Natural sources of vitamins -
One mcg RAE is equivalent to 1 mcg retinol, 2 mcg supplemental beta-carotene, 12 mcg dietary beta-carotene, or 24 mcg dietary alpha-carotene or beta-cryptoxanthin [ 5 ]. The units of measurement for vitamin A are now mcg RAE, but International Units IUs were previously used [ 10 ].
To convert IU to mcg RAE, use the following [ ]:. RAE can only be directly converted into IUs if the sources of vitamin A are known. For example, the RDA of mcg RAE for adolescent and adult men is equivalent to 3, IU if the food or supplement source is preformed vitamin A retinol or if the supplement source is beta-carotene.
This RDA is also equivalent to 18, IU beta-carotene from food or to 36, IU alpha-carotene or beta-cryptoxanthin from food. Therefore, a mixed diet containing mcg RAE provides between 3, and 36, IU vitamin A, depending on the foods consumed. Concentrations of preformed vitamin A are highest in liver, fish, eggs, and dairy products [ 1 ].
Most dietary provitamin A in the U. diet comes from leafy green vegetables, orange and yellow vegetables, tomato products, fruits, and some vegetable oils [ 1 , 5 , 14 ]. Vitamin A is routinely added to some foods, including milk and margarine [ 1 , 2 ].
Some ready-to-eat cereals are also fortified with vitamin A. Among U. Cooking and heat treatment can increase the bioavailability of beta-carotene from foods [ 19 ]. Table 2 lists a variety of foods and their vitamin A content per serving. The foods from animal sources in Table 2 contain primarily preformed vitamin A, the plant-based foods have provitamin A, and the foods with a mixture of ingredients from animals and plants contain both preformed vitamin A and provitamin A.
Food and Drug Administration FDA developed DVs to help consumers compare the nutrient contents of foods and dietary supplements within the context of a total diet.
FDA does not require food labels to list vitamin A content unless vitamin A has been added to the food. The U. Vitamin A is available in stand-alone supplements and most multivitamins, often in the form of retinyl acetate, retinyl palmitate, provitamin A beta-carotene, or a combination [ 1 , 21 ].
Average daily intakes of vitamin A from foods and beverages in the United States were mcg RAE for men age 20 and older and mcg RAE for women in —, according to the National Health and Nutrition Examination Survey NHANES [ 23 ].
For children age 2—19, mean daily intakes of vitamin A from foods and beverages ranged from to mcg RAE. population [ 24 ]. The remainder comes from preformed vitamin A, mostly in the form of retinyl esters.
population, depending on age, uses supplements containing vitamin A [ 25 ]. Adults age 71 years or older and children younger than 9 are more likely than members of other age groups to take supplements containing vitamin A.
Frank vitamin A deficiency is rare in the United States. However, vitamin A deficiency is still common in many developing countries, often as a result of limited access to foods containing preformed vitamin A from animal-based food sources and to foods containing provitamin A carotenoids because of poverty or traditional diets [ 1 , 26 ].
Limited research suggests that vitamin A deficiency may also be influenced by genetic variability in conversion rates of beta-carotene to vitamin A. Certain polymorphisms in the BCMO1 gene have been found to reduce the activity of the BCMO1 enzyme in humans [ 8 , 9 ], and a study in the Philippines among children and adolescents found an inverse association between vitamin A status and the AV TT variant in the BCMO1 gene [ 7 ].
The first sign is night blindness, or the inability to see in low light or darkness as a result of low rhodopsin levels in the retina [ 1 , 27 , 28 ]. Xerophthalmia also affects the cornea and can eventually lead to permanent blindness; vitamin A deficiency is one of the top causes of preventable blindness in children [ 28 ].
Chronic vitamin A deficiency has also been associated with abnormal lung development, respiratory diseases such as pneumonia , and an increased risk of anemia and death [ 26 , 27 , 29 ]. Another effect of chronic vitamin A deficiency is increased severity and mortality risk of infections particularly measles and infection-associated diarrhea [ 26 ].
In , 94, children in low-income and middle-income countries died of diarrhea and 11, died of measles as a result of vitamin A deficiency [ 27 ]. Preterm infants have low liver stores of vitamin A at birth, and their plasma concentrations of retinol often remain low throughout the first year of life [ 30 , 31 ].
