Vitamins

2. Introduction

2.1 Definition of Vitamins

Vitamins are organic compounds which the body needs to function normally. They cannot be manufactured by the body (with few exceptions); therefore, they must be supplied by food. In their absence, disease will develop.

2.2 Discovery of Vitamins

The first vitamin was discovered in 1897 by a Dutch biologist named Eijkman. He found that when bran was removed from rice, people consuming the refined rice developed beriberi, a serious disease. Eijkman also observed that when people ate the rice with the bran intact, no beriberi resulted. This finding directed Eijkman and other scientists to chemically analyze rice for the substance which, when not present in adequate amounts, resulted in the development of beriberi. Thiamine, named vitamin B1, was discovered to be this mystery substance.

In the following years, scientists found that there are many chemicals in food which are necessary for maintenance of health. One by one, as they were discovered, names were given to these chemicals As a group, they were named “vitamins.”

2.3 Sources of Vitamins

It is crucial to understand that scientists have not isolated every substance in food that is essential for normal functioning of the body. Thus, we must depend on food, not vitamin pills, for good nutrition. There is no vitamin pill that contains all the vitamins the body needs.

2.4 Function of Vitamins

Vitamins function in the body as coenzymes. To understand this function, consider an analogy. Suppose you were trying to build a house. The size of the house is strictly limited by your budget. You begin the process by buying the major raw materials: cement, wood and outdoor siding material. Once you have laid the foundation and framed the walls, you go to the store and buy all the windows you need. The number of windows is obviously limited by the spaces you have built in the walls for windows. For proper function of the house, you need windows.

Vitamins are like the windows in the house. Your body has a need for vitamins (windows) when it is trying to manufacture something: new tissue, energy, etc. (a house). Your body determines the exact amount it wishes to produce and brings together just enough raw materials for the purpose of construction (cement, wood, etc.). The body manufactures the necessary amount of apoenzyme (window frame) to combine with the vitamin coenzyme (window) to form an active enzyme. The active enzyme then makes a chemical reaction progress quickly (it catalyzes the reaction) leading to the formation of the desired end-product.

2.5 Vitamins Are Inert

“Vitamin function” is a commonly used phrase, as is “vitamin action.” Yet these expressions convey a misconception Vitamins cannot act, since they are inert chemical substances. In any and all physiological processes, it is the body that acts. Vitamins are used by the body for many purposes. Usually, vitamins combine chemically with other substances, thereby fulfilling the mandate of the body. It is crucial to remember that it is the body that acts on the vitamin, not the vitamin that acts on the body.

2.6 Vitamins Work Together and With Other Nutrients

Although this lesson discusses vitamins exclusively, it is important to realize that vitamins do not function alone or in a vacuum within the body. Vitamins work together; for instance, production of energy by the body when food is burned in the cells depends not only on vitamin B1, but also on vitamins B2 and niacin.

Furthermore, vitamins work together with all other nutrients such as fats, carbohydrates and proteins. For instance, vitamin B6 is needed for the normal metabolism of protein. So, even though this is a lesson on vitamins, don’t think of vitamins alone when you consider the functioning of the body. Vitamins are only one small part of the metabolic machinery of the body.

3. A Study Of Each Individual Vitamin

The discovered vitamins will be studied one by one. You will learn about their discovery, measurement, chemistry, physiology, functions, requirements, sources, effects of deficiency and effects of excess.

3.1 The Fat-Soluble Vitamins

Vitamins can be categorized according to their properties. The two basic groupings of vitamins are the fat-soluble vitamins (A, D, E and K) and the water-soluble vitamins (vitamin C and the B-complex vitamins).

