Vitamin D is both a vitamin and a hormone. It's a vitamin because your body cannot absorb calcium without it; it's a hormone because your body manufactures it in response to your skin's exposure to sunlight.
There are two major forms of vitamin D, and both have the word calciferolin their names. In Latin, calciferol means "calcium carrier." Vitamin D 3 (cholecalciferol) is made by the body and is found in some foods. Vitamin D 2 (ergocalciferol) is the form most often added to milk and other foods, and the form you're most likely to use as a supplement.
Strong evidence tells us that the combination of vitamin D and calcium supplements can be quite helpful for preventing and treating osteoporosis. Vitamin D is experiencing renewed attention for many potential health benefits, and research has not yet caught up with clinical evidence for its usefulness in preventing and treating a number of conditions. This is part of the reason why many potential uses of vitamin D currently have little supporting research evidence.
There is vitamin D toxicity that can result from over exposure to vitamin D. Taking too much in the form of a supplement or over-exposure to the sun can cause vitamin D toxicity (not to mention a sunburn).
When taken at recommended dosages, vitamin D appears to be safe. However, when used at considerable excess, vitamin D can build up in the body and cause toxic symptoms. At an intake level of about 40,000 IU daily (about 100 times the recommended daily intake) vitamin D can cause dangerous elevations in blood calcium levels. 1 Doses five times higher than this were consumed by a few individuals due to a manufacturing error; the resulting toxicity was severe and may have caused death in one individual. 2 However, short of these vastly excessive dosages, it is not clear at what level vitamin D becomes toxic.
According to updated recommendations from the Institute of Medicine,44 the safe upper limits (UL) for vitamin D daily intake are as follows:
There is no disagreement that people with sarcoidosis or hyperparathyroidism should never take vitamin D without first consulting a physician.
Taking vitamin D and calcium supplements might interfere with some of the effects of drugs in the calcium-channel blocker family. 3 It is very important that you consult your physician before trying this combination.
The combination of calcium, vitamin D, and thiazide diuretics could potentially lead to excessive calcium levels in the body. 4 If you are taking thiazide diuretics, you should consult with a physician about the right doses of vitamin D and calcium for you.
Without question, if you are concerned about osteoporosis , you should take calcium and vitamin D. The combination appears to help prevent bone loss. 28,29 1 This is true even if you are taking other treatments for osteoporosis; after all, you can't build bone without calcium, and you can't properly absorb and utilize calcium without adequate intake of vitamin D. Interestingly, vitamin D may also help prevent the falls that lead to osteoporotic fractures .
Other uses of vitamin D are less well documented.
Some evidence suggests that getting adequate vitamin D may help prevent cancer of the breast, colon, pancreas, prostate, and skin, but the research on this question has yielded mixed results. 30-49,90,105 2 One study suggests that combined use of calcium plus vitamin D, but not either supplement separately, can help reduce risk of colon cancer. 84 3 However, an extremely large study involving over 36,000 post-menopausal women found that supplementing the diet with 1,000 mg of calcium plus 400 IU of vitamin D daily did not lower the risk of breast cancer over a period of 7 years. 106 4 Based on the results of this placebo-controlled study, there does not appear to be a connection between vitamin D and breast cancer risk.
Weak evidence hints that adequate vitamin D intake might reduce the risk of hypertension 50-53,98 5 and diabetes . 74-76 6 7 A very large randomized, placebo-controlled trial of over 36,000 postmenopausal women found daily supplementation with 1,000 mg of calcium plus 400 IU of vitamin D did not reduce or prevent hypertension during 7 years of follow-up. These results are possibly limited by non-study calcium use. 107 8 One preliminary study suggests that supplementation with vitamin D and calcium may be helpful for women with polycystic ovary syndrome. 54 9 A meta-analysis (formal statistical review) of published studies found some evidence that use of vitamin D at recommended levels may reduce overall mortality. 102 10 This article suggested, but did not attempt to establish, just how vitamin D might accomplish this.
Vitamin D is sometimes mentioned as a treatment for psoriasis . However, this recommendation is based on Danish studies using calcipotriol, a variation of vitamin D 3 that is used externally (applied to the skin). 55 11 Calcipotriol does not affect your body's absorption of calcium, so it is a very different substance from the vitamin D you can purchase at a store.
