营养素知识: Vitamin A, RAE

LogixPath Chef 首页 > 食品标签上的营养素 > 营养素知识

营养成分主要信息
营养素名称:	Vitamin A, RAE
营养素类别:	Vitamins and Other Components
计量单位:	µg
概要:	Vitamin A is important for vision, skin tissues, reproduction, embryonic development, bone growth, and immune function.
营养素功效:	The main forms of Vitamin A are: Preformed (active form) Vitamin A: The primary dietary form is retinol. They naturally exist in meats, fish, and dairy products. Body can convert retinol to retinal (reversible conversion), and convert retinal to retinoic acid (irreversible conversion). Retinoic acid is actively transported into the cell nucleus where it regulates thousands of genes. Retinol, retinal, and retinoic acid are collectively called Vitamin A retinoids. Provitamin A carotenoids: beta-carotene, an orange pigment. It is a precursor of Vitamin A. It is converted into retinol in the intestine and liver. Beta-carotene exists in vegetables, fruits, and plant-based oils. The absorption and conversion rate from beta-carotene to retinol is not that efficient. The conversion rate from plant based beta-carotene to vitamin A RAE is 12 mcg beta-carotene to 1 mcg RAE. In addition to be a Provitamin A, beta-carotene also acts as an antioxidant in the body. Body storage form of retinol: retinyl ester. Most of Vitamin A are stored in liver in the form of retinyl esters for later use. Retinyl esters are often used in the supplements, and fortified foods. RAE stands for Retinol Activity Equivalents. RAE value is used as the recommended daily value for Vitamin A. 1 microgram (mcg or µg) of retinol is 1 RAE. 12 mcg of dietary beta-carotene is 1 RAE. Each form of vitamin A performs a specific function in the body. Benefits to eye health: 1) Retinal is required by the eye to transduce light into the neural signals necessary for color vision and low-light vision. 2) Retinoic acid is required to maintain crystal-clear cornea and conjunctiva membranes (which covers the surface of your eye), thus to prevent xerophthalmia. Benefits to skin tissue health: Outside and inside body is covered by epithelial cells. 1) Outside skin epithelial cells: vitamin A and beta-carotene help protect against skin damage from sunlight. It can stimulate skin cell growth. 2) Inside body epithelial cells: mucous membranes for mouth, stomach, intestines, lungs, various passageways, etc. Vitamin A helps to maintain their integrity and health. Supporting reproduction: 1) For men, retinol of Vitamin A participates in sperm development. 2) For women, vitamin A supports normal embryonic development during pregnancy. Role in bone growth: Bone growth includes 2 steps: 1) dismantle old bone cells (osteoclasts) 2) generate new bone cells (osteoblasts). Vitamin A participates in the old bone cell dismantling process. Support immune function: Retinoic acid form of Vitamin A participates in the cell replication and specialization that supports immune T-cells and antibody production and the anti-inflammatory response. T-cells is a type of white blood cell that protects your body from infection. Help red blood cell formation: Vitamin A helps iron mobilization from stores, thus improves hemoglobin concentrations. Vitamin A is a fat-soluble vitamin. Taking with a meal containing fats can increase its absorption.

Vitamin A Foods

Vitamin A Chemistry Structure

食物来源

Preformed Vitamin A (retinol) exists naturally in animal-based foods. The efficiency of preformed vitamin A absorption is higher (from 70 to 90%). The primary food sources are:
• Liver
• Fish: such as bluefin tuna fish, king mackerel, trout, salmon
• Dairy products: such as various cheese
• Egg yolk

Dietary Provitamin A carotenoids exist in vegetables, fruits, and plant-based oils. The efficiency of Provitamin A carotenoids absorption and conversion is relatively lower (~ 9-22%). The primary food sources are:
• Sweet potatoes
• Carrots
• Orange color pumpkin and butternut squash
• Deep orange fruits: such as cantaloupe, apricots, and mangos
• Dark green leafy vegetables: such as spinach, Swiss chard, kale, and broccoli
• Red peppers

Foods fortified with vitamin A:
• Low-fat and nonfat milk
• Fortified grains and cereals
• Margarine

Notes:
• Dietary fat may enhance the absorption of Vitamin A.
• Cooked carrots and spinach has greater absorption rate of Vitamin A.
• Alcohol consumption may negatively affect vitamin A stores in liver.

富含营养素食物示例: Vitamin A, RAE 查阅更多主要食物来源
	食物描述	营养含量¹	每日需量%²
	Beef, variety meats and by-products, liver, cooked, braised 类别: Beef Products 类似食物: beef liver	9,442 µg	1,049.11%
	Pork, fresh, variety meats and by-products, liver, cooked, braised 类别: Pork Products 类似食物: cooked pork by-products	5,405 µg	600.56%
	Fish, tuna, fresh, bluefin, cooked, dry heat 类别: Finfish and Shellfish Products 类似食物: cooked tuna fish	757 µg	84.11%
	Sweet potato, cooked, baked in skin, flesh, without salt 类别: Vegetables and Vegetable Products 类似食物: cooked sweet potato	961 µg	106.78%
	Carrots, cooked, boiled, drained, without salt 类别: Vegetables and Vegetable Products 类似食物: carrot	852 µg	94.67%
	Mustard greens, cooked, boiled, drained, without salt 类别: Vegetables and Vegetable Products 类似食物: mustard green	618 µg	68.67%
	Spinach, cooked, boiled, drained, with salt 类别: Vegetables and Vegetable Products 类似食物: spinach	524 µg	58.22%
	Egg, yolk, raw, fresh 类别: Dairy and Egg Products	381 µg	42.33%

