Vitamin A Supplements Review, Including Beta-Carotene
and Cod Liver Oil
Find the Best Vitamin A
Supplement. Best Quality Vitamin A Supplements Identified, Including Cod Liver
Oil.
Medically reviewed and
edited by Tod Cooperman, M.D. 
Last Updated
: 09/24/2021 | Initially Posted:
10/20/2018
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Table of Contents
Summary
·
How much vitamin A should I take? Unless you're
deficient in vitamin A or have a condition that can cause deficiency, you probably don't need to take a
vitamin A supplement. Americans are more likely to get too much vitamin A from their diets than
too little. The daily requirement for vitamin A is 900
mcg (or 3,000 IU in the retinol form) for men, 700 mcg (2,333 IU) for women,
and is lower for children.
·
Changing vitamin A labels: Be aware that
supplement labels are in the process of being updated to show vitamin A in
"mcg" (micrograms) of retinol activity equivalents - RAE. This is
more scientifically correct than the older "IU" format. For reference,
900 mcg = 3,000 IU of vitamin A as retinol or 6,000 IU of beta-carotene, since
retinol (and related retinyl forms) have greater biological activity than
beta-carotene.
·
How much vitamin A is too much? Too much vitamin A
(for adults, over 3,000 mcg RAE daily -- or 10,000 IU in the retinol form)
can cause problems, and is of particular concern
for women who are pregnant. Although safe when consumed from fruits and
vegetables, there are some concerns with taking beta-carotene, which is converted, as needed,
to vitamin A in the body.
·
Is cod liver oil better than synthetic vitamin A? The vitamin A in
fish oil is the same as the synthetic vitamin A in most supplements -- retinyl
palmitate, so it doesn't matter which you use. Cod liver oil tends to cost more
but can provide significant amounts of vitamins D and E as well as omega-3
fatty acids (EPA and DHA).
·
Best choice for vitamin A supplements? Among the
supplements that passed testing, we selected those that provide the best quality
and value as our Top Picks,
including selections for an overall vitamin A supplement (including optional
selections for very high dose vitamin A and fish-free vitamin A), as well as
for vitamin A from beta-carotene and from cod liver oil.
What It Is:
Vitamin A
Vitamin A is a fat-soluble vitamin necessary to maintain good vision and skin,
and important to the immune system. In supplements, "vitamin A"
usually refers to its "preformed" or retinol forms (including retinyl
palmitate and retinyl acetate) as well as beta-carotene. Preformed vitamin A is
found in animal-derived foods, primarily liver and dairy products. Cod liver
oil and other fish liver oils are excellent sources of vitamin A, while
traditional fish oil supplements (from the oil in fish meat) are not.
Beta-carotene
Beta-carotene is a member of the carotenoid family of
orange, red and yellow pigments, and the most common carotenoid found in fruits
and vegetables. It is an antioxidant that protects cells against damage from
unstable oxygen molecules called "free radicals." Beta-carotene is
referred to as pro-vitamin A; it is converted in the body to vitamin A based on
the body's need for vitamin A. This makes beta-carotene a safer form of vitamin
A by reducing the risk of vitamin A overdose, although some risks remain
(See Concerns and Cautions). Beta-carotene also has
other activities in the body independent of its conversion to vitamin A.
Beta-carotene is found in fruits, vegetables and other foods. Rich food sources
include apricots, carrots, collard greens, kale, spinach, squash, sweet peppers
and sweet potatoes.
What It Does:
Vitamin A (preformed - as retinol)
Vitamin A is used to treat people with vitamin A deficiency, which can
cause night blindness, dry skin, and increased risk
of infection. It may also cause loss of taste (Bromley, Am Fam Physician 2000). Vitamin A
deficiency is rare in the general population in the U.S. where, according to
the CDC 2012, less than 1% of the population is
deficient and 2% is actually at-risk for excess vitamin A
(including 4.8% of older adults).
Vitamin A deficiency can occur when there is liver
disease, malabsorption, or severe malnutrition. For example, there is
evidence that people with Crohn's disease, particularly those who
have a low BMI (body mass index) and low bodyfat, may have an increased risk of
vitamin A deficiency (Weisshof, Curr Opin Clin Nutr Metab Care 2015).
Progressive loss of night vision was reported in a 60-year-old man with Crohn's
disease who had undergone multiple resections and a very low blood level of
vitamin A. He was given a daily dose of 100,000 IU vitamin A intramuscularly
for 3 days, followed by 50,000 IU daily for 2 weeks, and then a given a daily
oral dose of 25,000 for one year, at which time his blood levels had increased
from 11 mcg/dL to 78 mcg/dL and his vision improved. However, oral
supplementation was not sufficient to maintain adequate blood levels of vitamin
A, and he eventually became deficient again, with worsening night vision, and
was placed again on intramuscular injections (Lima, Int Ophthalmol 2014).
