified margarine. The only significant, natural sources of vitamin D in foods are fatty fish (e.g. cod liver oil), eggs (if chickens have been fed vitamin D), and possibly some wild mushrooms.2 The vegan diet contains little, if any, vitamin D without fortified foods or supplements.
A 2009 report from Adventist Health Study-2 (AHS2) showed no difference in vitamin D levels between vegetarians and non-vegetarians among people aged 51 to 70 years. About 4% of the vegetarians were vegan.
Although vegetarians would normally have higher vitamin D intakes than vegans, the study showed that dietary vitamin D intake was a minor factor in someone’s vitamin D status at the levels that vitamin D is normally found in the diet. All groups got between 119 and 165 IU of vitamin D per day (the DRI is 400 IU) from their diet.
The good news from the AHS2 report was that vegetarians were no worse off than non-vegetarians. The bad news was that many of them were deficient. The table below shows the deficiency levels from the study.
|Vitamin D Status of Diet Groups in Adventist Health Sutdy-221|
|Vegetariana||Partial Vegb||Non-Veg||Vegetarian||Partial Veg||Non-Veg|
|Sufficient ( > 75 nmol/L)||51%||46%||56%||21%||16%||17%|
|Insufficient (50 – 74.9 nmol/L)||37%||37%||26%||63%||23%||28%|
|Deficient ( < 50 nmol/L)||12%||17%||18%||55%||61%||55%|
|aIncluded lacto-ovo-vegetarians and vegans.
bIncluded semivegetarians (ate meat and fish < 1 time/wk) and pescovegetarians (ate meat < 1 time/mo, and fish > 1 time/mo).
The variable causing the greatest difference in s25(OH)D concentrations was not diet but ethnicity. This is mostly due to the fact that people with dark skin need much longer amounts of time in the sun to produce adequate vitamin D.22
To start this discussion, it is important to remember that these days many of us go from our house, to our car, to our office building, back to our car, back to our house; and when we are in the sun, we are wearing sunscreen. You might not get as much sun as you think.
For many years, people thought that extra amounts of vitamin D made by the sun during the summer could be stored in the body and used during the winter. Probably due to modern lifestyles and the use of sunscreen, we are now finding that most people, whether vegan or not, do not sustain optimal levels throughout the winter, and many don’t even sustain them through the summer – especially in non-equatorial regions of the world.
A 2003 study by Heaney et al.7 indicates that male adults in good health, living in Nebraska, and starting with a healthy supply of vitamin D still need about 12 mcg (480 IU) per day of vitamin D during the winter to keep their stores from diminishing. And what may be even more important is how PTH levels changed over the course of the winter. (A high PTH level can be an indication of vitamin D deficiency; see more below.) PTH levels of the men changed in the following way:
|Vitamin D per day||PTH change|
|< 5 mcg (200 IU)||rose 6%|
|25 mcg (1,000 IU)||none|
|125 mcg (5,000 IU)||none|
|250 mcg (10,000 IU)||fell 24%|
The fact that 250 mcg per day of vitamin D caused PTH levels to drop indicates that these men may not have had ideal vitamin D levels even at the beginning of the winter.
A vitamin D intake of 250 mcg (10,000 IU) per day is a lot. The RDA for vitamin D is 5 mcg (200 IU) for people aged 1 to 50, and 10 mcg (400 IU) for people over 50. The current Upper Tolerable Limit for vitamin D is 50 mcg (2,000 IU) per day for adults. Heaney et al. state, “[T]he evidence available today indicates that a value of [50 mcg per day] for the tolerable limit level is too low. As already noted, the data presented here indicate an average daily need perhaps twice that much.”
A 2008 randomized, placebo-controlled, double-blind study on women aged 20 to 40 from Ireland, showed that 15 mcg (600 IU) per day for 22 weeks during the winter was not enough to prevent 25(OH)D levels from falling (75.9 to 69.0 nmol/L) or PTH levels from rising (38.4 to 43.0 ng/ml).27 A dose of 15 mcg (600 IU) was much better at mainting levels than 10 mcg (400 IU).
