Exposure to sunshine, especially ultraviolet B rays, creates more vitamin D which can be used by the body, but you can also get it from foods like trout, tuna, mackerel, herring, salmon, sardines, eggs, cheese, and cod liver oil in capsule form. Some fortified milk, soy milk and cereals will contain more vitamin D than natural sources.

If you do not have enough vitamin D in your diet, especially breastfeeding mothers from countries with little sunshine, soft bones can form in their children called rickets. This occurs mostly in the legs and will result in a curved shape of the skeleton. Those over the age of 65 also need to take extra vitamin D to help keep their bones strong.

There is already evidence of too little vitamin D causing an increased risk of people developing osteoporosis, certain cancers, high blood pressure and diabetes. Researchers have also found an association between vitamin D and the proper functioning of the lungs as well as preventing fractures in older people.

If you combine cod liver oil capsules with a vitamin D supplement you could be taking in too much. The recommended safe limit is 50mcg per day. Symptoms of toxicity are anorexia, nausea and vomiting, the increased need to urinate, increased thirst, weakness, nervousness, and eventually renal failure.

Vitamin D regulates the calcium and phosphorous levels in the blood and affects the immune system by promoting anti-tumor activity which is why it helps prevent high blood pressure and cancer. Vitamin D is actually made up of 5 different vitamins all of which work closely together. The most important ones which are used by the body are vitamin D2 and vitamin D3.