By Cat, June 2007; Updated May 2019
It is difficult to talk about Vitamin A without also discussing Vitamin D, as they are so intricately linked, metabolically, and are both fat soluble. Unfortunately, combining them in one article made it too long, so I have moved Vitamin D to a separate post.
Vitamin A was the first of the fat-soluble vitamins to be discovered. A dietary lack led to night blindness and other vision problems; if the deficiency is prolonged, it could lead to defective formation of bones and teeth. But even centuries before the discovery and isolation of the vitamin, ancient Egyptians discovered that eating certain foods (liver, etc.) could cure night blindness; and ancient Nordic and Scottish people understood that cod liver oil boosted their stamina in cold weather at sea. (8A)
- Includes: 1. Vitamin A; 1a. Animal vs Plant Vitamin A (includes discussion of carotenoids in AREDS2 supplement); 1b. Dietary Sources of Vitamin A; 2. Vitamin A:D Ratio; 2a. Cod Liver Oil Debate
- See Also: 1.Diet & Health Menu; 2. Vitamins: Intro; 3. Supplements vs Whole Foods (Intro); 4. Vitamin B complex; 5. Vitamin C; 6. Fat-Soluble Vitamin D; 7. Vitamin E; 8. Vitamin F; 9. Vitamin K;
NOTE: Consult with your health practitioner before taking any supplements. Overuse of supplements, just as overuse of drugs, can lead to other health problems, and some supplements can interact negatively with other supplements or drugs.
Remember that the best way to get your vitamins, minerals and other nutrients is from fresh whole foods. See Vitamins: Intro for
- Introduction: Vitamins
- Vitamin Supplementation vs Whole Foods
Animal- vs Plant-Sourced Vitamin A
Animal-sourced forms of vitamin A are different from that found in plant sources, but only the form from animal sources is active in humans. That from plant sources, such as beta-carotene, must first be converted to the active form. Some people have difficulty with this conversion, so to be on the safe side, it’s good to include animal-source vitamin A in your diet (such as cod liver oil, or liver).
Animal-Source forms of Vitamin A
In 1938, the form of vitamin A in cod liver oil was determined to be Vitamin A palmitate (an ester of vitamin A and palmitic acid – an ester is typically a fatty acid joined with an alcohol), and comprises about 3% of the total esters in the oil. (10) But in which active form is the vitamin A in the palmitate? Retinol, retinal, and retinoic acid are all forms of vitamin A, with each having its own unique purpose in the animal (11A):
- Retinoic acid acts as a hormone to affect transcription.
- Retinol and retinal are involved in vision.
- Retinal binds to a protein to form the visual pigment.
- Retinol (as retinyl ester) is the stored form found in foods (such as cod liver oil);
- Retinol and retinoic acid play a role in embryonic development.
- All forms are required for normal functioning of the immune system.
- Retinoids are also important for red-blood cell formation.
Plant-Source Carotenoid Family of Phytochemicals
In addition to vitamin A (retinol), this family includes many other members found in plants; some have vitamin A activity and others do not (but have other health benefits for humans). The most most well-known carotenoids are (11B):
- Provitamin A (can be converted to active vitamin A in our bodies):
- Carotenoids that cannot be converted to vitamin A in humans, and have no vitamin-A activity)
- zeaxanthin: important for eye health
- lutein: important for eye health
Prevention & Treatment of Macular Degeneration
A precise combination of vitamins and minerals, known as AREDS2,* is used to prevent macular degeneration/treat this condition that eventually causes lack of sight. Two carotenoids are included in the formula: lutein and zeaxanthin. AREDS stands for “Age-Related Eye Disease Study.” The AREDS2 formula is (14):
- lutein (10 mg)
- zeaxanthin (2 mg)
- vitamin C, an anti-oxidant (500 mg )
- vitamin E, an anti-oxidant (400IU)
- zinc oxide, needed for certain enzymes (80 mg or 25 mg zinc; either dose works equally well)
- cupric oxide, added because the added zinc can lead to copper deficiency (2 mg copper)
‘* NOTE: the original AREDS formula contained beta-carotene but no lutein nor Zeaxanthin; it also contained slightly less amounts of Vitamins C and E, zinc and copper than the AREDS2 formula in a daily dose.
