Vitamin E obtained from food usually does not pose a risk for toxicity. Supplemental vitamin E is not recommended due to lack of evidence supporting any added health benefits. Megadoses of supplemental vitamin E may pose a hazard to people taking blood-thinning medications such as Coumadin also known as warfarin and those on statin drugs.
Vitamin K is naturally produced by the bacteria in the intestines, and plays an essential role in normal blood clotting, promoting bone health, and helping to produce proteins for blood, bones, and kidneys. Good food sources of vitamin K are green, leafy-vegetables such as turnip greens, spinach, cauliflower, cabbage and broccoli, and certain vegetables oils including soybean oil, cottonseed oil, canola oil and olive oil.
Animal foods, in general, contain limited amounts of vitamin K. To help ensure people receive sufficient amounts of vitamin K, an Adequate Intake AI has been established for each age group Table 1. Without sufficient amounts of vitamin K, hemorrhaging can occur.
Vitamin K deficiency may appear in infants or in people who take anticoagulants, such as Coumadin warfarin , or antibiotic drugs. Newborn babies lack the intestinal bacteria to produce vitamin K and need a supplement for the first week.
Those on anticoagulant drugs blood thinners may become vitamin K deficient, but should not change their vitamin K intake without consulting a physician. People taking antibiotics may lack vitamin K temporarily because intestinal bacteria are sometimes killed as a result of long-term use of antibiotics.
Also, people with chronic diarrhea may have problems absorbing sufficient amounts of vitamin K through the intestine and should consult their physician to determine if supplementation is necessary. Although no Tolerable Upper Intake Level UL has been established for vitamin K, excessive amounts can cause the breakdown of red blood cells and liver damage.
People taking blood-thinning drugs or anticoagulants should moderate their intake of foods with vitamin K, because excess vitamin K can alter blood clotting times. Large doses of vitamin K are not advised. Table 1. There may be some overlap in specific nutrient requirements.
Berdanier, C. Advanced Nutrition: Macronutrients, Micronutrients, and Metabolism. Duyff, R. Gropper, S. Advanced Nutrition and Human Metabolism. Holick, M. Vitamin D deficiency: a worldwide problem with health consequences. American Journal of Clinical Nutrition, 87 4 , Institute of Medicine US. Kozil, graduate student. Original fact sheet revised by L. Bellows, Colorado State University Extension food and nutrition specialist and assistant professor; and R.
Preformed vitamin A, or retinol, is more likely to cause toxicity than beta-carotene, so choosing supplements containing mainly beta-carotene is safer than consuming those high in retinol. However, even high amounts of beta-carotene can cause adverse effects, turning your skin an orange color and potentially increasing cancer and heart disease risk for smokers or former smokers, according to the Office of Dietary Supplements.
You're unlikely to consume enough vitamin D from food to experience toxicity symptoms, according to the Office of Dietary Supplements, and your body won't produce toxic amounts of vitamin D from sunlight, leaving supplements as the main cause of vitamin D toxicity. Don't take supplements regularly in amounts higher than the RDA unless your doctor prescribes them. This table also shows the tolerable upper intake limit UL , which is the highest level of daily intake considered safe for For children, it ranges from 1, IU mcg to 2, IU mcg.
However, vegans may be at risk, since pre-formed vitamin A is only found in animal-sourced foods. Although provitamin A is abundant in many fruits and vegetables, it is not always efficiently converted into retinol, the active form of vitamin A. Deficiency is also widespread in some developing countries where food variety is limited. It is common in populations whose diet is dominated by refined rice, white potatoes or cassava and lacking in meat, fat and vegetables.
A common symptom of early deficiency includes night blindness. As it progresses, it may lead to more serious conditions, such as:. Severe vitamin A deficiency may lead to blindness. Other symptoms may include hair loss, skin problems and an increased risk of infections.
Overdosing on vitamin A leads to an adverse condition known as hypervitaminosis A. Its main causes are excessive doses of vitamin A from supplements, liver or fish liver oil. In contrast, high intake of provitamin A does not cause hypervitaminosis.
