Some more In Depth Information on Vitamin D

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Vitamin D

 

This file: http://www.notmilk.com/vitamind.txt

 

http://www.notmilk.com/pigmilk.txt

 

" At one time, Vitamin D-2 was added to milk. Vitamin D-2 is

manufactured by exposing bacteria and algae to ultra-violet light. D-

2 imparted a bitter taste to dairy products, and so was replaced by

vitamin D-3. "

 

" Basically D-3 always is derived from an animal. The sunlight

reaction that

converts 7-dehydrocholesterol to vitamin D-3 is a 'pure' chemical

reaction that occurs in your skin in certain cells. "

 

Sources of D3:

 

Pig skin, sheep skin, raw fish liver, and pig brains.

 

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http://www.nutritionfarm.com/focus/Vitamins/vitamin_D.htm

 

Forms:

 

Vitamin D1 (a molecular compound of lumisterol and vitamin D2)

Vitamin D2 (calciferol, ergocalciferol)

Vitamin D3 (cholecalciferol, activated 7-dehydrocholesterol)

Vitamin D4 (22:23-dihydroergocalciferol)

Calcitriol (1,25-dihydrocholecalciferol)

 

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AN INTRODUCTION TO VITAMIN D : With Emphasis on the Topics of

Chemistry, Sources, Production, Presence in Milk and Nutritional

Importance

 

Prepared by:

 

Professor Anthony W. Norman;

Department of Biochemistry & Biomedical Sciences

University of California

Riverside CA 92521.

E-MAIL: Norman

(December 12, 2000)

 

Purpose of this statement:

 

The objective of this brief statement is to provide some biological

and nutritional background on vitamin D, which is a precursor of a

steroid hormone [1,25(OH)2D3]

in higher animals, including humans.

 

This will be followed by brief descriptions of vitamin D's

chemistry, nutritional importance, sources, production and presence

in milk.

 

What is a vitamin?

 

A vitamin is a substance (organic molecule) whose presence is

crucial to the normal every day life function of animals. However

vitamins can not be directly produced by the animal's body.

 

Accordingly the daily requirements for the vitamin must be met

through regular dietary intake of appropriate quantities of the

vitamin(s).

 

There are two general chemical categories of

vitamins based on their solubility: water soluble vitamins (the B

vitamins and others) and fat soluble vitamins (A, D, E and K).

 

What is a hormone?

 

A hormone is a chemical messenger that is produced and secreted by

specific glands and cells within the body of animals.

 

After secretion of the hormone,

it is transported through the bloodstream to designated target

organs where the hormone by binding to its specific receptor

delivers its " message " to that set of cells.

 

These cells then promptly produce biological responses specific for

that hormone.

 

What is vitamin D and why is it important:

 

Chemistry:

 

There are two chemical forms of vitamin D, namely vitamin D2

(sometimes referred to as ergocalciferol) and vitamin D3 (sometimes

referred to a cholecalciferol). The natural form of vitamin D for

animals and man is vitamin D3 that is produced in their bodies from

cholesterol and 7- dehydrocholesterol.

 

An alternative vitamin D2 is derived from the yeast

sterol ergosterol by chemical procedures.

 

The molecular structure of vitamin D is closely allied to that of

the classical steroid hormones, e.g. cortisol, estradiol,

progesterone,

aldosterone, and testosterone (1).

 

All steroid hormones and vitamin D3 are chemically related to the

well known sterol cholesterol.

 

Cholesterol in animals and man is a precursor substance for all

steroid hormones and as well vitamin D3.

 

Technically the molecule called vitamin D3 is not really a vitamin

because it can be produced by exposure of the skin (higher animals

and humans) to ultraviolet light or sunlight. The skin of many

animals and man has a high concentration of the sterol cholesterol

which is converted by enzymes in the skin to the sterol 7-

dehydrocholesterol.

 

Exposure of skin (including human skin) to sunlight for regular

intervals results in the photochemical conversion of 7-

dehydrocholesterol into vitamin D3. This sunlight- generated

vitamin D3 is a precursor of the steroid hormone 1,25(OH)2D3.

 

Under these circumstances vitamin D3 is not a vitamin because it has

been produced by the body (with the assistance of sunlight).

 

However, if the animal or man lives in the absence of sunlight

(e.g., Alaska in the winter) or exclusively

indoors, then there is indeed an absolute regular requirement for

the fat

soluble vitamin D, that must be met through proper dietary intake.

 

Therefore for nutritional and public health reasons, vitamin D3

continues to be classified even today in 2000 officially as a

vitamin.

Thus many vitamin capsules and food sources including cows milk are

supplemented with vitamin D3 to improve their nutritional value. In

the 1940's this milk supplementation process reduced the incidence

rate of juvenile rickets by 85% in the United States.

 

Importance:

 

Vitamin D3 is essential for life in higher animals. Classically

vitamin D3 has been shown to be one of the most important biological

regulators of calcium metabolism through stimulating the absorption

of calcium from food across the intestine and participating in the

incorporation of the absorbed calcium in to the skeleton (2).

