Preformed vitamin A occurs naturally in dairy products, eggs, fish and meat, especially liver. How much vitamin A is safe during pregnancy?
The Tolerable Upper Intake Levels for pregnancy have been set at 3, micrograms of preformed vitam Should I take vitamin A if I don't have a deficiency? Michael Gloth, III. The main role of vitamin A is related to vision , including night vision. However, it also intervenes in various functions of the body including growth , tissue regeneration skin, intestinal mucous membranes , and immunity.
In addition to the properties of vitamin A, beta-carotene can act as an antioxidant. This property is associated with a reduced risk of bladder, mouth, larynx, respiratory tract, breast, and esophageal cancer, and probably colon cancer as well. Beta-carotene, or provitamin A, is exclusively found in plant-based foods , with the exception of eggs and butter. You can take high-dose beta-carotene supplements…Nothing could be further from the truth! The World Cancer Research Fund has convincingly demonstrated that the daily use of a beta-carotene supplement increases lung cancer risk in smokers and subjects exposed to asbestos.
As a precaution, it is therefore better to take in beta-carotene through food. When you prepare vegetables rich in beta-carotene, like carrots, always use a bit of oil, butter, or margarine to help you absorb this fat-soluble provitamin. A decrease in visual acuity , especially in night vision , is one of the first noticeable signs of a vitamin A deficiency in humans.
Primarily found in plant sources. It is a red-orange pigment found in fruits and vegetables. Sources of retinol are meat, liver, cod liver oil, kidneys, liver plate, butter, cheese, egg yolk and oily fish. Source of B-carotene are green leafy vegetables and fruits like carrots, spinach, tomatoes, parsley, rosehips, kale, peas, mango etc. Deficiency Vitamin A deficiency is rare in Western countries but may occur.
Also at risk are adults and children who eat a very limited diet due to poverty or self-restriction. Mild vitamin A deficiency may cause fatigue, susceptibility to infections, and infertility. The following are signs of a more serious deficiency. Toxicity Vitamin A toxicity may be more common in the U. Vitamin A is also fat-soluble, meaning that any amount not immediately needed by the body is absorbed and stored in fat tissue or the liver.
If too much is stored, it can become toxic. The tolerable upper intake of 3, mcg of preformed vitamin A, more than three times the current recommended daily level, is thought to be safe.
However, there is some evidence that this much preformed vitamin A might increase the risk of bone loss, hip fracture [], or some birth defects.
Signs of toxicity include the following. In contrast to preformed vitamin A, beta-carotene is not toxic even at high levels of intake. The body can form vitamin A from beta-carotene as needed, and there is no need to monitor intake levels as with preformed vitamin A.
Therefore, it is preferable to choose a multivitamin supplement that has all or the vast majority of its vitamin A in the form of beta-carotene; many multivitamin manufacturers have already reduced the amount of preformed vitamin A in their products. However, there is no strong reason for most people to take individual high-dose beta-carotene supplements.
Smokers in particular should avoid these, since some randomized trials in smokers have linked high-dose supplements with increased lung cancer risk. There have been claims that vitamin A in the form of retinol or retinyl palmitate added to some sunscreens, moisturizers, and lip balms can cause vitamin A toxicity or cancer if used excessively.
However, there has not been evidence to date to support this. Vitamin A in topical creams is not absorbed into the bloodstream and therefore would not contribute to toxic levels. The concern with cancer stemmed from studies in mice conducted by the FDA. Retinoids in skin creams can cause skin to become highly sensitive to bright light, so it is advised to apply vitamin A creams at night and to avoid strong sun after their use.
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