Certain common characteristics distinguish the fat-soluble vitamins from the water-soluble vitamins:

Fat-soluble vitamins are absorbed into the body as fat and with fat and are soluble in fat solvents (alcohol and ether), whereas water-soluble vitamins are soluble in water.
Fat-soluble vitamins are excreted mainly by the fecal pathway, whereas water-soluble vitamins are excreted via the urinary pathway.
A text which states that the fat-soluble vitamins are stored in the body but that water-soluble vitamins are not goes on to state in a later chapter that vitamin C, a water-soluble vitamin, can be stored. They state, “It has been shown that human beings are able to store
some vitamin C; healthy, well-fed subjects store about 1500 mg. On vitamin C deprivation diets, these stores are used at an average rate of three percent of the existing reserve (pool) per day and supply the body with vitamin C for a period of about three months.” As you can see, significant amounts of this vitamin can be stored in the body.
3.1.1 Vitamin A

Discovery. This fat-soluble vitamin was discovered by McCollum and Davis of the University of Wisconsin and by Osborne and Mendel of Yale University in 1913. They found that rats on a diet with lard as the only source of fat developed eye problems and failed to grow. It was later found that a shortage of carotene, the yellow pigment of plants, led to the development of these problems. Carotene is converted into vitamin A within the organism.
Measurement. Vitamin A is measured in international units. A complicated formula exists whereby micro-grams (1/millionth gram) of vitamins are converted into international units (IUs). Amounts of vitamin A in foods and requirements for this vitamin are expressed as IUs.
Chemistry. Vitamin A is relatively stable to heat but is easily destroyed by ultraviolet radiation (as in sunlight). Chemically, it occurs in many forms: retinal, retinol and retinoic acid.
Physiology. Most dietary vitamin A is in the form of carotene, the yellow pigment of plants. About half of the carotene consumed is converted into vitamin A in the body and the other half is utilized as a hydrocarbon. Because vitamin A is fat-soluble, if the diet is devoid of fat, or if too little bile is secreted by the liver (bile is needed to digest fat), or if too little thyroid hormone is secreted, there will be poor absorption of vitamin A in the intestines. This vitamin is stored in the liver.
Functions. Vitamin A is used by the body in many important ways. The body needs it to maintain normal vision in dim light. Vitamin A is also needed for synthesis of mucus, a secretion the body uses to maintain the health of membranes lining the eyes, mouth and gastrointestinal, respiratory and genitourinary tracts. When enough vitamin A is present, when other nutrients are sufficient, and when the body is not toxic, these membranes will be in a high state of health. However, if there is not a vitamin A deficiency, taking more of this vitamin will not protect the body from diseases nor “cure” diseases. This is a myth that has been scientifically disproven many times.
Vitamin A is also needed for normal skeletal and tooth development, for formation of sperm, for the normal progression of the reproductive cycle of the female, for formation of the adrenal hormone cortisone from cholesterol, and for maintenance of the stability of all cell membranes.
Requirements. Male adults need 5000 IUs, female adults 4000 IUs, pregnant or lactating females 5000 IUs and infants about 1/10th the adult requirement of vitamin A per day. Infant needs are easily supplied by breast milk.
Sources. Healthful sources of vitamin A include dark green leafy vegetables (lettuce and other greens), green stem vegetables (broccoli, asparagus), yellow or orange vegetables (carrots, etc.) and yellow or orange fruits (peaches, cantaloupe, etc.).
Effects of deficiency. A deficiency of vitamin A is rare in the U.S. and is usually only seen in chronic diarrhea from colitis and other such diseases, liver disease or use of mineral oil. A deficient person manifests night blindness and degeneration of membranes (eye, nose, sinuses, middle ear, lungs, genitourinary tract).
Effects of Excess. Intake of excess vitamin A results in toxicity (poisoning), causing a loss of appetite, increased irritability, drying and flaking of skin, loss of hair, bone and joint pain, bone fragility, headaches and enlargement of liver and spleen. An overdose of this vitamin is about 50,000 IUs per day in adults and 20,000 IUs in infants.
3.1.2 Vitamin D