 

These important biological effects are only achieved as a

consequence of the metabolism of vitamin D into a family of daughter

metabolites, including 1,25(OH)2-vitamin D3 [1,25(OH)2D3].

 

1,25(OH)2D3, is considered to be a steroid hormone because the

general mechanism by which it produces the biological responses

attributed to vitamin D is similar to those of steroid hormones

(3;4).

 

It has become increasingly apparent since the 1980s that 1,25(OH)2D3

also plays an important multidisciplinary role in tissues not

primarily related to mineral metabolism, e.g. the hematopoietic or

blood system, effects on cell differentiation and proliferation

including important interactions with keratinocytes and cancer

cells, and participation in the processes of parathyroid hormone and

insulin secretion (3)

 

Vitamin D Deficiency:

 

The classic deficiency state resulting from a dietary

absence of vitamin D3 or lack of ultraviolet (sunlight) exposure is

the bone disease called rickets in children or osteomalacia in

adults. The clinical features of rickets and osteomalacia depend

upon the age of onset.

 

The classical skeletal disorder of rickets includes deformity of

the bones, especially in the knees, wrists, and ankles, as well as

associated changes in the rib joint functions, which have been

termed by some as the rachitic rosary (1).

 

A regular access to vitamin D3 throughout life is important to

facilitate the normal absorption into the body of dietary calcium

which, in turn, is essential for normal bone health and may diminish

or prevent the onset in the elderly of the bone disease

osteoporosis.

 

Requirements for vitamin D:

 

Since vitamin D3 is produced in the skin after exposure of 7-

dehydrocholesterol to sunlight, the human does not have a

requirement for vitamin D when sufficient sunlight is available.

 

Man's tendency to wear

clothes, to live in cities where tall buildings block adequate

sunlight from reaching the ground, to live indoors, to use synthetic

sunscreens that

block

ultraviolet rays, and to live in geographical regions of the world

that do

not receive adequate sunlight, all contribute to the inability of

the skin

to biosynthesize sufficient amounts of vitamin D3 (5). Thus, vitamin

D3

does become an important nutritional factor in the absence of

sunlight. It

is known that a substantial proportion of the U.S. population is

exposed to

suboptimal levels of sunlight. This is particularly true during

winter

months (6;7). Under these conditions, vitamin D becomes a true

vitamin

which dictates that it must be supplied in the diet on a regular

basis.

 

Since vitamin D3 can be produced by the body and since it is

retained for long periods of time by animal tissues, it has been

difficult to determine with precision the minimum daily requirements

for this fat soluble vitamin.

 

The requirement for vitamin D3 is also known to be dependent on the

age, sex, degree of exposure to the sun, season, and the amount of

pigmentation in the skin (.

 

The current " adequate intake " allowance of vitamin D recommended in

1998 by the Food and Nutrition Board of US Institute of Medicine is

200 IU/day (5 grams/day) for infants, children and adult males and

females up to age 51

(9).

For females ages >51 or males ages > 70, the adequate indicated

level is set at 400 IU/day (10 g/day) or 600 IU (15 ug/day),

respectively.

 

The adequate allowance for pregnancy and lactation is set at 200

IU/day (5

g/day). These recommendations are all summarized in a 1998

publication from

the Food and Nutrition Board of the Institute of Medicine (9).

 

In the United States adequate amounts of vitamin D3 can readily be

obtained from the diet and/or from casual exposure to sunlight. The

ultraviolet exposure can be as little as 3 X per week exposure of

the face and hands to ambient sunlight for 20 minutes (10).

 

However, in some parts of the world where food is not routinely

fortified and sunlight is often limited during

some periods of the year, obtaining adequate amounts of vitamin D

becomes more of a problem. As a result, the incidence of rickets in

these countries is higher than in the United States.

 

What are the sources of vitamin D for humans?

 

Animal products constitute the bulk source of vitamin D that occurs

naturally in unfortified foods. Salt water fish such as herring,

salmon,

sardines, and fish liver oils are good sources of vitamin D3.

Small quantities of vitamin D3 are also found in eggs, veal, beef,

butter, and vegetable oils while plants, fruits, and nuts are

extremely poor sources of vitamin D. In the United States,

fortification of foods such as milk (both fresh and evaporated),

margarine and butter, cereals, and chocolate mixes help in meeting

the adequate intake (RDA) recommendations (11). Because only

fluid milk is fortified with vitamin D, other dairy products

(cheese, yogurt, etc.) only provide the vitamin that was produced by

the animal itself.

 

How is vitamin D produced commercially for food supplementation?

 

When the critical importance to human health of a regular dietary

access to vitamin D3 was understood (in the 1930's), milk suppliers

realized it would be advantageous to their customers' health to

market milk which had been supplemented with vitamin D3.

 

Thus there developed in the 1940's, and continues to the present, a

large business of industrial production of vitamin D3 used for the

supplementation of foods for human consumption: milk

(both homogenized and evaporated), some margarine and breads.

