"Britain had little or no rickets in the 1950s because of supplementation, " he said.
Once authorities started adding the vitamin to milk, rickets, a previously common bone deformity, virtually disappeared.
In areas where sunlight is scarce or where culture prevents sun exposure, rickets was more common.
Rickets was a common, even endemic, disease, and therefore not terribly difficult to study.
The number of cases of rickets in the US has risen in recent years.
But in northern Europe, diseases related to vitamin D deficiency, such as rickets, would have become common.
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But is the prevention of severe vitamin D deficiency such as rickets all we need to know?
Rickets is rarely fatal but can soften bones and result in bowing of the legs and impede growth.
Since the 1930s, most milk in the U.S. has been fortified with D to prevent rickets, a bone-softening disease.
It has long been known that vitamin D prevents rickets and children were once given food supplements like cod liver oil.
We know that vitamin D is necessary to prevent rickets, and that, combined with calcium, it is needed to prevent osteoporosis.
Breastfed babies may need a top up of Vitamin D to ensure they do not develop rickets, US experts have warned.
Stephen Nussey, professor of Endocrinology at St Georges Hospital in London, explained that rickets is a severe aspect of vitamin D deficiency.
Researchers from Wake Forest University and the University of North Carolina studied 30 children diagnosed with nutritional rickets over a 10-year period.
It said vitamin D and folic acid supplements should be offered by health staff to help ward off conditions such as rickets and spina bifida.
Still, we can try to correlate vitamin D levels with obvious deficiency diseases such as rickets, but the environmental studies that look at other possible effects are problematic.
The consultant paediatrician told BBC Breakfast that the hospital saw about one severe case a month of rickets - softening of bones through lack of vitamin D in childhood.
Rohan Wray and his wife Channa, from Islington in north London, were accused of killing their four-month-old son Jayden in July 2009 - it was later established he had severe rickets.
Healthy levels are about 50 nanomole per litre - less than 30 nanomole per litre can cause the softening and weakening of bones, leading to rickets in children and osteomalacia in adults.
Consequently, many develop rickets, pneumonia or limb deformities.
Ms. Warner recounts what life was like in poor areas before the introduction of vitamins into food substances, the fortification of white flour and milk, and the widespread availability of items like orange juice: Many people suffered from rickets (because of insufficient vitamin D and calcium), scurvy (vitamin C), pellagra (vitamin B3) and beriberi (vitamin B1).
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