A study among 61 children and adolescents with inflammatory bowel disease that
included 40 participants with Crohn's disease, found that supplementation with
a daily multivitamin (providing 1000 IU of vitamin A as vitamin acetate) for one year normalized blood levels of vitamin A in all of the
participants who were deficient at the beginning of the study. There was no
association between blood levels of vitamin A and Crohn's disease activity
index scores (Santucci, J Ped Gastroenterol Nutr 2014).
One study showed that high doses of vitamin A plus vitamin E enhanced healing
rate and vision improvement after photorefractive keratectomy (PRK) laser
eye surgery to correct near-sightedness (Vetrugno, Br J Opthalmol 2001).
Increased vitamin A in the diet has been associated with reduced risk
of cataracts, but it is not known if the same is true with vitamin A
supplements (Cumming, Ophthalmology 2000).
There is mixed evidence regarding the use of vitamin A to
reduce the risk of cancer. Early research suggested that oral
supplementation with pre-formed vitamin A (but not beta-carotene) may improve
survival among people with lung cancer (Pastorino, J Clin Oncol 1993). However, a more
recent review of the research found little benefit from supplementing with
naturally occurring vitamin A in people with lung cancer, although there was
some benefit with a synthetic analogue, rexinoid
bexarotene (Fritz, PLoS
One 2011). Population studies suggest that vitamin A (both
pre-formed and beta-carotene) might reduce the risk of breast cancer (Zhang, J Natl Cancer Inst 1999),
but these results need to be confirmed by human studies looking at the effects
of vitamin A supplements.
Vitamin A together with beta-carotene has not been found to prevent colorectal, esophageal, pancreatic or stomach
cancers. And vitamin A alone does not prevent ovarian cancer.
However, one review of human studies found that antioxidants (including
beta-carotene and vitamin A) do not interfere with, and may enhance, the
effects of cancer treatments (chemotherapy and/or radiation)
and reduce their side effects.
Vitamin A may reduce the risk of melanoma, a
deadly skin cancer. A large study found that adults (ages 50 to 76) taking
vitamin A supplements had a 40% lower risk of developing melanoma over an
average of 6 years than adults not supplementing with vitamin A (Asgari, J Invest Dermatol 2012). Melanoma
risk reduction was greater for locations on the head and limbs (areas
associated with greater sun exposure) than on the trunk. The protective effect
was strongest and most statistically significant among women. The effect was
seen only among people taking 4,000 IU or more of vitamin A (as retinol) daily,
and not among those getting lesser amounts of vitamin A from multivitamins.
There was no association of melanoma risk with intake of carotenoids (e.g.,
beta-carotene) or intake of vitamin A from foods.
With regard to squamous cell carcinoma, adults with
the highest intakes (about 21,691 IU daily) of vitamin A (as retinol and
carotenoids including beta-carotene) had a 17% lower risk of developing this
skin cancer compared to those with the lowest intakes (about 6,808 IU daily).
The study tracked more than 120,000 women and men over approximately 27 years.
However, unlike melanoma (discussed above), the apparent benefit was largely
driven by dietary, rather than supplemental, intake: Higher intakes of vitamin
A from foods alone were associated with a 14% decrease in cancer risk (Kim, JAMA Dermatol 2019).
A small study of children ages 4 to 6 in China with an autism
spectrum disorder (ASD) found that they had significantly lower blood levels of
retinol than those who did not have an ASD (average level of 0.54 µmol/L vs.
0.82 µmol/L, respectively). The children with ASDs were subsequently given a
single, large dose of vitamin A (200,000 IU). When tested again six months
later, average blood levels of retinol had increased to 0.79 µmol/L and
significant improvements were noted on the overall score and specific measures
of the childhood autism rating scale (CARS): relating to people, adaptation to
change, anxiety, and verbal and non-verbal communication. However, the study
lacked a placebo control group, making it impossible to know if these changes
were not random. Blood levels of serotonin (which have been found in other
studies to be elevated in children with ASDs) were found to be significantly
higher in the children with ASDs compared to those without ASDs, and these
levels significantly decreased after vitamin A supplementation (Guo, Brain Res Bull 2017). A study in the U.S.
found that children with ASDs between 4 to 8 years of age consumed, on average,
less than the recommended daily intake of vitamin A, while younger children
tended to consume excessive amounts (i.e., above the UL) (Hyman, Pediatrics 2012).