 

Since the 1960's vitamin D3 has been used also for the

supplementation of farm animal and poultry food.

 

In 1973 in the United States some 290 trillion (290 x 1012)

International Units of vitamin D3 was manufactured and sold for over

3 million dollars. This vitamin D3 is the equivalent of

approximately 8 tons;

[see page 62 of reference (2)].

 

The commercial production of vitamin D3 is completely dependent on

the availability of either 7-dehydrocholesterol or cholesterol.

 

7- Dehydrocholesterol can be obtained via organic solvent extraction

of animal skins (cow, pig or sheep) followed by an extensive

purification.

 

Cholesterol typically is extracted from the lanolin of sheep wool

and after thorough purification and crystallization can be converted

via a laborious chemical synthesis into 7-dehydrocholesterol.

It should be appreciated that

once chemically pure, crystalline 7-dehydrocholesterol has been

obtained, it

is impossible to use any chemical or biological tests or procedures

to determine the original source (sheep lanolin, pig skin, cow skin,

etc.) of the cholesterol or 7-dehydrocholesterol.

 

Next the crystalline 7-dehydrocholesterol is dissolved in an organic

solvent and irradiated with ultraviolet light to carry out the

transformation

(similar to that which occurs in human and animal skin) to produce

vitamin D3. This vitamin D3 is then purified and crystallized

further before it is

formulated for use in dairy milk and animal feed supplementation.

 

The exact

details of the chemical conversion of cholesterol to 7-

dehydrocholesterol

and the method of large-scale ultraviolet light conversion into

vitamin D3 and subsequent purification are closely held topics for

which there have been many patents issued (2).

 

The major producers of vitamin D3 used for milk and other food

supplementation are the companies F. Hoffman La Roche, Ltd

(Switzerland) and BASF (Germany).

 

What is the source of vitamin D in milk?

 

Milk from all lactating animals, including humans, contains vitamin

D3 that has been produced photochemically from 7-dehydrocholesterol

present in the skin.

 

In cow's milk it has been determined that the concentration of

vitamin D3 in milk provided by the cow is roughly 35-70

International Units

per quart as determined via biological assay (12) and approximately

5080 International Units as determined by modern chemical mass

spectrometric procedures (13). However these are rather low levels

of vitamin D3 from the

perspective of providing the 200-400 IU per day as recommended by

the Food

and Nutrition Board of the Institute of Medicine (9).

 

Accordingly, as discussed above, the business practice of

supplementing cows milk with chemically synthesized vitamin D3 was

initiated.

At the present time almost

all milk sold commercially in the United States has 400 IU of

chemically synthesized vitamin D3 added per quart.

 

Any vendor of milk for human

consumption containing added vitamin D3 is required by the US Food

and Drug

Administration (FDA) to include a notice on the milk carton label.

Usually

this label states " 400 IU of added vitamin D3 " .

 

However it is not required

by law to indicate either the manufacturer of the added vitamin D3

or the

sources of the cholesterol and 7-dehydrocholesterol used for its

production.

 

It is a fact that most milk sold in the US will contain vitamin D3

with two origins. (a)

That vitamin D3 made by the cow using sunlight to irradiate 7-

dehydrocholesterol present in her skin. (b) That vitamin D3 made by

a chemical process and then added to the cow milk as a nutritional

supplement. It is simply not possible to distinguish the origins of

the two vitamin D3 preparations by any biological or chemical

procedure, because they are the same molecular structure.

 

Further, there is no legal requirement for the

manufacturer of the vitamin D3 formulated for human food

supplementation to

specify the animal sources of the precursor molecules that were

employed in the synthesis of the D vitamin.

 

If a " food product " is construed to include a chemically pure

substance that

is the same in all animal species, then those individuals with

strict

religious reasons for avoiding food products from a particular

species have,

in the instance of milk and vitamin D3, a dilemma.

 

Selected references:

 

Additional information on vitamin D is available in the list of

references

presented on the next page.

 

Also the WEB sites for the Vitamin D Workshop:

http://vitamind.ucr.edu/workshop.html and the WEB sites of BASF and

Hoffmann-La Roche, LTD [two of the largest industrial producers of

vitamin

D3 in the world] provide other general information related to

vitamin D:

http://www.basf-ag.basf.de/basf/html/e/health/index.htm and:

http://www.roche.com/fitamins/what/general/vitd.html

 

Reference List

 

1. Norman,A.W. and Litwack,G.L. Hormones, Academic Press, San Diego,

CA.(1997).

 

2. Norman,A.W. Vitamin D: The calcium homeostatic steroid hormone.,

Academic Press, New York.(1979). 3. Bouillon,R., Okamura,W.H., and

Norman,A.W. Structure-function relationships in the vitamin D

endocrine

system. Endocr.Rev. 16 (1995) 200-257.

