Vitamin D in the Diet - Slideshow

Developed by Maulishree Jhawer, BHSc, MSc

Reviewed by The Medindia Medical Review Team on Jan 23, 2014

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Vitamin D - Synthesis

Vitamin D is a fat soluble vitamin whose synthesis in the body is dependent on factors like latitude, atmospheric pollution, clothing, skin pigmentation, duration and time of exposure to sunlight. Naturally sunlight causes the production of vitamin D endogenously in the skin from 7-dehydrocholesterol present in the subcutaneous fat. Ten minutes of exposure of the skin over the arms and face to sunlight daily is adequate to avoid deficiency.

Vitamin D - Importance

Vitamin D is crucial for calcium metabolism and its homeostasis. Adequate vitamin D is necessary:

► To maintain peak bone mass.

► To reduce the risk of osteoporosis later in life.

► To avert muscle weakness and risk of fractures.

► To help fight against cancer, autoimmune diseases, infectious diseases, type 2 diabetes and cardiovascular disease.

Vitamin D - Recommendations

Age	Male	Female
0-12 months	400 IU (10 mcg)	400 IU (10 mcg)
1-13 years	600 IU (15 mcg)	600 IU (15 mcg)
14-18 years	600 IU (15 mcg)	600 IU (15 mcg)
19-50 years	600 IU (15 mcg)	600 IU (15 mcg)
51-70 years	600 IU (15 mcg)	600 IU (15 mcg)
>70 years	800 IU (20 mcg)	800 IU (20 mcg)

Source: Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D.

*The RDAs are set on the basis of minimal sun exposure.

Vitamin D Deficiency - Causes

There are various causes of severe vitamin D deficiency in the current time. They are:

► Changing food fads and food habits

► Genetic factors: Inability to synthesize the active form of the vitamin

► Inadequate sun exposure

► Increased pollution

Vitamin D - Dietary Sources

Although very few foods in nature contain vitamin D, fatty fish (such as herring, salmon, tuna, and mackerel) and fish liver oils are among the best sources. Mushrooms are the only plant sources of vitamin D. Small amount of vitamin D2 is synthesized in mushrooms by exposure to naturally occurring UV light during growing or processing.

Vitamin D Rich Foods

Food	Serving	Vit D (IU)
Herring, cooked	75g	162
Salmon, Atlantic, cooked	75g	246
Salmon, chum, canned	75 g	168
Salmon, pink, canned	75g	435
Salmon, sockeye, canned	75g	585
Egg yolk	1	25
Mackerel, cooked	75g	81
Tuna fish, canned in water, drained	3 ounces	154
Cod liver oil	1 tablespoon	1,360

Source: U.S. Department of Agriculture, Agricultural Research Service. 2011. USDA National Nutrient Database for Standard Reference

IUs = International Units. DV = Daily Value.

Vitamin D Fortified Foods

For vegetarians, fortified foods such as milk, soy drinks, ready to eat cereals, yoghurt are the only way of getting the vitamin through diet. Food labels are not required to list vitamin D content unless a food has been fortified with this nutrient. Foods providing 20 percent or more of the daily value (DV) for vitamin D are considered a good source.

Food	Serving	Vit D (IU)
Orange juice fortified with vitamin D	1 cup	137
Milk, nonfat, reduced fat, and whole, vitamin D-fortified	1 cup	115-124
Yogurt, fortified with 20% of the DV for vitamin D	6 ounces	80
Ready-to-eat cereal, fortified with 10% of the DV for vitamin D	0.75-1 cup	40

It is mandatory for all Infant formulas to be fortified with vitamin D.

Vitamin D Deficiency - Indian Context

Habitual Indian diets do not provide even 10 percent of the requirement. More and more studies are reporting reduced circulating levels of serum 25-Hydroxyvitamin D concentrations in children of school age and adults.

According to the Expert group of Indian Council of Medical Research ensuring adequate exposure to sunlight is a way of achieving both adequate vitamin D status and controlling overweight and obesity in the population. Under situations of minimal exposure to sunlight, a recommendation of a daily supplement of 400 IU (10 microgram ) is suggested.

Vitamin D Deficiency - Prevention and Treatment

Ensuring adequate exposure to sunlight is the way out to prevent deficiency. But with minimal sun exposure and dietary intake, supplementation becomes essential. Most multiple vitamin supplements contain vitamin D.

People over 50 years of age or adults with minimal sun exposure are recommended to take a supplement between 400 IU to 2000 IU each day depending on the extent of deficiency and age.

Breastfed babies less than 1 year of age need 400 IU of vitamin D from a supplement each day.