Annual Guide to Vitamins 2002

B Vitamins · Vitamin C · Vitamin E

HSR: Health Supplement Retailer is pleased to present its sixth annual "Guide to Vitamins," offering an overview of the health benefits and research on some of the most popular vitamins available as dietary supplements. HSR has partnered with Intramedicine, a global online research database, to bring you the latest information in an easy-to-read format to share with your customers. Intramedicine offers online databases, updated in real time, for health professionals, retailers and consumers. To obtain more information on these vitamins or story references, or to learn about using Intramedicine in your retail operation, visit www.intramedicine.com or call (877) 559-9422.

B Vitamins

The B vitamins consist of 11 water-soluble nutrients; they are considered co-enzymes that help the body metabolize food into energy, synthesize antibodies for the immune system and provide support for the daily mechanics of life. Even though this vitamin comes in many forms, it is easy to become deficient in B vitamins, especially for vegetarians, since meat is a naturally abundant source of these nutrients.

Biotin

Biotin is one of the more recently discovered B vitamins. It was first isolated in 1936, and the structure was identified in 1942 and the structure of the vitamin was synthesized in 1943. It is essential for the activity of many enzyme systems.

Biotin absorption takes place in the proximal small intestine. Dietary biotin, which is protein-bound, must be acted upon by intestinal enzymes in order to liberate free biotin for absorption. Some biotin is also absorbed from the distal small intestine where it is biosynthesized by the normal flora in the intestine. Biotin deficiency in humans is very rare, probably due to the fact that biotin is synthesized by beneficial bacteria in the human gastrointestinal (GI) tract.

Biotin plays a vital role in the production of energy from the metabolism of carbohydrates and fats. It is involved in the manufacture of fats and the excretion of byproducts from protein metabolism. It is also known as the vitamin that produces healthy hair and helps prevent graying.

Applications include:

Brittle nails: Sixty-three percent of patients gained up to a 25-percent increase in nail thickness.¹

Diabetes Mellitus: Biotin is needed to metabolize glucose² and lower blood sugar levels.³

Diabetic peripheral neuropathy: A biotin-dependent enzyme, pyruvate carboxylase, influences nervous system metabolism.⁴

Seborrheic dermatitis: Seborrheic dermatitis results from biotin deficiency, especially in infants.^5,6

SIDS: Liver biopsies of infants who died of sudden infant death syndrome (SIDS) reveal low biotin levels.⁷

Uncombable Hair Syndrome: Uncombable hair syndrome in children responds to biotin supplementation.⁸

Choline

Classifying choline as a vitamin is questionable since humans synthesize it; however, because the rate of synthesis is normally insufficient to meet human metabolic needs, choline has been included as an essential vitamin nutrient. The primary dietary source of choline is in the form of the phospholipid phosphatidylcholine (PC).

Choline is readily absorbed throughout the small intestine. Most foods contain choline in the form of PC. Both pancreatic secretions and cells in the intestinal mucosa contain enzymes that are capable of hydrolyzing PC, which releases the choline for absorption.

Choline plays a critical role in the higher level cerebrocortical functions of thoughts, memory and intellect. It is a precursor to and component of the neurotransmitter acetylcholine (ACh), which is involved in regulating a wide range of neurological activities, including the functions of movement, coordination and the stimulation of muscle contraction. High doses of PC may improve memory and cognitive function. It also functions in the metabolism of fat and the transport of fat from the liver, and can serve as a methyl donor in many important biochemical pathways. Its clinical applications include:

Alzheimer's disease: Treatment with choline slows the progression of Alzheimer's disease.¹ Alzheimer's patients treated with a combination of choline and piracetam achieved dramatic improvements in cognitive function, far greater than the improvements with either choline or piracetam.^2,3

Manic depression: Choline is an effective adjunctive treatment with lithium in the treatment of manic depression.⁴

Memory enhancement: Choline supplementation improves short-term memory probably because it is the precursor to ACh.^5,6,7

Parkinson's disease: Treatment with CDP-choline provides some symptomatic improvement.^8,9

Cobalamin (B12)

Cobalamin is the generic name of vitamin B12 because it contains the heavy metal cobalt, which gives this water-soluble vitamin its red color. Vitamin B12 is an essential growth factor and plays a role in the metabolism of cells, especially those in the gastrointestinal tract, bone marrow, and nervous tissue.

