Vitamins, what do you need and how much?
I’m always being asked what is the correct dosage for vitamins. I tend to go on the Recommended Daily Allowance but appreciate that massive infusions of C and B may well help with countering the effects of Hepatic Encephalopathy.
A diet naturally high in vitamins and minerals can be the best defense against many diseases. Fresh fruits and vegetables and whole grains are the primary sources of vitamins, carotenoids, and phytochemicals, as well as of fiber and important minerals.
A balanced diet will provide the vitamins you need. Pregnant women may benefit from prenatal supplements and many adults benefit from supplementary vitamin D. The body can manufacture only three vitamins (D, K, and the B vitamin biotin) from nondietary sources.
The Recommended Dietary Allowance (RDA) for vitamins is gradually being replaced by a new standard called the Dietary Reference Intake (DRI). The DRI represents a shift in nutritional emphasis — from preventing deficiencies to lowering risks of chronic diseases, such as cardiovascular disease.
Vitamins and Health
Many fresh fruits and vegetables contain chemicals that may fight many cancers, including lung, breast, colon, and prostate cancers.
Smokers, however, should note that taking beta carotene supplements produce an increase in lung cancer and the overall death rates in this population. Beta carotene from food appears safe
Studies have reported that a diet high in fruits and vegetables containing beta carotene, lycopene, and other carotenoids may reduce the risk of heart attack. Diets low in lycopene (particularly from tomatoes) have been associated with a significantly higher risk of heart disease and stroke.
Carotenoids, especially lutein lycopene, and zeaxanthin are especially eye-protective and may help prevent cataracts and macular degeneration.
Studies are mixed whether vitamin supplements protect against upper respiratory infections. The weight of evidence suggests there is little or no benefit. It is possible that vitamin C or multivitamin supplements may be helpful in specific people.
Vitamins do not share a common chemistry, but they do share certain characteristics. They are all organic nutrients that are necessary in small amounts for normal body functioning and good health. Your diet or any supplements you take provide most vitamins. The body can manufacture only three vitamins (D, K, and the B vitamin biotin) from nondietary sources. Unlike carbohydrates, fats, and proteins, vitamins are not sources of energy. Instead, vitamins are chemical partners for the enzymes involved in the body’s metabolism, cell production, tissue repair, and other vital processes.
Vitamins are either fat soluble or water soluble. The fat-soluble vitamins, which include A, D, E, and K, are absorbed by the body using processes that closely parallel the absorption of fat. They are stored in the liver and used up by the body very slowly. The water-soluble vitamins include vitamin C and the B complex vitamins. The body uses these vitamins very quickly. Excess amounts are eliminated in urine.
Guidelines for Adequate Intake of Vitamins
The Recommended Dietary Allowance (RDA) for vitamins, set by the Food and Nutrition Board of the National Academy of Sciences-National Research Council, has been used for years as a guide for determining the amount of vitamins needed to prevent deficiency diseases. The RDA refers to an estimate of the average requirements of dietary components such as calories, vitamins, minerals, and proteins that are required to prevent deficiency. Different values apply to different groups based on gender and age.
The RDA is gradually being replaced by a new standard called the Dietary Reference Intake (DRI). The DRI represents a shift in nutritional emphasis — from preventing deficiencies to lowering risks of chronic diseases, such as cardiovascular disease. The DRI values comprise four categories:
The recommended dietary allowance (RDA). This is the current rating on most vitamins.
The estimated average requirement (EAR). This is the amount that will meet the nutritional requirements of 50% of the population.
Adequate intake (AI). This is an amount that will be used if there is insufficient data to calculate the RDA.
Tolerable upper intake level (UL). This is the maximum dose likely to be safe in 98% of the population.
Food and supplement labels now typically list the Daily Value (DV). This is the percentage of the amount of a nutrient that experts believe a person needs in their daily diet. On food labels it is usually based on one serving size for a person who takes in 2,000 calories a day.
Regulation of dietary supplements by the U.S. Food and Drug Administration (FDA) is a complex issue.