 

4. Norman,A.W.: Vitamin D. In Present knowledge in nutrution (PKN7).

Ziegler,E.E. and Filer,L.J., Eds., International Life Sciences

Institute,

Washington (1996) pp. 120-129 .

 

5. Holick,M.F. Environmental factors that influence the cutaneous

production

of vitamin D. Am.J.Clin.Nutr. 61 Suppl. (1995) 638S-645S.

 

6. Webb,A.R. and Holick,M.F. The role of sunlight in the cutaneous

production of vitamin D3. Ann.Rev.Nutr. 8 (1988) 375-399.

 

7. Webb,A.R., Pilbeam,C., Hanafin,N., and Holick,M.F. An evaluation

of the

relative contributions of exposure to sunlight and of diet to the

circulating concentrations of 25-hydroxyvitamin D in an elderly

nursing home

population in Boston. Am.J.Clin.Nutr. 51(6) (1990) 1075-1081.

 

8. Harris,S.S. and Dawson-Hughes,B. Seasonal changes in plasma 25-

hydroxyvitamin D concentrations of young American black and white

women.

Am.J.Clin.Nutr. 67 (1998) 1232-1236.

 

9. Food and Nutrition Board. Dietary reference intakes: A risk

assessment

model for establishing upper intake levels for nutrients. 1998) , 1-

71.

Washington, D.C., National Academy Press, Institute of Medicine.

 

10. Adams,J.S., Clemens,T.L., Parrish,J.A., and Holick,M.F. Vitamin-

D

synthesis and metabolism after ultraviolet irradiation of normal and

vitamin-D-deficient subjects. New Engl.J.Med. 306 (1982) 722-725.

 

11. Collins,E.D. and Norman,A.W.: Vitamin D In Handbook of vitamins.

Machlin,L.J., Ed., Marcel Dekker, New York (1990) pp. 59-98 .

 

12. Hollis,B.W., Roos,B.A., and Lambert,P.W.: Vitamin D compounds in

human

and bovine milk In Advances in nutritional research. Draper,H.H.,

Ed.,

Plenum Press, New York (1994) pp. 59-75 .

 

13. Adachi,A. and Kobayashi,T. Identification of vitamin D3 and 7-

dehydrocholesterol in cow's milk by gas chromatography-mass

spectrometry and

their quantitation by high-performance liquid chromatography.

J.Nutr.Sci.Vitaminol. 25 (1979) 67-78.

 

(republished with permission)

 

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http://www.bookman.com.au/vitamins/vitd.html

 

Vitamin D

 

Vitamin D is both a hormone and a vitamin. It was identified in the

1920s

after a long search for the cause and cure of rickets, which had

been a

significant health problem since the industrialization of northern

Europe.

Vitamin D is obtained from food sources and is also manufactured in

the skin

through the action of sunlight.

 

There are three forms of vitamin D: vitamin

D1 (calciferol), vitamin D2 (ergocalciferol) and vitamin D3

(cholecalciferol).

 

Vitamin D2 is the form most commonly added to foods and

nutritional supplements. These forms of vitamin D are converted in

the liver

and kidneys to the hormone, calcitriol, which is the physiologically

active form of vitamin D.

 

What it does in the body

 

Bones and teeth

 

The most important role of vitamin D is to maintain blood calcium

levels

within an acceptable range. It stimulates intestinal calcium

absorption and

re-absorption in the kidneys, and regulates the metabolism of

calcium and

phosphorus, which are vital for many body functions including the

normal

growth and development of bones and teeth. It enables bones and

teeth to

harden by increasing the deposition of calcium into these structures

and may

also assist in the movement of calcium across body cell membranes.

 

Cell growth

 

Vitamin D is involved in normal cell growth and maturation and may

play a

part in cancer prevention. In test tube experiments, calcitriol

seems to

have anticancer properties, inhibiting the growth of human leukemia,

colon

cancer, skin cancer and breast cancer cells.

 

Immune system

 

Vitamin D is involved in the regulation of the immune system. It has

several

functions including effects on white blood cells known as monocytes

and

lymphocytes and seems to suppress function of several parts of the

immune

system.

 

Hormones

 

Vitamin D plays a role in the secretion of insulin by the pancreas,

thus

aiding in the regulation of blood sugar. Vitamin D suppresses both

the

action of the parathyroid gland and the action of a hormone from

this gland

and may play a role in the treatment of an overactive parathyroid.

 

Nervous system

 

Careful regulation of calcium levels is vital for normal nerve

impulse

transmission and muscle contraction. Vitamin D plays a role in the

functioning of healthy nerves and muscles by regulating the level of

calcium

in the blood.

 

Absorption and metabolism

 

As with other fat soluble vitamins, fat in the intestine is

necessary for

vitamin D absorption. Vitamin D from food and supplements is

absorbed

through the intestinal walls and can be stored in the fat cells of

the

liver, skin, brain and bones in amounts sufficient for many months'

consumption. Exposure to sunlight in spring, summer and autumn

usually makes

up for any shortfall in dietary vitamin D and even brief exposure to

sunlight during these times is adequate. There may, however, be

problems in

winter months in some climates. The production of vitamin D in the

body is

blocked by anything which blocks ultraviolet light including skin

pigment,

smog, fog, sunscreen, windows and hats.