Discovery. Vitamin D was chemically isolated in food in 1930. For hundreds of years previous to the 20th century, people had used cod liver oil to supply, a factor which the body needed to maintain normal bone structure. Scientists in the 1900s were able to identify vitamin D as the necessary substance.
Measurement. Vitamin D requirements and the amounts present in foods are expressed in international units. One international unit (IU) of vitamin D is equal to 0.025 meg (a meg is one millionth of a gram) of vitamin D.
Chemistry. Chemically, vitamin D is very stable. Neither heat nor oxygen will destroy this substance. Vitamin D is produced when the skin (or flesh) of animals is exposed to ultraviolet light.
Physiology. Like vitamin A, vitamin D is fat-soluble. Therefore, bile salts are needed for absorption. Vitamin D is stored mainly in the liver. Significant amounts of this vitamin are formed by the skin of human beings exposed to sunlight.
Functions. The body needs vitamin D to maintain normal calcium and phosphorus metabolism in the body and to maintain the health of bones and teeth. With adequate D, the body is able to regulate the absorption of calcium and phosphorus from the intestines and the amount of phosphorus eliminated through the kidneys.
Requirements. Men, women and children need approximately 400 IUs of vitamin D per day. Moderate exposure to sunlight allows the body to produce all the vitamin D it needs. In the summer the body produces excess vitamin D and stores it in the liver. In the winter, when there is less sunlight, the body draws upon the stores of D in the liver to maintain normal vitamin D metabolism.
Sources. Clothing prevents formation of D in the skin with sunlight exposure, and window glass, fog and smog may also interfere. There is no scientific evidence, however, that sunlight exposure will not allow the body to produce sufficient vitamin D if the skin is exposed to light for enough time. One-half hour per day in the warm months should suffice.
Effects of deficiency. A deficiency of vitamin D will, result in rickets in infants and osteomalacia in adults. The body cannot maintain normal bone structure when too little vitamin D is present. Rickets is characterized by soft and fragile bones, especially in the legs; curvature of the spine; enlargement of certain joints; poor development of many muscles; irritability and restlessness; poor dental structure; and abnormality of the blood. Osteomalacia also is characterized by soft bones, plus leg and lower back pain, general weakness, and fractures that occur without significant trauma.
Effects of excess. Excess vitamin D results in nausea, diarrhea, loss of weight, frequent urination, all in mild cases; kidney damage, calcium deposits with damage to the heart, blood vessels and other tissue, in severe cases. A dose of vitamin D approximately 100 times the amount needed will cause poisoning and the above symptoms.
3.1.3 Vitamin E

Discovery. Shortage of another organic compound which dissolves in fat solvents was discovered in 1922 to result in destruction of the fetus in the uterus of animals. In 1936 vitamin E was chemically isolated as this substance.
Measurement. Amounts of vitamin E are expressed as international units (IUs). One IU is equal to 1 mg (1/1000th gram) of vitamin E.
Chemistry. Vitamin E is relatively stable but will break down on exposure to ultraviolet light and when exposed to rancid fats, lead or iron.
Physiology. Since vitamin E is a fat-soluble vitamin, bile salts are needed for absorption (see under vitamin A). Most vitamin E is stored in muscle and fat tissue.
Functions. The body uses vitamin E mainly as an antioxidant. It chemically combines with oxygen, and, as a result of this, other organic compounds are not destroyed by oxygen. Scientists think that vitamin E is also needed for production of certain essential tissues, especially red blood cells.
Requirements. The amount of vitamin E needed for normal body function is about 15 IUs per day. Fortunately, one of the richest sources of E in nature is un-saturated fats (oils, as found in seeds and nuts). This vitamin is also found in fruits, vegetables, sprouted grains and sprouted legumes.
Effects of deficiency. Symptoms of deficiency in animals continue to baffle scientists. When E is in extremely short supply, disease in many areas of the body results. There is breakdown of the reproductive system, muscular system, nervous system and vascular (blood vessel) system. But the conditions needed to produce such destruction in animals involve such extreme deficiency that scientists think no such problems develop in human beings from a dietary deficiency of vitamin E. Therefore, impotence, infertility, heart disease and other such problems in people are not from vitamin E deficiency and will not be helped by taking excess vitamin E.
Effects of excess. Excess intake of vitamin E, long thought to be harmless, has now been implicated in the causation of cholesterol deposits in blood vessels, elevated blood fat levels, interference in the blood-clotting process, enhanced growth of lung tumors, interference with vitamin A and iron, disturbances of the gastrointestinal tract, skin rashes, interference with thyroid gland function and damage to muscles. Megadoses of vitamin E are certainly not to be considered harmless.
3.1.4 Vitamin K

