Liver and cod liver oil are nutrient-packed super-food supplements that can help boost energy, libido, muscle growth, brain power, and general health. They are abundant sources of nutrients difficult to obtain elsewhere, such as vitamin A, arachidonic acid, DHA, and the B vitamins.
Liver contains an unidentified "anti-fatigue factor" that was found to greatly boost swimming endurance in rats. It is probably extremely rich in carnitine, lipoic acid, and other energy-related nutrients whose food sources have not been sufficiently researched.
This article will cover the benefits of liver and cod liver oil. To skip to specific product recommendations for liver, cod liver oil, and dessicated liver, click here.
Liver and Cod Liver Oil Are Rich in Vitamin A
Liver and cod liver oil are by far the richest sources of vitamin A.
Vitamin A has traditionally been understood to promote healthy vision, promote healthy fertility in males and females, and allow for proper embryonic development.
More recently, researchers have found vitamin A to be important to many other processes. These include preventing childhood mortality,1 preventing childhood asthma,2,3 promoting pubertal development4 protecting against oxidative stress,5 protecting against environmental toxins,6 preventing kidney stones,7 regulating the amount of fat tissue in the body,8 regulating blood sugar,9 and protecting against fatty liver disease.10
Almost one third (27 percent) of Americans surveyed in the Third National Health and Nutrition Examination Survey had vitamin A intakes below 50 percent of the RDA.11
Even the RDA may be too low — we still do not know what the optimal intake of vitamin A is, especially with respect to its more newly discovered roles.
Many people claim that beta-carotene from carrots and other vegetables is sufficient to provide the requirement for vitamin A. In 1994, researchers observed that pregnant women in Indonesia were consuming what should have been three times the vitamin A requirement as beta-carotene according to the World Health Organization's criteria but were nevertheless showing signs of marginal vitamin A deficiency. In 2002, the Institute of Medicine cut these conversion factors in half, but that would still lead one to estimate the Indonesian mothers to be consuming 50 percent more than their vitamin A requirement and still suffering from deficiency. The same year, Clive West and other researchers from the Netherlands argued from field studies that on a mixed diet, it took on average 21 units of beta-carotene from fruits and vegetables to yield one unit of true vitamin A — a conversion factor 75 percent less efficient than the one used by the Institute of Medicine.12
Table 1 below uses the conversion factors suggested by West's group for five plant foods near the top of the list for carotene content and compares them to five animal foods near the top of the list for true vitamin A content. As you can see from this table, one would have to eat two 100-gram servings of sweet potatoes and three or more 100-gram servings of most other carotene-rich vegetables per day just to meet the RDA of 3,000 IU per day. By contrast, one could meet this requirement by consuming one-half teaspoon of high-vitamin cod liver oil four days a week or eating liver once a week.
It is difficult to find reliable data about the vitamin A intakes of hunter-gatherer societies. The Greenland Inuit were consuming an average of 30,000 IU per day in 1953.13 This is ten times the RDA and probably higher than other hunter-gatherer societies closer to the equator that relied to a lesser degree on animal foods. Whether it is on the whole beneficial, harmful, or neutral cannot be said with any certainty, but 30,000 IU per day is clearly within the range of a natural diet and can quite clearly only be obtained by consuming liver or cod liver oil.
Table 1: Vitamin A Yield From Plant and Animal Foods
A Yield (IU/100g)
A Yield (IU/100g)
Liver is Rich in EFA — Arachidonic Acid and DHA
In my thoroughly researched and extensively referenced Special Report, How Essential Are the Essential Fatty Acids?, I concluded that the only fatty acids for which there is convincing evidence of essentiality to humans and other mammals are the polyunsaturated fatty acids arachidonic acid and DHA. Arachidonic acid is necessary for growth, proper hydration, healthy skin and hair, gut health, and fertility, while DHA is necessary for learning, intelligence, and visual acuity.
According to NutritionData.Com, liver appears to contain 141 mg of arachidonic acid per serving. Thus, it is an even richer source of this nutrient than egg yolks. High-vitamin cod liver oil (discussed further in the product recommendations section) contains between 70 and 360 mg of DHA. Liver from land animals does not appear to contain significant quantities of DHA, but it probably does when the animals are fed grass, which is higher in omega-3 fatty acids than grain.
