 
Vitamin D
Vitamin D is
also crucial for bone health since it helps the body absorb calcium. The recommended daily intake is:
- 200 IU for people younger than 50
- 400 IU for people ages 51 to 70
- 600 IU for people older than 70
Foods containing vitamin D are: The table of selected food sources of vitamin D suggests
dietary sources of vitamin D.
- liver
- butter
- cream
- egg yolks
- dairy products made
from milk such as cheese, yogurt, & ice cream are generally not fortified w/vitamin D
- milk fortified w/vitamin D: Prior to the fortification of milk products in the 1930's, rickets (a bone
disease seen in children) was a major public health problem in the US
- milk in the US:
is fortified w/10 micrograms (400 IU) of vitamin D per quart & rickets is now uncommon in the US 7
- 1 cup of vitamin D
fortified milk supplies about 1/4 of the estimated daily need for this vitamin for adults
- fortified breakfast cereals: fortified foods are the
major dietary sources of vitamin D 4
- fatty fish: naturally contain significant amounts of vitamin D, including fatty fish &
fish oils 4
the body can synthesize vitamin D from sunlight
but not if you use sunblock & not in the winter in northern climates
It's important to remember that:
Balanced
diet is most important aspect is your diet which 'no amount od supplements can replace. Supplements can't give you fiber &
many miconutrients & other chemicals ( known & unknown ones ) needed by your body.
More of supplements are of not much use. Rather
excess of some vitamins can be harmful like Vitamin A & D
Costly brand names may not be more beneficial.
Always remember to tell your doctor any vitamins
or minerals or other supplements you are taking.
When can vitamin D deficiency occur?
A deficiency of vitamin D can occur when dietary intake of vitamin D is inadequate, when there is limited exposure
to sunlight, when the kidney cannot convert vitamin D to its active form, or when someone can't adequately absorb vitamin
D from the gastrointestinal tract.7
The classic vitamin D deficiency diseases are
rickets & osteomalacia. In children, vitamin D deficiency causes rickets, which results in skeletal deformities. In
adults, vitamin D deficiency can lead to osteomalacia, which results in muscular weakness in addition to weak bones. 5,6,7
Who may need extra vitamin D to prevent a deficiency?
Older Americans (greater than age 50) are thought to
have a higher risk of developing vitamin D deficiency. 9 The ability of skin to convert
vitamin D to its active form decreases as we age. 4, 10-12
The kidneys, which help convert vitamin
D to its active form, sometimes do not work as well when people age. Therefore, some older Americans may need vitamin D from
a supplement.
It's important for individuals w/limited
sun exposure to include good sources of vitamin D in their diets. 8, 13-15 Homebound
individuals, people living in northern latitudes such as in New England & Alaska, women who cover their body for religious
reasons & individuals working in occupations that prevent exposure to sunlight are at risk of a vitamin D deficiency.
If these individuals are unable to meet their
daily dietary need for vitamin D, they may need a supplement of vitamin D.
Individuals who have reduced ability to absorb
dietary fat (fat malabsorption) may need extra vitamin D because it is a fat soluble vitamin.
Some causes of fat malabsorption are pancreatic
enzyme deficiency, Crohns disease, cystic fibrosis, sprue, liver disease, surgical removal of part or all of the stomach &
small bowel disease . 6
Symptoms of fat malabsorption include diarrhea
& greasy stools. 1
Vitamin D supplements are often recommended
for exclusively breast-fed infants because human milk may not contain adequate vitamin D.17-20
The Institute of Medicine states
that "With habitual small doses of sunshine breast- or formula-fed infants do not require supplemental vitamin D."
Mothers of infants who are exclusively breastfed
& have a limited sun exposure should consult w/a pediatrician on this issue. Since infant formulas are routinely fortified
w/vitamin D, formula fed infants usually have adequate dietary intake of vitamin D.
What are some current issues & controversies about vitamin D?
Vitamin D & osteoporosis
It's estimated that over 25 million adults in the US
have, or are at risk of developing osteoporosis. 21 Osteoporosis is a disease characterized
by fragile bones. It results in increased risk of bone fractures. Having normal storage levels of vitamin D in your body helps
keep your bones strong & may help prevent osteoporosis in elderly, non-ambulatory individuals, in post-menopausal women
& in individuals on chronic steroid therapy.