Discovery. Vitamin K was discovered in 1935. A doctor in Scandinavia found that this substance was necessary for normal clotting of the blood.
Measurement. Amounts of vitamin K are expressed as micrograms, one millionth of a gram.
Chemistry. Vitamin K is the fourth of the fat-soluble vitamins (others are A, D and E). It is easily destroyed by light but is stable to heat.
Physiology. Vitamin K is a vitamin that does not need to be supplied in food. Bacteria which live in the human intestine are fully capable of producing the vitamin  K needed  for normal  functioning of the bloodclotting apparatus. Vitamin K, being fat-soluble, is absorbed with fat and as a fat and therefore requires the presence of bile salts.
Functions. The liver produces certain organic compounds needed for the bloodclotting process. Vitamin K is required by the liver for production of these compounds.
Requirements. A dietary requirement has never been set for vitamin K because it is supplied by intestinal bacteria. A deficiency of vitamin K is unknown.
Sources. Dietary sources of vitamin K are kale and other green leafy vegetables, cabbage and cauliflower.
Effects of deficiency. A deficiency of vitamin K results in failure of the bloodclotting system, resulting in hemorrhage. This is found only in premature infants of mothers taking anti-bloodclotting drugs, in people with intestinal malabsorption and patients on sulfa drugs and antibiotics (which kill the intestinal bacteria that produce vitamin K). Intestinal malabsorption can occur as a result of liver or gallbladder disease, severe diarrhea, colitis and some other conditions; it can result in deficiency of any essential nutrient.
Effects of excess. The effects of excess vitamin K are unknown.
3.2 The Water-Soluble Vitamins

3.2.1 Vitamin C

Discovery. Vitamin C, also known as ascorbic acid, was isolated chemically in 1932 at the University of Pittsburgh. Feeding this organic compound was found to prevent scurvy. Almost 200 years previous to the chemical identification of vitamin C, Dr. James Lind, a British physician, found that scurvy would not occur if citrus fruits were consumed.
Measurement. Amounts of vitamin C are expressed in milligrams, 1/1000th of a gram.
Chemistry. Vitamin C and all the B vitamins dissolve in water but not in fat as with A, D, E and K. Vitamin C is more easily destroyed than any of the other vitamins. Heat, light, copper, and iron are especially destructive.
Physiology. Most forms of life synthesize the vitamin C they need and thus do not need a dietary source. However, humans do not synthesize this vitamin. When vitamin C is supplied to the body, the tissues quickly become saturated and excesses are eliminated in the urine.
Functions. The body uses vitamin C in many important ways. The main one is in the formation of connective tissue, the underlying structure of bone, cartilage, blood vessel walls and most other tissues. Without vitamin C, the body cannot rebuild injured tissue.
There are many other important roles of vitamin C: It is needed for normal cellular metabolism and enzyme function, for the normal metabolism of iron and folic acid (a B vitamin) and for the formation of adrenal gland hormones.
Requirements. There is much controversy about the requirement for vitamin C. The recommended dietary allowance is no more than l/10th of a gram, yet Linus Pauling states that we need 100 times that amount. Scientific evidence clearly states that l/10th of a gram,  100 milligrams, is more than enough. Some evidence indicates that slightly more than this amount may be desirable. On a Hygienic diet, with its great abundance of raw fruits and vegetables, it is easy to get over 500 milligrams per day. There is certainly no need for supplements, despite the allegations of Dr. Pauling.
Sources. Vitamin C is supplied in fruits and vegetables, especially citrus fruits, tomatoes and bell peppers. Other foods also contain small amounts of this vitamin.
Effects of deficiency. A deficiency of vitamin C results in poor connective tissue structure. Symptoms include joint pain, irritability, growth retardation, anemia, shortness of breath, poor wound healing, bleeding of gums and pinpoint hemorrhages. If the diet contains enough vitamin C and these symptoms still develop, causes other than vitamin C deficiency must be searched for. Taking large amounts of vitamin C for diseases which are not the result of a vitamin C deficiency may alleviate symptoms but will not remove the cause of the problem.
Effects of excess. Excess vitamin C, even though water-soluble and so not stored in large amounts in the body, can be harmful to your health. Problems include destruction of red blood cells; irritation of the intestinal lining; kidney stone formation; interference with iron, copper, vitamin A and bone mineral metabolism; interference with the reproductive tract, causing infertility and fetal death; diabetes; and, believe it or not, scurvy. Intake of excess amounts of vitamin C, as with most vitamins, is only possible when pills or crystals are taken.
3.2.2 Vitamin B1

