The history of the
allergy pandemic is well documented, enabling us to put the
vitamin D hypothesis into its historical context. The purpose of this study is to compare the prevalence of
rickets,
vitamin D supply, and
allergy prevalence at 50-year intervals by means of a retrospective analysis of the literature since 1880. English cities in 1880 were characterized by an extremely high
rickets prevalence, the beginning of commercial
cod liver oil production, and the near absence of any allergic diseases. By 1930
hay fever prevalence had risen to about 3% in English-speaking countries where
cod liver oil was preferentially used for the treatment of
rickets. In 1980
vitamin D was used nation-wide in all industrialized countries as supplement to industrial baby food, thus eradicating nearly all cases of
rickets. At the same time the
allergy prevalence reached an all-time high, affecting about 30% of the population. Time trends are therefore compatible with the
vitamin D hypothesis although direct conclusions cannot be drawn. It is interesting, however, to note that there are at least two earlier research papers linking synthesized
vitamin D intake and
allergy (Reed 1930 and Selye 1962) published prior to the modern
vitamin D hypothesis first proposed in 1999.