Page 129 - Vitamin D and Cancer

116 R. Scragg

NHANES National Health and Nutrition Examination Survey
PTH Parathyroid hormone
TNF Tumor necrosis factor
UV Ultraviolet

6.1 Introduction

Opinions about the effect of vitamin D on risk of cardiovascular (CV) disease have
changed substantially over the last half century. From the 1950s to the end of the
1970s, the dominant viewpoint was that vitamin D was a cause of CV disease.
During the 1980s and 1990s, an increasing number of studies were published show-
ing benefits from vitamin D, challenging the earlier opinions that vitamin D was
harmful and resulting in a period of flux where researchers increasingly were open
to the possibility that vitamin D could protect against CV disease. This coincided
with a substantial increase in research on vitamin D and cancer, which along with
the identification of vitamin D receptors in many body tissues, resulted in an
increased acceptance by vitamin D researchers that the effects of vitamin D were
not restricted to bone disease, but could affect the health of many organs and body
systems. During the first decade of this century, the weight of scientific opinion has
shifted 180° from that of 50 years ago, and the prevailing focus of research is on
identifying the potential beneficial effects of vitamin D against CV disease. This
latter period has coincided with a rapid increase in the number of publications on
vitamin D and CV disease (Fig. 6.1). There are lessons to be learnt from this story,
and the current generation of researchers needs to be mindful of the possibility that
opinions may change again in the future.
The purpose of this review is to describe the key developments in research on
vitamin D and CV disease over the last 50 years, to summarize the findings from
recent large epidemiological studies which strongly support a beneficial effect from
vitamin D against CV disease, and to give an overview of the possible mechanisms
by which vitamin D may protect against CV disease.

6.2 1950s to 1970s: Adverse Vascular Effects from Vitamin D

6.2.1 Vascular Lesions from Vitamin D Intoxication

An epidemic of cases of infantile hypercalcemia occurred in Great Britain during
1953–1955 which was attributed to vitamin D fortification of commercial milk
powders and infant cereals, and vitamin D supplements [1]. In response, the British
government reduced the amount of vitamin D in fortified foods so that by 1957–
1958 daily intake of vitamin D by infants had halved. However, the number of