Discovery. The existence of vitamin B1, also known as thiamine, was first theorized in 1897 by a Dutch doctor who found that eating polished rice would result in a serious disease called beriberi. When unpolished and unrefined rice was eaten, however, beriberi did not develop. In the 1920s and 1930s, thiamine was chemically isolated from rice bran.
Measurement. Amounts of vitamin B1 are expressed in milligrams (mg), 1/1000th of a gram, or micro-grams (meg), 1/millionth of a gram.
Chemistry. Vitamin B1 is readily destroyed in the cooking process.
Physiology and functions. This important vitamin plays a crucial role in the body’s energy-producing processes. In the body, when glucose is burned in the cells, energy is produced. This energy is stored when an organic substance named ATP is produced. Vitamin B1 is needed for the formation of ATP.
Requirements. The requirement for vitamin B1 is approximately 1/2 mg daily for infants and children, 1-1.5 mg daily for adults.
Sources. If mainly fruits and vegetables are eaten, as we recommend, significant amounts of vitamin B1 will be supplied. Other sources are nuts,  seeds, sprouted legumes and sprouted grains. When grains are refined, much of the vitamin B1 (and other vitamins) is lost.
Effects of Deficiency. A deficiency of vitamin B1 results in serious breakdown of cellular metabolism. Manifestations of this breakdown include fatigue, emotional upsets, appetite loss, weakness, vomiting and abdominal pain, heart failure and nervous system destruction (generalized weakness and/or paralysis occur). Again, it is essential to note that there are many other causes of these problems. If the diet contains enough vitamin B1, these problems will not be helped by getting more of this vitamin.
Effects of excess. The problems which develop when excess vitamin B1 is consumed have not been investigated. We can be sure, however, that problems will result when “megadoses” are ingested.
3.2.3 Vitamin B2

Discovery. In the late 1920s and early 1930s, scientists discovered a substance in food which the body needed for normal nervous system function. This substance was chemically identified and named riboflavin, also called vitamin B2.
Measurement. As with thiamine, amounts of riboflavin are expressed as milligrams or micrograms.
Chemistry. Vitamin B2 is more stable to heat than vitamin B1, but it is easily destroyed by light.
Physiology and functions. The function of vitamin B2 is much the same as B1, although neither vitamin can substitute for the other. Riboflavin is needed for the synthesis of ATP.
Requirements. The requirement for riboflavin is about the same as for thiamine. About 1/2 mg daily is needed by infants, and 1-1.5 mg per day is needed for older children and adults.
Sources. Riboflavin is supplied by green leafy vegetables, seeds and nuts.
Effects of deficiency. Symptoms of a vitamin B2 deficiency include the eyes becoming sensitive to light, easy fatigue of the eyes, blurred vision, itching and soreness of the eyes, cracks in the skin at the corners of the mouth, purplish red appearance of the lips and tongue, and eczema.
Effects of excess. Symptoms of excess intake of riboflavin have not been clearly elucidated.
3.2.4 Niacin

