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Vitamin Glossary

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Vitamin Glossary "A"

• Vitamin A  - Cell differentiation, bone growth, immunity, tooth development, reproduction, healthy skin, hair, mucous membranes and vision. A fat-soluble vitamin needed for the normal functioning of the eyes. It also helps the body resist infection, keeps skin cells moist, and is important in the functioning of the nervous, reproductive and respiratory systems. The best natural sources are liver—especially fish liver and fish-liver oils—whole milk, cheese and eggs. Vitamin A does not exist in plants. However, leafy green and yellow vegetables and yellow fruits contain a pigment called carotene, which the liver can convert into Vitamin A. Among the best sources of carotene are dandelion and turnip greens, carrots, collards, cantaloupe, sweet potatoes and apricots.

  Beta carotene is one of a group of substances called carotenoids which are converted to vitamin A in the intestinal wall and the liver, as the body requires. About 30 of the more than 600 carotenoids which have been identified can be converted to vitamin A in the human body. Beta carotene is the best known of the carotenoids as it has high pro-vitamin A activity and is abundant in many foods. Other carotenoids include lutein, zeaxanthin, beta-cryptoxanthin, lycopene and alpha carotene.

  What it does in the body
  The beneficial effects of beta carotene are partly due to its conversion to vitamin A but it also has potent activity of its own. Beta carotene is an antioxidant. One molecule of beta carotene can wipe out up to 1000 free radicals and may also prevent them from forming. This antioxidant ability may underlie the protective effect of beta carotene against disorders such as heart disease and cancer.

  IMMUNE SYSTEM
  Beta carotene has been shown to stimulate and enhance many immune system processes. It increases the numbers of immune cells such as B and T lymphocytes and natural killer cells. T cells play a very important role in determining immune status and are produced by the thymus gland, which is particularly sensitive to free radical and oxidative damage. Beta carotene may also protect macrophages, cells which engulf and destroy foreign substances, facilitate communication between immune cells and make the stimulatory action of interferon on the immune system more powerful.

  CANCER Research suggests that high levels of beta carotene can protect against certain types of cancer. Many population studies have shown that cancer victims often have lower dietary and/or blood beta carotene levels than healthy individuals. The evidence from these studies is strongest for lung cancer and is reasonably consistent for stomach cancer. Some research also suggests an increased risk of breast, prostate, colorectal, ovarian and cervical cancers with low beta carotene levels. It has also been found that women with low beta carotene levels in their cervical tissues may be at increased risk of cervical cancer even though their blood levels are normal. Increasing intake of beta carotene may help to overcome this "tissue specific" deficiency.

  The Western Electric Company study, which looked at the intakes of several nutrients among over 1500 men in the 1950s, recently reported an association between dietary beta carotene intake and decreased cancer risk. Those men with higher beta carotene intakes had lower rates of death from cancer and cardiovascular disease.

  People who get a lot of vitamin A from plants, in the form of carotenoids may be at less risk of developing cancer than people who obtain vitamin A from animal food sources, which suggests a protective role for beta carotene outside its pro-vitamin A activity. Drinking alcohol and smoking have been shown to decrease beta carotene levels. Beta carotene may protect against damage to cell membranes and DNA thus preventing abnormal cell formation and may also slow or halt the growth of tumors by enhancing communication between cells.

  HEART DISEASE AND STROKE High dietary beta carotene intake may be associated with a lower risk of cardiovascular disease. As an antioxidant, beta carotene has been shown to inhibit oxidative damage to cholesterol. Several studies suggest that beta carotene may protect against heart disease. These include the Nurses Health Study which was established in 1976. This study involves over 120,000 female US nurses and has found a lower risk of cardiovascular disease in those with higher beta carotene intakes.

  Another US study involving 1299 elderly people found that those in the highest beta carotene intake group had almost half the risk of death from cardiovascular disease of those in the lowest intake group.

  The Health Professionals Follow-up Study looked at the risk of cardiovascular disease in over 51 000 men aged between 40 and 75. Results showed that the risk of disease for those in the highest beta carotene intake group was 30 per cent less than for those in the lowest intake group.

  WOUND HEALING
  As beta carotene has antioxidant and anti-inflammatory properties it may promote wound healing.

  EYES
  Free radical damage is implicated in the formation of cataracts and as an antioxidant beta carotene may exert protective effects by reducing oxidative damage. It may also act as a filter and protect against light-induced damage to the fiber portion of the lens. Beta carotene may also protect against macular degeneration, a disease affecting the retina to which older people are particularly susceptible.

  Absorption Carotenes need bile acids for absorption. Beta carotene is absorbed into the wall of the small intestine where some conversion to vitamin A takes place. Only 40 to 60 per cent of beta carotene is absorbed. Low stomach acid decreases the absorption of beta carotene. Beta carotene may be stored in the lung, liver, kidneys, skin and fat.