Researchers know that normal bone is constantly
being remodeled (broken down & rebuilt). During menopause, the balance between these two systems is upset, resulting in
more bone being broken down (resorbed) than rebuilt. Estrogen replacement, which limits symptoms of menopause, can help slow
down the development of osteoporosis by stimulating the activity of cells that rebuild bone.
Vitamin D deficiency, which occurs more often
in post-menopausal women & older Americans -4,9,10-12 has been associated w/greater
incidence of hip fractures. 22 A greater vitamin D intake from diet & supplements has
been associated w/less bone loss in older women. 23
Since bone loss increases the risk of fractures,
vitamin D supplementation may help prevent fractures resulting from osteoporosis.
In a group of women w/osteoporosis hospitalized
for hip fractures:
- 50% were found to have signs of vitamin D deficiency
Treatment of vitamin D deficiency 22 can result in decreased incidence of hip fractures & daily supplementation w/20 mcg (800 IU) of vitamin
D may reduce the risk of osteoporotic fractures in elderly populations w/low blood levels of vitamin D. 24
Your physician will discuss your need for vitamin
D supplementation as part of an overall plan to prevent and/or treat osteoporosis when indicated.
Vitamin D & cancer
Laboratory, anima & epidemiologic evidence suggest that vitamin D may be protective against
some cancers. Some dietary surveys have associated increased intake of dairy foods w/decreased incidence of colon cancer.
25-27
Another dietary survey associated a higher calcium
& vitamin D intake w/a lower incidence of colon cancer. 28 Well-designed clinical
trials need to be conducted to determine whether vitamin D deficiency increases cancer risk, or if an increased intake of
vitamin D is protective against some cancers.
Until such trials are conducted, it's premature
to advise anyone to take vitamin D supplements to prevent cancer.
Vitamin D & steroids
Corticosteroid medications are often prescribed to reduce inflammation from a variety of medical problems.
These medicines may be essential for a persons medical treatment, but they have potential side effects, including decreased
calcium absorption. 29,30
There's some evidence that steroids may also
impair vitamin D metabolism, further contributing to the loss of bone & development of osteoporosis associated w/steroid
medications. 30
For these reasons, individuals on chronic steroid
therapy should consult w/their physician or registered dietitian about the need to increase vitamin D intake through diet
and/or dietary supplements.
Vitamin D & Alzheimers Disease
Adults w/Alzheimers disease have increased risk of hip fractures. 31
This may be because many Alzheimers patients
are homebound, and frequently sunlight deprived. Alzheimers disease is more prevalent in older populations, so the fact that
the ability of skin to convert vitamin D to its active form decreases as we age also may contribute to increased risk of hip
fractures in this group (4,10-12).
One study of women with Alzheimers disease found
that decreased bone mineral density was associated w/a low intake of vitamin D and inadequate sunlight exposure (32). Physicians
evaluate the need for vitamin D supplementation as part of an overall treatment plan for adults with Alzheimers disease.
Table of Selected Food Sources of Vitamin D
|
Food |
International Units |
%DV * |
|
Cod Liver Oil, 1 tbsp. |
1,360 IU |
340 |
|
Salmon, cooked, 3 1/2 oz |
360 IU |
90 |
|
Mackerel, cooked, 3 1/2 oz |
345 IU |
90 |
|
Sardines, canned in oil, drained,3 1/2 oz |
270 IU |
70 |
|
Eel, cooked, 3 1/2 oz |
200 IU |
50
|
|
Milk, nonfat, reduced fat, & whole, vitamin D fortified,
1 cup |
98 IU |
25 |
|
Margarine, fortified, 1 tbsp. |
60 IU |
15 |
|
Cereal grain bars, fortified w/ 10% of the DV, 1 each |
50 IU |
10 |
|
Pudding, 1/2 c prepared from mix & made w/vitamin D fortified
milk |
50 IU |
10 |
|
Dry cereal, Vit D fortified w/10%* of DV, 3/4 cup
* Other
cereals may be fortified w/more or less vitamin D |
40-50 IU |
10 |
|
Liver, beef, cooked, 3 1/2 oz |
30 IU |
8 |
|
Egg, 1 whole (vitamin D is present in the yolk) |
25 IU |
6 |
|
* DV = Daily Value. DVs are reference numbers based
on the Recommended Dietary Allowance (RDA). They were developed to help consumers determine if a food contains very much of
a specific nutrient. The DV for vitamin D is 400 IU. The percent DV (%DV) listed on the nutrition facts panel of food labels
tells adults what percentage of the DV is provided by one serving. Percent DVs are based on a 2,000-calorie diet. Your Daily
Values may be higher or lower depending on your calorie needs. Foods that provide lower percentages of the DV will contribute
to a healthful diet. |
This Fact Sheet was developed by the Clinical Nutrition
Service, Warren Grant Magnuson Clinical Center, National Institutes of Health (NIH), Bethesda, MD, in conjunction with the
Office of Dietary Supplements (ODS) in the Office of the Director of NIH.
