Table 3.

The intermediate results (A–D from Figure 1) and final outcome of each scenario. E > C indicates that, by following the exposure scenario, a sufficient vitamin D level can be synthesized in the skin to maintain winter vitamin D status with 25(OH)D ≥ 25 nmol/L for 97.5% of the population.

Method Step	Result
End summer month	September
End summer 25OHD target, A + (nmol/L)	80.5
Monthly 25OHD spend, B (nmol/L/month)	6.25
Summer dose required, C (SED)	38 *
Acceptable daily dose (SED)	1
Time for fixed daily dose (S1–3), D (minutes)	9
Time range (S4) for daily dose of 1 SED at noon in June. Time (minutes) varies with latitude from S England to N Scotland	9–13
S1: E > C 35% skin area March–September	Y
S2: E > C 10% skin area March–May + September plus 35% skin area June–August	Y **
S3: E > C 10% skin area all summer	N
S4: E > C 35% skin area, June–August, D adjusted for latitude to give 1 SED	Y

⁺ Ensures 97.5% population remain ≥ 25 nmol/L in February and 50% will be ≥ 50 nmol/L [8]. * The dose is calculated using a horizontal surface. The adjustment for a vertical body has been made in calculation of the exposure received at the skin under a range of scenarios [23] (see Section 2.5). ** Easily achieved in southern England and marginal in northern Scotland.