Topical creams, gels and serums:
Naturally-occurring vitamin A derivatives such as retinol, retinyl-palmitate,
retinyl-acetate, retinaldehyde are common ingredients in over-the-counter skin
creams, gels and serums promoted to reduce acne or to reduce
wrinkles and improve tone and texture of aging skin. A previously
prescription-only, synthetic form of retinyl-palmitate, adapalene, (the active
ingredient in Differin gel)
is now sold without a prescription (providing 0.1% adapalene). Topical
formulations of more potent, naturally-occurring vitamin A derivatives such as
tretinoin, isotretinoin, alitretinoin may be prescribed to treat a variety of
skin conditions, including acne, psoriasis, hyperkeratosis (abnormal thickening
of the skin) and premature aging/UV damage. In addition to exerting
antibacterial, anti-inflammatory and antioxidant effects in the top layer of
the skin, topical retinoids may increase synthesis and inhibit degradation of
collagen (Opinion on Vitamin A, European
Commission SCCS 2016). There is evidence that topical products
containing at least 0.04% to 0.1% retinol may modestly improve skin tone and
decrease the appearance of facial fine lines (Kikuchi, J Dermatolog Treat
2009; Babamiri, Aesthet Surg J 2010).
Although some studies have found an association between high intakes of retinol
from foods and supplements and reduced bone mineral density and increased risk
of fractures, the evidence is mixed, and this does not appear to be a concern
with topical products (see Concerns and Cautions).
Nevertheless,
topical retinoids can cause other side effects. Some people may
experience skin reactions including redness, scaling, dryness,
and stinging/burning when first using topical retinoids. These
side effects usually lessen with continued use (>4 weeks) and using a
moisturizer or reducing the frequency of application may reduce these effects
in some people. Use of other skin irritants, such as abrasive soaps or other
cosmetics that have drying effects, may worsen these skin
reactions, so these products should be used with caution in combination with
topical retinoids (Differin Prescribing Information, Last Updated 2/2012).
People using topical retinoids such as Differin gel
should use caution when outdoors, as exposure to sunlight, wind, or cold can
cause skin irritation. Use of sunscreen products and protective
clothing over treated areas of the skin is recommended (Differin Prescribing Information, Last Updated 2/2012).
Experts advise women who are pregnant or planning to become pregnant to
avoid topical retinoids, based on isolated case reports suggesting a link
between topical retinoid use and birth defects. It is unclear if
retinoids pass into breastmilk when used by breastfeeding mothers, although
some experts state that the amount, if any, is probably too small to be harmful
(Browne, Obstet
Gynaecol 2014).
Beta-carotene
Beta-carotene has specifically been used to reduce
sensitivity to sunlight in people with a genetic condition called erythropoietic
porphyria. Similarly, beta-carotene may provide modest protection
from sunburn in people who are sun-sensitive, but does not
reduce the risk of skin cancer from sun exposure.
A large study known as AREDS (Age-Related Eye Disease Study)
evaluated a combination of vitamin A (as beta-carotene), vitamin C, vitamin E
and zinc for preventing loss of vision and decreasing
progression of advanced age-related macular degeneration (AMD). The
supplement combination reduced the risk of disease progression by 25% over a
period of 5 years compared to a placebo. However, it was not known if these
benefits were due to a single ingredient or some combination of ingredients. A
later study (AREDS2) found that
removing vitamin A (as beta-carotene) from the formula, did not diminish the
benefits — i.e., beta-carotene provided no additional benefit to the formula (AREDS2 Res Grp. JAMA 2013).
For more information about supplements for AMD see our Product Review of Eye Health
Supplements.
Limited human research suggests that beta-carotene might prevent
exercise-induced asthma, lessen symptoms of oral
leukoplakia and slow the progression of osteoarthritis.
Population studies suggest that diets high in beta-carotene might reduce the
risk of breast cancer in postmenopausal women, reduce the risk
of ovarian cancer in postmenopausal women, and improve exercise
ability and muscle strength in older people.
For more information, see Concerns and Cautions for potential
side-effects and toxicities.
Quality Concerns and
Tests Performed:
Neither
the U.S. Food and Drug Administration (FDA) nor any other federal or state
agency routinely tests supplements for quality prior to sale. ConsumerLab.com,
as part of its mission to independently evaluate products that affect health,
wellness, and nutrition, purchased many vitamin A supplements sold in the U.S.
All were tested for their amounts of claimed forms of vitamin A (as provitamin
A or beta-carotene). Products containing whole herbs and/or more than 250 mg of
minerals per daily dose as well as all fish liver products were tested for
contamination with lead, cadmium and arsenic. Products made from fish liver oil
were also tested for freshness. Fish liver products tested through ConsumerLab.com's voluntary Quality Certification Program were
additionally tested for PCBs. All non-chewable and non-time-release tablets or
caplets were tested for their ability to break apart properly to release their
ingredients. See How Products Were Evaluated for
more information.
What CL Found:
Among the nine supplements ConsumerLab.com selected and tested,
seven met quality standards and FDA labeling requirements, and two did not.
Through ConsumerLab.com's voluntary Quality Certification Program,
in which products undergo the same testing, three additional products were
found to meet quality standards.
The two products that failed testing -- designated as "Not Approved"
in the results table further below -- contained
lower amounts of vitamin A than claimed, and these deficiencies were confirmed
in tests in a second independent laboratory:
·
Solaray Vitamin Dry A 25,000 IU
(a combination of retinyl palmitate and beta-carotene) was found to
contain 15,997.4 IU per capsule —just 64% of its claimed amount of total
vitamin A. It contained its listed amount of beta-carotene, but had just 44% of
the listed retinyl palmitate.