As described in my Special Report, the need for these fatty acids is extremely low for healthy adults. The requirement increases during infancy and childhood, pregnancy and lactation, recovery from injury, and diseases involving oxidative stress. Bodybuilders and others interested in building new muscle tissue should probably make sure to get some of these fatty acids.
Cod liver oil and fish oils contain EPA, a fatty acid that is probably not essential to mammals and interferes with arachidonic acid. When the total intake of polyunsaturated fatty acids (PUFA) is low, the EPA should be efficiently converted to DHA. When total PUFA intake or EPA intake is very high, however, the EPA may interfere with arachidonic acid metabolism and contribute to deficiency symtoms such as growth retardation, dehydration, flaky and scaly skin, hair loss, gastrointestinal syndromes, or infertility. Moreover, all of the PUFA contribute to oxidative stress when consumed in high amounts, a phenomenon that contributes to heart disease, cancer, fatty liver, diabetes, brain disease, DNA damage, and ageing. Therefore, it makes sense to obtain these precious fatty acids in small amounts. This means avoiding vegetable oils and excessive supplementation with fish oils and obtaining essential fatty acids from liver, muscle meat, butter, occasional fatty fish and very small amounts of high-vitamin cod liver oil.
A recent review by Darisuh Mozaffarian of Brigham and Women's Hospital and Harvard Medical School, cited in Issue 14 of my free newsletter, concluded that the benefits from fish oils plateau at 250 mg of omega-3 fatty acids per day. This is based on studies of populations consuming far too much total PUFA and a great excess of omega-6 fatty acids, and it still only justifies the consumption of one or two servings of fatty fish per week or one-half teaspoon of high-vitamin cod liver oil per day.
Cod liver oil should thus only be consumed in amounts higher than this in order to obtain the fat-soluble vitamins, and one should only consume these higher amounts within the context of a diet rich in vitamin B6, magnesium, and other minerals, low in total PUFA, and balanced by reasonable quantities of liver, muscle meat, and butter to provide adequate arachidonic acid and prevent EPA-induced deficiency symptoms.
B Vitamins, Lipoic Acid, Iron, Vitamin C, and Other Nutrients in Liver
The liver is the main metabolic engine of the body. It is thus an excellent source of energy-related nutrients.
Before the nutrients we eat make it through the blood to our other organs, they are first cleared through the liver. When blood glucose levels fall, the liver releases glucose from stored glycogen or produces new glucose from amino acids and other molecules. When we need to burn fat for energy, fat is released to the liver, which turns that fat into ketones that can be used by other organs.
In order to perform all these functions, the liver must concentrate a number of nutrients. These include all of the B vitamins, carnitine, and lipoic acid. Liver is extremely rich in biotin, and is even a decent source of vitamin C!
Charts of the nutrients found in liver can be found here and here.
Product Recommendations for Liver, Dessicated Liver, and High-Vitamin or Fermented Cod Liver Oil
Whether you choose to use liver, dessicated liver supplements, or cod liver oil will depend on your personal tastes and nutritional needs. Liver provides energy-related nutrients such as B vitamins, iron, vitamin A, and the fertility-boosting arachidonic acid, but it does not provide much vitamin D. Cod liver oil provides vitamins A and D and the brain-boosting DHA, but does not provide B vitamins or iron. Dessicated liver is generally defatted, so it supplies water-soluble nutrients like B vitamins and iron, but not fat-soluble vitamins or essential fatty acids.
If you like liver, the best thing to do is find a source of local, fresh, grass-fed liver. To locate a source, contact your local Weston A. Price Foundation chapter. Personally, I mail order liver from North Star Bison, which consistently has the best-tasting, freshest liver that I can find.
NOW Foods consistently has the best-priced supplements with the least additives. The company sells an additive-free liver powder as well as a dessicated liver supplement with minimal additives. Dr. Ron's sells a grass-fed version of this supplement, although it is much more expensive.