It has been suggested that since vitamin D levels in the body drop in the wintertime, vitamin D supplements might be helpful for seasonal affective disorder ("winter blues"). A small double-blind, placebo-controlled trial conducted during winter on 44 people found that vitamin D supplements produced improvements in various measures of mood. 79 12 However, a double-blind, placebo-controlled study of 2,217 women over 70 failed to find benefit. 91 13 It has been hypothesized that light therapy (used successfully for SAD) works by raising vitamin D levels, but there is some evidence that this is not the case. 92 14 Vitamin D supplements also do notappear to help enhance growth in healthy children. 80 15
Individuals with severe osteoporosis often have low levels of vitamin D. 56,58 1 Supplementing with vitamin D alone is probably no more than minimally helpful, at best, 59,60,81,99,100 2 but the combination of calcium and vitamin D is probably more effective. (See the [Calcium][2] article for more information.)
Interestingly, vitamin D may offer another benefit for osteoporosis in seniors: most (though not all) studies have found that vitamin D supplementation improves balance in seniors (especially female seniors) and reduces risk of falling. 77,78,82,83,85-87,93-97,99,103,104 3 Since the most common adverse consequence of osteoporosis is a fracture due to a fall, this could be a meaningful benefit. Why vitamin D should offer this benefit, however, remains a mystery.
Supplementation with vitamin D plus calcium may aid healing aftera fracture has occurred. ^[6] 4
Getting adequate vitamin D may help prevent the development of hypertension.45-49
As with vitamin A , dosages of vitamin D are often expressed in terms of international units (IU) rather than milligrams. The Institute of Medicine's updated (November 2010) recommendations for daily intake of vitamin D44 are as follows. The first number is the Recommended Dietary Allowance (RDA), and the second number is the Upper Intake Level (UL), the highest daily dose that is considered safe:
These recommendations were updated because growing evidence suggests that prior recommendations may have been too low. In a study of military personnel in submarines, use of 400 IU of vitamin D daily was inadequate to maintain bone health, while six days of sun exposure proved capable of supplying enough vitamin D for 49 sunless days. 89 1 In addition, a study of veiled Islamic women living in Denmark found that 600 IU of vitamin D daily was insufficient to raise vitamin D levels in the blood to normal levels. 1 2 The authors of this study recommend that sun-deprived individuals should receive 1,000 IU of vitamin D daily.
There is very little vitamin D found naturally in the foods we eat (the best sources are coldwater fish). In many countries, vitamin D is added to milk and other foods like breakfast cereals and margarine, contributing to our daily intake.
As indicated by the study of submarine personnel noted above, by far the best source of vitamin D is sunlight. However, current recommendations which stress sun avoidance and the use of sunblock may have the unintended effect of increasing the prevalence of vitamin D deficiency. Severe vitamin D deficiency was common in England in the 1800s due to coal smoke obscuring the sun. During that time, cod liver oil, which is high in vitamin D, became popular as a supplement for children to help prevent rickets. (Rickets is a disease caused by vitamin D deficiency in which developing bones soften and curve because they aren't receiving enough calcium.)
Vitamin D deficiency is known to occur today in the elderly (who often receive less sun exposure) as well as in people who live in northern latitudes and don't drink vitamin D-enriched milk. 5,7 3 The consequences of this deficiency may be increased risk of hypertension , osteoporosis , and several forms of cancer . 8 4 Additionally, phenytoin (Dilantin) , primidone (Mysoline) , and phenobarbital for seizures; corticosteroids ; cimetidine (Tagamet) for ulcers; the blood-thinning drug heparin ; and the antituberculosis drugs isoniazid (INH) and rifampin may interfere with vitamin D absorption or activity. 9-27 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
As with vitamin A , dosages of vitamin D are often expressed in terms of international units (IU) rather than milligrams. The Institute of Medicine's updated (November 2010) recommendations for daily intake of vitamin D44 are as follows. The first number is the Recommended Dietary Allowance (RDA), and the second number is the Upper Intake Level (UL), the highest daily dose that is considered safe:
These recommendations were updated because growing evidence suggests that prior recommendations may have been too low. In a study of military personnel in submarines, use of 400 IU of vitamin D daily was inadequate to maintain bone health, while six days of sun exposure proved capable of supplying enough vitamin D for 49 sunless days. 1 In addition, a study of veiled Islamic women living in Denmark found that 600 IU of vitamin D daily was insufficient to raise vitamin D levels in the blood to normal levels. 2 The authors of this study recommend that sun-deprived individuals should receive 1,000 IU of vitamin D daily.