 

Deficiency

 

Vitamin D deficiency leads to increased production of parathyroid

hormone

and the removal of calcium from the bones. In children, this results

in

rickets, a disorder in which the bones are so soft that they become

curved

from supporting the weight of the body. The equivalent in adults is

osteomalacia which involves a softening of bones and causes bone

pain and

tenderness and muscle weakness. Other signs of deficiency include

severe

tooth decay and hearing loss, which is due to a softening of the

bones in

the inner ear.

 

Studies show that elderly people, particularly those who are

housebound or

in institutions, may be at high risk of vitamin D deficiency. A

study

published in 1998 in the New England Journal of Medicine found

vitamin D

deficiency in 57 per cent of a group of 290 patients who were

admitted to

hospital. In a subgroup of the patients who had no known risk

factors for

vitamin D deficiency, the researchers found that 42 per cent were

deficient.

They concluded that vitamin D deficiency was probably a substantial

problem.1

 

There is some concern that the increasing use of sunscreens as skin

cancer

preventives may increase the risk of vitamin D deficiency.

 

This is unlikely

to be a problem in children and young people who do not usually wear

sunscreen every time they go outside.

 

However, older people who may be more

concerned about sun damage to skin and who may go outside less often

are

more likely to be at risk.

 

Vitamin D deficiency is more common in winter in cold climates. This

decline

may lead to an increased risk of bone loss in elderly men and women

according to a 1997 study by researchers at Tufts University in

Boston. They

examined vitamin D levels in 182 men and 209 women aged over 65.

Levels

were

found to be lower in women. In wintertime levels were lower than in

summertime. Travel, vitamin D intake and time spent outdoors

increased the

vitamin D concentrations.2

 

Other groups at risk of deficiency include alcoholics, those with

gastrointestinal malabsorption disorders such as celiac disease,

those

taking anticonvulsant drugs, those who don't drink milk or get much

sunlight, those with absorption problems and darker skinned people

living in

colder climates. As vitamin D is converted in the liver and kidneys

to

calcitriol, its active form, sufferers of kidney and liver diseases

may also

be at risk of vitamin D deficiency.

 

Osteoporosis

 

Vitamin D regulates bone mineral density and a deficiency may lead

to

osteoporosis, a disease in which bones become lighter, less dense

and more

prone to fractures. (See page 653 for more information.) People with

a

certain type of vitamin D receptor may be more susceptible to

osteoporosis.

As the structure of the vitamin D receptor is genetically

determined, this

may eventually lead to a test to identify women at risk of the

disease.

Research suggests that women with different types of vitamin D

receptor

respond differently to vitamin D supplements given to build bone.3

 

Arthritis

 

Osteoarthrtitis

 

New research suggests that people with osteoarthritis who have low

vitamin D

intakes suffer more severe symptoms than those whose intakes are

high. In a

study done in 1996 researchers at Boston University studied more

than 500

elderly people with osteoarthritis of the knee. They found that

those with

the lowest intakes and blood levels of vitamin D were three times

more

likely to see their disease progress than people with high intakes

and blood

levels. Vitamin D may help reduce the cartilage damage seen in

osteoarthritis.4

 

Rheumatoid arthritis

 

Severe rheumatoid arthritis is associated with bone loss. In a 1998

study,

German researchers investigated the links between disease activity

and serum

levels of vitamin D in 96 patients. They found that high disease

activity

was associated with alterations in vitamin D metabolism and

increased bone

breakdown. Low levels of vitamin D may also increase the

proliferation of

white blood cells and may accelerate the arthritic process in

rheumatoid

arthritis.5 Vitamin D supplements are likely to be useful in

retarding these

adverse effects of alterations in metabolism.

 

Cancer

 

Low levels of vitamin D have been linked to several cancers

including those

of the colon, prostate and breast. Laboratory experiments show that

vitamin

D can inhibit the growth of human prostate cancer6 and breast cancer

cells7.

Lung cancer and pancreatic cancer8 cells may also be susceptible to

the

effects of vitamin D. Sunlight also seems to be protective against

several

types of cancer, including ovarian9 and breast cancers, and this

effect may

be mediated by vitamin D levels.