Labels on vitamins and other dietary supplements now include nutrient information and list all ingredients, including identifying parts of plants from which ingredients may be taken. Unlike the labels for drugs, however, labels for vitamins and supplements may not claim to prevent or treat any specific disease. Labels for vitamins and supplements include one of the following:
Health claim — description of how the substance may reduce the risk of a health-related condition
Nutrient claim — description of the amount of the nutrient in the product or
Structure or function claim — description of how the product may affect organs or systems of the body, without claiming to prevent or treat specific disease
The quality of dietary supplements depends on the manufacturer and is not regulated by FDA. The U.S. government does not require that supplements be standardized, meaning that the amounts or quality of nutrients may vary depending on the batch. So, more expensive supplements are not necessarily better than the less expensive ones. Government regulations are in the process of catching up to the boom in the supplement industry. In the meantime, some companies voluntarily adhere to rigorous quality controls, while others do not.
The U.S. Pharmacopeia (USP), an independent organization that sets quality standards for drugs, has also implemented standards for vitamins. Consumers may look for the USP label on products of companies that adhere to these standards. USP verification means the following:
What is in the bottle matches what is listed on the label.
There are no harmful levels of contaminants.
The supplement will be absorbed properly into the body.
It has been produced according to good manufacturing standards.
The FDA does not require manufacturers to provide any scientific evidence that dietary supplements are safe and effective before a product is sold (unlike drugs, which must be proven both safe and effective through clinical trials). If a supplement causes side effects in people once it is for sale, the government may place restrictions on the supplement or withdraw it from the market. The FDA may also withdraw products from the market if their labels are misleading or false.
People Who Should Take Vitamin Supplements
About 30% of Americans take at least one vitamin or mineral supplement daily. However, studies evaluating the population as a whole found that there was no difference in mortality rate between those who took vitamin supplements and those who didn’t. Most people who have a healthy diet do not need vitamins, but there are some exceptions.
Pregnant and Breast-feeding Women. Women who are pregnant or who are breast-feeding generally need additional vitamins. Folic acid and vitamins B6 and B12 are particularly important. Women who are vegetarians must be sure to avoid vitamin B12 deficiencies, which can harm their offspring. Folic acid reduces the risk for neural tube defects and possibly facial abnormalities, such as cleft palate. Studies also show that low folate levels during pregnancy are associated with low birth weight, a risk factor for the development of cardiovascular disease in adulthood. A woman’s best approach is to take extra folic acid plus multivitamin supplements (which have additional benefits), starting them before becoming pregnant.
The human body stores several years’ worth of vitamin B12, so nutritional deficiency of this vitamin is extremely rare. However, people who follow a strict vegetarian diet and do not consume eggs or dairy products may require vitamin B12 supplements.
Pregnant women with healthy diets may have low folate levels and need to take supplements. Requirements are as follows:
The recommended dietary allowance (RDA) for folic acid prior to conception is 400 mcg, and during pregnancy it is 600 mcg.
During breastfeeding 500 mcg is recommended.
Some women have low vitamin A reserves in their liver. It is important to note, however, that too much vitamin A significantly increases the risk for birth defects. Daily amounts of 10,000 IU (international units) of vitamin A in supplements and food can pose a danger. Experts recommend that pregnant women take in no more than 2,500 IU/day and avoid eating liver.
Infants and Children. Infants who are breast-fed by healthy mothers receive enough vitamins except, in some cases, vitamins K and D. Human milk has low levels of vitamin K, and the newborn’s immature intestinal tract may not produce enough of the baby’s own supply. Most babies are given an injection of this vitamin at birth. Infants being breast-fed by malnourished women or those who lack sufficient exposure to sunlight may be deficient in vitamin D. In these cases, supplements of 200 – 300 IU are recommended.
Formulas are required to contain sufficient vitamins and minerals. Beyond infancy, most American children receive all the vitamins they need from their diet, unless they are living in severely deprived circumstances.
Smokers. Smoking interferes with absorption of several vitamins, importantly vitamins C and D. Smoking can interfere with the metabolism of vitamin D, resulting in poor muscle function.