There is very little vitamin D found naturally in the foods we eat (the best sources are coldwater fish). In many countries, vitamin D is added to milk and other foods like breakfast cereals and margarine, contributing to our daily intake.
As indicated by the study of submarine personnel noted above, by far the best source of vitamin D is sunlight. However, current recommendations which stress sun avoidance and the use of sunblock may have the unintended effect of increasing the prevalence of vitamin D deficiency. Severe vitamin D deficiency was common in England in the 1800s due to coal smoke obscuring the sun. During that time, cod liver oil, which is high in vitamin D, became popular as a supplement for children to help prevent rickets. (Rickets is a disease caused by vitamin D deficiency in which developing bones soften and curve because they aren't receiving enough calcium.)
Vitamin D deficiency is known to occur today in the elderly (who often receive less sun exposure) as well as in people who live in northern latitudes and don't drink vitamin D-enriched milk. 3 The consequences of this deficiency may be increased risk of hypertension , osteoporosis , and several forms of cancer . 4 Additionally, phenytoin (Dilantin) , primidone (Mysoline) , and phenobarbital for seizures; corticosteroids ; cimetidine (Tagamet) for ulcers; the blood-thinning drug heparin ; and the antituberculosis drugs isoniazid (INH) and rifampin may interfere with vitamin D absorption or activity. 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Individuals with severe osteoporosis often have low levels of vitamin D. 1 Supplementing with vitamin D alone is probably no more than minimally helpful, at best, 2 but the combination of calcium and vitamin D is probably more effective. (See the Calcium article for more information.)
Interestingly, vitamin D may offer another benefit for osteoporosis in seniors: most (though not all) studies have found that vitamin D supplementation improves balance in seniors (especially female seniors) and reduces risk of falling. 3 Since the most common adverse consequence of osteoporosis is a fracture due to a fall, this could be a meaningful benefit. Why vitamin D should offer this benefit, however, remains a mystery.
Supplementation with vitamin D plus calcium may aid healing aftera fracture has occurred. 4
Getting adequate vitamin D may help prevent the development of hypertension.45-49
Without question, if you are concerned about osteoporosis , you should take calcium and vitamin D. The combination appears to help prevent bone loss. 1 This is true even if you are taking other treatments for osteoporosis; after all, you can't build bone without calcium, and you can't properly absorb and utilize calcium without adequate intake of vitamin D. Interestingly, vitamin D may also help prevent the falls that lead to osteoporotic fractures .
Other uses of vitamin D are less well documented.
Some evidence suggests that getting adequate vitamin D may help prevent cancer of the breast, colon, pancreas, prostate, and skin, but the research on this question has yielded mixed results. 2 One study suggests that combined use of calcium plus vitamin D, but not either supplement separately, can help reduce risk of colon cancer. 3 However, an extremely large study involving over 36,000 post-menopausal women found that supplementing the diet with 1,000 mg of calcium plus 400 IU of vitamin D daily did not lower the risk of breast cancer over a period of 7 years. 4 Based on the results of this placebo-controlled study, there does not appear to be a connection between vitamin D and breast cancer risk.
Weak evidence hints that adequate vitamin D intake might reduce the risk of hypertension 5 and diabetes . 6 7 A very large randomized, placebo-controlled trial of over 36,000 postmenopausal women found daily supplementation with 1,000 mg of calcium plus 400 IU of vitamin D did not reduce or prevent hypertension during 7 years of follow-up. These results are possibly limited by non-study calcium use. 8 One preliminary study suggests that supplementation with vitamin D and calcium may be helpful for women with polycystic ovary syndrome. 9 A meta-analysis (formal statistical review) of published studies found some evidence that use of vitamin D at recommended levels may reduce overall mortality. 10 This article suggested, but did not attempt to establish, just how vitamin D might accomplish this.