The main symptoms and consequences of toxicity include fatigue, headache, irritability, stomach pain, joint pain, lack of appetite, vomiting, blurred vision, skin problems and inflammation in the mouth and eyes. It may also lead to liver damage, bone loss and hair loss.
At extremely high doses, vitamin A can be fatal People are advised to avoid exceeding the upper limit for intake, which is 10, IU mcg per day for adults. Higher amounts, or , IU mg , may cause acute hypervitaminosis A in adults.
Children can experience harmful effects at much lower amounts Individual tolerance varies considerably. Children and people with liver diseases like cirrhosis and hepatitis are at an increased risk and need to take extra care.
Pregnant women should also be especially careful, since high doses of vitamin A may harm the fetus. Doses as low as 25, IU per day have been linked with birth defects High doses of vitamin A may lead to hypervitaminosis A, which is associated with various symptoms. Pregnant women should avoid eating high amounts of vitamin A because of the risk of birth defects. While supplements are beneficial for those who suffer from deficiency, most people get enough vitamin A from their diet and do not need to take supplements.
Yet, controlled studies suggest that vitamin A supplements may benefit certain people even if their diet meets the basic requirements.
For instance, vitamin A supplements may help treat measles in children 20 , Studies suggest that vitamin A acts by suppressing the measles virus Supplements mainly benefit those who are low or deficient in vitamin A.
One exception is children with measles, as studies show that supplements may help treat the disease. Vitamin A, also known as retinol, is a fat-soluble vitamin traditionally associated with vision and eye health.
It can also be derived from provitamin A carotenoids found in red, yellow and orange vegetables, as well as some leafy, dark-green vegetables. Deficiency is rare in developed countries, but is most common among people who follow diets lacking in diversity, especially those dominated by rice, white potatoes and cassava. Early symptoms of vitamin A deficiency include night blindness, and severe deficiency may eventually lead to total blindness.
Pregnant women should be extra careful not to eat excessive amounts of vitamin A because of the risk of birth defects. It is best known for its beneficial effects on bone health, and deficiency makes you highly susceptible to bone fractures. Vitamin D is a collective term used to describe a few related fat-soluble compounds. Dietary vitamin D can be classified as vitamin D2, found in mushrooms and plants, and vitamin D3, found in animal-derived foods. Vitamin D has numerous roles and functions, but only a few are well researched.
These include the following:. Once absorbed into the bloodstream, the liver and kidneys change calciferol into calcitriol, which is the biologically active form of vitamin D. It can also be stored for later use in the form of calcidiol. Vitamin D3 is more efficiently converted into calcitriol than vitamin D2 24 , One of the most important functions of vitamin D is the maintenance of calcium and phosphorus levels in blood. It benefits bone health by promoting the absorption of these minerals.
Your body can produce all the vitamin D it needs as long as you regularly expose large parts of your skin to sunlight However, many people spend little time in the sun or do so fully clothed. Justifiably, others cover their skin with sunscreen to prevent sunburns.
While sunscreen use is highly recommended, it reduces the amount of vitamin D produced by your skin. Few foods naturally contain vitamin D. The best dietary sources are fatty fish and fish oil, but mushrooms that have been exposed to ultraviolet light may also contain significant amounts. The chart below shows the amounts of vitamin D in 3. To find out more ideas of foods you can eat to increase your vitamin D intake, read this article.
Your body can produce the vitamin D it needs if you regularly expose large parts of your skin to sunlight. Use precise geolocation data. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads. Create a personalised ads profile.
Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. We take vitamins and supplements to bolster those we get from the foods we eat and the sunlight we are exposed to. They are absorbed into the body in different ways and excreted from the body at different rates. We can broadly classify them as being either water-soluble or fat-soluble. Water-soluble vitamins are those that are dissolved in water and readily absorbed into tissues for immediate use.
Because they are not stored in the body, they need to be replenished regularly in our diet. Any excess of water-soluble vitamins is quickly excreted in urine and will rarely accumulate to toxic levels.
0コメント