Several different cobalamin compounds exhibit vitamin B12 activity. The most stable form is cyanocobalamin, which contains a cyanide group that is well below toxic levels. To become active in the body, cyanocobalamin must be converted to either methylcobalamin or adenosylcobalamin. A protein in gastric secretions called intrinsic factor binds to vitamin B12 and facilitates its absorption. Without intrinsic factor, only a small percentage of vitamin B12 is absorbed. Once absorbed, relatively large amounts of the vitamin can be stored in the liver.

Vitamin B12 primarily functions as a methyl donor, transferring methyl groups to synthesize DNA and to convert homocysteine to methionine. It functions as a hydrogen carrier in hydrogen transfer reactions and is necessary for the maturation of red blood cells. It plays a major role in the functioning and maintenance of the nervous system and is required for the synthesis of myelin, the insulation around nerves.

AIDS: Low intrinsic factor secretion is common in AIDS and contributes to vitamin B12 malabsorption;¹ B12 also inhibits HIV replication in vitro.²

Atherosclerosis prevention: Homocysteine concentrations, when elevated, are a risk factor for atherosclerotic disease. Vitamin B12 is necessary for the metabolism of homocysteine.³

Cognitive enhancement: A literature review of recent research has noted subclinical differences in nutritional status of certain B vitamins among older adults may influence certain aspects of cognitive performance. Supplementation with cobalamin, folate and pyridoxine has been effective in enhancing cognitive performance in older adults.⁴

Crohn's disease: Sufferers typically have low vitamin B12 levels, and the vitamin is needed to repair damaged intestinal cells.⁵

Depression: Depression without anemia is a common result of cobalamin deficiency in the elderly.⁶

Diabetes: Vitamin B12 may help prevent peripheral neuropathy in diabetics.⁷

Folic Acid (B9)

Isolated in 1946 from spinach leaves, its name comes from folium, the Latin word for "leaf." In the body, folic acid is converted to its biologically active form tetrahydrofolic acid (THFA). Niacin and vitamin C are necessary for this conversion.

Folic acid absorption occurs primarily in the first part of the small intestine via two separate mechanisms: active transport, which requires a folate-binding protein, and passive diffusion, which accounts for 20 percent to 30 percent of folate absorption.

Like cobalamin, folic acid is necessary for the synthesis of DNA and RNA. It is essential for proper cellular division and the transmission of the genetic code to all newly formed cells. It is required for some methylation reactions, such as the conversion of homocysteine to methionine. Folic acid is involved in the synthesis of proteins and various amino acids and is essential for healthy blood cells. It may be best known as the vitamin that is necessary for the closure of the neural tube during pregnancy.

Alcoholism: Alcohol inhibits folate absorption and alcoholics are usually deficient.¹

Atherosclerosis: Homocysteine concentrations, when elevated, are a risk factor for atherosclerotic disease. Folic acid lowers homocysteine levels, which decreases atherogenesis.^2,3,4

Birth defects: Adequate folic acid is necessary to prevent neural tube defects such as spina bifida.⁵

Cervical dysplasia: The condition is often due to a folic acid deficiency, and many hysterectomies could be prevented with adequate folic acid supplementation.⁶

Depression: Many patients with major depression and schizophrenia improve with folic acid therapy.⁷

Osteoporosis: Folic acid lowers homocysteine levels. Homocysteine interferes with collagen crosslinking, which leads to a defective bone matrix.⁸

Inositol

Inositol is a compound that has been known for a long time, but it was in 1940 scientists first realized that it was an essential nutrient. It is found in the liver, kidney, skeletal and heart muscle. It is also present in the leaves and seeds of many plants. In animal tissues, inositol occurs as a component of phospholipids; in plants, it usually occurs as phytic acid, the hexaphosphate ester of inositol. In humans, inositol is synthesized in the intestinal tract by beneficial bacteria.