 

Colorectal cancer

 

Several studies have suggested a link between low dietary vitamin D

intake

and colorectal cancer risk. In a 1996 study, researchers conducted a

population-based case-control study to examine this relationship

among 352

people with colon cancer, 217 people with rectal cancer, and 512

healthy

people in Stockholm, Sweden. The researchers used questionnaires to

assess

the vitamin D intake for the preceding five years. The results

showed that

those with the highest vitamin D intakes were around half as likely

to get

cancers of the colon or rectum than those with the lowest intakes.10

 

Results from the Harvard Nurses Health Study published in 1996

suggest a

link between vitamin D and colorectal cancer. The study involved 89

448

female nurses and covered the time period from 1980 to 1992 during

which 501

cases of colorectal cancer were documented. The results showed a

link

between intake of total vitamin D and risk of colorectal cancer.11

 

Prostate cancer

 

Low vitamin D levels are linked to an increased risk of prostate

cancer. In

a study published in 1996, researchers at Brigham and Women's

Hospital in

Boston collected blood plasma samples from 14 916 participants in

the

Physicians' Health Study and measured vitamin D levels. Their

analysis

included 232 cases diagnosed up to 1992 and 414 age-matched control

participants. The results showed a slightly reduced risk of prostate

cancer

in those with high vitamin D levels.12

 

The way a man's body utilizes vitamin D could affect his risk of

prostate

cancer. A 1996 National Institute of Environmental Health Sciences

study has

found that men with a particular type of vitamin D receptor gene are

less

likely than others to develop the type of prostate cancer that

requires

surgery. Researchers looked at the receptor genes in 108 cancer

patients and

170 men without cancer. The results showed that 22 per cent of

cancer

patients had two copies of a particular gene, while only 8 per cent

of the

cancer-free men did. These findings support the theory that vitamin

D plays

an important role in prostate cancer.13

 

Multiple sclerosis

 

There is some suggestion that abnormalities in vitamin D metabolism

may be

linked to multiple sclerosis. The hormonal form of vitamin D can

prevent a

disease similar to multiple sclerosis in mice. Multiple sclerosis is

more

prevalent in areas where there is less exposure to sunlight and some

researchers believe that vitamin D protects against the disease.14

 

Diabetes

 

Vitamin D deficiency impairs glucose metabolism by reducing insulin

secretion. This is likely to increase the risk of diabetes mellitus.

Vitamin

D supplements are likely to be useful in preventing diabetes in

areas where

vitamin D deficiency is common.15

 

In a 1997 study looking at the links between environmental factors

and Type

II diabetes, vitamin D levels were assessed in 142 Dutch men aged

from 70 to

88 years of age. Thirty-nine per cent were found to have low vitamin

D

levels and tests showed that low vitamin D levels increased the risk

of

glucose intolerance.16

 

Heart disease

 

Low vitamin D levels may also increase the risk of atherosclerosis.

Research

published in 1997 in the American Heart Association journal

Circulation

suggests that a low level of vitamin D increases the risk of calcium

build-

up in atherosclerotic plaques and that higher levels reduce the risk

of

build-up. Researchers at UCLA School of Medicine measured the

vitamin D

levels in the blood of 173 men and women at risk of heart disease

and also

measured the build-up of calcium in coronary arteries (a common

finding in

coronary artery disease). The results suggest that calcium may

regulate

calcium deposition in the arteries as well as in the bone.17

 

Other effects

 

Vitamin D deficiency may also play a role in inflammatory bowel

disease,

tuberculosis, stroke and high blood pressure.

 

Sources

 

Fish liver oils, sardines, herring, salmon, tuna, liver, eggs and

some dairy

products are good dietary sources of vitamin D. Milk is often

fortified

with

vitamin D and is a good source, but dairy products other than milk

are not

usually fortified with vitamin D.

 

Medicinal cod liver oil 1 tbsp 2271 IU

 

Pink salmon, canned 100g 624 IU

 

Tuna, canned in oil 1 can 404 IU

 

Whole milk, dried 1 cup 380 IU

 

Oysters 6 oysters 269 IU

 

Mackerel, canned in oil 100g 252 IU

 

Shiitake mushrooms, dried 4 mushrooms 249 IU

 

Sardines, canned in tomato sauce 1 sardine 182 IU

 

Fortified milk, evaporated ½ cup 97.9 IU

 

Whole milk, fortified 1 cup 92.7 IU

 

Skim milk, fortified 1 cup 92.7 IU

 

Chocolate milk, fortified 1 cup 92.7 IU

 

Beef salami 1 slice (23g) 80.3 IU

 

Low fat milk, dried ¼ cup 79.0 IU

 

Sardines, canned in oil 2 sardines 65.3 IU

 

Herring, smoked 1 fillet 48.0 IU

 

Natural raisin bran 30g 45.6 IU

 

Shrimp 4 large 42.6 IU

 

All Bran 30g 42.0 IU

 

Bran flakes 30g 42.0 IU

 

Corn flakes 30g 42.0 IU

 

Special K 30g 42.0 IU

 

Egg yolk 1 large 24.6 IU

 

Pork sausages 1 sausage, 10cm long 14.6 IU

 

Recommended dietary allowances

 

USA

 

Men 200 IU (over 50) 400 IU (over 70) 600 IU

 

Women 200 IU (over 50) 400 IU (over 70) 600 IU

 

Pregnancy 200 IU

 

Lactation 200 IU

 

UK

 

Men 400 IU

 

Women 400 IU

 

Australia

 

Men 200 IU

 

Women 200 IU

 

Pregnancy 400 IU

 

Lactation 400 IU

 

The tolerable upper intake limit has been set at 2000 IU per day.