A 2009 experiment in Antarctica found that after 5 months of supplementation, the following vitamin D levels were achieved:
|Five Months of Vitamin D Supplemenation in Antactica (2009)26|
|Vitamin D per day||Serum 25(OH)D at Baseline
|Serum 25(OH)D at 5 Months
|50 mcg (2,000 IU)||45||71a|
|25 mcg (1,000 IU)||44||63a|
|10 mcg (400 IU)||44||57a|
|aSignificantly different from baseline.|
In a 2000 experiment, vegans in Finland were not able to maintain healthy levels of vitamin D or PTH during the winter.8 A follow-up study found an increase in lumbar spine density in 4 out of the 5 vegans who took 5 mcg (200 IU) per day of vitamin D2 for 11 months.3 (See below for information on vitamin D2 vs. D3.)
An article in USA Today, Your Health: Skin color matters in the vitamin D debate (updated 4/19/2009), quotes vitamin D researcher Michael Holick as saying:
“Though someone in Boston with pale skin can get adequate vitamin D by exposing their arms and legs to the sun for 10 to 15 minutes twice a week in the summer, someone with the darkest skin might need two hours of exposure each time[.]“
This was the most specific statement I could find by a vitamin D researcher on how much sun a dark-skinned person needs to produce adequate vitamin D. As Holick notes in the article, this much sun is impractical and could cause skin cancer. While dark-skinned people have lower rates of skin cancer than whites, they are more likely to get diagnosed past the time that the cancer can be cured. In fact, the American Academy of Dermatology recommends that people avoid the midday sun.
My view is that avoiding all UV rays probably does more harm than good and so I would recommend that dark-skinned people expose themselves to direct sun rays for 20 minutes per day (or take vitamin D supplements).
There are two types of vitamin D:
- Vitamin D3 – cholecalciferol; is derived from animals (usually from sheep’s wool or fish oil).
Vitamin D2 – ergocalciferol; vegan (usually obtained from yeast18); has vitamin D activity in humans.
Large, single doses of vitamin D2 do not last as long as large doses of D3. In a 2004 study by Armas et al.,17 subjects were given one dose of 50,000 IU of vitamin D2 or vitamin D3. Vitamin D2 was absorbed just as well as vitamin D3. However, after three days, blood levels of 25(OH)D started dropping rapidly in the subjects who were given vitamin D2, whereas those who received vitamin D3 sustained high levels for two weeks before dropping gradually. This indicates that vitamin D2 needs to be taken at least every three days to maintain 25(OH)D levels.
Trang et al.19 (1998) found that a daily dose of 4,000 IU of vitamin D3 for two weeks was 1.7 times more effective in raising 25(OH)D levels (increased 9.0 � 2 ng/ml) than 4,000 IU of vitamin D2 (increased 4.2 � 2 ng/ml). More recently, Holick et al18 (2007) found that a daily dose of 1,000 IU of vitamin D2 over 11 weeks increased 25(OH)D levels (from 16.9 to 26.8 ng/ml) the same as did vitamin D3 (from 19.6 to 28.9 ng/ml). It took 6 weeks for 25(OH)D levels to plateau on that regimen.
It should be noted that at the beginning of the 2007 study by Holick et al, 60% percent of the subjects were vitamin D deficient (25(OH)D < 20 ng/ml) and 87% were insufficient (25(OH)D < 30 ng/ml) even though 29% took a daily multivitamin that contained 400 IU vitamin D and 47% drank about 1.2 glasses of milk per day. The study was conducted in Boston and started in February.
- The Daily Value for vitamin D is 10 mcg (400 IU). Therefore, if a food label says it has 25% of the daily value, it means it has 2.5 mcg (100 IU) per serving.
- Vitamin D fortified soy, almond, or rice milk normally has 2-3 mcg (80-120 IU) per Cup
- Country Life, a supplement company whose products are sold in many natural food stores, has a vitamin D2 (ergocalciferol) supplement. It is fairly inexpensive.
As mentioned in the recommendation section above, elderly people need 30 minutes a day of direct sunlight in order to produce adequate vitamin D.23, 24, 25
A 2009 study from Ireland showed that people aged 64 years or older needed 15 mcg (600 IU) per day to bring vitamin D levels from an average of 55 nmol/L to 74 nmol/L.22 The researchers estimated that it would take about 40 mcg (1600 IU) per day to raise 97.5% of the participants’ vitamin D levels to 80 nmol/L.
There is not enough evidence to know that there is much of a difference between 74 and 80 nmol/L. For this reason, the recommendation of 25 mcg (1,000 IU) should suffice for people aged 64 and older.