Taking high doses of antioxidant vitamins, especially beta carotene, is harmful to smokers. Instead of taking supplements, smokers should be sure their diets are rich in fresh fruits, vegetables, and whole grains. Of course, smoking cessation is the most important intervention of all.
Alcoholics. Alcoholics often suffer from multiple vitamin deficiencies. The most dangerous deficiencies are in vitamins B1 (thiamin), folic acid, B6 (pyridoxine), B2 (riboflavin), and vitamin C. Low levels of vitamin B6 are associated with increased risk of colorectal cancer in men who drink large amounts of alcohol.
People Who Have Had Gastric Bypass Surgery. Vitamin deficiency is a recognized complication of gastric bypass surgery. Women, African-Americans of both sexes, and adults who have had laparoscopic Roux-en-Y bypass surgery are at highest risk. The deficiency is treated with water-soluble vitamin supplements.
Strict Vegetarians. Strict vegetarians need supplements of vitamin B12, unless they get enough of it from fortified cereals and other grain products.
Dieters and Vegetarians. People on weight-reduction diets with less than 1,000 calories a day should probably take a multivitamin and should also check regularly with a physician.
Vegetarians may need riboflavin, vitamin B12, and vitamin D supplements. Vegans, who do not eat dairy or eggs as well as meat, may be at further risk for vitamin A deficiencies if they do not also have plenty of dark colored fruits and vegetables. Those who eat eggs and dairy products need only watch their iron levels.
Deficiencies in vegetarian children may be particularly harmful. (One study, for example, reported that adolescents who had been on macrobiotic diets before age 6 and were deficient in vitamin B12 scored lower on psychological tests.) Pregnant and breast-feeding women who are vegetarians must be sure to have sufficient vitamins. Of special note, maternal deficiencies in vitamin B12 may cause delayed growth and neurologic problems in newborns.
Older Adults. Deficiencies of vitamins and important minerals have been observed in almost a third of elderly people. Often their dietary habits slip and they fail to eat balanced meals regularly. In addition, older adults are more likely to be taking medications for a variety of conditions. Multiple drug regimens may prevent absorption of some vitamins. Elderly people, particularly if they are not exposed to sunlight, may be deficient in vitamin D. They also may have low levels of important B vitamins. (Older adults showing signs of dementia should be checked for B12 deficiencies as well as other disorders causing mental disturbances.) One study reported that the immune systems of elderly people may benefit from higher levels of vitamin E than the dietary recommended dosage. It should be noted, however, that metabolism slows down as a person ages, and in elderly people it takes the liver longer to eliminate drugs and vitamins from the body. The effect of some vitamin supplements, therefore, may be intensified. Dosage levels of vitamin A, for instance, which might be harmless in a younger adult, could be toxic in an elderly patient.
People Who Avoid Sunlight. People who avoid sunlight or are housebound, and whose diet is low in foods that contain vitamin D should take supplements. People with darker skin are at higher risk for deficiencies than those with whiter skin. (Note: vitamin D is toxic in high doses, and no one should exceed the recommended dietary intake of vitamin D except under the direction of a physician.)
Vitamin A and Provitamin A Carotenoids (Beta Carotene)
Essential for growth, bone development, vision, reproduction, and healthy skin.
Recommended dietary allowance (RDA), AI, or dietary reference intake (DRI)
(mcg = micrograms, mg = milligrams, IU = international units)
Vitamin A RDA and Upper Limit (when toxicity is risk) are the following:
For children: 1,000 IU ages one to three (upper limit is 2,000 IU); 1,333 IU ages 4 – 8 (upper limit is 3,000 IU); and 2,000 IU for 9 – 13 (upper limit is 5,665 IU).
For nonpregnant women: 2,333 IU ages 14 through adulthood. (Upper limit is 9,335 IU for ages 14 – 18 and 10,000 IU for women over 19.)
For pregnant women: 2,500 IU for pregnant women under 18; 2,565 IU for pregnant women over 19. (Upper limit is 9,335 IU for ages 14 – 18 and 10,000 IU for women over 19. It should be noted that some experts recommend 8,000 IU as the upper limit during pregnancy.)
