Vitamin and mineral supplements are a good thing. But too much of a good thing can negate any health benefits — and even pose health risks. With calcium, vitamin A and vitamin D, “more is not necessarily better,” cautions Melissa Young, MD, of the Center for Integrative Medicine. Why it matters: Calcium plays a critical role in building and maintaining healthy bones. For decades, experts have recommended high-dose calcium supplements to prevent osteoporosis. The bone-thinning disease is responsible for fractures that cause many elderly men and women to lose their independence — and sometimes their lives. How too much can hurt: “More and more studies are showing increased risks for heart attack and stroke among men and women taking calcium 1,000 to 1,200 milligrams (mg) per day as directed,” says Dr. Young. Researchers believe that without adequate vitamin D to help absorb it, the extra calcium settles in the arteries instead of the bones. There, it helps form plaques that threaten the heart and brain.
Excess calcium can also cause muscle pain, mood disorders, abdominal pain and kidney stones. What to do about it: “We recommend trying to get your calcium from food,” says Dr. Young. “The body absorbs and utilizes calcium better from food than from supplements.” Probably the best source of dietary calcium is fat-free organic Greek yogurt. It gives you 450 mm of calcium per serving, plus vitamin D and protein, and two servings fulfill your calcium needs for a full day. Other sources of calcium include: Why it matters: Vitamin D works in tandem with calcium to fortify your bones, and research shows it improves asthma and depression. Vitamin D also strengthens the immune system and boosts immunity. Your skin manufactures the vitamin after exposure to the sun’s ultraviolet rays. “Yet we are an indoor society and, unlike our ancestors, we wear clothing (and sunscreen) when we go outdoors,” says Dr. Young. Most Americans are deficient in vitamin D and have blood levels in the 20s.
So most doctors recommend vitamin D supplements to bring blood levels up to 30 ng/mL. “Past studies have suggested improved benefits when vitamin D levels are closer to 50 ng/mL, so that is our target in the Center for Integrative Medicine,” says Dr. Young. New studies question the benefits of vitamin D supplements for prevention and survival from diseases. However, “in the Center for Integrative Medicine, we see significant improvement in patients’ pain, mood and quality of life with vitamin D supplements,” says Dr. Young. How too much can hurt: Vitamin D blood levels exceeding 100 ng/mL can be dangerous. The extra vitamin D triggers extra calcium absorption. This can cause muscle pain, mood disorders, abdominal pain and kidney stones. It may also increase risk for heart attack and stroke. “Most reports of toxicity involve patients taking synthetic vitamin D2, so we prescribe natural vitamin D3,” says Dr. Young. What to do about it: “We recommend starting with a simple blood test to determine your levels of vitamin D, and then prescribing vitamin D3 supplements,” says Dr. Young.
You should see your doctor every three months until you reach steady vitamin D blood levels. That usually takes six to 12 months. After that, checkups every year or every other year are fine. Why it matters: Vitamin A is important for visual health. It also contributes to healthy skin and hair, and boosts your immunity. Signs of deficiency include night blindness, dry, scaly skin around your eyes, coarse hair and respiratory infections. How too much can hurt: Fat-soluble vitamins like vitamin A can lead to toxicity because the body stores any excess in fat and does not excrete it. Two signs of vitamin A toxicity are headache and skin rashes. Research also suggests that extra vitamin A may work against vitamin D and cause osteoporosis. Vitamin A’s presence in so many different supplements compounds the problem. “Patients who take a variety of supplements are getting much more vitamin A than they should,” says Dr. Young. “We recommend no more than 5,000 international units (IU) per day from both supplements and your diet long-term.”
She does not recommend cod liver oil; it has pre-formed vitamin A that can lead to toxicity. What to do about it: It’s better to get vitamin A from orange-colored vegetables and fruit — carrots, sweet potatoes, squash and papayas. Dark green, leafy vegetables and egg yolks are also good dietary sources of A. It’s important to get as many vitamins and nutrients as you can from your food. “However, widespread changes in farming practices mean a lower nutrient content in our fruits and vegetables,” cautions Dr. Young. “Many people still benefit from their nutrient levels assessed and taking a high-quality daily multivitamin.”Almost 60,000 instances of vitamin toxicity are reported annually to US poison control centers.According to National Health and Nutrition Examination Survey (NHANES) data, in 2003–2006 33% of the United States population aged 1 year and older took a multivitamin supplement in a given month. [3] In a 2009 survey, 56% of US consumers said they take vitamins or supplements, with 44% saying they take them daily.
[4] (See Pathophysiology and Etiology.) Owing to their ability to accumulate in the body, fat-soluble vitamins have a higher potential for toxicity than do water-soluble vitamins. Iron-containing vitamins are the most toxic, especially in pediatric acute ingestions. (See Prognosis, Workup, Treatment, and Medication.) An important fat-soluble vitamin, vitamin A’s basic molecule is a retinol, or vitamin A alcohol. After absorption, retinol is transported via chylomicrons to the liver, where it is either stored as retinol ester or reexported into the plasma in combination with retinol-binding protein for delivery to tissue sites. Dietary vitamin A is obtained from preformed vitamin A (or retinyl esters), which is found in animal foods (liver, milk, kidney, fish oil), fortified foods, and drug supplements. Dietary vitamin A is also obtained from provitamin A carotenoids from plant sources, principally carrots. Dietary vitamin A is available mainly as preformed vitamin A in western countries and as provitamin A carotenoids in developing countries.