·
Vitacost Cold Water Arctic Cod
Liver Oil contained only 85.6% of the retinyl palmitate it claimed,
providing 5,644.3 IU instead of the listed 6,600 IU.
All products made with
fish liver oils passed standards for oil freshness and none exceeded limits on
contamination by lead, cadmium, and arsenic. (See our Product Review of Fish Oil/Omega-3
Supplements for tests of other fish oils). All products that
contained plant-based ingredients (such as Solaray
Vitamin Dry A, which contained carrot powder) were also tested for lead,
cadmium and arsenic and none exceeded contamination limits. None of the
products tested for PCBs exceeded strict limits.
The recommended daily serving of the products ranged from just 425 IU (127.5
mcg RAE) in a children's supplement to 25,000 IU (7,500 mcg RAE) in several
products. Keep in mind that the amount of vitamin A in the retinol form in
nearly all products far exceeds the daily requirements and, in many cases,
also exceeds the daily upper tolerable intake levels, representing a risk of
adverse effects (see Cautions and Concerns).
Vitamin A can be obtained very inexpensively. In fact, you could spend as
little as 1 cent per 1,500 mcg RAE (5,000 IU) of vitamin A (as retinol) from
higher-dose products. However, you could spend as much as $2.29 to get the same
amount of vitamin A, as discussed further below. See the last column of
the Results table for price and cost
comparisons.
Top Picks:
Among
the products that were Approved for their quality in testing, ConsumerLab selected the following as its Top Picks in
the following categories:
·
Overall Top Pick — If you need to greatly increase vitamin
A intake using a supplement, you can get vitamin A at lowest cost (just 1 cent
per 1,500 mcg RAE or 5,000 IU) from either NOW Vitamin A (7,500
mcg RAE or 25,000 IU per softgel) or Spring
Valley [Walmart] Vitamin A 2,400 mcg. Our Top Pick among
the two is Spring Valley (providing 2,400 mcg RAE or
8,000 IU of retinyl palmitate) because it is lower-dose, allowing more flexibility
in dosing and it does not exceed the adult upper tolerable intake level at one softgel daily. Be aware that these and several other
products in the review include vitamin A derived from fish. If you are allergic
to fish or simply don't want to eat fish-based products, consider,
instead, Bronson Vitamin A 10,000 IU (3,000 mcg RAE)
from synthetic retinyl palmitate, costing 4 cents per softgel
— although this dose is right at the upper limit for adults.
·
Top Pick for Beta-Carotene — If you want vitamin A from
beta-carotene, GNC Beta-Carotene 25,000 IU is also a
good high-dose choice, providing 25,000 IU of beta-carotene (3,750 mcg RAE) in
one softgel for 3 cents — making it the
lowest-in-cost product for getting beta-carotene. Unlike the retinol form of
vitamin A, there is no established upper limit for beta-carotene; however, be
aware that there are some potential risks when taking high doses like this, and
certain people should avoid beta-carotene supplements.
·
Top Pick for Cod Liver Oil — Cod liver oil will provide not just
vitamin A, but vitamin D, and omega-3 fatty acids such as EPA and DHA. If you
are seeking all of these, then cod liver oil is a good way to go. Our Top
Pick is The Vitamin Shoppe Cod Liver Oil. Each
teaspoon provides 4,500 IU (1,350 mcg RAE) of vitamin A in the retinol form, as
confirmed in our tests. It also claims to provide 450 IU of vitamin D (getting
you a long way toward the daily requirement of 600 IU for adults up to age 79
and 800 IU for older adults) as well as 400 mg of DHA and 450 mg of EPA
(substantial amounts, similar to that from a serving of oily fish). CL did not
test for the vitamin D and DHA and EPA claims. It is a bit expensive, at 31 cents
per serving ($29.99 for a 16 fl. oz. bottle). However, it is more concentrated
in vitamin A than Carlson Kid's Norwegian Cod Liver Oil, making it
a less expensive source of vitamin A, although Carlson's remains
a good option (especially for adults looking for a low dose of
vitamin A, with one teaspoon providing 850 IU (255 mcg RAE). Unfortunately, the
least expensive cod liver oil that we tested, Vitacost
Cold Water Arctic Cod, fell a bit short of its claimed amount of vitamin A.
Note that although many other vitamin A supplements list cod or
other fish as ingredients, the vitamin A (in the form of retinyl palmitate) in
them has been extracted from the fish without bringing along
additional nutrients, such as vitamin D and omega-3 fatty acids, as would be found
in products specifically marketed as "cod liver oil."
Test Results by Product:
Listed
alphabetically below are the test results for twelve products. Nine were
selected by ConsumerLab.com and three (each indicated with a CL flask) were
tested at the request of their manufacturers/distributors through ConsumerLab.com's Quality Certification Program.
