Vitamins are essential to man and in the former articles, we have been discussing on the benefits that each makes to health. Today, the last article of this series focuses on vitamin E and vitamin K.
Vitamin E (The Tocopherols)
The name vitamin E is given to a group of four closely related compounds called tocopherols. They are designated by letters of the Greek alphabet as alpha tocopherol, beta tocopherol, gamma tocopherol and delta tocopherol. These substances belong to the fat-soluble group of vitamins and they are found almost exclusively in plants: in nearly all green leaves and whole grains as well as in wheat germ oil, peanut oil and lettuce.
Vitamin E seems to be required by all animal cells, but its function is unknown. According to numerous studies, it has been shown that a lack of vitamin E leads to sterility in rats and to muscular dystrophy (imperfect nutrition of the muscles) in guinea pigs. However, there is little evidence of vitamin E deficiency in human beings. For instance, it has been indicated that the red blood cells of newborn infants are liable to be dissolved when subjected to dilute solutions of hydrogen peroxide and that resistance to this substance is restored to the cells by vitamin E. However, the significance of this discovery is not clear.
Overall, it is believed that normal adults need about five milligrams of mixed tocopherols every day and this dosage can be readily obtained from the diet.
Let us go back to 1929 when a Danish investigator called Henrik Dam discovered that if newly hatched chicks were placed on a fat-free diet, their blood did not coagulate readily and they developed hemorrhages in the skin, mucous membranes and other parts of their bodies. Dam found that a fat-soluble vitamin obtained from green vegetables could prevent this condition and so he called this substance vitamin K, from the first letter of the Danish word Koagulation, which means “coagulation.” This vitamin later came to be known as K1.
Years later, an American biochemist, Edward A. Doisy, succeeded in isolating a related substance, which was called K2 and then in 1943, both Dam and Doisy received a joint Nobel Prize award for their contributions. A synthetic compound called menadione, with vitamin K activity was then developed.
Vitamin K is usually found in alfalfa, spinach, carrot tops, soybean oil, tomatoes, chestnut leaves, oat sprouts, rice bran, casein and putrefying fish meal. It is also manufactured by certain bacteria, which are generally present in the intestinal tract.
This vitamin is essential for the formation, in the liver, of prothrombin, an important factor in blood clotting. Prothrombin, in the presence of other substances, is converted into thrombin. Thrombin then acts upon the protein called fibrinogen to produce coagulation of the blood. If a person suffers from a lack of vitamin K, his blood-clotting time is lengthened and he is much more likely to suffer from hemorrhages than the ordinary person does.
Normal adults rarely lack vitamin K since the bacteria in their intestinal tracts can synthesize it. However, newborn infants are particularly liable for vitamin K deficiency. The quantity of the vitamin derived from the mother before birth is small. At birth, the intestines do not contain the bacteria necessary to manufacture vitamin K and the ordinary diet during the first few days of life does not supply it. As a result, mild vitamin K deficiency is the rule rather than the exception in the newborn. If their prothrombin falls to very low levels as a result of the deficiency, hemorrhages occur.
Now, in the case of older children and adults, severe vitamin K deficiency may develop if abnormal conditions within the body interfere with proper absorption of the vitamin. This takes place in the case of diseases such as obstructive jaundice, dysentery, sprue and celiac disease. There are also other conditions that may bring about a deficiency in the blood-clotting vitamin. Besides, certain drugs such as sulfonamides and antibiotics may destroy the bacteria that manufacture vitamin K in the intestine.
So, now we come to the end of this series on vitamins, where we have dealt with the specific contributions each makes to health and bodily growth. If you liked this series, please share your comments!