10.6 Exercise, Nutrition, Hormones and Bone Tissue
10.6 Exercise, Nutrition, Hormones and Bone Tissue
Learning Objectives
By the end of this section, you will be able to:
- Describe the effect exercise has on bone tissue
- List the nutrients that affect bone health
- Discuss the role those nutrients play in bone health
- Describe the effects of hormones on bone tissue
All the organ systems of your body are interdependent, and the skeletal system is no exception. The food you take in via your digestive system and the hormones secreted by your endocrine system affect your bones.
Exercise and Bone Tissue
During long space missions, astronauts can lose approximately 1 to 2 percent of their bone mass per month. This loss of bone mass is thought to be caused by the lack of mechanical stress on astronauts’ bones due to the low gravitational forces in space. Lack of mechanical stress causes bones to lose mineral salts and collagen fibres, and thus strength. Similarly, mechanical stress stimulates the deposition of mineral salts and collagen fibres. The internal and external structure of a bone will change as stress increases or decreases so that the bone is an ideal size and weight for the amount of activity it endures. That is why people who exercise regularly have thicker bones than people who are more sedentary. It is also why a broken bone in a cast atrophies while its contralateral mate maintains its concentration of mineral salts and collagen fibres. The bones undergo remodelling because of forces (or lack of forces) placed on them.
Numerous, controlled studies have demonstrated that people who exercise regularly have greater bone density than those who are more sedentary. Any type of exercise will stimulate the deposition of more bone tissue, but resistance training has a greater effect than cardiovascular activities. Resistance training is especially important to slow down the eventual bone loss due to ageing and for preventing osteoporosis.
Nutrition and Bone Tissue
The vitamins and minerals contained in all the food we consume are important for all our organ systems. However, there are certain nutrients that affect bone health.
Calcium and Vitamin D
You already know that calcium is a critical component of bone, especially in the form of calcium phosphate and calcium carbonate. Since the body cannot make calcium, it must be obtained from the diet. However, calcium cannot be absorbed from the small intestine without vitamin D. Therefore, intake of vitamin D is also critical to bone health. In addition to vitamin D’s role in calcium absorption, it also plays a role, though not as clearly understood, in bone remodelling.
Milk and other dairy foods are not the only sources of calcium. This important nutrient is also found in green leafy vegetables, broccoli, and intact salmon and canned sardines with their soft bones. Nuts, beans, seeds, and shellfish provide calcium in smaller quantities.
Except for fatty fish like salmon and tuna, or fortified milk or cereal, vitamin D is not found naturally in m