[Cat’s note: both zinc and copper are essential nutrients, that are heavy metals and can be toxic in the wrong form, or if you get too much; it is far better to get them in an organic form, rather than salt (oxide) form, and to keep the dose low. For example, zinc methionine and copper gluconate, as in Jarrow’s Zinc Balance supplement (see iHerb code JRW-13008] are organic forms; zinc and copper oxide are salt forms..
I don’t have AMD (yet), but I do get all of this combo in my Mercola Whole Food Multi (see iHerb code MCL-01035 for men and MCL-01939 for women); they provide 6 mg lutein, 1 mg zeaxanthin, 15 mg zinc and 0.05 mg copper per daily dose.
I used to take Jarrow’s Carotenol and Zinc Balance which provide the following daily doses:
- beta-carotene, 1200 mcg
- lutein, 10 mg
- zeaxanthin, 2 mg
- lycopene, 10 mg
- astaxanthin, 500 mcg
- alpha-carotene, 500 mcg
- gamma tocopheral, 10 mg (antioxidant to protect the carotenes)
- Zinc Balance
- Zinc, 15 mg
- Copper, 1 mg
Dietary Sources of Vitamin A
True vitamin A is only found in animal foods. Butter made from the cream of pasture-raised, grass-fed dairy animals is perhaps the best whole-food form of vitamin A (9A), followed by liver and cod liver oil. Raw cream and raw products made from cream (cheese, sour cream, etc.) are also good sources. Eggs from pasture-fed hens are also an excellent source. All of these sources contain both true vitamin A and true vitamin D.
[NOTE: commercial, pasteurized milk is NOT a good source of natural vitamin A, because pasteurization destroys most of the vitamin A activity. Most commercial milk is supplemented with synthetic vitamin A in attempt to compensate for the loss.]
Reduced-fat dairy products are lower in vitamin A than full-fat products (even those that are supplemented with a synthetic vitamin A) because it is fat soluble and thus removed with the fat portion of the milk.
Many plants contain carotenoids, but only about 10% of these are considered pro-vitamins that can be converted in the body to vitamin A. Beta-carotene is perhaps the best known, and is what gives carrots their orange color. Beta-carotene is half as potent as true vitamin A; alpha-carotene and beta-cryptoxanthin are 1/24 the potency of true vitamin A. (9)
For plant sources, think “yellow” or “orange,” as these colors come from beta-carotene. Thus carrots, oranges, peaches, mangos, etc. are good sources. But also many green veggies provide lots of beta-carotene. One rich source is wheatgrass, which is also rich in a vegetable form of vitamin D.
Here’s a comparison of some food sources (13):
Food Vitamin A Content (mcg)
- 60g boiled carrots 756
- ½ mango 225
- 1 boiled egg 116
- 1 tomato 91
- 300ml semi-skimmed milk 68
- 30g reduced-fat Cheddar cheese 54
Vitamin A Toxicity
Excessive vitamin A causes a toxic condition characterized by various symptoms including dry & scaly skin, hair loss, nausea, fatigue and bone pain. (12). “Liver toxicities in adults can occur at levels as low as 15,000 IU to 1.4 million IU per day, with an average daily toxic dose of 120,000 IU per day. In people with renal failure 4000 IU can cause substantial damage. Additionally excessive alcohol intake can increase toxicity. Children can reach toxic levels at 1500IU/kg of body weight.” (9A)
Problems associated with vitamin A toxicity:
- liver damage
- weakened bones (reduced bone density)
- eye problems
- congenital deformities in newborns
However, these problems are rare and usually result from excessive intake from supplements rather than from food. For this reason, I do not recommend taking most supplements unless directed by a physician. Especially if you are pregnant. (13)
Vitamin A:D Ratio for Optimum Intake
Vitamins A:D Ratio
It’s definitely a matter of balance between vitamins A and D, as each cannot properly function without the other, and each provides protection from the toxicity of the other. However, too much of either one can result in trouble.
Is there an optimum ratio of vitamins A and D?
- Dr. Mercola (1) believes the ratio of A:D should be approximately 1:5.