Preterm infants with vitamin A deficiency have a higher risk of eye and chronic lung diseases [ 32 , 33 ]. However, in high-income countries, clinical vitamin A deficiency is rare in infants and occurs only in those with malabsorption disorders [ 34 ]. Pregnant people need extra vitamin A for fetal growth and tissue maintenance and to support their own metabolism [ ].
However, in people with vitamin A deficiency, the vitamin A content of breast milk is not sufficient to maintain adequate vitamin A stores in infants who are exclusively breastfed [ 38 ]. About million preschool-age children one-third of all children in this age group , mostly in Africa and Southeast Asia, have vitamin A deficiency, according to the World Health Organization [ 27 , 39 ].
They have a higher risk of visual impairment and of illness and death from childhood infections, such as measles and infections that cause diarrheal diseases [ 1 , 39 ].
The World Health Organization estimates that 9. As a result, standard care for cystic fibrosis includes lifelong treatment with vitamin A daily amounts of mcg RAE to 3, mcg RAE, depending on age, are recommended in the United States and Australia , other fat-soluble vitamins, and pancreatic enzymes [ 41 , 43 ].
Although some evidence supports the use of vitamin A supplements in people with these disorders [ 46 ], other research has found that supplementation offers no benefit [ 47 ].
Some children and adults with newly diagnosed celiac disease also have vitamin A deficiency; a gluten-free diet can, but does not always, eliminate this deficiency [ ].
This section focuses on three diseases and disorders in which vitamin A or carotenoids might play a role: cancer, age-related macular degeneration AMD , and measles. Because of its role in regulating cell growth and differentiation, several studies have examined the association between vitamin A and various types of cancer.
However, the relationship between serum vitamin A levels or vitamin A supplementation and cancer risk or cancer-related death is unclear. This fact sheet does not include studies of all-trans retinoic acid, a vitamin A metabolite that is used as a drug in high doses to treat a form of leukemia [ 52 , 53 ].
Several systematic reviews and meta-analyses of observational studies have shown that higher dietary intakes of retinol, carotenoids, fruits and vegetables, or a combination are associated with a lower risk of lung cancer [ 54 ], non-Hodgkin lymphoma [ 55 ], pancreatic cancer [ 56 ], oral cavity cancer [ 57 ], laryngeal cancer [ 57 ], esophageal cancer [ 58 ], ovarian cancer [ 59 , 60 ], glioma [ 61 ], and bladder cancer [ 62 ].
However, other observational studies have found no association between intakes of different forms of vitamin A and risk of liver cancer [ 63 ], non-Hodgkin lymphoma [ 64 ], colorectal cancer [ 65 ], prostate cancer [ 65 ], or all cancers [ 66 ].
Some clinical trial evidence suggests that supplemental vitamin A might reduce the risk of certain cancers but increase the risk of other forms of cancer, cardiovascular disease morbidity and mortality, and all-cause mortality.
Examples are provided below. The Carotene and Retinol Efficacy Trial CARET included 18, male and female current and former smokers with at least a 20 pack-year history [equivalent to smoking 1 pack per day for 20 years or 2 packs per day for 10 years, for example] of cigarette smoking as well as some men occupationally exposed to asbestos who also have a higher risk of lung cancer , all age 45—74 years.
The study randomized participants to take supplements containing 30 mg beta-carotene plus 25, IU 7, mcg RAE retinyl palmitate or a placebo daily for about 6 years to evaluate the potential effects on lung cancer risk [ 67 ]. A subsequent study followed CARET participants for an additional 6 years after they stopped taking the study supplements [ 68 ].
The Alpha-Tocopherol, Beta-Carotene ATBC Cancer Prevention Study also found that beta-carotene supplements increased the risk of lung cancer in smokers [ 70 ]. In this study, 29, male smokers age 50—69 years who smoked an average of A subsequent study followed 25, of these participants for an additional 18 years [ 71 ].
During this period, participants were no longer taking the supplements, but most continued to smoke. The Age-Related Eye Disease Study 2 AREDS2 was a 5-year randomized clinical trial with 4, participants age 50—85 years examining the effects on AMD of a dietary supplement containing several ingredients with or without beta-carotene 15 mg [7, mcg RAE] [ 72 ].
No current smokers received the supplements containing beta-carotene. At the end of the trial, more lung cancers were discovered in the beta-carotene group than in the no beta-carotene group 23 vs.
