I wish I had bones as strong as yours,” the sports physician said as she looked at my bone density results. “It’s from all that running you’ve done,” she said approvingly. Putting stress on our bones by walking, running, dancing and lifting weights helps keeps our bones strong. Bones are not simply the scaffolding on which the rest of our body hangs. They are living, active tissue that’s continually breaking down and rebuilding. The outer bone is hard and compact but inside is a smaller amount of spongy honeycomb-like bone that is designed for strength – sort of like the steel rods inside a concrete building. And if you don’t use them, you lose them – with the calcium gradually seeping out of them until they become weak and brittle.

With all my nutritionist focus on calcium, exercise and osteoporosis I often forget about the other critical work that our bones do. Tucked safely away in the centre of our bones is the most amazing place – our blood cell birthing centre. It’s where all our blood cells are made – the red ones to carry oxygen around the body, the platelets for clotting so when we cut ourselves we don’t bleed to death, and the white ones to fight infection.

When the body is severely stressed – either physically or emotionally – the bones produce more white blood cells in an attempt to fight off the attack. It’s usually a good response that protects the body. But chronic stress that goes on and on may alter the genetic make-up of white blood cells so they don’t work as they should. One study on people who were caring for a family member with cancer found that their white cells were less responsive to the anti-inflammatory action of cortisol. One of the researchers said that in people with chronic stress, the “white blood cells are not able to receive the signal that tells them to shut down inflammation”. It’s like the stress has changed the white blood cells so they don’t hear the message to chill out and relax. They zealously keep on over-doing their job causing havoc in the body and increasing the risk of heart disease, cancer, diabetes, arthritis and depression.

Stress doesn’t happen only when you’re caring for a sick friend or relative. Being envious of someone else, feeling crushed by circumstances or people and marriage difficulties are all stressful. Perhaps this provides a physiological explanation for these ancient proverbs: “Envy rots the bones”, “A crushed spirit dries up the bones” and “A disgraceful wife is like decay in her husband’s bones”. When I think about envy, a crushed spirit and a stressful marriage there’s one word that comes to mind – stress.

So a bit of physical stress on the bones in the form of weight-bearing exercise is good but science seems to be discovering that chronic emotional stress is no good for that other essential part of our bones – the blood cell making centre.

In my next post I’ll talk about how to make good deposits in your bone bank so you have strong bones even in old age.

Related Post: Building your bone bank account – start early!