- Sally Fallon (8B) recommends for adults: 10,0000 vitamin A, and 1000 IU vitamin D (10:1 ratio), to avoid vitamin A toxicity. She asserts this is a “completely safe dose of natural vitamin A.” Most cod liver oil brands do not come close to this ratio, but Green Pasture’s Fermented Cod Liver Oil (the vitamins are not removed before processing as for non-fermented versions, so they preserve the original A:D ratio of 10:1. Weston A Price Foundation (WAP) gives a “Best” rating t0 Green Pasture’s Blue Ice High-Vitamin Fermented Cod Liver Oil, for this very reason. (See Amazon ASIN: B004QCMGTG for this product).
WAP gives a “Good” rating to several other brands, which have a lower A:D ratio; see WAP’s recommended brands of cod liver oil (8C).
Chris Masterjohn (8A) asserts that an optimum ratio cannot be determined that is universal for everyone. This is mainly because dark skinned persons may need higher dietary vitamin D than light-skinned people, because the dark pigments in the dark skin block the frequencies needed to activate vitamin D in the skin. However, he also recommends fermented cod liver oil.
And of course, we all get vitamins A and D from other sources as well.
The Cod Liver Oil Debate
In 2008, Dr. Cannell (through the vitamin D council), and subsequently Dr. Mercola (7A), warned against taking cod liver oil for vitamin D and Omega-3s, because of the high levels of vitamin A in the oil.
This alarmed me at first, but then I realized humankind have been consuming cod liver oil (from fermented cod livers), and fresh raw liver for a very long time to benefit their health. Also, Dr Mercola differentiates some versions of cod liver oil as worse than others
“However, even the Weston Price Foundation acknowledges that there are dangerous versions of cod liver oil out there, even from some highly reputable companies produce a cod liver oil that is clearly excessive in vitamin A as it only has 3 to 60 units of vitamin D per tablespoon but between 150 and 12,000 times as much vitamin A.”
The Weston A. Price foundation argues in favor of cod liver oil. They assert that vitamins A and D work together; that taking one without the other is where the problems come into play – each protects against the toxicity of the other. They recommend Blue Ice brand of Fermented Cod Liver Oil (cod liver oil from fermented cod livers, the kind Scandinavians have taken for eons). Their amounts of A and D vary from fish to fish, but the amount ranges are: 5000-12500 IU/tsp vitamin-A and 1,500-5,500 IU/tsp vitamin-D (8D; see also the quote, below) as reported by the manufacturer; calculated A:D ratio at low end of each is 10:3 or 3:1, and at high end of each is 25:1.
Dr Mercola’s 2008 article (7A) recommends Carlson’s brand of molecularly distilled cod liver oil (the natural vitamins are removed before heating then added back along with manufactured forms after processing), which has a calculated A:D ratio of 25:1 (from mcg/tsp amounts). See iHerb code CAR-01352 for more about content of this oil.
A WAP article in 2016 reports testing results of vitamins A and D in molecular distilled (heated) vs un-heated or fermented cod liver oil (8D). From that article:
WAPF also sent samples of three brands of cod liver oil to two different commercial labs to test for vitamins A, D2 and D3: Covance in Wisconsin and UBE laboratory in California. In general, results from UBE were considerably higher than those for Covance.
As expected, the molecularly distilled [heated] cod liver oil had low levels of vitamin A and no detectable levels of D3 or D2*, because much of the vitamin content, especially the vitamin D content, is removed during the distillation process.
Vitamin A was higher in the unheated and fermented brands of cod liver oil, with the fermented cod liver oil measuring about 30-40 percent higher than the unheated brand. Total retinol plus palmitate for the fermented cod liver oil was 6080 IU/teaspoon, in the lower range of values found by the manufacturer, which have varied between 5,000 and 12,500 IU/teaspoon.
As for vitamin D, neither lab found appreciable levels of vitamin D3 in any of the three brands. UBE found 540 IU/teaspoon of a form labeled D2 in the molecularly distilled cod liver oil, and about triple that amount in the unheated and fermented cod liver oils. Levels indicated as D2were similar in the unheated and fermented products. The manufacturer of fermented cod liver oil reports a range of 1,500-5,500 IU/teaspoon D2 in the product.
*As discussed in a previous article (Wise Traditions, Fall 2015), it is likely that the form of vitamin D identified as D2 by UBE labs is another, as yet unidentified, form of vitamin D.