Products listed as Approved met ConsumerLab.com's
quality standards. If products did not meet these standards, they are listed as
"Not Approved" with an explanation of the problem(s) found. Included
in the listings are the labeled serving sizes and claimed amounts and forms of
vitamin A. The last column provides cost comparisons, notable additional
ingredients, and notable features. A full list of ingredients is available for
each product by clicking on the word "Ingredients" in the first
column. Supplements that exceeded suggested safe limits of preformed vitamin A
for children, adolescents or adults For more
information about testing, see How Products Were Evaluated.
|
RESULTS OF CONSUMERLAB.COM TESTING OF VITAMIN A SUPPLEMENTS |
|||||
|
Product Name (Labeled
Serving Size and Suggested Daily Servings) |
Claimed Amount (and
Form) of Vitamin A Per Labeled Daily Serving |
—TEST RESULTS— |
Cost For Daily
Suggested Serving On Label |
||
|
OVERALL RESULTS: |
Contained Labeled
Amount of Vitamin A |
Did Not Exceed
Contamination Limits for Lead, Cadmium Arsenic (M)1, and PCB (P)2 |
|||
|
Vitamin A from Retinyl Palmitate |
|||||
|
|
10,000 IU |
APPROVED |
✔ |
✔M |
$0.07 |
|
|
25,000 IU |
APPROVED |
✔ |
✔M |
$0.04 |
|
|
10,000 IU |
APPROVED |
✔ |
✔M |
$0.07 |
|
|
8,000 IU |
APPROVED |
✔ |
✔M,P |
$0.02 |
|
Vitamin A from Retinyl Palmitate (Synthetic
Only) |
|||||
|
|
10,000 IU |
APPROVED |
✔ |
NA |
$0.04 |
|
Vitamin A from Beta-Carotene |
|||||
|
|
25,000 IU |
APPROVED |
✔ |
NA |
$0.03 |
|
|
25,000 IU |
APPROVED |
✔ |
NA |
$0.09 |
|
|
7,500 IU to 22,500 IU |
APPROVED |
✔ |
✔M |
$0.20-$0.60 |
|
Vitamin A from Beta-Carotene and Retinyl
Palmitate |
|||||
|
|
25,000 IU |
NOT |
Found only 6,614.3 IU
retinyl palmitate [1,984.3 mcg RAE] (44.1% of listed amount) and 15,997.4 IU
total vitamin A [3,391.8 mcg RAE] (64.0% of listed amount) |
✔M |
$0.10 |
|
Vitamin A from Cod Liver Oil |
|||||
|
|
425 IU to 850 IU |
APPROVED |
✔ |
✔M |
$0.19-$0.39 |
|
|
6,600 IU |
NOT |
Found only 5,644.3 IU
retinyl palmitate [1,693.3 mcg RAE] (85.6% of listed amount) |
✔M |
$0.13 |
|
|
4,500 IU |
APPROVED |
✔ |
✔M |
$0.31 |
|
|
|||||
|
Unless otherwise noted, information about the products
listed above is based on the samples purchased by ConsumerLab.com (CL) for
this Product Review. Manufacturers may change ingredients and label information
at any time, so be sure to check labels carefully when evaluating the products you use or buy. If a product's ingredients differ
from what is listed above, it may not necessarily be of the same quality as
what was tested. |
|||||
|
Copyright ConsumerLab.com, LLC, 2018. All rights reserved.
Not to be reproduced, excerpted, or cited in any fashion without the express
written permission of ConsumerLab.com LLC. |
|||||
ConsumerTips™:
What to
Consider When Buying:
Vitamin A (preformed - as retinol)
While supplement labels generally combine beta-carotene and retinol in
calculating their vitamin A content, many will also note the percent of vitamin
A that is contributed by beta-carotene.
Be aware that supplement labels are in the process of being updated to show
vitamin A in "mcg" (micrograms) of retinol activity equivalents -
RAE. This is more scientifically correct than the older "IU"
(International Units) format. For reference, 900 mcg = 3,000 IU of vitamin A as
retinol or 6,000 IU of beta-carotene, since retinol (and related retinyl forms)
have greater biological activity than beta-carotene.
Retinyl palmitate is the natural form of vitamin A in fish oil and is an ester
(i.e., a chemical combination) of retinol and palmitic acid. Your body will
separate out the retinol and further convert it to an active form of vitamin A.
Retinyl palmitate may also be produced synthetically, as is retinyl acetate.
Some fish-oil-based supplements will list vitamin A as "retinol" or
"retinol palmitate," but, either way, you are getting retinyl
palmitate. The molecular weights of these compounds are different due to the
weight of the "palmitate" or "acetate" that is bound to
retinol and needed to stabilize the retinol (55% of retinyl palmitate and 87%
of retinyl acetate is retinol). However, you don't have to worry about the
molecular weights since the labeled amounts are supposed to reflect only the
amount of retinol (or retinol activity units — RAE) being provided.