Phosphatidylinositol (PI) facilitates the production of arachidonic acid. As part of phospholipids in cellular membranes, PI helps to mediate cellular responses to external stimuli. Some studies have shown that inositol is as effective as the pharmaceutical imipramine in treating depression.¹ Studies have also shown inositol to provide significant improvement in patients with obsessive-compulsive disorder² and panic attacks.³ Inositol is useful in the prevention and treatment of diabetic neuropathy,⁴ and post-mortem studies have found the sciatic nerves of diabetic individuals contain significantly lower concentrations of inositol compared to controls.⁵

Niacin (B3)

Niacin, known as vitamin B3, can be synthesized in humans by converting tryptophan to niacin. It functions metabolically as a component of two important co-enzymes: nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), known as the pyridine nucleotides. These niacin-containing co-enzymes play an essential role in more than 200 chemical reactions in the body.

Niacin, which is also known as nicotinic acid, lowers elevated blood lipids and may reduce mortality.¹ In addition to being used alone, it has also been used in combination with cholesterol-lowering drugs to increase the lipid-lowering effect of the drugs.² Niacinamide, which is also known as nicotinamide, has been used in patients newly diagnosed with Type I diabetes to prevent further destruction of pancreatic beta cells,³ in patients with Type II diabetes who cannot be controlled with sulfonylureas,⁴ and in people with arthritis.⁵

Acne vulgaris: Research has shown 4 percent niacinamide topical gel may be superior to 1% clindamycin gel.⁶

Arthritis: Niacinamide has been used in both rheumatoid and osteoarthritis.^7,8

Cataracts: Combining niacin and riboflavin resulted in a 44-percent reduction in cataracts.⁹

Cholesterol and triglyceride lowering: Niacin, but not niacinamide, effectively lowers elevated LDL cholesterol while simultaneously raising HDL levels.¹⁰ Niacin also effectively lowers elevated levels of triglycerides.¹¹

Glucose tolerance: Niacin in combination with chromium improves glucose tolerance.¹²

Heart attack prevention: In individuals with a previous myocardial infarction, niacin provided an 11 percent reduction in subsequent heart attacks over 15 years.¹³

Panthothenic Acid (B5)

Roger Williams, Ph.D., discovered vitamin B5 in 1933 and, since it is present in all cells, he named it pantothenic acid from the Greek word pantothen, meaning "everywhere." Pantothenic acid plays a number of essential metabolic roles, including the production of some hormones and neurotransmitters, and is involved in the metabolism of all carbohydrates, fats and proteins.

Pantethine, which is the stable and most active form of pantetheine, has been reported to be effective at improving abnormal lipid profiles in both adults and children. It reportedly lowers elevated triglycerides and LDL cholesterol while raising levels of beneficial HDL cholesterol.¹ Pantethine has been reported to be especially effective at lowering elevated blood lipids in patients with diabetes without hindering blood sugar control.^2,3

It participates in the metabolism of acetaldehyde^4,5 and assists with synthesis of steroid hormones and proper functioning of the adrenal glands. Co-enzyme A (CoA), which is the active form of pantothenic acid, helps transfer two carbon units in a wide variety of biochemical reactions. CoA enhances the release of energy from carbohydrates in the Krebs cycle and assists the synthesis of phospholipids, fats, cholesterol, bile acids and acetylcholine.

Applications include:

Acne vulgaris: Pantothenic acid deficiency may be a primary cause of acne vulgaris.⁶

Adrenal support: Pantothenic acid is required for the synthesis of adrenal steroid hormones.⁷

Allergies: Some allergic individuals respond well to pantothenic acid therapy.⁸

Arthritis: Rheumatoid arthritis patients with low B5 levels have more severe disease symptoms.⁹

Constipation: At therapeutic doses, peristalsis is stimulated.¹⁰

Hyperlipidemia: Elevated cholesterol and triglycerides are lowered by pantethine but not pantothenic acid.¹¹

Surgery/wound healing: In combination, pantothenic acid and ascorbic acid significantly enhance postsurgical therapy and wound healing.¹²

Pyridoxine (B6)

Pyridoxine (vitamin B6) functions as a cofactor in more than 100 enzyme reactions. Many of its activities are related to the metabolism of amino acids and other proteins include hemoglobin, serotonin, hormones and prostaglandins. After entering a cell, vitamin B6 is phosphorylated and converted into its active form, pyridoxal 5 phosphate (PLP).