For more on this, see the WAP website for the following articles:
- The Cod Liver Oil Debate, by Christ Masterjohn (8A)
- A Response to Dr. Joe Mercola on Cod Liver Oil, by Sally Fallon (8B)
- Report on Cod Liver Oil, by Sally Fallon Morell (8D)
Caution: do not take more than the recommended daily dose (typically 1 tsp/day) of any brand/type of cod liver oil.
References 1 – 6 are common to all my vitamin pages; those specific with vitamins A and D begin with number 7.
- (6) dailyyonder.com/four-food-groups/2010/03/04/2623
- ncbi abstracts (3B – 3G originally cited in Supplements for Insulin Resistance, as numbers 21A – 21F)
- (new) ncbi.nlm.nih.gov/pubmed/23183291
- (21A in Supplements for IR) ncbi.nlm.nih.gov/pubmed/7622343
- (21B) ncbi.nlm.nih.gov/pubmed/6278902
- (21C) ncbi.nlm.nih.gov/pubmed/22986984
- (21D) ncbi.nlm.nih.gov/pubmed/9169302
- (21E) ncbi.nlm.nih.gov/pubmed/3017301
- (21F) ncbi.nlm.nih.gov/pubmed/8131066
- (9A) ncbi.nlm.nih.gov/pubmed/19091068 for Nutrition Journal, December 17, 2008 on PubMed
- (D9) ncbi.nlm.nih.gov/pubmed/21865327
- (D11) ncbi.nlm.nih.gov/pmc/articles/PMC2870528/
- (D13) ncbi.nlm.nih.gov/pubmed/12897318
- Selene River Press, by and about Dr Royal Lee, regarding Dr W. A. Price’s XFactor:
- Dr Royal Lee’s original article on Dr Weston A. Price’s XFactor: seleneriverpress.com/historical/dr-royal-lee-on-the-x-factor-of-dr-weston-a-price/; or see the original article: 6sd6hj41ya-flywheel.netdna-ssl.com/images/pdfs/40_weston_price_vitamin_f.pdf (I’ve also saved it as a pdf: CATSFORK > PDF FILES / Price-VitaminF-XFactor_Dr RoyalLee.pdf)
- Butter, Vitamin E, and the X-Factor (historical archive of Dr Lee’s article) (seleneriverpress.com/historical/butter-vitamin-e-and-the-x-factor-of-weston-a-price/)
- Lectures of Dr. Royal Lee, Vitamin News (seleneriverpress.com/shop/lectures-of-dr-royal-lee-volume-i-pdf-ebook/
- Vitamin News, a collection of all the biannual issues in one book: (seleneriverpress.com/shop/vitamin-news/
- SRP Historical Archives: seleneriverpress.com/srp-historical-archives/
- Articles on The X-Factor of Dr. Weston A. Price:
- More articles by Dr. Royal Lee: soilandhealth.org/wp-content/uploads/02/0203CAT/royal.lee.lets.live.articles.htm
- Mercola: differences from vitamin b references list begins here
- (A7) articles.mercola.com/sites/articles/archive/2008/12/23/important-cod-liver-oil-update.aspx
- (D1) articles.mercola.com/sites/articles/archive/2008/12/27/important-vitamin-d-update.aspx
- (D2) articles.mercola.com/sites/articles/archive/2011/12/14/study-shows-vitamin-d-cuts-flu-by-nearly-50.aspx?e_cid=20111209_DNL_artTest_C5
- (D6) articles.mercola.com/sites/articles/archive/2011/12/19/why-are-cancer-cases-rising-by-nearly-50-in-the-next-20-years.aspx
- (D7) articles.mercola.com/sites/articles/archive/2009/12/01/Important-New-Vitamin-D-Research-Papers.aspx
- (D8) articles.mercola.com/sites/articles/archive/2011/11/13/vitamin-d-for-depression.aspx
- (D10) articles.mercola.com/sites/articles/archive/2008/11/18/do-flu-shots-work-ask-a-vaccine-manufacturer.aspx
- (D15) articles.mercola.com/sites/articles/archive/2008/02/12/why-vitamin-d-supplements-are-not-the-same-as-sunlight.aspx
- Weston A Price:
- (A1) The Nature of Vitamin A in Cod Liver Oil: jbc.org/cgi/reprint/125/2/475.pdf
- (A2) Oregon State Univ:
- Cyber North
- (A8) weightlossresources.co.uk/nutrition/vitamins/vitamin_a.htm
- World’s Healthiest Foods:
- (D17) naturalhealth365.com/vitamin-d-levels-cancer-2617.html
- Colorado State:
- (D16) sciencedaily.com/releases/2008/01/080125223302.htm
- Virology Journal, John J. Cannell ,et. al., On the epidemiology of influenza:
- (replacesD14; Dr Ron’s no longer carries these) Green Pastures:
- Fermented cod liver oil: greenpasture.org/public/products/fermentedcodliveroil/, also available on Amazon (ASIN B002LZYPS0);
- Fermented cod liver oil and concentrated butter oil: greenpasture.org/public/products/fermentedcodliveroilconcentratedbutteroilblend/, also available on Amazon (ASIN B00OZHWX1I)
- Hormone Health Network: Vitamin D (hormone.org/hormones-and-health/hormones/vitamin-d)
- References for Vitamin A info (original): all moved to combined list
(A1) http://www.jbc.org/cgi/reprint/125/2/475.pdf (A2) http://lpi.oregonstate.edu/infocenter/vitamins/vitaminA/ (A3) http://www.cyber-north.com/vitamins/vitamina.html (A4) http://en.wikipedia.org/wiki/Vitamin_A (A5) Weston A Price: (A7) http://articles.mercola.com/sites/articles/archive/2008/12/23/important-cod-liver-oil-update.aspx (A8) https://www.weightlossresources.co.uk/nutrition/vitamins/vitamin_a.htm
- References for Vitamin D info:
(D1) http://articles.mercola.com/sites/articles/archive/2008/12/27/important-vitamin-d-update.aspx (D2) http://articles.mercola.com/sites/articles/archive/2011/12/14/study-shows-vitamin-d-cuts-flu-by-nearly-50.aspx?e_cid=20111209_DNL_artTest_C5 (D3) http://whfoods.org/genpage.php?tname=nutrient&dbid=110 (D4) http://www.cyber-north.com/vitamins/vitamind.html (D5) .vivo.colostate.edu/hbooks/pathphys/endocrine/thyroid/calcium.html (D6) http://articles.mercola.com/sites/articles/archive/2011/12/19/why-are-cancer-cases-rising-by-nearly-50-in-the-next-20-years.aspx (D7) http://articles.mercola.com/sites/articles/archive/2009/12/01/Important-New-Vitamin-D-Research-Papers.aspx (D8) http://articles.mercola.com/sites/articles/archive/2011/11/13/vitamin-d-for-depression.aspx (D9) www.ncbi.nlm.nih.gov/pubmed/21865327 (D10) http://articles.mercola.com/sites/articles/archive/2008/11/18/do-flu-shots-work-ask-a-vaccine-manufacturer.aspx (D11) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870528/ http://www.ncbi.nlm.nih.gov/sites/entrez?orig_db=PubMed&db=pubmed&cmd=Search&term=Epidemiology%20and%20infection%5BJour%5D%20AND%201129%5Bpage%5D%20AND%202006%5Bpdat%5D (D12) www.vivo.colostate.edu/hbooks/pathphys/endocrine/otherendo/vitamind.html (D13) http://www.ncbi.nlm.nih.gov/pubmed/12897318
- (D14) http://www.drrons.com/order-dr-rons-supplements-body-care.htm#fermentedCLO link no longer valid – he no longer sells product. Find another link.
(D15) http://articles.mercola.com/sites/articles/archive/2008/02/12/why-vitamin-d-supplements-are-not-the-same-as-sunlight.aspx (D16) http://www.sciencedaily.com/releases/2008/01/080125223302.htm
- References for Vitamin A: Vitamin D Ratio:
- (AD1) http://www.westonaprice.org/A-Response-to-Dr.-Joe-Mercola-on-Cod-Liver-Oil.html
- (AD2) http://www.westonaprice.org/Cod-Liver-Oil-Basics-and-Recommendations.html
- (AD3) http://www.westonaprice.org/The-Cod-Liver-Oil-Debate.html
- (AD4) http://www.vitaminuk.com/pages/articles/codliveroil.htm