Debate on the merits of cod liver oil has been ricocheting around the internet of late, sparked by a recent posting from Dr. Joseph Mercola, in which he withdrew his recommendation to take cod liver oil. Mercola’s remarks dovetail with establishment bias against this old-fashioned superfood. Cod liver oil has come under attack as a “dangerous” source of vitamin A. And while vitamin A has fallen to the bottom of the Vitamin Hit Parade, vitamin D has risen to the top, with many voices calling for extensive supplementation and an increase in the RDA for the sunshine vitamin.
The establishment view is as follows: the animal form of vitamin A is toxic and also interferes with vitamin D metabolism, so we should avoid foods rich in vitamin A, like liver, organ meats and cod liver oil; we can get all the vitamin A we need from the conversion of carotenes in plants; it is impossible to obtain adequate vitamin D from food, so we need to take vitamin D supplements.
In recent articles, we have put these mistaken notions to rest by showing the extensive scientific literature on the benefits of cod liver oil and vitamin A, as well as on the synergistic-rather than antagonistic-relationship of vitamins A and D. To bolster our premise that vitamin A is not toxic and that vitamin D can be obtained from food sources, we have published many articles on traditional diets, showing the high levels of vitamins A and D in traditional foods. For example, the traditional Scottish diet, described in a recent article, was rich in fish liver oils, organ meats, shellfish and fats, thus corroborating the discoveries of Dr. Weston A. Price, who found that emphasis on foods rich in vitamins A and D was universal among primitive populations.
However, care must be taken in the choice of cod liver oil. Most brands contain synthetic vitamins A and D and many have the wrong ratio of A to D. Please visit the following links for information on cod liver oil, the number one superfood:
- Cod Liver Oil
- Vitamin A Benefits and Toxicity
- Vitamin A for Fetal Development
- Vitamin A On Trial: Does Vitamin A Cause Osteoporosis?
- Vitamin A Saga (Discusses the myth of carotenes as an adequate source of Vitamin A)
- Vitamin D Benefits and Toxicity
- The Good Scots Diet (Traditional Diet in Scotland)
Recent Studies on Cod Liver Oil
The following are references to recent articles published since 2000 in the scientific literature showing the myriad benefits of cod liver oil. Because modern diets are deficient in vitamins A and D, we recommend a daily dose of good quality cod liver oil for young and old.
Vitamin D Status: In Norway, three mølje meals (consisting of cod liver and fresh cod-liver oil) provided an amount of vitamin D equal to 54 times the recommended daily dose. Subjects with food consumption habits that included frequent mølje meals during the winter sustained satisfactory vitamin D levels in their blood, in spite of the long “vitamin D winter” (Public Health Nutr. 2004 Sep;7(6):783-9).
Vitamin D Status and Bone Loss: Inclusion of cod liver oil in the diet appears to attenuate the seasonal variation of vitamin D status in early postmenopausal women at northerly latitudes where quality of sunlight for production of vitamin D is diminished. Cod liver oil can thus protect against greater bone turnover, bone loss and obesity (Bone. 2008 May;42(5):996-1003).
Hip Fracture: Multivitamin or cod liver oil supplementation was associated with a significantly lower risk of any fracture. “We found no evidence to support any skeletal harm associated with increased serum indices of retinol exposure or modest retinol supplementation in this population” (J Bone Miner Res. 2005 Jun;20(6):913-20).
Multiple Sclerosis: In Arctic climates, supplemental cod-liver oil during childhood may be protective against multiple sclerosis later in life (J Neurol. 2007 Apr;254(4):471-7).
Breast Cancer: Reduced breast cancer risks were associated with increasing sun exposure and cod liver oil use from ages ten to nineteen. “We found strong evidence to support the hypothesis that vitamin D could help prevent breast cancer. However, our results suggest that exposure earlier in life, particularly during breast development, maybe most relevant” (Cancer Epidemiol Biomarkers Prev. 2007 Mar;16(3):422-9).
