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Vitamin A, Vitamin D and Cod Liver Oil: Some Clarificationsby Sally Fallon and Mary G. Enig, PhDSeveral visitors to our website have noted inconsistencies in various statements about vitamin A, vitamin D and cod liver oil. These issues revolve around questions of dosage and safety. Vitamin A DosageWe have pointed out that concerns about vitamin A toxicity are exaggerated. While some forms of synthetic vitamin A found in supplements can be toxic at only moderately high doses, fat-soluble vitamin A naturally found in foods like cod liver oil, liver, and butterfat is safe at up to ten times the doses of water-soluble, solidified and emulsified vitamin A found in some supplements that produce toxicity.(1) Additionally, the vitamin D found in cod liver oil and butterfat from pasture-raised animals protects against vitamin A toxicity, and allows one to consume a much higher amount of vitamin A before it becomes toxic.(1-3) Liver from land mammals is high in vitamin A but low in vitamin D, and should therefore be consumed with other vitamin D-rich foods such as lard or bacon from pasture-raised pigs, egg yolks, and oily fish, or during months in which UV-B light is sufficient to provide one with adequate vitamin D. As a general guideline, we recommend the following doses of vitamin A from cod liver oil, along with a nutrient-dense diet that contains other vitamin A-rich foods:
Please note that these recommended doses are 2-5 times greater than the U.S. RDA for children, 4 times greater than the U.S. RDA for adults and 8 times greater than the U.S. RDA for pregnant women. The RDA values are based on studies conducted in the general population, which is now recognized to be largely deficient in vitamin D. For a discussion of studies showing that vitamin A consumption up to 30,000 IU per day by pregnant women does not result in a greater risk of birth defects, see Vitamin A for fetal development. This article also describes the vital role played by vitamin A in the development of the fetus. Pregnant women may wish to consult their health practitioner about taking cod liver oil during pregnancy. Individuals under stress or wishing to use cod liver oil to treat a disease condition may take much larger doses, even up to doses providing 90,000 IU vitamin A per day, for a period of several weeks. Vitamin DOur recommended brands of cod liver oil (see below) will provide with the above recommended dosages for cod liver oil about 500-1000 IU vitamin D for children, 1000-2000 IU vitamin D for adults, 2000-4000 IU vitamin D for pregnant and nursing women and up to 9000-18,000 IU for those taking large amounts of cod liver oil to deal with stress and disease. In 1997, the Food and Nutrition Board of the US Institute of Medicine set the tolerable upper intake level (TUIL) for vitamin D at 2000 IU per day. However, the vitamin D content experts on the Upper Limits Panel objected to this limit, and several prominent vitamin D researchers have called for an upward revision of the limit. Experiments show that even during the winter with a low vitamin D intake, humans will exhaust stores of vitamin D at a rate of 3000-4000 IU per day, an amount that many people require to maintain optimal levels of the vitamin in the blood. Extensive exposure to summer sun at mid latitudes naturally produces levels of vitamin D in the blood equivalent to what is attained by supplementing with a continued daily dose of 10,000 IU, suggesting humans are designed to tolerate such large amounts of vitamin D.(4) If you are a lifeguard or spend a lot of time in the sun, you do not need to take supplemental vitamin D; however you still need to consume adequate vitamin A. Animal studies show that even moderate amounts of vitamin D increase the body's need for vitamin A, whether the vitamin D is provided in the diet or by UV light (2,5). So, if you cut back or eliminate cod liver oil in the summer, be sure to consume plenty of oily fish, liver, butterfat and egg yolks from grass-fed hens to ensure adequate vitamin A. For a discussion of Vitamin D Toxicity, see http://www.vitamindcouncil.org/vitaminDToxicity.shtml This does not mean we do not recommend that some individuals have their vitamin D levels tested. Such testing can be very useful in determining vitamin D status and the effectiveness of cod liver oil or vitamin D supplements. Optimal serum vitamin D levels should be in the range of 30-50 ng/mL (see discussion of "Potential Dangers of Vitamin D, page 24 of Spring 2009 Journal). Brand RecommendationsMost brands of cod liver oil go through a process that removes all of the natural vitamins. The resultant product contains very low levels of vitamin A and virtually no vitamin D. Some manufacturers add manufactured vitamins A and D to the purified cod liver oil and until recently, one manufacturer added the natural vitamins removed during processing back into the cod liver oil. Fortunately, we now have available in the U.S. a naturally produced, unheated, fermented high-vitamin cod liver oil that is made using a filtering process that retains the natural vitamins. The high-vitamin fermented cod liver oil is sold as a food so does not contain vitamin levels on the label. However, after numerous tests, the approximate values of A and D have been ascertained at 1900 IU vitamin A per mL and 390 IU vitamin D per mL. Thus 1 teaspoon of high-vitamin fermented cod liver oil contains 9500 IU vitamin A and 1950 IU vitamin D, a ratio of about 5:1. Based on these values, the dosage for the high-vitamin fermented cod liver oil is provided as follows:
Please note that the fermented cod liver oil contains many co-factors that may enhance the body's uptake and usage of vitamins A and D; in fact, many have reported results equivalent to those obtained from high-vitamin cod liver oil with half the recommended dose, that is ¼ teaspoon or 1.25 mL for children age 3 months to 12 years; ½ teaspoon or 5 capsules for children over 12 years and adults; and 1 teaspoon or 10 capsules for pregnant and nursing women. As of Spring, 2009, we recommend the following brands of cod liver oil. Sources of high-vitamin fermented cod liver oil and high-vitamin cod liver oil with natural vitamins added are in the BEST category; sources of processed cod liver oil with synthetic vitamins in the right proportions are in the GOOD category. We do not recommend brands of cod liver oil that have only low levels of vitamins A and D. In the United StatesBEST (Available Online/Mail Order):
GOOD (and available in Stores):
In EuropeBEST:
GOOD:
In AustraliaBEST:
GOOD (in stores):
In New ZealandBEST:
In CanadaBEST:
In Hong KongBEST:
Please read this December 2008 Cod Liver Oil update. Information update on Cod Liver Oil December 2008. References
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