Vitamin B6 is readily absorbed in the intestines. The mucosal cells contain the enzyme pyridoxal kinase, which catalyzes the conversion to the active form PLP. Vitamin B6 can be neurotoxic when taken in large doses. In both case reports and clinical studies, doses of 1 g/d to 6 g/d have been associated with neurotoxicity.^1,2 All patients recovered without problems after discontinuing or substantially reducing their intake of vitamin B6.

Pyridoxine is required for the production of neurotransmitters derived from amino acids such as serotonin, gamma amino butyric acid (GABA), norepinephrine, acetylcholine and histamine. It regulates amino acid metabolism and is necessary for the formation of hemoglobin and the growth of red blood cells.

Applications include:

Arthritis: Patients with rheumatoid arthritis have been found to be deficient in vitamin B6.³

Asthma: Taking 50 mg two times per day dramatically decreased frequency and severity of attacks for many asthmatics.⁴

Atherosclerosis: Taken with folic acid and vitamin B12, vitamin B6 may lower homocysteine concentrations.⁵

Autism: About 30 percent of autistics experience substantial improvement with high-dose B6 therapy.⁶

Depression: Vitamin B6 is necessary for the synthesis of serotonin.⁷

Kidney stones: Pyridoxine may prevent formation of calcium oxalate stones.⁸

MSG sensitivity: Vitamin B6 is necessary to metabolize monosodium glutamate.⁹

PMS: Research shows that 50 mg/d reduces symptoms for a majority of women.¹⁰

Riboflavin (B2)

Riboflavin is essential for normal growth and development, reproduction, lactation, physical performance and well-being. It participates in essential biochemical reactions, especially those that yield energy. Vitamin B2 is water-soluble and must be supplied daily. Riboflavin belongs to a group of yellow fluorescent pigments called flavins. In its pure state, it is a yellow crystalline powder with a slight odor. When excreted, it gives the urine a characteristic bright yellow color.

Riboflavin combines with phosphoric acid to become part of two important flavin co-enzymes, FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide). FMN and FAD are known to bind to more than 100 flavoprotein enzymes. These riboflavin-containing enzymes, which function as hydrogen carriers, catalyze many of the oxidation-reduction reactions in cells.¹

Vitamin B2 is absorbed from the upper part of the small intestine, and is better absorbed when taken with food. Only approximately 15 percent is absorbed if taken alone versus 60 percent if taken with food. The conversion of riboflavin into its coenzymes takes place in most cells throughout the body, but especially in the cells of the small intestine, liver, heart and kidneys.

Riboflavin has antioxidant activity, both by itself and as part of the enzyme glutathione reductase. It plays a role in the conversion of carbohydrates to ATP in the production of energy and is necessary for growth and reproduction. FMN and FAD play roles in fatty acid synthesis.

Thiamine (B1)

Vitamin B1, also known as thiamine, was the first of the B vitamins to be discovered. It was isolated in 1926 as a water-soluble, crystalline, yellowish-white powder with a salty, slightly nutty taste. In 1936, Roger Williams, Ph.D., synthesized it and determined the chemical formula.

Thiamine plays a vital role in the conversion of blood sugar (glucose) to energy in the Krebs cycle and is involved in the synthesis of acetylcholine. Its metabolic activities primarily affect the nerves, muscles and cardiovascular system.

Beriberi is the classic vitamin B1 deficiency syndrome. When beriberi occurs in the United States, it is most commonly seen in severely malnourished infants or elderly people. In adults, alcoholism, hemodialysis or peritoneal dialysis, malabsorption syndromes and diets consisting primarily of highly processed, refined foods can be causes of vitamin B1 deficiency.¹ gastrointestinal symptoms can include anorexia, indigestion and weight loss.