Depression: Regular use of cod liver oil is negatively associated with high levels of depressive symptoms in the general population (J Affect Disord. 2007 Aug;101(1-3):245-9).
Wound Healing: The combination of zinc oxide and cod liver oil was found to be superior to the formulations containing only one active ingredient. This combination was also found to be most efficient in accelerating wound healing when it is retarded by repeated dexamethasone treatment (Dtsch Tierarztl Wochenschr. 2006 Sep;113(9):331-4).
Arthritis and Joint Stiffness
- Pain and Joint Stiffness: Cod liver oil application allows reduction of the dose of nonsteroidal anti-inflammatory drugs, and improves chief clinical symptoms, reducing pain and morning joint stiffness (Klin Med Mosk 2005;83(10):51-7).
- Pain in Rheumatoid Arthritis: Cod liver oil supplements were better than controls in relieving pain and can be used as NSAID-sparing agents in rheumatoid arthritis patients (Rheumatology (Oxford). 2008 May;47(5):665-9).
- Rheumatoid Arthritis: Use of cod liver oil decreased occurrence of morning stiffness, swollen joints and pain intensity in patients suffering from rheumatoid arthritis (Adv Ther. 2002 Mar-Apr;19(2):101-7).
Diabetes and Circulation
- Diabetes: Use of cod liver oil in the first year of life was associated with a significantly lower risk of type 1 diabetes. Use of other vitamin D supplements during the first year of life and maternal use of cod liver oil or other vitamin D supplements during pregnancy were not associated with lower risk of type 1 diabete (Am J Clin Nutr. 2003 Dec;78(6):1128-34).
- Diabetes-Related Cardiovascular Disorders: Cod liver oil treatment in diabetic rats completely prevented endothelial deficiency and partly corrected several biochemical markers for cardiovascular disorders (J Pharm Pharmacol. 2007 Dec;59(12):1629-41).
- Diabetic Nephropathy: Substitution of cod liver oil for soybean oil in mice reduced oxidative stress and nephropathy induced by daunomycin, an anti-cancer agent (Lipids. 2002 Apr;37(4):359-66).
Birth Weight, Breast Milk, and Children’s Health
- Higher Birth Weight: Women who used liquid cod liver oil in early pregnancy gave birth to heavier babies, even after adjusting for the length of gestation and other confounding factors. “Higher birth weight has been associated with a lower risk of diseases later in life and maternal cod liver oil intake might be one of the means for achieving higher birthweight” (BJOG. 2005 Apr;112(4):424-9).
- Breast Milk: Women using cod liver oil had a significantly higher levels of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in their breast milk. “As this may have an impact on the health and development of breast-fed infants in later life, regular maternal cod liver oil intake could be relevant for the infant as well as for the nutritional adequacy of the maternal diet” (Ann Nutr Metab. 2006;50(3):270-6).
- Fat-Soluble Vitamins in Breast Milk: Maternal use of cod liver oil resulted in higher levels of fat-soluble vitamins in breast milk, especially vitamins E and A. (Ann Nutr Metab. 2001;45(6):265-72).
- Intelligence in Children: Children who were born to mothers who had taken cod liver oil during pregnancy and lactation scored higher on intelligence tests at age four compared with children whose mothers had taken corn oil (Pediatrics. 2003 Jan;111(1):e39-44).
- Ear Aches in Children: Children prone to ear aches (otitis media) receiving cod liver oil plus selenium needed lower amounts of antibiotics during supplementation compared to before supplementation (Ann Otol Rhinol Laryngol. 2002 Jul;111(7 Pt 1):642-52).
- Upper Respiratory Tract Infections in Children: Children supplemented with cod liver oil had a decrease in upper respiratory tract infections and pediatric visits over time (Ann Otol Rhinol Laryngol. 2004 Nov;113(11):891-901).