Three other clinical trials have found no relationship between taking vitamin A or beta-carotene supplements and lung cancer incidence or mortality [ 74 ]. One trial randomized 22, male physicians age 40—84 years to take 50 mg beta carotene on alternate days or a placebo for 12 years [ 75 ].
The results showed no differences between the groups in number of cases of lung cancer or any malignant neoplasms or number of deaths from cancer. Another trial randomized 7, women mean age None of the supplements had any significant effect on total cancer incidence or cancer mortality, including from lung cancer.
A third trial included 29, healthy men and women age 40—69 years who were living in Linxian, China, where micronutrient deficiencies are common [ 77 ]. The study randomized participants to take either a placebo or one of four vitamin and mineral combinations including one providing retinol and zinc and another providing beta carotene, vitamin E, and selenium for 5.
The investigators followed participants for an additional 10 years after they stopped taking the supplements. The nutrient doses in the supplements were equivalent to or twice as high as U.
recommended intakes, but the study report did not provide the exact doses. During both the intervention and follow-up periods, lung cancer death rates did not differ among the five groups, even when the investigators further analyzed the results for differences by age, sex, and smoking status.
The CARET and ATBC study results suggest that large supplemental doses of beta-carotene with or without retinyl palmitate have detrimental effects in current or former smokers and workers exposed to asbestos.
However, the other studies described above that used similar vitamin A doses but had smaller proportions of current or former smokers do not raise this concern. Among nonsmokers, beta-carotene and vitamin A supplements do not appear to affect the risk of cancer.
Animal products like meat, fish, dairy, and eggs are good sources of vitamin A. Many fruits and vegetables are also rich in provitamin A and can help you meet your needs. Vitamin A is a fat-soluble vitamin that plays an essential role in maintaining vision, body growth, immune function, and reproductive health 1.
Getting adequate amounts of vitamin A from your diet should prevent the symptoms of deficiency, which include hair loss , skin problems , dry eyes, night blindness, and increased susceptibility to infections 1.
Deficiency is a leading cause of blindness in developing countries. In contrast, most people in developed countries get enough vitamin A from their diet 1.
The recommended dietary allowance RDA is micrograms mcg for males, mcg for females, and — mcg for children and adolescents 2. Put simply, a single daily value DV of mcg is used as a reference on nutrition labels in the United States and Canada 3.
This article lists 20 foods that are rich in vitamin A, plus an additional 20 fruits and vegetables rich in provitamin A. Vitamin A1, also known as retinol, is only found in animal-sourced foods, such as oily fish, liver, cheese, and butter.
Your body can produce vitamin A from carotenoids found in plants. These carotenoids include beta-carotene and alpha-carotene, which are collectively known as provitamin A. Depending on your genetics, the following vegetables might provide considerably less vitamin A than indicated.
You can easily meet your requirements for vitamin A by regularly eating some of the foods listed in this article. Many foods also contain added vitamin A, including cereals, margarine, and dairy products.
Since vitamin A is fat-soluble, it is more efficiently absorbed into the bloodstream when eaten with fat. You can improve your absorption of provitamin A from plant sources by adding a dash of oil to your salad.
However, as mentioned above, some people have a genetic mutation that makes the conversion of provitamin A into vitamin A much less efficient 24 , Because of this, people following a vegetarian or vegan diet should take supplements or make sure to eat plenty of the fruits and vegetables listed above.
Fortunately, foods abundant in vitamin A are usually easy to come by and most are an excellent addition to a healthy diet. Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available. VIEW ALL HISTORY. This article lists 20 foods that are high in vitamin E.
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New research shows little risk Digestive enzyme activity soruces from prostate Sourdes. Discrimination at work Natural sources of vitamins linked to Anti-angiogenesis and cancer prevention blood surces. Icy fingers and toes: Poor circulation or Raynaud's phenomenon? Vitamins and minerals are as essential for living as air and water. Not only do they keep your body healthy and functionalthey protect you from a variety of diseases. Last Water weight reduction methods and practices November This article was created by familydoctor. org editorial staff Osurces reviewed by Vitaimns S. Natural sources of vitamins, MD, FAAFP, FACSM. Micronutrients are votamins vitamins and minerals found in food. They nourish your body and are essential to your overall health. Choosing foods each day that are rich in vitamins and minerals is the best way to give your body what it needs to be healthy. This is because it is easier for your body to absorb micronutrients through food than a multivitamin alone.
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