10.17:
Role of Vitamins in Maintaining Bone Health
Vitamins— A, C, D, K, and B12 are crucial for maintaining bone strength and health in the human body.
Vitamin A plays a significant role in stimulating osteoblasts activity and differentiation. While in children, it promotes bone growth; in adults, it influences the maintenance of bone health.
Vitamin C acts as a cofactor for the enzymes responsible for the hydroxylation of specific residues on the collagen that increase their stability.
Vitamin D helps in the uptake of dietary calcium and phosphate from the gastrointestinal tract. These minerals are essential for the formation of bone matrix.
Osteocalcin— a protein secreted by osteoblasts requires Vitamin K for its carboxylation and enzymatic activation.
This carboxylated osteocalcin has a high calcium-binding affinity and aids in bone mineralization.
As a result, vitamin K deficiency can lead to a rise in the level of uncarboxylated osteocalcin, reducing bone mineral density and increasing the risk of fractures.
Similarly, vitamin B12 deficiency can also lead to low bone mineral density and even contribute to osteoporosis, especially in women.
10.17:
Role of Vitamins in Maintaining Bone Health
The growth and maintenance of bone are regulated by a combination of nutritional factors, including vitamins, such as vitamin A, B12, C, D, and K.
Vitamin A
Vitamin A is involved in the process of bone remodeling. Retinoic acid, the active metabolite of Vitamin A, has nuclear receptors in osteoblasts and osteoclasts, which are involved in bone remodeling.
Vitamin B12
Vitamin B12 acts as a cofactor during the formation of osteoblast-related proteins, such as osteocalcin. Vitamin B12 plays a role in iron metabolism, which is involved in bone formation.
Vitamin C
Vitamin C is a cofactor for enzymes required to maintain a stable triple-helical conformation of collagen. Also, vitamin C stimulates the activity of the enzyme alkaline phosphatase. This enzyme is a marker for osteoblast formation and helps in bone mineralization.
Vitamin D
Calcium cannot be absorbed from the small intestine without vitamin D. Insufficiency of vitamin D is therefore linked to osteoporosis, which can be associated with an increased risk of fractures.
Vitamin K
Vitamin K is necessary for the γ-carboxylation of osteocalcin, the principal non-collagenous protein of bone. Specifically, vitamin K is a cofactor of γ -carboxylase, an enzyme involved in γ -carboxylation of glutamic acid residues in proteins, including osteocalcin. Carboxylated osteocalcin helps in the mineralization of the bone matrix.
This text is adapted from Openstax, Anatomy and Physiology 2e, Section 6.6: Exercise, Nutrition, Hormones, and Bone Tissue.