¹ 100克食物中的营养素含量
² 以FDA基于2000卡路里的饮食作为日需量参考

更多营养素信息
概要	Vitamin A is important for vision, skin tissues, reproduction, embryonic development, bone growth, and immune function.
缺乏营养对健康的影响	A person's Vitamin A status depends on the level of Vitamin A storage and the retinol-binding protein which transports retinol from storage to target tissues. People will not notice the Vitamin A deficiency until their Vitamin A stores are depleted. Here are possible health problems caused by Vitamin A deficiency: Blindness (Xerophthalmia): the initial symptom is not able to see well in low lights. Xerophthalmia is the most specific clinical effect of vitamin A deficiency. It has various stages including night blindness, conjunctival xerosis (dry cornea), Bitot’s spots (triangular gray spots on eye), corneal xerosis (dry and hazy appearance of the cornea), corneal ulceration and scarring, and then corneal degeneration and blindness. The night blindness is caused by a lack of vitamin A at the retina in the back of the eye; total blindness is caused by a lack of vitamin A at the cornea in front of the eye. Outside and inside body surfaces: Vitamin A deficiency causes the body's outer surface skin to become dry, rough, and scaly, and causes inside body's epithelial tissues weaken, as a result, the the respiratory tract, the GI tract, etc. will more likely to get infection. Reduced immune function: Vitamin A deficiency decreases immune function, so increases the risk of infectious morbidity and mortality, such as respiratory infection, diarrhea, and measles virus. Vitamin A deficiency impairs iron mobilization from stores.
超过上限对健康的影响	As a fat-soluble vitamin, vitamin A is not readily excreted. The risk of toxicity is relative high when eating large amount of preformed vitamin A from animal foods (such as beef liver), fortified foods, or supplements. The excessive unused vitamin A can potentially damage cells. Preformed vitamin A toxicity (hypervitaminosis A) may be acute or chronic. Beta-carotene from fruits and vegetables is not so efficiently converted to the active form of vitamin A retinol, so the toxicity risk is low, though over consumption may turn the skin to yellow. However, overconsumption of beta-carotene supplements will make it act as a prooxidant which induces oxidative stress and damages cells and tissues. Vitamin A toxicity effects: • Excessive vitamin A may stimulate bone-dismantling activity that reduces bone density and weaken the bones. This contributes to fractures and osteoporosis. • High doses of Vitamin A (≥ 7,800 mg/day) during the first trimester of pregnancy may cause infant birth defects such as teratogenicity. • High doses of vitamin A (5,500-6,750 mg/day) may cause intracranial and skeletal abnormalities for infants. • Liver is the main storage of vitamin A, excessive vitamin A may cause liver abnormalities. Vitamin A acute toxicity symptoms: • Blurred vision • Nausea and vomiting • Headache and dizziness • Muscular incoordination Note: People with high alcohol intake, pre-existing liver disease, hyperlipidemia, or severe protein malnutrition should lower the intake Upper Limit.
参考资料	The National Academies of Science, Engineering, Medicine publication: Dietary Reference Intakes NIH (National Institutes of Health) articles: Vitamin A Nutrition Science Book: Understanding Nutrition by Ellie Whitney and Sharon Rady Rolfes Wiki article: Vitamin A British Journal of Nutrition by Cambridge University Press: A review of vitamin A equivalency of β-carotene in various food matrices for human consumption healthline.com article: Vitamin A: Benefits, Deficiency, Toxicity and More

日需量年龄组	每日需量建议	日摄入量上限
幼儿1至3岁:	300 µg	600 µg
儿童4至8岁:	400 µg	900 µg
男性9至13岁:	600 µg	1,700 µg
男性14至18岁:	900 µg	2,800 µg
男性19至30岁:	900 µg	3,000 µg
男性31至50岁:	900 µg	3,000 µg
男性51至70岁:	900 µg	3,000 µg
男性71岁或以上:	900 µg	3,000 µg
女性9至13岁:	600 µg	1,700 µg
女性14至18岁:	700 µg	2,800 µg
女性19至30岁:	700 µg	3,000 µg
女性31至50岁:	700 µg	3,000 µg
女性51至70岁:	700 µg	3,000 µg
女性71岁或以上:	700 µg	3,000 µg
女性孕妇(18岁以上):	770 µg	3,000 µg
女性哺乳期(18岁以上):	1,300 µg	3,000 µg
FDA（基于2000卡路里的日常饮食）:	900 µg

	营养成分参考摄入量数据和营养成分知识来自于美国国立医学研究院2006年。膳食参考摄入量：营养需求基本指南。华盛顿特区:国家科学院出版社。National Academies' Institute of Medicine 2006. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press. https://doi.org/10.17226/11537
	营养成分知识基于美国食品和药物管理局（USFDA）营养教育资源文章。 https://www.accessdata.fda.gov/scripts/interactivenutritionfactslabel/
	营养成分知识基于美国国立卫生研究院的膳食补充剂情况说明书(Dietary Supplement Fact Sheets)。 https://ods.od.nih.gov/factsheets/list-all
免责声明	此处提供的营养信息不应取代医疗建议。我们鼓励您与您的医疗保健提供者（例如您的医生）讨论对您的整体健康最有利的饮食需求。我们还建议您阅读本页提及的，但不限于，组织机构或专业参考文选或文章。此页面中的任何提及和参考链接并不代表我们对其服务和建议的代言（endorsement）。

查阅主要食物来源 | 食物营养成分查询 | 营养素搜索 | 了解食品标签上的营养素