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nutritional navigation
vitamins
vitamin d- you are here!
minerals
Vitamin D, calciferol, is a fat-soluble
vitamin.
- It's found in food
- It can be made in your body after exposure
to ultraviolet rays from the sun 1,2
so get outside! morning walks are great for minimal ultraviolet rays!
Vitamin D exists in several forms, each with
a different activity. Some forms are relatively inactive in the body & have limited ability to function as a vitamin.
The liver & kidney help convert vitamin
D to its active hormone form. 3 The major biologic function of vitamin D is to maintain normal blood levels of calcium
& phosphorus. 4
Vitamin D aids in the
absorption of calcium, helping to form & maintain strong bones.
It promotes bone mineralization in concert
w/a number of other vitamins, minerals & hormones.
Without vitamin D, bones can become:
- thin
- brittle
- soft
- misshapen
Vitamin D prevents rickets in children &
osteomalacia in adults, which are skeletal diseases that result in defects that weaken bones. 5,6
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Exposure to sunlight is an important source of vitamin D.
Ultraviolet (UV) rays from sunlight trigger
vitamin D synthesis in the skin.7,8
Season, latitude, time of day, cloud cover,
smog & suncreens affect UV ray exposure. 8
For example, in Boston the average amount
of sunlight is insufficient to produce significant vitamin D synthesis in the skin from November - February.
Sunscreens w/a sun protection factor of 8
or greater will block UV rays that produce vitamin D, but it's still important to routinely use sunscreen whenever sun exposure
is longer than 10 to 15 minutes.
It's especially important for individuals
w/limited sun exposure to include good sources of vitamin D in their diet.
What is the health risk of too much vitamin D?
There is a high health risk associated w/consuming too
much vitamin D. 33
Vitamin D toxicity can cause:
- nausea
- vomiting
- poor appetite
- constipation
- weakness
- weight loss 34
It can also raise blood levels of calcium ,
causing mental status changes such as confusion. High
blood levels of calcium also can cause heart rhythm abnormalities. Calcinosis, the deposition of calcium &
phosphate in soft tissues like the kidney can be caused by vitamin D toxicity. 4
Consuming too much vitamin
D through diet alone is not likely unless you routinely consume large amounts of cod liver oil. It's much more likely to occur
from high intakes of vitamin D in supplements.
The Food & Nutrition
Board of the Institute of Medicine considers an intake of 25 mcg (1,000 IU) for infants up to 12 months of age & 50 mcg
(2,000 IU) for children, adults, pregnant & lactating women to be the tolerable upper intake level (UL).
A daily intake above the
UL increases the risk of adverse health effects & isn't advised.
Selected Food Sources of Vitamin D (4, 36, 37)
As the 2000 Dietary Guidelines for Americans state,
"Different foods contain different nutrients. No single food can supply all the nutrients in the amounts you need." 35
The table in the left hand column
- suggests dietary sources of vitamin D.
As the table indicates, fortified foods are
a major source of vitamin D. Breakfast cereals, pastries, breads, crackers, cereal grain bars & other foods may be fortified
w/10% to 15% of the DV for vitamin D.
It's important to read the nutrition facts panel
of the food label to determine whether a food provides vitamin D.
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