 

Supplements

 

Vitamin D supplements are often available in the form of cod liver

oil.

Anyone on long-term anticonvulsant drug therapy, older people, and

those who

follow a strict vegan diet may benefit from supplements.

 

Toxic effects of excess intake

 

High daily doses of dietary vitamin D over an extended period of

time can

produce excessive calcium levels in the blood with symptoms of

unusual

thirst, metallic taste, bone pain, fatigue, sore eyes, itching skin,

vomiting, diarrhea, urinary urgency, abnormal calcium deposits in

blood

vessel walls, liver, lungs, kidney and stomach. High doses also

cause the

build-up of calcium in the muscles which impairs their function.

Doses of

less than 1000 IU daily are unlikely to cause any adverse effects

and

prolonged exposure to sunlight does not cause toxic effects.

 

Large doses of vitamin D can irritate the urinary tract. There may

be a link

between excessive vitamin D intake and heart attacks,

atherosclerosis and

kidney stones in people who are susceptible.

 

Very high doses of vitamin D supplements may actually increase the

risk of

osteoporosis. In an article published in 1997, researchers at the

Cedars

Sinai Medical Center in Los Angeles reported four cases of

osteoporosis

linked to excessive use of vitamin D supplements. Each of the four

patients

had high levels of calcium and vitamin D metabolites in their urine

and were

taking dietary supplements which contained unidentified amounts of

vitamin

D. When the patients stopped taking the supplements, bone mineral

density

increased. Excessive vitamin D supplementation for six months or

longer

upsets calcium balance and affects bone mineral density.18

 

Therapeutic uses of supplements

 

Supplements are used to treat vitamin D deficiency and its symptoms.

 

Osteoporosis

 

Vitamin D is recommended in the treatment of osteoporosis in

postmenopausal

women. Several research studies suggest that vitamin D supplements

reduce

the occurrence of fractures in elderly people.

 

In a study published in 1997, researchers at Tufts University in

Boston

assessed the effects of calcium (500 mg per day) and vitamin D (700

IU per

day) in 176 men and 213 women aged 65 years or older. When bone

density was

measured after a three-year period, those taking the supplements had

higher

bone density at all body sites measured. The fracture rate was also

reduced

by 50 per cent in those taking the supplements.19

 

Vitamin D supplements may also be useful in preventing bone loss in

patients

taking corticosteroid drugs. In a study published in 1996,

researchers at

the University of Virginia found that calcium and vitamin D

supplements

helped prevent the loss of bone mineral density in those taking the

drugs

for arthritis, asthma and other chronic diseases.20

 

However, other studies have not shown any reduction in fracture

rates in

those taking vitamin D supplements. A 1996 study which was carried

out in

Amsterdam looked at the effects of either vitamin D or a placebo on

2500

healthy men and women over the age of 70 who were living

independently. The

participants received a placebo or a daily dose of 400 IU of vitamin

D for a

three-and-a-half-year period. Dietary calcium intake was the same in

both

groups. Forty-eight fractures were observed in the placebo group and

58 in

the vitamin D group.21

 

Other uses

 

Synthetic vitamin D analogs are used to treat the skin disorder,

psoriasis,

and are also being investigated for their ability to prevent and

treat

cancer.

 

Because of its effects on the immune system, many researchers are

investigating the possibility of using vitamin D and related

compounds to

treat autoimmune disorders and to suppress rejection of transplanted

organs.

 

Interactions with other nutrients

 

Vitamin D is necessary for calcium and phosphorus absorption and

metabolism.

Pantothenic acid is necessary for the synthesis of vitamin D.

 

Interactions with drugs

 

The cholesterol-lowering drug, cholestyramine, and mineral oil

laxatives

interfere with the absorption of vitamin D. Alcohol interferes with

the

conversion of vitamin D to its biologically active form.

 

People taking certain anticonvulsant drugs, such as phenytoin, may

decrease

the activity of vitamin D by increasing its metabolism. People

taking this

drug are likely to be at increased risk of osteoporosis and have

high

vitamin D requirements

 

Cautions

 

Vitamin D supplements should not be given to those with high calcium

levels

or high phosphorus levels, and should be given with caution to those

suffering from cardiac or kidney diseases.

 

1 Thomas MK; Lloyd Jones DM; Thadhani RI; Shaw AC; Deraska DJ; Kitch

BT;

Vamvakas EC; Dick IM; Prince RL; Finkelstein JS. Hypovitaminosis D

in

medical inpatients. N Engl J Med, 1998 Mar, 338:12, 777-83

 

2 Dawson Hughes B; Harris SS; Dallal GE Plasma calcidiol, season,

and serum

parathyroid hormone concentrations in healthy elderly men and women.

Am J

Clin Nutr, 1997 Jan, 65:1, 67-71

 

3 Graafmans WC; Lips P; Ooms ME; van Leeuwen JP; Pols HA;

Uitterlinden AG.

