Page 295 - Vitamin D and Cancer

282 G.M. Zinser et al.

Fig. 12.1 Proposed stages of vitamin D deficiency and sufficiency according to serum
25-hydroxyvitamin D. Vitamin D deficiency leading to rickets in children and osteomalacia in
adults is associated with circulating concentrations of 25-hydroxyvitamin D (25D) below 50 nM.
In contrast, data from epidemiological studies suggest that serum 25D concentrations between 50
and 100 nM are associated with an increased risk of chronic diseases, including cancer. Toxicity,
which is associated with soft tissue calcification and renal stones, occurs when 25D increases
above 250 nM. Thus, the preferred range of 25D for optimal health is likely between 100 and
150 nM, which may not be attainable without dietary supplementation (2,000 IU/day or higher in
individuals with limited sun exposure)

with increased risk for breast cancer. Similar data generated on serum 25D in
relation to other chronic diseases support the concept that a healthy 25D range for
adults is between 100 and 150 nM, which is well below the toxic range associated
with calcemic overload (above 250 nM). A summary of the proposed relationship
between serum 25D, health and disease is provided in Fig. 12.1.

12.2.3 Prevalence of Vitamin D Insufficiency

Unfortunately, it is difficult for most people to maintain serum 25D in the proposed
healthy range (100–150 nM) from dietary sources alone due to the low amounts of
vitamin D in natural foods [14]. Particularly relevant to the possible relationship
between vitamin D and breast cancer, vitamin D deficiency has been reported in a
high percentage of women, including during adolescence, pregnancy/lactation and
after menopause, even in sunny climates [15–17]. The amount of vitamin D usually
present in over the counter supplements (400 IU) is too low to significantly elevate
serum 25D [18]. Supplementation studies suggest that 2,000 IU/day (and possibly