High-Vitamin Cod Liver Oil and Fermented Cod Liver Oil
I recommend using high-vitamin cod liver oil because the polyunsaturated fatty acids found in cod liver oil are only necessary for healthy adults in very small quantities. Small amounts are healthful, but large amounts are likely to be dangerous. I explain this in my Special Report, How Essential Are the Essential Fatty Acids?
The Blue Ice brand also produces a fermented cod liver oil and fermented skate liver oil. These products are also high-vitamin, but more easily digestible and, because the fermentation process produces additional nutrients, more nutrient-dense. Skate liver oil is lower in vitamin A but higher in vitamins E and D than cod liver oil. The fermented high-vitamin oils can be found at Dr. Ron's, and GreenPasture.Org.
You can peruse the references, share this article, or leave a comment below.
Read more about the author, Chris Masterjohn, PhD, here.
1. Sommer A, Tarwotjo I, Djunaedi E, West KP Jr, Leoden AA, Tilden R, Mele L. Impact of vitamin A supplementation on childhood mortality. A randomised controlled community trial. Lancet. 1986 May 24;1(8491):1169-73.
2. Arora P, Kumar V, Batra S. Vitamin A status in children with asthma. Pediatr Allergy Immunol. 2002 Jun;13(3):223-6.
3. Mizuno Y, Furusho T, Yoshida A, Nakamura H, Matsuura T, Eto Y. FERUM vitamin A concentrations in asthmatic children in Japan. Pediatr Int. 2006 Jun;48(3):261-4.
4. Zadik Z, Sinai T, Zung A, Reifen R. Vitamin A and iron supplementation is as efficient as hormmonal therapy in constitutionally delayed children. Clin Endocrinol (Oxf). 2004 Jun;60(6):682-7.
5. Ciaccio M, Valenza M, Tesoriere L, Bongiorno A, Albiero R, Livrea MA. Vitamin A inhibits doxorubicin-induced membrana lipid peroxidation in rat tisúes in vivo. Arch Biochem Biophys. 1993 Apr;302(1):103-8.
6. Stohs SJ, Hassan MQ, Murray WJ. Effects of BHA, d-alpha-tocopherol and retinol acetate on TCDD-mediated changes in lipid peroxidation, gluathione peroxidase activity and survival. Xenobiotica. 1984 Jul;14(7):533-7.
7. Sakly R, Achour A, Zouaghi H. [Antilithogenic and litholytic action of vitamin Avis-a-vis experimental calculi in rats]. Ann Urol (Paris). 1994;28(3):128-31.
8. Ziouzenkova O, Orasanu G, Sharlach M, Akiyama TE, Berger JP, Viereck J, Hamilton JA, Tang G, Dolnikowski GG, Vogel S, Duester G, Plutzky J. Retinaldehyde represses adipogenesis and diet-induced obesity. Nat Med. 2007 Jun;13(6):695-702.
9. Shin DJ, McGrane MM. Vitamin A regulates genes involved in hepatic gluconeogenesis in mice: phosphoenolpyruvate carboxykinase, fructose-1,6-bisphophatase and 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. J Nutr. 1997 Jul;127-7):1274-8.
10. Kang HW, Bhimidi GR, Odom DP, Brun PJ, Fernandez ML, McGrane MM. Altered lipid catabolism in the vitamin A deficient liver. Mol Cell Endocrinol. 2007 Jun;271(1-2):18-27.
11. Dixon LB, Winkleby MA, Radimer KL. Dietary Intakes and Serum Nutrients Differ between Adults from Food-Insufficient and Food-Sufficient Families: Third National Health and Nutrition Examination Survey, 1988-1994. J Nutr. 2001 Apr;131(4):1232-46.
12. West CE, Eilander A, van Lieshout M. Consequences of Revised Estimates of Carotenoid Bioefficacy for Dietary Control of Vitamin A Deficiency in Developing Countries. J Nutr. 2002;132:2920S-2926S.
13. Deutch B, Dyerberg J, Pedersen HS, Ashlund E, Hansen JC. Traditional andmodern Greenlandic food — Dietary composition, nutrients and contaminants. Sci Tot Environ. 2007;384:106-119.