Discovery. Niacin deficiency disease, called pellagra, was written about hundreds of years ago. It was not until the 20th century, however, that this disease was related to a dietary deficiency. This took place when a researcher placed subjects on a diet identical to that which caused pellagra-type symptoms in certain groups of people in the South. When these symptoms occurred in the experimental subjects, the researcher concluded that pellagra is a deficiency disease. Soon after, other scientists found that niacin was the missing link.
Measurement. Amounts of niacin are expressed in milligrams.
Chemistry. This important B vitamin (called B3 by some nutritionists) is more stable than most other B vitamins; it is not easily destroyed by heat, light or exposure to oxygen.
Physiology. Not all the niacin needed by the body need be supplied as niacin. Tryptophan, an amino acid (subunit of protein), is easily converted by the body into niacin. Therefore, to have a niacin deficiency, the diet must be deficient in both niacin and tryptophan.
Functions. Niacin is intimately involved in cellular metabolic reactions which release energy from the oxidation (“burning”) of fats, carbohydrates and proteins. In this function it is quite similar to vitamins Bl and B2, but niacin cannot substitute for or be replaced by other B vitamins.
Requirements. The requirements for niacin are about 5-10 mg per day for infants and children and 15-20 mg per day for adults.
Sources. There are many sources of niacin in the diet: green leafy vegetables, potatoes, nuts arid seeds, to name a few.
Effects of deficiency. Deficiency of niacin leads to development of pellagra. This disease involves the gastrointestinal tract, skin and nervous system. Common symptoms include fatigue; headache; weight loss; backache; appetite loss; poor general health; red sore tongue; sore throat and mouth; lack of hydrochloric acid in the stomach (which results in anemia from vitamin B12 deficiency); nausea; vomiting; diarrhea; red, swollen and cracked skin; confusion; dizziness; poor memory and, in advanced cases, severe mental illness.
If the diet contains sufficient amounts of niacin, and if a person suffers from any of the aforementioned symptoms, taking extra niacin will have no beneficial effect.
Effects of excess. Intake of excess niacin has been found to cause liver damage, high levels of blood sugar, unsafe levels of uric acid in the bloodstream, and gastrointestinal distress (“stomachache”).
3.2.5 Vitamin B6

Discovery. A deficiency of vitamin B6, or pyridoxine, was first produced in animals in 1926. In. 1938, this vitamin was isolated from food and identified. In 1939, scientists synthesized it in the laboratory.
Measurement. Amounts of vitamin B6 are expressed in micrograms or milligrams.
Chemistry. Vitamin B6 is easily destroyed by light but is somewhat stable to heat.
Physiology and functions. Vitamin B6, sometimes referred to as pyridoxine, is deeply involved in the metabolism of protein. When amino acids (subunits of protein) are converted into other substances (such as tryptophan to niacin), vitamin B6 is often needed. Also, when non-protein substances are converted into amino acids, vitamin B6 is often needed.
Requirements. Infants and children require about .5-1 mg of vitamin B6 per day. Adults need about 2 mg per day.
Sources. Vegetables are the main source of vitamin B6 in the diet.
Effects of deficiency. Deficiency of vitamin B6 leads to problems in the skin, nervous system and blood in animals. It has been difficult for researchers to produce any deficiency in adult humans. In extreme experimental situations, skin disease has resulted in adults from a vitamin B6 deficiency.
Effects of excess. Generalized symptoms of toxicity (poisoning) have been recorded in rats upon intake of excess vitamin B6. Future research will certainly find damage in human beings from intake of excess vitamin B6.
3.2.6 Pantothenic Acid

Discovery. Pantothenic acid was first isolated in 1938. Two years later researchers synthesized this vitamin in the laboratory.
Measurement. Pantothenic acid is measured in milligrams.
Chemistry.  It is relatively stable, yet significant amounts are lost in cooking.
Physiology and functions. Pantothenic acid is part of coenzyme A, an organic substance which plays a critical role in many cellular metabolic pathways.
Requirements. Four to seven mg of pantothenic acid per day will fulfill the body’s needs in both adults and children.
Sources. Sources of pantothenic acid include fruits, vegetables, sprouted legumes and grains.
Effects of deficiency. A deficiency of pantothenic acid has been observed only in laboratory animals. This vitamin is widely available in common foods so that deficiency outside of the laboratory is unlikely. Symptoms of deficiency include vomiting, fatigue, a feeling of generalized sickness, pain in the abdomen, burning cramps, personality changes and blood abnormalities.
Effects of excess. Diarrhea is the only symptom thus far shown to result when excess pantothenic acid is taken.
3.2.7 Biotin