Beta-carotene:
Beta-carotene supplements are available in either oil- or water-dissolvable
forms. The water-dissolvable forms seem to raise blood beta-carotene levels
better than the oil forms. 0.6 mcg of beta-carotene equals 1 IU of vitamin A
but just 0.15 mcg RAE.
Fermented cod liver oil
Fermented cod liver oil, which is generally more expensive than regular cod
liver oil, is sometimes touted as a more natural, superior source of vitamins A
and D, and the omega-3 fatty acids EPA and DHA. The fermentation process allows
the oil and fat- soluble vitamins to separate from the cod liver without the
use of heat or high pressure. However, there does not appear to be any clinical
evidence demonstrating that fermented cod liver oil is more beneficial than
regular cod liver oil. And, unlike many regular cod liver oil supplements, most
fermented cod liver supplements do not list their amounts of vitamin A, D, or
EPA and DHA on the label — so there is no way to know exactly how much you are
getting.
Fermented cod liver oil can have a stronger taste and smell than regular cod
liver oil. Some people report a burning sensation in the mouth or throat. For
this reason, manufactures sometimes offer flavored liquids, or capsules — but
be aware that you may have to take a large number of capsules to get an
equivalent dose.
What to Consider When Using:
Vitamin A (preformed - as retinol):
The Recommended Dietary Allowance (RDA) for vitamin A from any form is 300 mcg
RAE (1,000 IU as retinol or 2,000 IU as beta-carotene) for children 1 to 3
years old, 400 mcg RAE (1, 333 IU as retinol or 2,666 IU as beta-carotene) for
those 4 to 8, and 600 mcg RAE (2,000 IU as retinol or 4,000 IU as
beta-carotene) for those 9 to 13. For males 14 years and up, the RDA is 900 mcg
RAE (3,000 IU as retinol or 6,000 IU as beta-carotene). For females 14 years
and older, 700 mcg RAE (2,333 IU as retinol or 2,666 IU as beta-carotene) is
recommended. These amounts can be obtained from the food sources mentioned
above.
To see the daily requirements in table format, see https://www.consumerlab.com/rdas/vitamin-a/.
The daily dose to enhance healing rate and vision improvement after laser
surgery to correct near-sightedness is 25,000 IU vitamin A (as retinyl
palmitate) (7,500 mcg) plus 230 mg vitamin E (as alpha tocopheryl
nicotinate). Vitamin A doses this high require medical supervision to prevent
side effects.
Taking over 4,000 IU (1,200 mcg RAE) per day of vitamin A has been associated
with a greatly reduced risk of melanoma in women. (Asgari, J Invest
Dermatol 2012).
If you are using a liquid form of vitamin A from a bottle, such as a cod liver
oil product, consider using a measuring device (e.g., a small measuring cup)
rather than an ordinary spoon to assure accurate dosing.
Beta-carotene
Beta-carotene supplements are not generally
recommended for most people because dietary beta-carotene is abundantly
available from food sources mentioned above. Experts recommend five daily
servings of fruit and vegetables, which may provide 6 mg to 8 mg of
beta-carotene (1,250 to 2,000 mcg RAE).
A long-term study of Americans found the risk of dying during the course of the
study (about 14 years) was lowest when beta-carotene levels in the blood serum
were above the lowest levels (the bottom 20% of the population, i.e. above 0.13
micromol/liter) but did not change significantly when
levels were further increased (Goyal, Cancer Epidemiol Biomarkers Prev
2013).
A large study known as AREDS found that a daily dose of 28,640 IU of vitamin A
as beta-carotene (4,296 mcg RAE), 452 mg of vitamin C, 400 IU of vitamin E,
69.6 mg of zinc, and 1.6 mg of copper slowed the progression of advanced
age-related macular degeneration (AMD). However, a later, second study which
tested variations of this original formula (AREDS2) found that removing beta-carotene
from the original formula did not change the risk of disease
progression, while substituting lutein and zeaxanthin for beta-carotene did reduce
disease risk. Accordingly, lutein and zeaxanthin may be preferable to
beta-carotene found in some visions formulas. (See the
special section on the AREDS studies in the Vision Supplements Review for
more information.)
For modest sunburn protection in sun-sensitive people the daily dose is 25 mg
of beta-carotene (6,250 mcg RAE or 41,666 IU). Keep in mind that beta-carotene
supplements are unlikely to protect other people from sunburn and do not reduce
the risk of skin cancer from sun exposure.
Concerns and Cautions:
Vitamin A (preformed - as retinol)
Too much vitamin A from retinol (including retinyl palmitate and retinyl
acetate) can be a problem. The most important risk involves pregnant women:
vitamin A given in modestly excessive doses can cause birth defects.