Americans are constantly being urged to consume more calcium in order to prevent osteoporosis. It is practically impossible to meet the recommendations without large amounts of cows’ milk, calcium-fortified foods, or supplements.
Enter vegan diets. Because vegans do not eat dairy products, their calcium intakes tend to be low. The Dietitian’s Guide to Vegetarian Diets (2004) lists 45 studies that have surveyed vegetarians’ calcium intakes in Appendix G. The daily calcium intakes in these studies tended to be about:
- vegans: 500 – 600 mg
- lacto-ovo vegetarians: 800 – 900 mg
- non-vegetarians: 1,000 mg
Only one study included supplements. In it, daily calcium intakes were: 840 mg (vegan males), 720 mg (nonvegetarian males), 710 mg (vegan females), and 855 mg (nonvegetarian females).
|1 – 3||500||2500|
|4 – 8||800||2500|
|9 – 18||1300||2500|
|19 – 50||1000||2500|
|*Do not exceed the upper limit.|
Thus, vegans tend to be quite lower than lacto-ovo vegetarians, nonvegetarians, and the U.S. recommendations. Traditionally, the vegan community has had a response as to why our lower calcium intakes do not harm us:
- Osteoporosis is a disease of calcium loss from the bones, not a lack of calcium intake in the diet. Calcium loss from the bones is due to eating too much protein, especially animal protein, which increases calcium excretion in the urine. Not only does dairy not protect against osteoporosis, it actually contributes to it. Therefore, calcium intake isn’t very important for protecting against osteoporosis and vegans are protected due to the lack of animal protein in our diet.
In the last twenty years or so, there has been some evidence to support this theory and some evidence that contradicts it. Since the late 1990s, Vegan Outreach has cautioned vegans that the jury was still out on these issues and that vegans should try to meet the U.S. recommended intakes for calcium. Recently, evidence has been mounting.
Genetics may play a strong role in osteoporosis. Possibly related, estrogen levels in women play a role. Among factors that can be controlled by lifestyle and diet, there has traditionally been evidence for the following:
- Weight-bearing exercise throughout one’s lifetime.
- Higher body weight (not recommended because of other diseases).
- Adequate intake of calcium, vitamin D, vitamin K, phosphate, potassium, magnesium, and boron.
- High sodium and caffeine intake.
- Excessive amounts of, or too little, protein.
- Excessive vitamin A (retinol, not beta-carotene).
Let’s look more closely at some of these dietary factors: calcium and vitamin D, and protein.
Calcium is important for bones because it is a major component of bones, which are constantly being broken down and built back up. Vitamin D regulates calcium absorption and excretion, especially when calcium intake is low.
Calcium is a component of bones, but is more immediately needed in the blood to keep muscles, such as the heart, contracting efficiently. The body preserves blood calcium levels at the expense of bone calcium.
When calcium levels in the blood drop, parathyroid hormone (PTH) is released. PTH causes calcium to be released from the bones, thus raising the low calcium levels in the blood. Osteoporosis may result from chronically high levels of PTH.
Vitamin D is the building block of the hormone calcitriol which works synergistically with PTH. Vitamin D is modified by the liver to become 25-hydroxyvitamin D (also known as 25(OH)D). 25(0H)D is then modified in the kidneys to become calcitriol. This conversion is somewhat regulated by PTH levels.4
Calcitriol increases absorption of calcium and phosphorus (another major component of bones) from the intestines and decreases their excretion in the urine. In so doing, calcium levels in the blood rise and PTH levels drop.
Calcitriol has many other functions. How the body regulates the processes of conversion of vitamin D into calcitriol and the resulting net increase or decrease of bone calcium are not fully known.
What is more important, calcium or vitamin D?
Most Americans seem to be getting enough calcium, whereas vitamin D is a bigger concern. A 2003 report from the Nurses Health Study showed vitamin D to be more important than calcium intake for preventing hip fractures in postmenopausal women.5 In 2007, a meta-analysis of prospective studies and randomized controlled trials found that calcium intake and calcium supplements were not associated with a lower risk for hip fractures.15
In addition to people being more likely to be deficient in vitamin D than calcium, vitamin D also appears to be more important for bones in conjunction with lower calcium intakes (typical in most vegan diets) than in diets that have large amounts of calcium.5
As mentioned above, there is a theory that protein, especially through the sulfur-containing amino acids, increase the renal acid load, causing calcium to be excreted in the urine. Sulfur-containing amino acids are more prevalent in animal products, although they are also found in high amounts in many grains. The counter to this argument is that protein also causes an increase of calcium absorption from the gut which counteracts the loss of calcium in the urine.29
An interesting article on the subject is Dietary Protein and Calcium: Are They Friends or Foes? from the Summer 2004 issue of The Soy Connection. The article concludes:
Recent evidence has demonstrated that increased intake of common proteins does not necessarily affect bone health adversely. The composition of the protein source as well as co-existing factors in the total diet determines the renal acid load. In healthy individuals consuming high protein foods, in the context of typical mixed diets, the renal acid load does not seem to reach a “threshold” that affects calcium homeostasis.