The effect of vitamin D supplementation on the bone mineral density

of the

femoral neck is associated with vitamin D receptor genotype. J Bone

Miner

Res, 1997 Aug, 12:8, 1241-5

 

4 McAlindon TE; Felson DT; Zhang Y; Hannan MT; Aliabadi P; Weissman

B; Rush

D; Wilson PW. Relation of dietary intake and serum levels of vitamin

D to

progression of osteoarthritis of the knee among participants in the

Framingham Study. Ann Intern Med, 1996 Sep, 125:5, 353-9

 

5 Oelzner P; Müller A; Deschner F; Hüller M; Abendroth K; Hein G;

Stein G.

Relationship between disease activity and serum levels of vitamin D

metabolites and PTH in rheumatoid arthritis. Calcif Tissue Int, 1998

Mar,

62:3, 193-8

 

6 Feldman D; Skowronski RJ; Peehl DM Vitamin D and prostate cancer.

Adv Exp

Med Biol, 1995, 375:, 53-63

 

7 Brenner RV; Shabahang M; Schumaker LM; Nauta RJ; Uskokovic MR;

Evans SR;

Buras RR The antiproliferative effect of vitamin D analogs on MCF-7

human

breast cancer cells. Cancer Lett, 1995 May, 92:1, 77-82

 

8 Colston KW; James SY; Ofori Kuragu EA; Binderup L; Grant AG.

Vitamin D

receptors and anti-proliferative effects of vitamin D derivatives in

human

pancreatic carcinoma cells in vivo and in vitro. Br J Cancer, 1997,

76:8,

1017-20

 

9 Lefkowitz ES; Garland CF Sunlight, vitamin D, and ovarian cancer

mortality

rates in US women. Int J Epidemiol, 1994 Dec, 23:6, 1133-6

 

10 Pritchard RS; Baron JA; Gerhardsson de Verdier M. Dietary

calcium,

vitamin D, and the risk of colorectal cancer in Stockholm, Sweden.

Cancer

Epidemiol Biomarkers Prev, 1996 Nov, 5:11, 897-900

 

11 Martínez ME; Giovannucci EL; Colditz GA; Stampfer MJ; Hunter DJ;

Speizer

FE; Wing A; Willett WC Calcium, vitamin D, and the occurrence of

colorectal

cancer among women. J Natl Cancer Inst, 1996 Oct, 88:19, 1375-82

 

12 Gann PH; Ma J; Hennekens CH; Hollis BW; Haddad JG; Stampfer MJ

Circulating vitamin D metabolites in relation to subsequent

development of

prostate cancer. Cancer Epidemiol Biomarkers Prev, 1996 Feb, 5:2,

121-6

 

13 Taylor JA; Hirvonen A; Watson M; Pittman G; Mohler JL; Bell DA

Association of prostate cancer with vitamin D receptor gene

polymorphism.

Cancer Res, 1996 Sep, 56:18, 4108-10

 

14 Hayes CE; Cantorna MT; DeLuca HF Vitamin D and multiple

sclerosis. Proc

Soc Exp Biol Med, 1997 Oct, 216:1, 21-7

 

15 Boucher BJ; Mannan N; Noonan K; Hales CN; Evans SJ Glucose

intolerance

and impairment of insulin secretion in relation to vitamin D

deficiency in

east London Asians. Diabetologia, 1995 Oct, 38:10, 1239-45

 

16 Baynes KC; Boucher BJ; Feskens EJ; Kromhout D Vitamin D, glucose

tolerance and insulinaemia in elderly men. Diabetologia, 1997 Mar,

40:3,

344-7

 

17 Watson KE; Abrolat ML; Malone LL; Hoeg JM; Doherty T; Detrano R;

Demer LL

Active serum vitamin D levels are inversely correlated with coronary

calcification. Circulation, 1997 Sep, 96:6, 1755-60

 

18 Adams JS; Lee G. Gains in bone mineral density with resolution of

vitamin

D intoxication. Ann Int Med, 1997 Aug; 127:3, 203-6

 

19 Dawson Hughes B; Harris SS; Krall EA; Dallal GE Effect of calcium

and

vitamin D supplementation on bone density in men and women 65 years

of age

or older. N Engl J Med, 1997 Sep, 337:10, 670-6

 

20 Buckley et al.Calcium and vitamin D3 supplementation prevents

bone loss

in the spine secondary to low-dose corticosteroids in patients with

rheumatoid arthritis. A randomized, double-blind, placebo-controlled

trial.

Ann Intern Med 1996 Dec 15;125(12):961-968

 

21 Lips P, Graafmans WC, Ooms ME, Bezemer PD, Bouter LM. Vitamin D

supplementation and fracture incidence in elderly persons. A

randomized,

placebo-controlled clinical trial. Ann Intern Med 1996 Feb 15;124

(4):400-406

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DietaryTipsForHBP

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