Much higher doses of vitamin A can cause other forms of harm, such as
abnormalities in the liver, central nervous system, bone and skin. The
Tolerable Upper Intake Level (UL) for daily intake should not exceed 600 mcg
(2,000 IU) for children 1 to 3 years old, 900 mcg (3,000 IU) for those 4 to 8,
1,700 mcg (5,666 IU) for those under 9 to 13, 2,800 mcg (9,333 IU) for those 14
to 18, and 3,000 mcg (10,000 IU) for adults.
To minimize the risk of birth defects such as cleft palate, heart defects, and
hydrocephalus, the March of Dimes recommends that a pregnant woman
should not use a multivitamin or prenatal supplement that contains more than
1,500 mcg (5,000 IU) of preformed vitamin A, such as retinyl palmitate. It
also advises that a pregnant woman not take any vitamin A supplements beyond
that amount and minimize consumption of liver, which contains preformed vitamin
A. However, these ULs apply only to vitamin A consumed from supplements,
fortified foods, and animal sources, and does not include vitamin A as
beta-carotene or beta-carotene intake from fruits, vegetables and other foods.
Children are more at risk than adults for overdoses of vitamin A. Store
vitamin A-containing products away from children and follow dosing
directions carefully. When possible, choose products containing beta-carotene
for children, they are safer and less likely to cause problems in kids.
Too much vitamin A can cause liver damage. People with liver
problems should talk with their doctor before using vitamin A supplements to
prevent further liver damage. Vitamin A can also increase the risk of liver
damage when taken with prescription drugs that can cause liver damage as a side
effect. Ask your doctor or pharmacist to review your medications before using
vitamin A supplements to prevent unwanted effects.
Higher blood levels of vitamin A have been associated with
increased blood levels of uric acid, a risk factor for gout. A
study among adults in the U.S. ages 20 years and older found that those with
higher blood levels of vitamin A (73.93 mcg/dL or more) also had higher blood
levels of uric acid (5.92 mg/dL) compared to those with lower levels of vitamin
A (47.1 mcg/dL or less; average blood level of uric acid: 4.81 mg/dL) (Ford, Nutr Res 2015). It is unclear if
elevated blood levels of vitamin A are associated with increased risk of gout,
as those with the highest blood levels of vitamin A still had uric acid levels
within the normal range (1.5 to 6 mg/dL in women; 2.5 to 7.0 mg/dL in men) (Jin, Front Biosci 2012).
Avoid taking vitamin A if you take prescription medications in the
"retinoid" family, drugs derived from vitamin A. Taking vitamin A
with "retinoid" drugs increases the risk of preventable side effects.
Retinoid family drugs include: Accutane (isotretinoin), Avage
(tazarotene), Renova (tretinoin), Retin-A
(tretinoin), Soriatane (acitretin), Targretin
(bexarotene), and Tegison (etretinate).
Long-term use of retinol supplementation was associated with an increased
risk of lung cancer (Satia, Am J Epidem 2009 -- Vitamins and Lifestyle Study).
It should not be recommended for lung cancer prevention, particularly among
smokers or those who have been occupationally exposed to asbestos (Omenn, 1996
N Engl J Med).
There is evidence that excessive intake
(i.e., more than 1,500 to 3,000 mcg (5,000 to 10,000 IU) daily of vitamin A as
retinol (but not as beta-carotene) may increase the risk of osteoporosis
and hip fractures (Office of Dietary Supplements Fact Sheet on Vitamin A and
Carotenoids). For example, a study in Sweden among 175 women ages 28
to 74 found that dietary intakes of retinol above 1,5000 mcg per day were
associated with a 10% and 14% reduction in femoral neck and lumber spine bone
mineral density, respectively compared to intakes of less than 500 mcg per day
(Melhus, Ann Intern Med 1998). However, a much
larger population study in Denmark found no increased risk of hip, forearm or
spinal fracture in men and women taking oral or injected retinoids
(isotretinoin and acitretin), even at very high doses (> 14, 000 mcg per
day) compared to a similar group of adults not taking retinoids. There was also
no association between use of topical retinoids and fracture risk (topical
retinoids do not appear to increase blood levels of vitamin A or vitamin A
derivatives) (Vestergaard, Arch Dermatol 2010; Opinion on Vitamin A, European
Commission SCCS 2016).
A review of clinical studies found a small increase in mortality (i.e.,
more people died during studies) associated with the use of supplements
containing higher doses of vitamin A (Bjelakovic, Cochrane Database 2012). Adding to
this, a long-term study of Americans found the risk of dying over the course of
the study (about 14 years) was lowest when vitamin A levels in the blood serum
were at or above 1.82 micromol/Liter. However, for
people in the top 20% of blood levels for vitamins A (i.e., at or above 2.44 micromol/Liter) the risk of death was higher than for
people with moderate levels (Goyal, Cancer Epidemiol Biomarkers Prev 2013).
Beta-carotene
A Tolerable Upper Intake Level (UL) for beta-carotene has not been established.
