The connection between cod liver oil and vitamin D is straightforward. Cod liver oil is an excellent source of vitamin D, which can be difficult to get in adequate amounts. Cod liver oil contains other nutrients as well, and there is no risk associated with supplementing the diet with moderate doses of cod liver oil.
Vitamin D is a fat soluble vitamin required for calcium absorption. Without sufficient levels of vitamin D, bones lose density, become brittle or even misshapen. Children who do not get enough vitamin D may develop rickets, while adults who do not get sufficient amounts have an increased risk of developing osteoporosis. Other benefits of vitamin D include protection from high blood pressure, some autoimmune diseases, and even some types of cancer.
Some people have a higher incidence of deficiency, and may benefit more from cod liver oil and vitamin D supplementation. The elderly, babies who are exclusively breastfed, people who are obese, and those with limited sun exposure may all find it difficult to maintain healthy vitamin D levels. Additionally, people with inflammatory bowel disease, such as Crohn's, and those with cystic fibrosis and other fat malabsorption diseases may have low levels of vitamin D.
Cod liver oil and vitamin D are mentioned together because cod liver oil is a rich source of vitamin D, however, cod liver oil also has other nutrients that make it a valuable addition to a healthy diet. Cod liver oil contains vitamin A, which is necessary for a healthy immune system and helps the body resist viruses and bacteria. Vitamin A is also necessary for healthy skin and eyesight.
Omega-3 fatty acids, EPA, and DHA are three fatty acids contained in cod liver oil. Omega-3 fatty acids have anti-inflammatory properties that may reduce some of the pain of arthritis. It also improves brain function, and can help with learning and behavioral disorders. Omega-3 fatty acids can also prevent allergies, relieve asthma symptoms and reduce stress.
EPA is important for cardiovascular health and also reduces inflammation. DHA is important for healthy skin, eyesight, and nervous system. One serving of cod liver oil provides all three of these essential fatty acids.
Taking cod liver oil and vitamin D together is not recommended, however, because the result can be an overdose of vitamin D. Vitamin D overdose typically results when someone supplements above the recommended range for an extended period of time, allowing the vitamin D to build up in the body. Symptoms of vitamin D overdose include vomiting, decreased appetite, irritability, dehydration, constipation, and fatigue. A high intake of vitamin D can also lead to a high concentration of calcium in the blood, which can result in itchy skin, nervousness, and kidney failure.