I don’t have any major conclusions on the protein-osteoporosis connection other than to say that the research below indicates that in typical free-living populations of vegans, lacto-ovo vegetarians, and non-vegetarians, it is a secondary issue.
Not a whole lot is known about the bone status of vegans. Some small, cross-sectional studies have shown vegans to have the same or slightly worse bone mineral density as non-vegans.9, 10, 11, 12, 13, 30 These studies were done on vegans who might not have gotten much vitamin D or might not have made an effort to get the recommended amount of calcium in their diet.
In 2009, researchers from Vietnam and Australia did a meta-analysis looking at the bone mineral density of vegetarians.32 They concluded that “[T]here is a modest effect of vegetarian diets, particularly a vegan diet, on [bone mineral density], but the effect size is unlikely to result in a clinically important increase in fracture risk.”
In February of 2007, the first study looking at vegan bone fracture rates was released.14 The EPIC-Oxford study recruited 57,000 participants, including over 1,000 vegans and almost 10,000 lacto-ovo vegetarians (LOV), from 1993 to 2000. They were asked to fill out a questionnaire to measure what they ate. About 5 years after entering the study, they were sent a follow-up questionnaire asking if they had suffered any bone fractures.
After adjusting for age alone, the vegans had a 37% higher fracture rate than meat-eaters. After adjusting for age, smoking, alcohol consumption, body mass, physical activity, marital status, and births and hormone replacement therapy for women, the vegans still had a 30% higher fracture rate. (Meat-eaters, fish-eaters, and LOV fracture rates did not differ in any of the analyses performed.)
Yet, there was some good news from this study. When the results were adjusted for calcium intake, the vegans no longer had a higher fracture rate. And among the subjects who got 525 mg of calcium a day (only 55% of the vegans compared to about 95% of the other diet groups), vegans had the same fracture rates as the other diet groups.
Does this mean lower calcium intakes are the cause of the fractures? It could be that people who ate more calcium also ate more or less protein or get more vitamin D. The authors noted that fracture rates did not correlate with protein or vitamin D intake among the people in this study. A separate analysis of EPIC-Oxford20 showed that calcium intake was related to an increased fracture risk in women (relative risk 1.75 (1.33-2.29) for < 525 mg/day compared to > 1200mgday), but not in men.
For now, we should assume that calcium is what the vegans with higher fracture rates were lacking.
The US recommended intake for calcium is 1,000 mg for most adults. The UK’s recommended intake is 700 mg. Given the results of the EPIC-Oxford study on vegan fracture rates, it is prudent to get 700 mg per day. For the average vegan, this probably means drinking one glass of fortified soymilk each day in addition to an otherwise balanced diet.
The soymilk brand Silk has a type of soymilk with the following breakdown per 8 oz. glass:
- 30% of the Daily Value for calcium (300 mg)
- 30% of the Daily Value for vitamin D (3 mcg / 120 IU)
- 50% of the Daily Value for vitamin B12 (3 mcg)
|Dietary Reference Intake (DRI) for Vitamin D|
|Age (yrs)||DRI mcg(b) (IU)||Upper LimitA
|< 1||5 (200)||25 (1000)|
|1-50 yrs old (incl. pregnancy)||5 (200)||50 (2000)|
|51-70 yrs||10 (400)||50 (2000)|
|Over 70||15 (600)||50 (2000)|
|A – Do not exceed the upper limit.
B – mcg = microgram = µg
1. Wardlaw GM. Perspectives in Nutrition, 4(th) Ed. Boston, MA: McGraw-Hill; 1999.
2. Vitamin D. Vegetarian Nutrition & Health Letter Loma Linda University School of Public Health. 2001;4(5):1-5.
3. Outila TA, Lamberg-Allardt CJ. Ergocalciferol supplementation may positively affect lumbar spine bone mineral density of vegans. J Am Diet Assoc 2000 Jun;100(6):629.