  Deficiency
  Diets low in beta carotene may reduce the effectiveness of the immune system and lead to an increased risk of cancer and heart disease.

  Sources
  Good sources of beta carotene include carrots, sweet potatoes, pumpkin and other orange winter squashes, cantaloupe, pink grapefruit, spinach, apricots, broccoli, and most dark green leafy vegetables. The more intense the green, yellow or orange color the more beta carotene the vegetable or fruit contains. Beta carotene is not destroyed by cooking which, in fact, may make it easier to absorb.

  Recommended dietary allowances
  There is no RDA for beta carotene. An intake of 6 mg beta carotene is needed in order to meet the vitamin A RDA of 1000 mcg RE. 1 RE is equivalent to 6 mcg beta carotene. Some experts recommend a daily intake of 10 to 30 mg. The RDA for vitamin A for women who are breast-feeding increases from 800 mcg RE to 1300 mcg RE. This can be met by increasing the intake of beta carotene rich foods.

  Supplements Beta carotene supplements are available in various forms, including synthetic forms and those extracted from algae and palm oil. Some studies suggest that those extracted from palm oil are absorbed more efficiently. Natural beta carotene may have greater beneficial effects than synthetic forms.

  Toxic effects
  Unlike vitamin A, beta carotene is not toxic in large amounts although it may turn the skin yellow. There is the possibility of menstrual problems with long term excessive intake.

  Therapeutic uses
  Beta carotene supplements have been used in cancer and cardiovascular disease prevention trials including the Finnish Alpha Tocopherol Beta Carotene Cancer (ATBC) Prevention Study, the US Carotene and Retinol Efficacy Trial (CARET) and the US Physicians Health Study. These studies have recently reported results which have received wide publicity.

  ATBC STUDY
  The ATBC Prevention group studied 29 000 men who smoked and drank alcohol. The results showed an 18 per cent increase in lung cancer deaths and an 11 per cent increase in ischemic heart disease deaths in men who took daily supplements of 20 mg beta carotene.

  CARET STUDY
  In January 1996 the CARET study was stopped 21 months early. This study was examining the role of beta carotene (30 mg daily) and retinol (7500 mcg RE daily) supplementation in the prevention of cancer and heart disease in over 18 000 smokers and asbestos exposed individuals. The trial was stopped halted when the results showed a 28 per cent increased risk of lung cancer, a 26 per cent increase in the risk of death from cardiovascular disease and a 17 per cent increase in overall deaths in the group receiving the supplements.

  PHYSICIANS HEALTH STUDY
  This study examined the effect on over 22 000 male doctors of 50 mg beta carotene taken every other day for 12 years. The results suggest that beta carotene has no effect, either positive or negative, on the risk of cardiovascular disease or cancer. Analysis of a subgroup of 333 men in the study with a prior history of heart disease suggested that beta carotene supplements reduced the risk of heart attacks and death by a small amount. There are a number of possible explanations for the adverse effects of beta carotene supplements found in these studies and for the failure of supplements to show the protective effects suggested by epidemiological studies.

  Beta carotene is susceptible to oxidative damage from alcohol and the gases in cigarette smoke which may lead to the formation of harmful by-products. Beta carotene may be dependent on protection from other antioxidants, such as vitamins C and E to exert protective effects. An individual's total dietary intake of antioxidants may therefore need to be considered when assessing protection by beta carotene.

  Further analyses of results from the ATBC trial suggest that smoking and alcohol consumption may contribute to the adverse effects of beta carotene. The adverse effects appeared stronger in men who drank alcohol and in those who smoked 20 cigarettes a day than in those who smoked less. This is confirmed by the CARET results which showed greater risk in current smokers than former smokers and in those who drank alcohol.

  Beta carotene exists in over 270 possible forms and some research suggests that the specific form chosen for use in these clinical trials was not the most active agent and that a mixture of various forms of beta carotene, such as that which occurs naturally, has the most beneficial effect. It is also possible that the large dose of one particular form of beta carotene competed with other, possibly more beneficial forms at vital sites in the body.

  The results of these trials point to the importance of considering total diet and a balanced mixture of nutrients when studying protection against cancer risk. High blood levels of carotene seem to predict lower risk and these high blood levels of beta carotene may be accompanied by high levels of other carotenoids which may also play a vital part in cancer protection. Both the ATBC and CARET studies found that those with higher blood beta carotene levels on entering the trials had a lower risk of lung cancer.

  Double blind placebo controlled studies may be more useful for evaluating a specific drug for one condition in one population group and less suitable for investigating multifactorial agents in complex, mixed population studies. These studies do not invalidate hundreds of other studies showing that diets high in fruits and vegetables protect against a variety of diseases.

