Effects of cod liver oil on allergies and asthma

By Dr. Ajith Amarasinghe

For ages parents have been forcing a spoonful of cod liver oil down the throats of little children or giving them cod liver oil capsules. The nasty aftertaste that it leaves makes you wonder why go through the trouble.

What does cod liver oil do anyway? In present day, the use of cod liver oil has decreased but there are still those faithful few that hold on to the notion that cod liver oil is a cure all especially in regards to allergies and asthma.

Cod fish are found on both sides of North Atlantic’s deep waters. They are valued for their flesh and the cod liver oil is one of the most important natural sources of vitamins A and D. It also is a good source for omega 3 fatty acids.

Vitamin A, vitamin D and omega 3 fatty acids are three important nutrients of the body. Vitamin A, a fat-soluble vitamin, plays an integral role in cell growth, vision, and the immune system as well as helps maintain the mucous membranes that trap microbes and fight infection.

Vitamin D is mostly known for keeping bones strong and healthy. In the late 19th and early 20th century, cod liver oil was used to treat rickets because of its strong source of Vitamin D. Omega 3 fatty acids also known as polyunsaturated fatty acids lowers LDL cholesterol and lowers risk for heart disease. By reviewing recent medical research on cod liver it seems as though it could be a cure for allergies and asthma too.

Allergies are due to an oversensitive immune system which leads to a misdirected immune response. The immune system normally protects the body against harmful substances such as bacteria and viruses. It reacts to substances (allergens) that are generally harmless but in a person with allergies the immune response is oversensitive.

When it recognises an allergen, it releases chemicals such as histamines. This causes itching, swelling, sneezing, rashes, and other symptoms which vary from person to person. Asthma is caused by inflammation in the airways. In sensitive individuals asthma symptoms can be triggered by breathing in allergy-causing substances (called allergens or triggers). Triggers include pet dander, dust mites, cockroach allergens, moulds, or pollens.

Fish oil and cod liver oil may reduce inflammation and allergic response. In Bergen, Norway, Birger Laerum and a team of researchers investigated the relationship between childhood and adult intake of cod liver oil and fish with risk for asthma. (Laerum, B. N., Wentzel- Larsen, T., Gulsvik, A., Omenaas, E., Gislason, T., Janson, C., and Svanes, C. (2007). Relationship of fish and cod oil intake with adult asthma. Clinical and Experimental Allergy, 37, 1616-1623.)

They used a Respiratory Health in Northern Europe (RHINE) study in which they sent out a postal questionnaire regarding fish intake in childhood and adulthood. Reports showed that in adults the higher amount of fish consumed the lower the susceptibility of allergies.

It also showed that children who ate fish had lower susceptibility, but this did not translate with age: In a relatively smaller study Linda Linday and other paediatric researchers designed a study to determine whether multivitamins with cod liver oil have an effect on sinusitis. (Linday, Linda; Dolitsky, Jay; Shindledecker, Richard. (2004). Nutritional supplements as adjunctive therapy for children with chronic/ recurrent sinusitis: pilot research. International Journal of Paediatric Otorhinolaryngology, 68, 785-793.)

They found that the dosages of multivitamins and cod liver oil were positive in lowering sinus effects. They noted that this treatment does not work on severe symptomatic sinusitis patients.

In a study done by Janet A. Dunstan, BAppSc, PGDip and others, School of Paediatrics and Child Health, University of Western Australia, Perth, Australia, fish oil supplementation in pregnancy modifies neonatal allergen-specific immune responses and clinical outcomes in infants at high risk of allergies.

One must remember that with taking cod liver oil as any supplement, there are some risks. Over-consumption of cod liver oil means over-consumption of vitamin A, which can cause toxicity in the body. Therefore it has to be taken in dosages recommended for a particular age.

(The writer, MBBS, DCH, MD (Sri Lanka), P.G Dip in Asthma and Allergy (CMC-Vellore), MRCP, MRCPCH (UK), MBA – Health Care (Manipal), is a Consultant Paediatrician.)