Two lipid-soluble forms of vitamin B1 are available. One is named thiamine propyl disulfide (TPD). The second is thiamine tetrahydrofurfuryl disulfide (TTHF), which is sometimes called fursulthiamine. There is some indication that these compounds are more efficiently absorbed and utilized than water-soluble thiamine hydrochloride and some companies are beginning to include them in product formulations.²

Thiamine plays an essential role in energy production, and plays a role in conversion of glucose to energy. It helps convert fatty acids to hormones such as cortisol and progesterone, and turn amino acids into proteins, hormones and enzymes.

Alcohol interferes with the absorption of vitamin B1, which is necessary for the metabolism of alcohol. Severe deficiency associated with alcohol consumption produces a condition called Wernicke-Korsakoff syndrome.³

Vitamin C

Vitamin C cures the world's oldest known nutritional deficiency disease, scurvy. It was first isolated by Albert Szent-Gyorgyi in 1928 from pork adrenal glands and called hexuronic acid. In 1933, its chemical structure was established. It was successfully synthesized, and the name was changed to ascorbic acid.

Humans are one of the few species that cannot manufacture vitamin C. We must depend on our diet, or nutritional supplements, as the source of this vitamin. Vitamin C exists in nature in both its reduced form, l-ascorbic acid, and in its oxidized form, l-dehydroascorbic acid. L-ascorbic acid is the most active form. However, in the body they convert back and forth to each other in a reversible equilibrium, and both prevent scurvy. Buffered vitamin C refers to the sodium, calcium, magnesium and potassium ascorbate salts. These forms of vitamin C are less acidic and may be less likely to cause gastric irritation when taken in higher doses.

Vitamin C is a water-soluble vitamin that is stored in many tissues throughout the body, but the adrenal glands contain the highest concentration. It is easily absorbed in the small intestine. There are no known toxicities associated with vitamin C, though large doses may interfere with tests to determine occult blood in the stool and tests to monitor blood glucose levels in diabetics.

Sub-clinical deficiencies of vitamin C are common. Deficiency symptoms include capillary fragility, muscular weakness, easy bruising, gums that bleed easily, poor wound healing, anemia, poor appetite and growth, and tender, swollen joints. Hemorrhage and nonspecific bleeding are also indications, and researchers have suggested testing for vitamin C deficiency in diagnosing nonspecific bleeding in surgical patients.¹ Stressful situations (both physical and emotional) also tend to deplete the body's stores of vitamin C quickly.

Diarrhea can occur due to large doses or an overdose of vitamin C, and can generally be controlled by lowering the dose of vitamin C until the diarrhea no longer occurs. Also, approximately 15 percent of people taking moderately high doses of vitamin C experience abdominal gas, bloating and cramping. The mineral ascorbates such as calcium or magnesium ascorbate are not acidic and may solve this problem.

Functions in the Body/Clinical Applications

Vitamin C has myriad activities in the body. It is an antioxidant, neutralizing free radicals and regenerating the antioxidant vitamin E. It has enzyme activity, as it is involved in oxidation-reduction reactions, energy production, tyrosine metabolism, reduction and storage of iron, and the activation of folic acid. It is essential in the synthesis of collagen and elastin, the major structural components of skin, tendons, bone matrix, blood vessels and connective tissues. This may contribute to its ability to increase wound healing. It increases production of white blood cells, levels of antibodies and production of interferon. It is also required for the synthesis of the body's main stress response hormones in the adrenal glands, including epinephrine, norepinephrine, cortisol and histamine. Stresses, such as fever, burns, exposure to cold, physical trauma, fractures, high altitude and radiation, all require larger doses of vitamin C.

With such a variety of activities, it also has many clinical applications:

Allergies: Vitamin C's antihistamine activity helps reduce allergy symptoms.² It has also been hypothesized that the antioxidant and free radical scavenging activity of vitamin C may reduce the inflammatory or hypersensitivity responses in the body.³

Asthma: Evidence shows that low vitamin C intake is a risk factor for asthma.⁴ Though not well defined, multiple therapeutic reviews and meta-analyses have evaluated the role of vitamin C in the treatment of asthma.^5,6,7