Vitamin D is sometimes mentioned as a treatment for psoriasis . However, this recommendation is based on Danish studies using calcipotriol, a variation of vitamin D 3 that is used externally (applied to the skin). 11 Calcipotriol does not affect your body's absorption of calcium, so it is a very different substance from the vitamin D you can purchase at a store.
It has been suggested that since vitamin D levels in the body drop in the wintertime, vitamin D supplements might be helpful for seasonal affective disorder ("winter blues"). A small double-blind, placebo-controlled trial conducted during winter on 44 people found that vitamin D supplements produced improvements in various measures of mood. 12 However, a double-blind, placebo-controlled study of 2,217 women over 70 failed to find benefit. 13 It has been hypothesized that light therapy (used successfully for SAD) works by raising vitamin D levels, but there is some evidence that this is not the case. 14 Vitamin D supplements also do notappear to help enhance growth in healthy children. 15
Vitamin D is a form of fat-soluble vitamins found naturally in plants, fish, and dairy products. Sunlight can help promote the synthesis of Vitamin D3 in our skin. There are two m, and the form both a vitamin and a hormone. It's a vitamin because your body cannot absorb calcium without it; it's a hormone because your body manufactures it in response to your skin's exposure to sunlight.
There are two major forms of vitamin D, and both have the word calciferolin their names. In Latin, calciferol means "calcium carrier." Vitamin D 3 (cholecalciferol) is made by the body and is found in some foods. Vitamin D 2 (ergocalciferol) is the form most often added to milk and other foods, and the form you're most likely to use as a supplement.
Strong evidence tells us that the combination of vitamin D and calcium supplements can be quite helpful for preventing and treating osteoporosis. Vitamin D is experiencing renewed attention for many potential health benefits, and research has not yet caught up with clinical evidence for its usefulness in preventing and treating a number of conditions. This is part of the reason why many potential uses of vitamin D currently have little supporting research evidence.
As with vitamin A , dosages of vitamin D are often expressed in terms of international units (IU) rather than milligrams. The Institute of Medicine's updated (November 2010) recommendations for daily intake of vitamin D44 are as follows. The first number is the Recommended Dietary Allowance (RDA), and the second number is the Upper Intake Level (UL), the highest daily dose that is considered safe:
These recommendations were updated because growing evidence suggests that prior recommendations may have been too low. In a study of military personnel in submarines, use of 400 IU of vitamin D daily was inadequate to maintain bone health, while six days of sun exposure proved capable of supplying enough vitamin D for 49 sunless days. 1 In addition, a study of veiled Islamic women living in Denmark found that 600 IU of vitamin D daily was insufficient to raise vitamin D levels in the blood to normal levels. 2 The authors of this study recommend that sun-deprived individuals should receive 1,000 IU of vitamin D daily.
There is very little vitamin D found naturally in the foods we eat (the best sources are coldwater fish). In many countries, vitamin D is added to milk and other foods like breakfast cereals and margarine, contributing to our daily intake.
As indicated by the study of submarine personnel noted above, by far the best source of vitamin D is sunlight. However, current recommendations which stress sun avoidance and the use of sunblock may have the unintended effect of increasing the prevalence of vitamin D deficiency. Severe vitamin D deficiency was common in England in the 1800s due to coal smoke obscuring the sun. During that time, cod liver oil, which is high in vitamin D, became popular as a supplement for children to help prevent rickets. (Rickets is a disease caused by vitamin D deficiency in which developing bones soften and curve because they aren't receiving enough calcium.)
