Page 28 - Spring2008

The best plant source of vitamin A is red palm oil. Its oily matrix tive safety and effi cacy of the two forms is still
makes its carotenes more readily converted to vitamin A and its high content controversial, vitamin D appears to be fi ve to
2
of vitamin E and low content of the polyunsaturated linoleic acid further ten times less effective at supporting long-term
augment the convertibility of its carotenes and also protect against their nutritional status. 19
potentially destructive effects. It is pure speculation, however, to suppose The RDA for vitamin D is 200 IU for in-
palm oil can be considered functionally equivalent to vitamin A-rich foods fants and adults through the age of 50, 400 IU for
such as liver and liver oils. Vegetarians should use red palm oil, but those adults between the ages of 50 and 70, and 600 IU
who are willing to include liver or liver oils in their diet would be better for adults over the age of 70. Evidence strongly
off for doing so. suggests, however, that the true requirement is
far higher. Supplements of 2,000 IU per day in
VITAMIN D infants under the age of one nearly obliterate the
Vitamin D is best known for its relation to calcium metabolism. By life-long risk of type 1 diabetes while supple-
supporting the absorption of calcium from food, it prevents and cures the ments of 800 IU or higher are required to reduce
childhood bone disease rickets and its adult counterpart osteomalacia. It the risk of fracture in the elderly. Nebraskans need
also protects against tetany, convulsions and heart failure in newborns, to supplement with 1,000 IU per day during the
helps prevent osteoporosis in the elderly, prevents the development of type coldest six months of the year to achieve blood
1 diabetes, and is believed by some researchers to have additional roles levels that maximize calcium absorption and with
in protecting against cancer, heart disease, high blood pressure, obesity, almost 5,000 IU per day during the same period
19
arthritis, multiple sclerosis and various other diseases. of time to achieve blood levels similar to those
Vitamin D was originally associated with cod liver oil and exposure achieved in sun-rich living conditions without

to ultraviolet light. It is found in the highest amounts in fish livers, the supplementation. These amounts of vitamin D

flesh of fatty fish, and the blood of land animals; and in smaller amounts should only be consumed in the context of a diet
in butter and lard from animals raised with plenty of exposure to sunshine. rich in vitamin A and vitamin K for maximal
2
Skin contains a precursor to cholesterol called 7-dehydrocholesterol that effi cacy and safety. 19
converts to vitamin D upon exposure to sunlight in the UV-B range, which Figure 2 shows the distribution of vitamin
is available year-round in the tropics but absent during an increasing por- D in foods. The easiest way to obtain dietary
tion of the year with increasing distance from the equator. 19 vitamin D is to eat fatty fish or supplement with

While humans and animals synthesize vitamin D , a second form of high-vitamin cod liver oil. Obscure mushroom
3
the vitamin called vitamin D is found in some vegetarian foods, especially products can provide large amounts of vitamin
2
mushrooms that have been exposed to ultraviolet light. Although the rela- D , but the safety and effi cacy of this form is
2

FIGURE 2. VITAMIN D CONTENT OF SELECTED FOODS

These figures are obtained from Reinhold Vieth’s chapter in the second edition of the textbook, Vitamin D , edited by
Feldman and others, except cod liver oil, which is taken from information provided by commercial manufacturers, and
pork or bovine blood, which is estimated based on blood concentrations expected in a sun-rich environment. All values
are assumed to be vitamin D unless otherwise specified.
3
FOOD (100 g unless otherwise specified) Vitamin D (IU) FOOD (100 g unless otherwise specified) Vitamin D (IU)
Dried Woody Ear or Silver Ear Fungus 16,000 (D ) Grunt and Rainbow Trout 600
2
Anglerfish Liver 4,400 Eel 200 - 560
Summer Pork or Bovine Blood (1 cup) 4,000 Cultured Red Sea Bream 520
High-Vitamin Cod Liver Oil (1 tbsp) 3,450 Mackerel 345 - 440
Indo-Pacific Marlin 1,400 Salmon 360
Chum Salmon 1,300 Canned Sardines 270
Standard Cod Liver Oil (1 tbsp.) 1,200 Chicken Egg 120
Herring 1,100 Common Mushroom 100 (D )
2
Cultured Bastard Halibut 720 Pork Liver 50
Fatty Bluefin Tuna 720 Unfortified Summer Milk (1 liter) 40
Duck Egg 720 Beef Liver 30
Dried Shitake Mushroom 640 (D ) Pork 28
2
28 Wise Traditions SPRING 2008