Atherosclerosis: Evaluation of an association between vitamin C and atherosclerosis has been studied for decades and continues to this day.⁸ Studies have noted the association between low levels of vitamin C and the presence of various forms of atherosclerotic disease,^9,10 but a link to myocardial infarction is questioned.¹¹ In one study, vitamins C and E demonstrated retardation of the early progression of transplant-related coronary arteriosclerosis.¹²

Cancer: A large meta-analysis and epidemiological studies have shown that vitamin C along with other dietary vitamins reduces the risk of many different types of cancers, especially those along the digestive tract.^13,14,15

Cataracts: Long-term vitamin C supplementation substantially reduced the risk of developing cataracts.¹⁶ In fact, 158 patients were followed for three years, it was found that daily use of beta-carotene, vitamin C and vitamin E demonstrated a small deceleration in the progression of age-related cataracts.¹⁷

Cervical dysplasia: Women with cervical dysplasia were found to have low levels of vitamin C.¹⁸

Cholesterol lowering: Vitamin C has demonstrated an ability to increase HDL levels¹⁹ and has prevented the oxidation of LDL cholesterol.²⁰ However, there has been some debate regarding the clinical impact of using antioxidants such as vitamin C in conjunction with standard Western medical practices. A study involving 153 patients with coronary artery disease evaluated the clinical impact of antioxidant supplementation, including vitamin C, vitamin E, beta-carotene and selenium, on people with low HDL levels in an effort to improve the HDL-to-LDL ratio. Investigators noted that antioxidant use apparently blunted the beneficial impacts of pharmaceuticals in improving the ratio.²¹

Common cold: Analysis of 14 placebo-controlled trials showed a 35-percent average reduction in the duration of colds and a decrease in the severity of symptoms when using vitamin C at dosages above RDA levels.²²

Diabetes: Most diabetics have a greater need for vitamin C.²³

HIV: Preliminary research and observation has noted that extremely high doses, 50 g/d to 200 g/d, can suppress the symptoms of the disease and can markedly reduce the tendency for secondary infections.²⁴ In order to assess the immunological and virological effects of short-term, high-dose antioxidant treatment in patients with HIV infection, eight patients with HIV infection were given high doses of N-acetylcysteine (NAC) and vitamin C for six days. Though further study is warranted, the five patients with the most advanced immunodeficiency did experience a rise in CD4+ lymphocyte count, a reduction in HIV RNA plasma level and improvements in other measures.²⁵

Immunity: Using supplements with 1 g/d to 3 g/d provides a variety of immunostimulatory effects.²⁶

Osteoporosis: Bone loss and decreases in bone mineral density are inevitable as we age. It is important to slow this process, maintain strong healthy bones and thus decrease the risk of bone fractures. According to the National Osteoporosis Foundation, over half of Americans older than 50 have low bone mineral density, and 80 percent of those are women.²⁷ Especially when used with other therapies, vitamin C supports bone mineral density.^28,29,30,31

Wound healing: Overall, studies identify a possible role for the vitamin in wound healing, and some support the role of vitamin C in properly caring for and treating healing wounds.^32,33,34

Vitamin E

In 1932, researchers discovered that something in vegetable oils was necessary for reproduction in rats--namely, vitamin E. They referred to it as the antisterility vitamin, which turned out to be an unfortunate designation since it was subsequently found not to have this activity in humans. The same researchers isolated the pure substance from wheat germ oil in 1936 and elucidated the structure in 1938, giving it the chemical name of tocopherol (after the Greek words tokos, meaning "offspring," and phero, meaning "to bring forth").

Vitamin E is actually a group of eight compounds, including four tocopherols (alpha, beta, gamma and delta) and four additional tocotrienol derivatives. Alpha-tocopherol is the most common form. It is usually what is meant by the term vitamin E. Pure vitamin E compounds are easily oxidized, so they are manufactured as acetate or succinate esters.