Vitamin D deficiency is known to occur today in the elderly (who often receive less sun exposure) as well as in people who live in northern latitudes and don't drink vitamin D-enriched milk. 3 The consequences of this deficiency may be increased risk of hypertension , osteoporosis , and several forms of cancer . 4 Additionally, phenytoin (Dilantin) , primidone (Mysoline) , and phenobarbital for seizures; corticosteroids ; cimetidine (Tagamet) for ulcers; the blood-thinning drug heparin ; and the antituberculosis drugs isoniazid (INH) and rifampin may interfere with vitamin D absorption or activity. 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Without question, if you are concerned about osteoporosis , you should take calcium and vitamin D. The combination appears to help prevent bone loss. 1 This is true even if you are taking other treatments for osteoporosis; after all, you can't build bone without calcium, and you can't properly absorb and utilize calcium without adequate intake of vitamin D. Interestingly, vitamin D may also help prevent the falls that lead to osteoporotic fractures .
Other uses of vitamin D are less well documented.
Some evidence suggests that getting adequate vitamin D may help prevent cancer of the breast, colon, pancreas, prostate, and skin, but the research on this question has yielded mixed results. 2 One study suggests that combined use of calcium plus vitamin D, but not either supplement separately, can help reduce risk of colon cancer. 3 However, an extremely large study involving over 36,000 post-menopausal women found that supplementing the diet with 1,000 mg of calcium plus 400 IU of vitamin D daily did not lower the risk of breast cancer over a period of 7 years. 4 Based on the results of this placebo-controlled study, there does not appear to be a connection between vitamin D and breast cancer risk.
Weak evidence hints that adequate vitamin D intake might reduce the risk of hypertension 5 and diabetes . 6 7 A very large randomized, placebo-controlled trial of over 36,000 postmenopausal women found daily supplementation with 1,000 mg of calcium plus 400 IU of vitamin D did not reduce or prevent hypertension during 7 years of follow-up. These results are possibly limited by non-study calcium use. 8 One preliminary study suggests that supplementation with vitamin D and calcium may be helpful for women with polycystic ovary syndrome. 9 A meta-analysis (formal statistical review) of published studies found some evidence that use of vitamin D at recommended levels may reduce overall mortality. 10 This article suggested, but did not attempt to establish, just how vitamin D might accomplish this.
Vitamin D is sometimes mentioned as a treatment for psoriasis . However, this recommendation is based on Danish studies using calcipotriol, a variation of vitamin D 3 that is used externally (applied to the skin). 11 Calcipotriol does not affect your body's absorption of calcium, so it is a very different substance from the vitamin D you can purchase at a store.
It has been suggested that since vitamin D levels in the body drop in the wintertime, vitamin D supplements might be helpful for seasonal affective disorder ("winter blues"). A small double-blind, placebo-controlled trial conducted during winter on 44 people found that vitamin D supplements produced improvements in various measures of mood. 12 However, a double-blind, placebo-controlled study of 2,217 women over 70 failed to find benefit. 13 It has been hypothesized that light therapy (used successfully for SAD) works by raising vitamin D levels, but there is some evidence that this is not the case. 14 Vitamin D supplements also do notappear to help enhance growth in healthy children. 15
Vitamin D is typically taken at doses between the Recommended Daily Allowance (RDA) and the Upper Level Intake (UL), the upper limit of what is considered safe. Therapeutic doses are usually closer to the UL. These recommendations were updated in 2010 by the Institute of Medicine, and they vary for people of different ages and pregnancy/lactation status. See Requirements/Sources for more details.
Sometimes, vitamin D is recommended or prescribed at doses that exceed what is typically considered "safe." In these cases, physician supervision is recommended. (See Side Effects & Warnings for more information.)
Individuals with severe osteoporosis often have low levels of vitamin D. 1 Supplementing with vitamin D alone is probably no more than minimally helpful, at best, 2 but the combination of calcium and vitamin D is probably more effective. (See the Calcium article for more information.)
Interestingly, vitamin D may offer another benefit for osteoporosis in seniors: most (though not all) studies have found that vitamin D supplementation improves balance in seniors (especially female seniors) and reduces risk of falling. 3 Since the most common adverse consequence of osteoporosis is a fracture due to a fall, this could be a meaningful benefit. Why vitamin D should offer this benefit, however, remains a mystery.
Supplementation with vitamin D plus calcium may aid healing aftera fracture has occurred. 4
Getting adequate vitamin D may help prevent the development of hypertension.45-49
