Vitamin D Deficiency

Rickets has been around for centuries, but its roots as a symptom of vitamin D deficiency began only in the 17th century, when Francis Glisson published his findings on the disease and proposed that it was a disease of the rich rather than the poor. When the industrial revolution took place in the 1800’s, the number of children with rickets soared, only, this time, it affected more than half the children in the overcrowded and highly polluted industrialized areas.

As early as 1822 the researcher Sniadecki recognized its association with poor or reduced sunlight exposure, and in a few more decades, it was well known that cod liver oil was efficacious in treating this condition. Mellanby and McCollum pioneered the discovery of vitamin D as the effective agent in cod liver oil which prevented and treated rickets, which led to the addition of this vitamin to milk and other foods as a means of fortification against this disfiguring disease.

Vitamin D is a fat-soluble substance, and is therefore found in few foods of plant origin. It is therefore commonly ingested as a supplement or through the ingestion of fortified milk or milk products.

In most people, vitamin D is synthesized in the skin on exposure to a narrow wavelength band of ultraviolet radiation. This means that deficiency is more likely during winter in temperate regions, because outdoor exposure is limited, clothing is heavier and less skin is exposed, and the amount of sunshine is restricted. Moreover, the ultraviolet rays in this band are absorbed by the atmosphere during winter. Older people produce the vitamin less efficiently than younger people.

Vitamin D deficiency is likely when the serum level of 25-hydroxy cholecalciferol drops below 30 nmol/L. This is the inactive storage form of the vitamin. The following table shows the levels of the vitamin associated with health risks.

Table 1: Serum concentrations of 25-hydroxycholecalciferol in health and disease

Concentration (nmol/L)

Health status


Vitamin D deficiency: rickets or osteomalacia, depending on age


Potential risk of deficiency, poor overall health


Adequate to maintain health

In order to avoid deficiency, recommended dietary allowances (RDAs) have been worked out, and range from 400 to 800 IU (10-20 mcg) based on the age. These RDAs do not allow for sunlight exposure, to prevent deficiency in case of limited outdoors activity. The table below details the RDA at various ages for diverse population groups:

Table 2: Recommended dietary allowances for vitamin D


RDA for vitamin D (IU)

<12 months


1-13 years


14-70 years


> 70 years



Reasons for vitamin D deficiency

The chief causes for low vitamin D levels include:

Conditions caused by vitamin D deficiency

Rickets and osteomalacia are the classical deficiency diseases caused by inadequate vitamin D.


Occurring in children with vitamin D deficiency, this is caused by failure of mineralization of bone, leading to soft, pliable and eventually deformed bones. This was because the unmineralized osteoid of the bone tissue could not support the body’s weight nor the strain caused by various body movements. Rickets is still found throughout the world.

The peak incidence of rickets is between 3 and 18 months of age. Subtle manifestations of vitamin D deficiency in childhood may occur before the actual bone signs, and include:

Rickets may manifest in one of two ways:

Early rickets presents with symptoms such as bone pain, delay in milestones such as standing and walking, frequent falls, and delayed growth. Severe calcium deficiency due to low vitamin D intake may also occur in the period of infancy. Some common signs and symptoms of hypovitaminosis D include:

In the established stage, it is called florid rickets. Its manifestations include:

Breastfeeding may cause rickets under the following conditions:

Reasons for rickets in children

Diagnosis of rickets


This is the effect of vitamin D deficiency in adults, and means weak bones. It manifests with bone pain and muscular weakness, often subtle in the first stages. It is due to the failure of mineralization of organic osteoid because of low calcium and phosphate levels. Its characteristic manifestations include:


Abnormalities of immune function

Vitamin D stimulates innate immunity and prevents chronic disease conditions due to failure of immunity

Stages of vitamin D deficiency

Clinical signs of vitamin D deficiency

Risk groups for vitamin D deficiency


Further Reading

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.

Last updated Feb 27, 2019


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