Bones: Protecting the Organ that Protects Us

Bones provide us with support, protect our organs, help us move, play a role in mineral and acid-base balance, and are the site for red blood cell production.

What Healthy Bones Need

On a basic level, bones need three things for growth and maintenance – ample nutrients for building materials, adequate testosterone and estrogen hormones for regulation, and a “stressor” for building strength and density (think weight bearing physical activity). Altogether, they direct the actions of osteoblasts (bone building cells) and osteoclasts (bone degrading cells) to build, breakdown or remodel bones as needed. Bones are surprisingly active organs!

Some loss of bone mass as we age is natural; the bone building cells do not get replaced at the same rate, hormone levels wane and we may not be as active as we once were. If too much bone loss occurs, however, the bones become porous and less dense, which can lead to bone pain, osteoporosis and increased risk of bone fracture. While we do have some control over our bones’ vigor, such as choosing a healthy lifestyle, there are some factors leading to poor bone health that are out of our control. Cancer is one of them.

Cancer and Bone Health

Cancer patients and survivors have an increased risk of bone loss and bone fractures due to either the cancer itself and/or resulting from cancer treatment. Cancers that directly harm bone, like multiple myeloma (a bone marrow cancer), or those that tend to metastasize to bone (prostate, breast and lung cancers) can cause bone pain and fractures.

More often, however, it is the cancer treatments themselves that result in bone mineral loss. Radiation therapy to treat cancer in the bone, or near it, can weaken the bone matrix. Hormone therapy used to treat prostate and breast cancer suppresses the sex hormones that promote healthy bones. Inadequate levels of testosterone in men and estrogen in women put bone maintenance in a negative balance, meaning the body is breaking down more bone than making or maintaining.

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Steroids such as hydrocortisone, dexamethasone, methylprednisolone and prednisolone are often employed to combat treatment side effects or as adjuvant therapy or stand alone treatment of various cancers, especially breast, prostate, blood and bone cancers. While there are great benefits to using steroids, long-term use (greater than three to four months) impairs bone metabolism and promotes bone loss.

Finally, certain chemo agents like cyclophosphamide and taxane-based chemotherapies suppress bone marrow growth and can stimulate osteoclast (the bone degrading cell) activity.

Taking Care of Your Bones

 

It might feel like cancer and the treatments are ganging up on your bones, but that just means one should be more vigilant than ever in protecting them. And it can be done!

Feed Those Bones

The first step – proper nutrition. Did you know that about 20 different nutrients are thought to be involved with bone health? It goes way beyond calcium and vitamin D. This includes: protein, calcium, phosphorus, magnesium, fluoride, zinc, copper, boron, manganese, potassium, iron, vitamins A, C, D and K and some B vitamins. Not having adequate nutrients is akin to a contractor not having sand and water to make cement. Minerals are the substrates and vitamins are the tools enabling the builders. So go ahead, eat to your bone’s health, and make sure to consume a variety of fruits, vegetables and whole grains to acquire the array of nutrients needed

The Big Players

While all nutrients are necessary, focusing on calcium and vitamin D to promote bone health is still very much warranted. Calcium mixes with phosphate to form hydroxyapatite – the main mineral base of bones. The RDA for calcium is 1,000 mg per day for men and women ages 19 – 50 and then bumps up to 1,200 mg per day for women after 50 (i.e. post-menopausal) and for men after 70. Luckily, many foods are rich calcium sources.

Supplements are available if you are unable to meet your needs through diet. The two main calcium supplements are calcium carbonate and calcium citrate. They are absorbed differently in your body so talk your doctor or a registered dietitian (RD) about which one may be best for you. Additionally, calcium can decrease absorption of iron so your doctor or RD will guide you on appropriate timing if you plan to take both calcium and iron supplements.