Warning: Use of preformed vitamin A, including the skin acne medication tretinoin (a vitamin A derivative), during pregnancy can cause birth defects.
For nursing women: 4,000 IU for nursing mothers under 18; 4,335 IU for nursing mothers over 19. (Upper limit is 9,335 IU for ages 14 – 18 and 10,000 IU for women over 19.)
For men: 3,000 IU ages 14 – 18; 3,000 IU for ages 19 and above. (Upper limit is 10,000 IU.)
Note: In determining the daily vitamin A allowance, experts also take note of provitamins, such beta carotene, that convert to vitamin A. Some experts recommend 3 – 6 mg of beta-carotene.
Vitamin A is also now being measured with a new unit called the Retinol Activity Equivalent (RAE). One RAE is equal to 1 mcg retinol, 12 mcg beta-carotene, 24 mcg alpha-carotene, and 24 mcg beta-cryptoxanthin. Retinol is the most active form of vitamin A.
Foods containing the vitamin
Animal products, such as liver, dairy products, eggs, and fish liver oil. Provitamin A carotenoids are also found in dark red, green, and yellow vegetables and fruits. Requires some dietary fat to be absorbed.
Effects of deficiencies
Skin disorders, severe diarrhea, and eye damage. In less developed countries severe deficiencies cause blindness in 250,000 children each year. Diets low in vitamin A may also increase the risk of developing cancer. Low dietary intake of vitamin A has been associated with impaired lung function in children.
People at risk for deficiencies
Preschool children and any child with inadequate intake of protein, calories, and zinc. Iron deficiency may also impair metabolism of vitamin A.
People with asthma.
People with serious disorders in the intestine, liver or pancreas, such as cystic fibrosis, steatorrhea, biliary obstruction, inflammatory bowel disease, cirrhosis, and others.
People who have undergone Roux-en-Y gastric bypass surgery.
Vegans (vegetarians who do not eat eggs and dairy). Such individuals should be sure to have plenty of deep-colored fruits and vegetables.
People who abuse alcohol. It should be noted, however, that although people with alcoholism may be at risk for vitamin A deficiency, a combination of high-dose vitamin A and alcohol may cause toxic liver damage.
Healthy adults usually have a year’s store of vitamin A in the liver, so temporary nutritional deficiencies or problems with fat absorption are unlikely to cause serious vitamin A deficiency problems.
Even moderately high doses appear to increase the risk of hip fractures.
Very toxic when taken in high-dose supplements for long periods of time.
Symptoms of overdose include dizziness, nausea, vomiting, headache, skin damage, mental disturbances, and, in women, infrequent periods.
Can affect almost every part of the body, including eyes, bones, blood, skin, central nervous system, liver, and genital and urinary tracts. Severe toxicity can cause blindness and may even be life threatening. In children, chronic overdose can cause fluid on the brain and as well as the same complications seen in adults. High consumption of vitamin A may also increase the risk of gastric cancer, osteoporosis, and fractures in both men and women.
Pregnant women who take amounts not much higher than RDA levels increase the risk for birth defects in their children. Liver damage can occur in children who take RDA-approved adult levels over prolonged periods of time or in adults who take as little as five times the RDA-approved amount for 7 – 10 years.
B Vitamins, part 1
B Vitamins: General Information
Vitamin B1 (thiamin)
The B vitamins have a wide and varied range of functions in the human body. Most B vitamins are involved in the process of converting blood sugar into energy.
Essential for converting blood sugar into energy and is involved in metabolic activities in nerves, heart, and muscles and in the production of red blood cells.
Recommended dietary allowance (RDA), AI, or dietary reference intake (DRI)
(mcg = micrograms, mg = milligrams, IU = international units)
RDA is 0.5 mg/day for children aged 1-3 years, 0.6 mg/day for children aged 4-8, 0.9 mg/day for children aged 9-13, 1.2 for teen boys and men (ages 14 and up), 1 mg/day for girls aged 14-18 years, and 1.1 mg for women aged 18 and older. The RDA for pregnant and nursing women is 1.4 mg/day.