For twelve seasons, the crime procedural drama Bones traced the exploits of an FBI agent and his forensic anthropologist partner who helped solve cases by examining human remains – the bones. Viewers watched the team bring the bad guys to justice while also learning a bit about human anatomy. I’ve learned still more in a recent flurry of reading (see below).
Our bones define our basic shape, protect our vital organs, and serve as the scaffolding on which all of our soft tissues hang. They house bone marrow in which our red blood cells, white blood cells, and platelets are produced. They also provide a storage repository for minerals essential for energy production and tissue growth. When our diets fall short on nutrients, our bodies take what they need from our bones. Unfortunately, a chronic nutritional shortfall puts our bones’ strength and stability at risk.
Bones consist of three concentric layers. The familiar skeleton from biology class or Halloween decorations reflects a densely-packed outer cortical sheath. A spongy cancellous (or trabecular) bone sits just inside its harder cousin and resembles a honeycomb. It provides support without added weight. The inner medullary cavity contains the marrow.
Our skeletal frame undergoes tremendous growth between infancy and adulthood. We achieve peak bone mass somewhere between age 20 and 30, yet bone remodeling remains a mainstay of our physiology for a lifetime. Osteoclasts break down and absorb old and weakened bone to make way for stronger material. Osteoblasts deposit collagen into these excavation sites for subsequent combination with lysine (an amino acid) and minerals (e.g., calcium, magnesium, phosphorous, potassium) to form new bone. Osteoclasts and osteoblasts need to work in lockstep to maintain healthy bones. Too little osteoclast activity can make for weakened bones and insufficient triggering to activate osteoblasts. Too little osteoblast activity causes bones to lose density.
Several vitamins and minerals contribute to bone development:
- Vitamin A helps regulate osteoclast and osteoblast activity
- Vitamins B6 and B9 keep homocysteine levels in check so as not to disrupt bone remodeling
- Vitamin C plays a role in making collagen and serves as an antioxidant
- Vitamin D increases calcium absorption in the intestines and stimulates the kidneys to reabsorb calcium from urine
- Vitamin K – specifically menaquinones 4 and 7 (MK4 and MK&) – helps clear excess calcium from joints and arteries, protects bone sheath flexibility, and supports calcium deposit in the bone matrix
- Calcium, magnesium, phosphorous, and trace minerals contribute to the hardening of bones
- Silicon improves bone matrix quality and facilitates bone mineralization
Hormones also get in on the action:
- Calcitonin (secreted by the thyroid gland) binds with osteoclasts and makes them less active so that osteoblasts can do their work
- Parathyroid hormone (secreted by the parathyroid gland) promotes calcium absorption in the intestine and reduces loss through urine
- Cortisol (secreted by the adrenal gland) assists bone growth in small amounts… and interferes in large amounts!
- Growth hormone (secreted by the pituitary gland) increases muscle mass and strengthens bones
- Thyroid hormones (secreted by the thyroid gland) control the rate of bone remodeling, although an excess may disproportionately increase bone resorption
- Sex hormones (estrogen and testosterone) stimulate bone formation; estrogen also keeps osteoclasts in check
And, of course, we need well-functioning digestive and liver function to ensure that we extract nutrients effectively from our food. So, just as our bones support our whole body, a whole lot of physiological elements need to come together to support our bones.
When a weakened physiology disrupts the activity of the aforementioned vitamins, minerals, and/or hormones, bone breakdown can outpace bone regeneration and render bones weak and porous. Physicians refer to the initial stage of disease as osteopenia and the advanced stage osteoporosis. More women than men are diagnosed with the disease due to the precipitous loss of estrogen during menopause. According to the International Osteoporosis Foundation, one in three women and one in five men worldwide over age 50 will sustain a fracture due to osteoporosis in their lifetimes.
Age is an obvious risk factor for bone loss given a general weakening in physiological function. Other risk factors include:
- Chronic nutritional deficiency that fails to satisfy the body’s need for essential vitamins and minerals
- Chronic low level acidosis which causes the body to leach calcium from the bones to maintain its slightly alkaline blood
- Poor digestive function which inhibits the absorption of nutrients from foods – e.g., Celiac disease, dysfunctional microbiome, leaky gut, low hydrochloric acid
- Chronic inflammation caused by long-term infection, food allergies, autoimmune disorders, and the like which elevates osteoclast activity
- Excess cortisol caused by unrelenting stress which suppresses bone growth
- Oxidative stress caused by poor diet, gastrointestinal disorders, hormonal imbalance, toxicity, stress, aging
- An inactive lifestyle that provides little incentive for the body’s construction team to build bone and muscle
- Use of certain prescription medications (e.g., glucocorticoids) that interfere with serum calcium and bone formation
Most of us do not pay much attention to our bones unless and until we sustain a fracture. Among older adults, such occasions may result in painful recuperation, loss of function, decreased quality of life, and even morbidity. A consultation with one’s physician complemented by a diagnostic bone scan can assess risk. No matter our age, a healthy lifestyle that is sensitive to skeletal health can help us preserve its function for many years to come.
- Bart L. Clarke, MD, Medical Editor, Mayo Clinic Guide to Preventing and Treating Osteoporosis: keeping your bones healthy and strong to reduce your risk of fracture, ©2014
- Joy M. Alexander, PhD and Karla A. Knight, RN, 100 Questions & Answers About Osteoporosis and Osteopenia, Second Edition, ©2011
- Felicia Cosman, MD, What Your Doctor May Not Tell You About Osteoporosis: Help Prevent – and Even Reverse – The Disease That Burdens Millions of Women, ©2003