Vitamin D promotes intestinal absorption of calcium and helps protect the calcium already in your bones, making it vital for bone health. The RDA is 400 IU for adults ages 19 – 70 and 600 IU for adults above 70. Food sources rich in this vitamin are fatty fish (salmon, mackerel, trout and tuna), fortified milk and maitake mushrooms. Our bodies can make vitamin D when exposed to sunlight, but living in cold wintry climates for over half the year limits this exposure, and our body produces less vitamin D as we get older.

Vitamin D is readily available as a supplement and best taken in the more bioactive form of D3 (calcitriol). Vitamin D can interfere with steroid medications so talk with your doctor prior to starting supplements. It is also recommended to know your serum vitamin D level before starting; you want between 30 – 50 nmol/L (12 – 20 ng/mL).

A Positive Stress Factor

Finally, in addition to good nutrition, let us not forget that exercise is an important factor in bone health. Weight bearing exercises exert a positive stress on the bone forcing it to respond by becoming denser and thus stronger. For example, when running or briskly walking, pressure is exerted on various bones (legs, hips, spine). To accommodate this pressure the osteoclasts build a kind of scaffolding called trabeculae that increase the strength of the bone. The same happens with resistance or strength training. As you push through the resistance or lift the weight, pull from your muscles exerts stress on the bone leading to increased trabeculae formation. The picture below demonstrates the difference in density between a normal bone and an osteoporotic bone. The latter has lost a significant amount of the scaffolding and it is easy to see how this leaves a bone fragile.

 

Additionally, physical activity will promote muscle strength, balance and coordination, all of which decreases one’s risk of falling and potentially breaking a bone. For more information on how to incorporate weight bearing exercises into your routine see our physical activity blog post on strength and resistance training. If you are feeling fatigued and need to ease into things check out our physical activity blog post on chair-based exercises that offer low-impact ways to get you moving again. Do consult a doctor before starting any exercise regimen as certain exercises may not be appropriate for those at high risk of fracture.

 

So now we know that bones are not simply these inert, calcified things in our bodies, but, in fact, are an organ in a continual state of activity throughout our lifetime. To keep them going, we need to feed them adequate nutrients, with a focus on calcium and vitamin D, and give them reason to strengthen through weight bearing exercise.


References

Drake, M. T., Clarke, B. L. and Khosla, S. (2008). Bisphosphonates: Mechanism of action and role in clinical practice. Mayo Clinic Proceedings: 83(9); 1032-1045. DOI: 10.4065/83.9.1032

Lukert, B. P. and Raisz, L. G. (1990). Glucocorticoid-Induced Osteoporosis: Pathogenesis and Management. Annals of Internal Medicine: 112(5); 352-364. DOI: 10.7326/0003-4819-112-5-352

Munch, J. (2010). Preventing bone loss and fractures in cancer patients. OncoLog: 55(3). Accessed on February 9, 2015, from http://www2.mdanderson.org/depts/oncolog/articles/10/3-mar/3-10-2.html.

Palacious, C. (2006). The role of nutrients in bone health: from A to Z. Critical Review in Food Science and Nutrition: 46(8); 621-628. DOI: 10.1080/10408390500466174

Wooldridge, J. E., Anderson, C. M. and Perry, M. C. (2001). Corticosteroids in advanced cancer. Oncology: 15(2); 225-236.

Cancer.Net, Osteoporosis. Accessed February 9, 2015, from http://www.cancer.net/navigating-cancer-care/side-effects/osteoporosis.

NIH Eunice Kennedy Shriver National Institute of Child Health and Human Development. How does physical activity help build healthy bones. Accessed February 10, 2015, from http://www.nichd.nih.gov/health/topics/bonehealth/conditioninfo/Pages/activity.aspx.

NIH Office of Dietary Supplements. Calcium. Accessed on February 10, 2015, from http://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/#h3.

NIH Office of Dietary Supplements. Vitamin D. Accessed on February 10, 2015, from http://ods.od.nih.gov/factsheets/VitaminD-Consumer/.

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