Smokers and people exposed to asbestos should avoid beta-carotene
supplements. Daily intake of 20 mg (5,000 mcg RAE or 33,333 IU) or more may
increase the risk of lung cancer and prostate cancer in these groups. Among
smokers, taking beta-carotene 20 mg or more daily increases the risk of strokes
and death from heart disease (N Engl J Med 2004). Eating foods rich in beta-carotene
has not been found to have these unwanted effects.
High doses of beta-carotene (including from foods) can cause the skin
to turn yellow. This is a harmless condition reversible by reducing
beta-carotene intake. However, yellowing of the skin can be a sign of other,
potentially serious health conditions. If your skin turns yellowish, contact
your doctor.
A review of clinical studies found a slight (5%) but statistically
significant increase in mortality (i.e., more people died
during studies) associated with the use of supplements containing beta-carotene
(Bjelakovic, Cochrane Database 2012). It
concluded that current evidence does not support the use of beta-carotene
supplements in the general population.
High doses of calcium or other minerals (magnesium, zinc,
and ferrous iron) from supplements may decrease the absorption of beta-carotene
(and other carotenoids, such as lycopene and astaxanthin) from foods
and/or supplements. This is likely due to a reaction between carotenoids and
the divalent ions of these minerals, making the carotenoids less bioavailable (Corte-Real, Food Chem 2016; Borel, Br J Nutr 2017). It is best to
take beta-carotene or any carotenoid supplement at a different time of day than
a supplement or meal containing large amounts of a mineral (e.g., hundreds of
milligrams of calcium or magnesium).
For more information, see the government report on vitamin A and carotenoids
at http://ods.od.nih.gov/factsheets/vitamina.asp.
Information on this site
is provided for informational purposes only. It is not an endorsement of any
product nor is it meant to substitute for the advice provided by physicians or
other healthcare professionals. The information contained herein should not be
used for diagnosing or treating a health problem or disease. Consumers should
inform their healthcare providers of the dietary supplements they take.
Latest Clinical Research Updates for Vitamin A
8/06/2019
A study showed that
people with higher intakes of vitamin A have a lower risk of developing
squamous cell cancer of the skin. Does mean that taking a vitamin A supplement
will help? Find out in the What It Does section
of the Vitamin A Supplements Review, where we also discuss the risk of melanoma. (Also see our Top Picks for
vitamin A supplements.)
8/06/2019
A study showed that
people with higher intakes of vitamin A have a lower risk of developing
squamous cell cancer of the skin. Does mean that taking a vitamin A supplement
will help? Find out in the What It Does section
of the Vitamin A Supplements Review, where we also discuss the risk of melanoma. (Also see
our Top Picks for vitamin A supplements.)
12/17/2017
Giving vitamin A to young
children with autism spectrum disorders and low blood levels of vitamin A (as
retinol) seemed to improve some symptoms of ASD, according to a pilot study.
For details, see the "What It Does" section of the Vitamin A Supplements Review
>>
Latest Supplement Recommendations
11/17/2013
New draft recommendations
on vitamin and mineral supplement use were published this week by the U.S. Preventive Services Task Force.
The recommendations apply only to healthy adults without nutritional
deficiencies. They focus only on the use of supplements for the prevention
of cardiovascular disease and cancer at doses not exceeding tolerable upper
intake levels. The recommendations are based on existing science and are
generally consistent with information already presented in ConsumerLab.com's
Product Reviews. We have summarized the recommendations below, with links
to more information in ConsumerLab.com's reports:
- Beta-Carotene and Vitamin E:
Supplementation with either does not provide a benefit. Vitamin E does
not pose a risk of harm, but beta-carotene increases the risk of lung cancer in
people at risk for lung cancer.
- Other Single Vitamins, Minerals, Pairs, and Multivitamins: There is
inadequate evidence regarding a benefit or a risk of harm.
The task force stressed that at excessive doses (above
tolerable upper intake levels) there is evidence of harm with supplementation,
such as with vitamin A and vitamin D.
Antioxidants: Too Much of a Good Thing?
8/25/2013
A new, long-term study of
Americans found the risk of dying over the course of the study (about 14 years)
was lowest when antioxidant levels in the blood were above the lowest levels
(the bottom 20% of the population). However, for people in the top 20% of blood
levels for vitamins A and E, the risk of death increased compared to people
with moderate levels. For selenium and beta-carotene, there was no significant
difference in the death rate between moderate and high levels, although for
vitamin C some additional benefit was seen at high, but not the highest,
levels.
The results suggest that
antioxidant supplements may be useful for those who are nutritionally
deficient, but, as noted by the researchers, "beyond a certain threshold, higher
levels do not lead to additional benefit, and may potentially be toxic."
More details (including specific serum levels) are found in the linked updates
to the following reviews, which include our test results and quality ratings of
products:
Vitamin A and Beta-Carotene
Supplements Review >>
Vitamin C Supplements Review
>>
Vitamin E Supplements Review
>>
Selenium Supplements Review
>>