Supplements are typically 10,000-50,000 international units (IU) per capsule. Fish-liver oils may contain more than 180,000 IU/g. The acute toxic dose of vitamin A is 25,000 IU/kg, and the chronic toxic dose is 4000 IU/kg every day for 6-15 months. (Beta-carotene [ie, provitamin A] is converted to retinol but not rapidly enough for acute toxicity.) IU is not a Joint Commission on Accreditation of Healthcare Organizations [JACHO]–approved abbreviation, and it must be spelled out on patients' charts and in prescriptions. Because the body can make use of both preformed vitamin A and provitamin A carotenoids that it converts into vitamin A (retinol), and these substances have different bioactivity levels, the recommended dietary allowances (RDAs) for vitamin A are given as mcg of retinol activity equivalents (RAE). The RDAs for vitamin A are as follows The RDAs for children is as follows: Vitamin B-1 (ie, thiamine) is found in organ meats, yeast, eggs, and green, leafy vegetables.
Vitamin B-1 supplements usually contain 50-500 mg of vitamin B-1 per tablet. This vitamin is a cofactor for pyruvate dehydrogenase in the Krebs cycle. The RDA is 1.5 mg (0.7 mg for children aged 1-4 y). The RDA for vitamin B-2 (riboflavin) is 1.7 mg (0.8 mg for children aged 1-4 y). Supplements usually are 25-100 mg. Vitamin B-3 (ie, niacin) is found in green vegetables, yeast (pumpernickel bagels may contain 190 mg of niacin), animal proteins, fish, liver, and legumes. Supplements are usually 20-500 mg per tablet. Vitamin B-3 synthesis requires tryptophan. Niacin is converted to nicotinamide adenine dinucleotide (NAD) or nicotinamide adenine dinucleotide phosphate (NADP). NAD and NADP are coenzymes for dehydrogenase-type reactions. In large doses, niacin decreases synthesis of LDL cholesterol level. The RDA is 20 mg (9 mg for children aged 1-4 y). Vitamin B-6 (ie, pyridoxine) is found in poultry, fish, pork, grains, and legumes. Supplements usually are 5-500 mg per tablet.
Vitamin B-6 functions in protein and amino acid metabolism. Pyridoxine is the treatment of choice for isoniazid overdose. It is also used by bodybuilders, as well as for the treatment, with varying results, of the following The RDAs for vitamin B-6 are as follows: The RDAs for children are as follows: Vitamin B-12 (ie, cyanocobalamin), which requires an intrinsic factor for absorption, is found in milk products, eggs, fish, poultry, and meat. Supplements usually contain 25-250 mcg of the vitamin per tablet. Vitamin B-12 is a treatment of pernicious anemia and cyanide poisoning. The RDAs for vitamin B-12 are as follows The RDAs in children are as follows: Vitamin C (ie, ascorbic acid) is found in citrus fruits and vegetables. An antioxidant and reducing agent, its controversial uses include treatment of upper respiratory tract infections and cancer. [8] Supplements are usually 100-2000 mg per capsule. The RDAs for vitamin C are as follows (it has been found that individuals who smoke need an additional 35 mg/day)
The RDAs for vitamin C in children are as follows: Vitamin D (ie, cholecalciferol) is present in most dairy products, egg yolks, liver, and fish. It increases serum calcium levels by facilitating calcium absorption and mobilizing calcium from bone. Supplements usually are 400 IU per tablet. The RDAs for vitamin D are as follows Vitamin E is any of a group of at least 8 related fat-soluble compounds with similar biological antioxidant activity, particularly alpha-tocopherol but also including other isomers of tocopherol and the related compound tocotrienol. Vitamin E is found in vegetable oil, nuts, sunflower, wheat, green leafy vegetables, and fish. It is a fat-soluble vitamin that acts as an antioxidant and free-radical scavenger in lipophilic environments. Bile is required for absorption; 25% of vitamin E is absorbed orally. Storage of the vitamin occurs in adipose tissue, the liver, and muscle. Vitamin E may block absorption of vitamins A and K. In addition, it decreases low-density lipoprotein (LDL) cholesterol level at doses more than 400 IU/day.
One milligram of synthetic vitamin E (all-rac-alpha-tocopherol acetate) is equivalent to 1 IU of vitamin E. One milligram of natural vitamin E (RRR–alpha tocopherol) is equivalent to 0.45 IU of vitamin E. In a 2000 report, the Food and Nutrition Board of the National Academy of Sciences specified the RDA of vitamin E as 15 mg/day and listed the tolerable upper intake level (UL) of any alpha-tocopherol form as 1000 mg/day (1500 IU/day). The UL is the upper level that is likely to pose no risk of adverse health effects to almost all people in the general population. While in most healthy adults, short-term supplementation with up to 1600 IU of vitamin E appears to be well tolerated and have minimal side effects, the long-term safety is questionable.Data suggest a possible increase in mortality and in the incidence of heart failure with long-term use of vitamin E (400 IU or more), especially in patients with chronic diseases. [11] Therefore, a UL of 1000 mg/day may be too high, especially if only the alpha-tocopherol form of vitamin E is used (vitamin E consists of 8 compounds and supplementing only one form can be detrimental).