Introduction to Human Nutrition

142 Introduction to Human Nutrition

HO7-Dehydrocholesterol

OH CH

3

CH

2

HO

H

C 3

OH

Previtamin D

Tachysterol

Vitamin D

calciol (cholecalciferol)

Slow

Light thermal isomerization

Light

CH

2

HO

OH

Calcidiol

(25-hydroxycholecalciferol)

Liver,

25-hydroxylase

CH

2

HO

OH

OH

24-Hydroxycalcidiol

CH

2

HO

OH

OH

Calcitriol

(1,25-dihydroxycholecalciferol)

Kidney,

24-hydroxylase

Kidney,

1-hydroxylase

Figure 8.4

Vitamin D synthesis and metabolism.