4. Groff J, Gropper S. Advanced Nutrition and Human Metabolism, 3rd ed. Wadsworth: 2000.
5. Feskanich D, Willett WC, Colditz GA. Calcium, vitamin D, milk consumption, and hip fractures: a prospective study among postmenopausal women. Am J Clin Nutr. 2003 Feb;77(2):504-11.
6. Statistically significant means that the finding had at least a 95% likelihood of not being due to random chance. At least 95% is the level necessary to be considered a true association.
7. Heaney RP, Davies KM, Chen TC, Holick MF, Barger-Lux MJ. Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol. Am J Clin Nutr. 2003 Jan;77(1):204-10.
8. Outila TA, Karkkainen MU, Seppanen RH, Lamberg-Allardt CJ. Dietary intake of vitamin D in premenopausal, healthy vegans was insufficient to maintain concentrations of serum 25-hydroxyvitamin D and intact parathyroid hormone within normal ranges during the winter in Finland. J Am Diet Assoc. 2000 Apr;100(4):434-41.
9. Barr SI, Prior JC, Janelle KC, Lentle BC. Spinal bone mineral density in premenopausal vegetarian and nonvegetarian women: cross-sectional and prospective comparisons. J Am Diet Assoc 1998 Jul;98(7):760-5.
10. Hu JF, Zhao XH, Jia JB, Parpia B, Campbell TC. Dietary calcium and bone density among middle-aged and elderly women in China. Am J Clin Nutr 1993 Aug;58(2):219-27.
11. Janelle KC, Barr SI. Nutrient intakes and eating behavior scores of vegetarian and nonvegetarian women. J Am Diet Assoc 1995 Feb;95(2):180-6, 189, quiz 187-8.
12. Lau EM, Kwok T, Woo J, Ho SC. Bone mineral density in Chinese elderly female vegetarians, vegans, lacto-vegetarians and omnivores. Eur J Clin Nutr 1998 Jan;52(1):60-4.
13. Parsons TJ, van Dusseldorp M, van der Vliet M, van de Werken K, Schaafsma G, van Staveren WA. Reduced bone mass in Dutch adolescents fed a macrobiotic diet in early life. J Bone Miner Res 1997 Sep;12(9):1486-94.
14. Appleby P, Roddam A, Allen N, Key T. Comparative fracture risk in vegetarians and nonvegetarians in EPIC-Oxford. Eur J Clin Nutr. 2007 Dec;61(12):1400-6. Epub 2007 Feb 7.
15. Bischoff-Ferrari HA, Dawson-Hughes B, Baron JA, Burckhardt P, Li R, Spiegelman D, Specker B, Orav JE, Wong JB, Staehelin HB, O’Reilly E, Kiel DP, and Willett WC. Calcium intake and hip fracture risk in men and women: a meta-analysis of prospective cohort studies and randomized controlled trials. Am J of Clin Nutr. 2007 Dec;86( 6): 1780-1790.
16. Schwalfenberg G. Not enough vitamin D: health consequences for Canadians. Can Fam Physician. 2007 May;53(5):841-54.
17. Armas LA, Hollis BW, Heaney RP. Vitamin D2 is much less effective than vitamin D3 in humans. J Clin Endocrinol Metab. 2004 Nov;89(11):5387-91.
18. Holick MF, Biancuzzo RM, Chen TC, Klein EK, Young A, Bibuld D, Reitz R, Salameh W, Ameri A, Tannenbaum AD. Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D. 2008 Mar;93(3):677-81. Epub 2007 Dec 18.
19. Trang HM, Cole DE, Rubin LA, Pierratos A, Siu S, Vieth R. Evidence that vitamin D3 increases serum 25-hydroxyvitamin D more efficiently than does vitamin D2. Am J Clin Nutr. 1998 Oct;68(4):854-8. (Abstract)
20. Key TJ, Appleby PN, Spencer EA, Roddam AW, Neale RE, Allen NE. Calcium, diet and fracture risk: a prospective study of 1898 incident fractures among 34 696 British women and men. Public Health Nutr. 2007 Nov;10(11):1314-20.