  OTHER USES
  Dutch researchers looking at the effect of foods rich in beta carotene on memory impairment and mental function have found protective effects. The researchers at the University of Rotterdam studied 5182 people aged 55 to 95 from 1990 to 1993. They found that those with intakes of less than 0.9 milligrams of beta carotene per day were almost twice as likely to have impaired memory, disorientation and problem solving difficulty as those with intakes of 2.1 milligrams of beta carotene.

  In addition to exerting protective effects against a wide range of diseases, beta carotene may slow the rate of aging in the skin and other organs by protecting against free radical damage caused by smoking, pollution, ultraviolet light and other chemicals. Beta carotene is used to decrease light sensitivity reactions in sufferers of the disease erythropoietic protoporphyria.

  Beta carotene supplements have been shown to have beneficial effects in cystic fibrosis by decreasing harmful lipid peroxidation. Fibrocystic breast disease, a painful cystic swelling of the breast which affects 20 to 40 per cent of premenopausal women may be helped by vitamin A and beta carotene.

  Interactions
  The conversion of beta carotene to vitamin A depends on vitamin C, zinc and thyroid hormones. Diabetics and people with hypothyroidism or liver disease have trouble converting beta carotene to vitamin A and should not rely solely on beta carotene to meet their vitamin A requirements. Large doses of beta carotene may increase the requirements for vitamin E. The function of beta carotene is enhanced by the levels of the other antioxidants, vitamin C, vitamin E and selenium.

  Cautions
  Recent research suggests that large doses of beta carotene may increase the risk of cancer in those who drink alcohol and smoke heavily. Vitamin C supplements may be useful in protecting against the damaging effects of large doses of beta carotene.

   

• abscess- a swollen or inflamed area of body tissue in which pus gathers.

   

• Acetaldehyde- an aldehyde found in cigarette smoke, auto exhaust, smog, and created in the liver from alcohol. Acetaldehyde autoxidizes (spontaneously oxidizes in the presence of air) to produce the organic peroxidase perecetic acid and damaging free radicals, and is a mutagen, carcinogen, and cross linker.

   

• acetylcholine- ACh, a natural chemical which is used as a neurotransmitter in the brain (especially for memory and the control of sensory input signals and muscular output signals), and as a neuromuscular transmitter (ACh released by muscle nerves makes muscles contract). It is made by the brain from the precursor nutrient choline.

   

• acid/alkaline balance- see pH balance.

   

• acid pH- see pH balance.

   

• acidosis- an excessive acidity of body fluids due to either an accumulation of acids or a loss of bicarbonate (the hydrogen ion concentrate is increased and thus the pH is decreased). See pH balance.

   

• acupoints- acupuncture points throughout the body, along the meridians, which corresponds to specific organs.

   

• acute- in medicine: having rapid onset, severe symptoms and short duration. Opposite of chronic.

   

• adaptogen- a substance with qualities which increase resistance and resilience to stress, enabling the body to adapt around the problem and to avoid reaching collapse. Adaptogens work through support of the adrenal glands.

   

• aerobic- oxygen-requiring metabolic processes and organisms.

   

• aging- the decline of the physiological functions which occurs with time, accompanied by a falling probability of survival.

   

• aging clocks- biological clocks which turn physiological processes on or of at specific genetically programmed times. Examples are menopause and male pattern balding.

   

• aldehydes- a class of organic compounds which have an end group with a carbon and oxygen double bonded to the same carbon. These compounds, related to formaldehyde, are cross-linkers, mutagens, and carcinogens. Malonaldehyde, created in the breakdown of peroxidized fats, is also carcinogenic, and an extremely potent cross-linker. Acetaldehyde is made from alcohol in the liver (the acetaldehyde is a major reason alcoholics have such heavily wrinkled skin) and is found in cigarette smoke and smog. Most aldehydes autoxidize, producing damaging free radicals.

   

• alkaline pH- see pH balance.

   

• allergens- substances that cause manifestations of allergy (these may or may not be antigens).

   

• alterative- a substance with properties that gradually restore proper functioning of the body, increasing health and vitality.

   

• alveoli- the air cells of a lung.

   

• amino acids- the building blocks of which proteins are constructed, and the end product of protein digestion.

   

• amyloid- a type of aging pigment which accumulates in the nerve cells and is believed to damage nervous tissues by compression and infiltration, and by blocking proper flow of vital nutrients. One type of amyloid is comprised of antibody-antigen complexes and is caused by an autoimmune disease.

   

• anaerobic- pertaining to an organism, the ability to live without oxygen.

   

• analgesic- a pain-relieving substance.

   

• androgens- male sex hormones.