Discovery. The discovery of biotin was made when large quantities of raw eggs were fed to animals before World War II. Scientists found that raw egg whites contain avidin, a substance that inactivates biotin. The diet high in raw eggs therefore led to development of deficiency symptoms in animals.
Measurement. Amounts of biotin are expressed in micrograms.
Chemistry. This vitamin is stable to heat and light but is sensitive to oxygen.
Physiology and functions. The body uses biotin as coenzymes needed for normal metabolism of protein, carbohydrate and fat.
Requirements. The requirement for biotin is about 150 micrograms per day for adults.
Sources. Nuts and seeds are high in biotin. Another excellent source is sprouted legumes.
Effects of deficiency. Biotin deficiency is produced only when many raw eggs are consumed. Symptoms which develop include skin problems, fatigue, muscle pain, lack of appetite, nausea and blood abnormalities.
Effects of excess. The effects of excess biotin have not yet been described.
3.2.8 Vitamin B12

Discovery. Vitamin B12 was not identified until 1955. Long before, in the early 1920s, foods high in this vitamin (such as liver) were used in cases of pernicious anemia.
Measurement. Amounts of this vitamin are expressed in micrograms.
Chemistry. Vitamin B12 is not damaged by heat, but it is inactivated by light. Very little is lost in cooking.
Physiology. The physiology of vitamin B12 is complex. To be aborbed into the bloodstream, vitamin B12 must combine with an organic substance secreted by the stomach called intrinsic factor. The resultant complex can then be absorbed only at the far end of the small intestine, the terminal ileum. Disease of the stomach often results in deficiency of intrinsic factor. This condition, not a dietary deficiency of vitamin B12, is called pernicious anemia.
Functions. All cells in the body need vitamin B12 to function normally, but certain tissues need more of this vitamin than do others. These include the gastrointestinal tract, nervous system and bone marrow (where blood cells are produced).
Requirements. Infants and children need about .5-2 meg of vitamin B12 per day, with the larger amounts needed in later years. Adults need about 3 meg per day; 1 meg additional is recommended for pregnant and lactating women.
Sources. Vitamin B12 should perhaps be called the “vegetarian’s nemesis,” since standard nutrition teaches that it is only present in animal foods (meats, eggs, dairy products) and that none is found in vegetables, fruits, seeds, nuts, sprouted legumes or sprouted grains. Yet vitamin B12 is produced by bacteria that are so widely prevalent in nature that many or most vegetarian foods contain small amounts of vitamin B12. Also, scientific evidence has shown that bacteria in the human intestine can produce vitamin B12. Although vegetarians often have low blood levels of vitamin B12, there has almost never been a well-documented case of a vegetarian who was sick from a dietary vitamin B12 deficiency. Therefore, there is no need for the subject of vitamin B12 to be a “vegetarian’s nemesis.”
Effects of deficiency. When the body has a poor supply of vitamin B12, pernicious anemia will result. Fewer red blood cells are formed in the bone marrow. Advanced cases of vitamin B12 deficiency show nervous system disease characterized by “pins and needles” sensations in the hands and feet, poor balance and mental depression.
Effects of excess. The effect of taking too much vitamin B12 has not been described.
3.2.9 Folic Acid

Discovery. An unknown organic substance, distinct from all other vitamins, was found in the early 20th century to be necessary for animal health. In the 1940s the chemical structure of folic acid was described. The name comes horn folium, Latin for leaf, since folic acid is present in such great amounts in green leaves.
Measurement. Amounts of folic acid are expressed in micrograms.
Chemistry. Folic acid is not stable to light and heat so that large amounts are lost in cooking.
Physiology and functions. Folic acid is needed for the normal functioning of the genetic material in cells (DNA), for metabolism of protein and some other organic substances.
Requirements. Adults need about 400 micrograms of folic acid per day. In pregnancy, an additional 400 meg are needed, while in lactation, an additional 200 meg will suffice: Needs in infancy, as with all vitamins, are much lower, about 50 mcg per day.
Sources. Folic acid is best derived from green leafy vegetables and sprouted grains.
Effects of deficiency. A deficiency of folic acid will lead to anemia. If anemia is from vitamin B12 deficiency and folic acid is given, the body will be able to correct the anemia. The nervous system disease from vitamin B12 deficiency, however, will not be affected by giving folic acid.
Effects of excess. Effects of excess folic acid intake have not been described.

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