A four-year study conducted by researchers from Harvard Medical School and other prominent universities found that individuals with retinitis pigmentosa who took daily supplements of vitamin A 15, IU and lutein 12 mg had a slower loss of peripheral vision than those who did not take the combined supplements.
Because beta-carotene is converted into vitamin A in the body, it's likely this provitamin A offers similar eye benefits as the pre-formed retinol type of vitamin A, though more research is needed to confirm this. And researchers at Columbia University Medical Center found that a synthetic, altered form of vitamin A might be able to slow the progression of Stargardt's disease , an inherited eye disease that causes severe vision loss in young people. When given to mice with the same genetic defect as humans with Stargardt's disease also called juvenile macular degeneration , the modified vitamin A inhibited the growth of clump-like deposits in the retina called "vitamin A dimers" that are associated with degenerative changes and vision loss.
Vitamin A deficiency is rare in the United States, but it is common among the poor in developing countries. It's estimated that approximately , to , malnourished children worldwide become blind each year due to vitamin A deficiency that could have been prevented with a proper diet. One of the first signs of vitamin A deficiency is night blindness.
In ancient Egypt, it was discovered that night blindness could be cured by eating liver, which later was found to be a rich source of vitamin A. A lack of vitamin A causes the cornea to become very dry, leading to clouding of the front of the eye, corneal ulcers and vision loss. Vitamin A deficiency also causes damage to the retina , which also contributes to blindness.
Because vitamin A also is important for resistance to infection and a healthy immune system, vitamin A deficiency can lead to death from respiratory and other infections.
Malnutrition: What you need to know
The concept of the Daily Value DV was developed to help consumers determine if a food contains a lot or a little of a nutrient, based on its Recommended Dietary Allowance. Vitamin A that comes from animal food sources is not water-soluble and therefore is not readily excreted from the body.
Instead, it is stored in body fat and, if ingested in excess amounts, can build up in the body and become toxic. Beta-carotene and other provitamin A carotenoids found in fruits and vegetables don't pose the same vitamin A toxicity risk. These compounds are water-soluble and are easily eliminated from the body, so vitamin A toxicity from vegetarian food sources is rare.
Beta-carotene supplements, however, may have serious risks for smokers. Two studies have found that smokers taking daily supplements containing 20 to 30 mg of beta-carotene had an increased risk of lung cancer compared with smokers who did not take the eye supplements. These studies are controversial, however, and a large study of more than 22, male physicians found no adverse health effects when these doctors took beta-carotene supplements of 50 mg every other day.
The Institute of Medicine has established the following upper intake levels for the animal-based, retinol form of vitamin A to reduce the risk of vitamin A toxicity:. Possible toxicity reactions from long-term daily consumption of vitamin A above these levels include birth defects, liver abnormalities, reduced bone mineral density that can lead to osteoporosis, and central nervous system disorders.
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Study links heavily processed foods to risk of earlier death
Some infants and children who follow a limited diet for any reason may be prone to scurvy. According to the World Health Organization WHO , million people worldwide are malnourished, and stunted development due to poor diet affects million children globally. Malnutrition during childhood can lead not only to long-term health problems but also to educational challenges and limited work opportunities in the future.
Malnourished children often have smaller babies when they grow up. It can also slow recovery from wounds and illnesses, and it can complicate diseases such as measles , pneumonia , malaria , and diarrhea. It can leave the body more susceptible to disease. Signs and symptoms of undernutrition include :. Eventually, there may be respiratory failure and heart failure , and the person may become unresponsive.
Total starvation can be fatal within 8 to 12 weeks.
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Children may show a lack of growth, and they may be tired and irritable. Behavioral and intellectual development may be slow, possibly resulting in learning difficulties. Even with treatment, there can be long-term effects on mental function, and digestive problems may persist.
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In some cases, these may be lifelong. Adults with severe undernourishment that started during adulthood usually make a full recovery with treatment. This may be caused by symptoms of an illness, for example, dysphagia , when it is difficult to swallow. Badly fitting dentures may contribute. Conditions such as depression, dementia , schizophrenia , anorexia nervosa , and bulimia can lead to malnutrition. Some people cannot leave the house to buy food or find it physically difficult to prepare meals. Those who live alone and are isolated are more at risk.
Some people do not have enough money to spend on food, and others have limited cooking skills. If the body does not absorb nutrients efficiently, even a healthful diet may not prevent malnutrition. People with Crohn's disease or ulcerative colitis may need to have part of the small intestine removed to enable them to absorb nutrients. Celiac disease is a genetic disorder that involves a gluten intolerance. It may result in damage to the lining of the intestines and poor food absorption.
Addiction to alcohol can lead to gastritis or damage to the pancreas. These can make it hard to digest food, absorb certain vitamins, and produce hormones that regulate metabolism.
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Alcohol contains calories , so the person may not feel hungry. They may not eat enough proper food to supply the body with essential nutrients. Not breastfeeding, especially in the developing world, can lead to malnutrition in infants and children. In some parts of the world, widespread and long-term malnutrition can result from a lack of food.
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There are several ways to identify adults who are malnourished or at risk of malnutrition, for example, the Malnutrition Universal Screening Tool MUST tool. MUST has been designed to identify adults, and especially older people, with malnourishment or a high risk of malnutrition. If the person is at low risk of malnutrition, their overall score will be 0. A score of 1 denotes a medium risk and 2 or more indicates a high risk. MUST is only used to identify malnutrition or the risk of malnutrition in adults. It will not identify specific nutritional imbalances or deficiences. Low risk : Recommendations include ongoing screening at the hospital and at home.
Medium risk : The person may undergo observation, their dietary intake will be documented for 3 days, and they will receive ongoing screening. High risk : The person will need treatment from a nutritionist and possibly other specialists, and they will undergo ongoing care.
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