Natural vitamin E is d-alpha tocopherol, whereas a synthetically produced vitamin E is a mixture consisting of both the d- and l- isomers as dl-alpha-tocopherol. It has been shown that natural vitamin E has a substantially greater bioavailability than synthetic vitamin E.¹

As with all fats, the intestinal absorption of vitamin E requires adequate production of bile salts and pancreatic enzymes. It is estimated that normally healthy humans absorb from 50 percent to 70 percent of dietary vitamin E. However, absorption efficiency falls to less than 10 percent with therapeutic doses above 200 mg/d. Natural vitamin E has approximately one and a half times the bioavailability of synthetic vitamin E.²

There are no known toxicities associated with vitamin E. Approximately 60 percent to 70 percent of the daily dose is excreted in the feces. Most individuals studied while taking large doses of vitamin E have not shown toxic effects. However, isolated cases of people taking over 1,000 IU daily reported side effects that included headache, fatigue, nausea, double vision, muscular weakness and GI distress. Symptoms of vitamin E deficiency include dry skin, dull dry hair, rupturing of red blood cells resulting in anemia, easy bruising, PMS, fibrocystic breasts, hot flashes, eczema, psoriasis, cataracts, benign prostatic hyperplasia, poor wound healing, muscle weakness and sterility.

Functions in the Body/Clinical Applications

Vitamin E is the body's most important fat-soluble antioxidant. As such, it ensures the stability and integrity of cellular tissues and membranes throughout the body by preventing free radical damage. A study involving 153 patients with coronary artery disease evaluated the clinical impact of antioxidant supplementation, including vitamin C, vitamin E, beta-carotene and selenium, on people with low HDL levels in an effort to improve the HDL-to-LDL ratio. The participants were followed for 12 months after randomization to one of three groups: placebo; simvastatin and niacin; or simvastatin, niacin plus antioxidants. The treatment groups compared to the placebo group had significant reductions in plasma cholesterol, triglycerides and LDL cholesterol. The desired increases in HDL were higher in the simvastatin/niacin group than in the simvastatin/niacin/antioxidant group. Investigators noted that antioxidant use apparently blunted the beneficial impacts of pharmaceuticals in improving the ratio.³

Vitamin E also works to decrease platelet adhesion, protecting blood vessels against developing atherosclerotic lesions and preventing oxidation of LDL cholesterol. During heavy exercise, vitamin E markedly reduces the amount of exercise-induced free radical damage to the blood and tissues, and also helps the body reduce the incidence of exercise-induced muscle injury. It has been shown to enhance the immune system and protect the eyes against cataracts and macular degeneration. Its clinical applications include:

Alzheimer's disease: Over a period of two years, vitamin E at 2,000 IU/d was shown to slow the progression of the disease.⁴

Atherosclerosis: Vitamin E retards LDL oxidation, inhibits the proliferation of smooth muscle cells, and reduces the damage to vascular endothelial cells.⁵

Cancer: Vitamin E may protect against carcinogenesis and tumor growth and could reduce the toxicity of several anticancer therapies.⁶

Cataracts: Vitamin E supplements result in a 50 percent decrease in risk of cataracts.⁷ In fact, 158 patients were followed for three years, and daily use of beta-carotene, vitamin C and vitamin E demonstrated a small deceleration in the progression of age-related cataracts.⁸

Cervical dysplasia: Women with cervical dysplasia have significantly lower plasma vitamin E levels.⁹

Crohn's disease: The comprehensive nutritional status was assessed in 32 patients and 32 healthy control subjects. Patients with Crohn's disease were found to have significantly lower levels of vitamin E compared to controls.¹⁰ Other studies have found low antioxidant levels, including vitamin E, in people with Crohn's disease and other inflammatory bowel disorders, but question the clinical significance of these findings.^11,12

Diabetes: Low vitamin E levels increase the risk of non-insulin dependant diabetes¹³, and supplementation with 900 IU/d of vitamin E improves insulin action.¹⁴

Heart attack prevention: Patients with a previous myocardial infarction who took 400 IU/d or 800 IU/d had a 47-percent reduction in secondary heart attacks.¹⁵

Osteoarthritis: At 400 IU/d, vitamin E produced significant reduction in pain scores, equal to the benefits other patients obtained from using Diclofenac.¹⁶

PMS: A dose of 400 IU/d produced significant improvement in certain affective symptoms and physical symptoms in some women with PMS.¹⁷

Rheumatoid arthritis: It was found that 1,200 IU/d of vitamin E may exert a small but significant analgesic in patients with RA.¹⁸