21. Chan J, Jaceldo-Siegl K, Fraser GE. Serum 25-hydroxyvitamin D status of vegetarians, partial vegetarians, and nonvegetarians: the Adventist Health Study-2. Am J Clin Nutr. 2009 May;89(5):1686S-1692S. Epub 2009 Apr 1.
22. Cashman KD, Wallace JM, Horigan G, Hill TR, Barnes MS, Lucey AJ, Bonham MP, Taylor N, Duffy EM, Seamans K, Muldowney S, Fitzgerald AP, Flynn A, Strain JJ, Kiely M. Estimation of the dietary requirement for vitamin D in free-living adults >=64 y of age. Am J Clin Nutr. 2009 May;89(5):1366-74.
23. Reid IR, Gallagher DJ, Bosworth J. Prophylaxis against vitamin D deficiency in the elderly by regular sunlight exposure. Age Ageing. 1986 Jan;15(1):35-40. (Abstract only.)
24. Toss G, Andersson R, Diffey BL, Fall PA, Larko O, Larsson L. Oral vitamin D and ultraviolet radiation for the prevention of vitamin D deficiency in the elderly. Acta Med Scand. 1982;212(3):157-61. (Abstract only.)
25. Gloth FM 3rd, Gundberg CM, Hollis BW, Haddad JG Jr, Tobin JD. Vitamin D deficiency in homebound elderly persons. JAMA. 1995 Dec 6;274(21):1683-6. (Abstract only.)
26. Smith SM, Gardner KK, Locke J, Zwart SR. Vitamin D supplementation during Antarctic winter. Am J Clin Nutr. 2009 Apr;89(4):1092-8. Epub 2009 Feb 18.
27. Cashman KD, Hill TR, Lucey AJ, Taylor N, Seamans KM, Muldowney S, Fitzgerald AP, Flynn A, Barnes MS, Horigan G, Bonham MP, Duffy EM, Strain JJ, Wallace JM, Kiely M. Estimation of the dietary requirement for vitamin D in healthy adults. Am J Clin Nutr. 2008 Dec;88(6):1535-42.
28. 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.
29. Kerstetter JE, O’Brien KO, Insogna KL. Dietary protein, calcium metabolism, and skeletal homeostasis revisited. Am J Clin Nutr. 2003 Sep;78(3 Suppl):584S-592S. Review.
30. Ho-Pham LT, Nguyen PL, Le TT, Doan TA, Tran NT, Le TA, Nguyen TV. Veganism, bone mineral density, and body composition: a study in Buddhist nuns. Osteoporos Int. 2009 Apr 7. [Epub ahead of print]
31. Marshall TG. Author’s reply to correspondence from Drs Grant, Garland, and Boucher. BioEssays 2008 30:510-511.
32. Ho-Pham LT, Nguyen ND, Nguyen TV. Effect of vegetarian diets on bone mineral density: a Bayesian meta-analysis. Am J Clin Nutr. 2009 Jul 1. [Epub ahead of print] PubMed PMID: 19571226.
Dawson-Hughes B. Racial/ethnic considerations in making recommendations for vitamin D for adult and elderly men and women. Am J Clin Nutr. 2004 Dec;80(6 Suppl):1763S-6S.
Houghton LA, Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. Am J Clin Nutr. 2006 Oct;84(4):694-7.
This paper argued that vitamin D2 should not be used for fortification or supplementation. The authors state:
“Vitamin D2, if given in high enough doses, prevents infantile rickets and is capable of healing adult osteomalacia. However, the inefficiency of vitamin D2 compared with vitamin D3, on a per mole basis, at increasing 25(OH)D is now well documented, and no successful clinical trials to date have shown that vitamin D2 prevents fractures (19 – 21, 47).”
But references 19-21 were not studies looking at whether D2 prevents fractures. They include references 19 (Trang et al.) and 17 (Aramas, et al.) cited above, as well as this study:
Mastaglia SR, Mautalen CA, Parisi MS, Oliveri B. Vitamin D2 dose required to rapidly increase 25OHD levels in osteoporotic women. Eur J Clin Nutr. 2006 May;60(5):681-7.
Their final citation was a book on vitamin D from 1985, and though I’m not certain, I’m skeptical that it includes any studies comparing D2 and D3′s affects on bone fractures:
Norman AW, Schaefer K, Grigoleit H-G, Vaamonde J, eds. Vitamin D, chemical, biochemical and clinical update. Berlin, Germany: Walter deGruyter, 1985;3-12