   

• anecdotal evidence- observations of treatment effects in nonscientific studies, without controls, not blind. These observations cannot prove anything in themselves but sometimes provide leads for useful research.

   

• angina- there are many kinds of angina, the most common being an inflammatory disease of the throat, accompanied by spasms, choking, and difficulty breathing.

   

• angina pectoris- a heart disease involving severe pain and a feeling of pressure in the chest. Sometimes the pain radiates to the left shoulder and arm.

   

• angioplasty- altering the structure of a vessel by surgical procedure or by dilating the vessel using a balloon.

   

• anoxia- the absence of oxygen.

   

• anthelmintic- a substance with the property to destroy or expel intestinal worms.

   

• antibacterial- a substance which has the property of destroying or stopping the growth of bacteria.

   

• antibiotics- any of a variety of natural or synthetic substances that inhibit the growth of, or destroy microorganisms.

   

• antibody- a large Y shaped protein molecule made by B-cells of the immune system which very selectively binds to other specific protein molecules called antigens. Specific antibodies combine with and inactivate specific viruses, while other specific antibodies mark invading bacteria and cancer cells for destruction by other cells of the immune system.

   

• antigen- a protein, carbohydrate, or fat carbohydrate complex with the ability to identify cells as harmless and belonging to the body, or as foreign cells to be destroyed. Antigens stimulate the production of antibodies which can neutralize or destroy invading organisms. Antigens on the body's own cells are called autoantigens. Antigens on all other cells are called foreign antigens.

   

• anti-inflammatory- a substance which soothes inflammation or reduces the inflammatory response of the tissue directly. Anti-inflammatories work in a number of different ways, but rarely inhibit the natural inflammatory reaction.

   

• antimicrobial- antimicrobials help the body destroy or resist pathogenic (disease-causing) microorganisms by helping the body strengthen its own resistance to infective organisms.

   

• antioxidant- a chemical which combines with free radicals and/or other chemicals that release free radicals that would otherwise attack molecules in the body, and abnormally oxidize them. Susceptible molecules include such vital entities as DNA, RNA, lipids (fats), and proteins. The antioxidant, by reacting with the oxidant, protects these important molecules from being damaged. Examples of antioxidants include vitamins A, C, E, B-1, B-5, B-6, the amino acid cysteine, the food antioxidants BHT and BHA, and the minerals selenium and zinc.

   

• antispasmodic- antispasmodics ease cramps in smooth and skeletal muscles. They alleviate muscular tension and, as many are also nervines, ease psychological tension as well.

   

• antiviral- any substance which bears the properties of opposing the actions of a virus.

   

• arterial occlusion- a closing or blockage of an artery.

   

• arteriosclerosis- used interchangeably with the term atherosclerosis: to describe a condition affecting the arteries.

   

• artifact- a peculiar test or experimental result which is due to some unusual detail in the procedure which invalidates the usual interpretation of the test or experiment. Example: our blood sugar appears to be lethally low on the glucose oxidase blood sugar test and lethally high on the orthotoluidine blood sugar test. Both of these results are artifacts because the high levels of antioxidants in our blood interfere with the chemical reactions in these test procedures. (Our blood sugar levels are normal when measured by the hexokinase test, in which high antioxidant levels in the blood do not interfere.)

   

• astringent- astringents have a binding action on mucous membranes, skin and other tissue. They reduce irritation and inflammation, and create a barrier against infection that is helpful to wounds and burns.

   

• atherosclerosis- term applied to a variety of conditions where there is a thickening, hardening, and/or loss of elasticity of the artery walls resulting in altered function of tissues and organs.

   

• ATP- adenosine triphosphate, the universal energy storage molecule. Energy released during the oxidation of foodstuffs to carbon dioxide and water are stored in the high energy phosphate bonds of ATP.

   

• autoantibodies- antibodies which attack other molecules or cells of their own body.

   

• autoimmune disease- a disease produced when the body's normal tolerance of its own antigenic markers on cells disappears. Autoantibodies are produced by B-lymphocytes and attack normal cells, whose surface contains a "self" antigen or autoantigen, causing destruction of tissue. Includes diseases such as: rheumatoid arthritis, multiple sclerosis, and Graves' disease.

   

• autonomic nervous system- the part of the nervous system that is concerned with the control of involuntary bodily functions. It regulates the function of glands, especially the salivary, gastric, and sweat glands, and the adrenal medulla; smooth muscle tissue, and the heart. The autonomic nervous system may act on these tissues to reduce or slow activity or to initiate their function.

   

• autoxidation- a spontaneous oxidation reaction in which a molecule reacts with oxygen via a free radical, self-catalyzed route. The development of rancidity in fatty foods, the formation of gum in old gasoline, and the spontaneous combustion of rags soaked with oil-base paint are examples of autoxidation.