When you receive a cancer diagnosis, bone health is not likely to be the first thing on your mind! However, keeping your bones healthy becomes increasingly important for health and longevity as we age, but this is often made more challenging by the effects of cancer treatment. Conditions of low bone mineral density (osteoporosis and its precursor, osteopenia) tend not to cause symptoms until a fracture happens. This makes it all the more important to be proactive in looking after your bones.
It can be tempting to think of your bones as inert; a scaffold like a steel framework that holds our living tissues together. However, bones are dynamic organs that are continuously being remodelled in response to the environment that they find themselves in. In simplified terms, there is a balance between cells that build new bone (called osteoblasts) and cells that break down old bone (osteoclasts).
A cancer diagnosis often has an impact on bone health due to the altered environment in the body. Treatment can plunge many women into menopause, and the drop in oestrogen favours the production of osteoclasts, which leads to reductions in bone mineral density. Add aromatase inhibitors (such as letrozole, anastrozole or exemestane) into the picture, and there is further risk of reduced bone mineral density(1). If active treatment has resulted in changes to appetite or digestive function, there may be deficiencies of the nutrients needed to keep the bones strong.
You can see that while it is wise for everyone to take measures to look after their bones, it is even more important after a cancer diagnosis!
Exercise
Exercise acts as information for your bones. As important as nutrition is, exercise is more critical for maintaining healthy bones. When tendons or ligaments pull on bones, the mechanical stress tells bones that they need to be strong. Exercise also improves balance, so that falls and resultant fractures are less likely(2).
Calcium
Calcium is the most abundant mineral in the human body, and most of that calcium is found in your bones and teeth. Your skeletal system acts as a storage site for calcium, and it can release calcium from the bones and into the circulation if more is required.
One common misconception is that if your serum calcium level is in normal range on a blood test, you are getting enough calcium from your diet and you have enough in your bones. Unfortunately, it is not possible to tell this from a serum calcium test. Blood concentrations of calcium are critical for many bodily functions, including regulating heart muscle function, facilitating nerve signalling and affecting the stability of the membranes around all body cells. Because calcium has such important roles, the body works hard to keep serum levels within a tight range, and it does this by accessing calcium stored in the skeleton. Serum calcium only tends to go out of range if there is an underlying medical condition which affects this careful balance.
Milk and dairy products are the most concentrated food sources of calcium. However, there are many other foods that also contain significant amounts of calcium, and often in a more bioavailable form. Calcium from cruciferous vegetables (such as kale or broccoli) is absorbed twice as efficiently as calcium from dairy. Small bones eaten with tinned sardines or salmon are a valuable source. Dark green leafy and cruciferous vegetables, soy products such as tofu, almonds and sesame seeds all contain significant amounts of calcium.
It is best to obtain as much of the calcium you need as possible from your diet. Excessive calcium supplementation can promote an insufficiency of magnesium (as we will soon discuss). However, follow your doctor’s advice if you have been prescribed calcium supplements. The UK recommended nutrient intake (RNI) for calcium is 700mg per day, although people taking treatments for osteoporosis may need up to 1000mg per day.
Here is a list of the calcium content in some dairy and non-dairy foods, but remember that this does not address differences in intestinal absorption.
| Food | Calcium content, mg |
|---|---|
| 100ml whole cows’ milk | 124 |
| 100g Greek yoghurt | 110 |
| 25g feta cheese | 123 |
| 100g sardines with bones | 382 |
| 100g extra firm tofu | 375 (although may be as much as 680mg, depending on the preparation method) |
| 240g chickpeas | 77 |
| 30g almonds | 70 |
| 100g kale | 72 |
| 1 tbsp tahini paste | 64 |
| 100g broccoli (approx ½ head) | 40 |
| 100g broad beans | 36 |
Vitamin D
Vitamin D is another key nutrient for bone health. Adequate vitamin D increases the amount of calcium and phosphorous that can be absorbed from food in your gut. Without enough vitamin D, only 10-15% of dietary calcium is absorbed; this increases to 30-40% in the presence of sufficient vitamin D(3).
Restoring vitamin D levels to adequate amounts also has also been shown to reduce the risk of falls in the elderly(4). Some research suggests that serum levels of 25(OH) vitamin D of at least 50 nmol/L are sufficient for optimum bone health, while other sources recommend 75 – 80 nmol/L as optimal levels. Remember that higher levels of 25(OH) vitamin D may be needed to support optimal immune function.
Vitamin K
Vitamin K is a fat-soluble vitamin, which means that eating some healthy fat along with foods that are rich in vitamin K increases their absorption. Vitamin K’s relevance to bone health is that it activates a protein called osteocalcin, which binds calcium into bone. In other words, vitamin K helps ensure that dietary calcium finds its way into your skeleton, where we want it to be. The most concentrated dietary sources of vitamin K are green leafy vegetables, such as kale, spinach and broccoli. Supplementation of vitamin K along with vitamin D and calcium has been found to increase bone mineral density in healthy postmenopausal women(5).
Magnesium
Although it is often overlooked, magnesium is as important for bone health as calcium. There are several reasons for this. Magnesium is needed to convert vitamin D into its active form. It stimulates the activity of the bone-building osteoblasts, and affects parathyroid hormone, which is involved in regulating calcium levels. A magnesium deficiency can promote inflammation, which results in higher activity of osteoclasts(6).
Calcium and magnesium compete with each other for absorption, so excessive consumption of one can lead to an insufficiency of the other. Some of the best dietary sources of magnesium are dark green leafy vegetables, legumes, nuts and seeds, wholegrains and tofu. Note that many of these are also good sources of calcium – the wisdom of nature!
Nutritional Factors that can Adversely Affect Bone Health
- A high caffeine intake (more than 2 cups of coffee per day) reduces calcium absorption in the gut
- A diet high in salt can increase the rate of urinary calcium excretion
- Dark soft drinks (mainly colas) contain phosphoric acid, which have an adverse impact on the bones(7), (8)
- Inflammation promotes osteoclast activity which leads to reduced bone mineral density(9) – another great reason to adopt an anti-inflammatory diet!
Finally, a low body mass index is consistently associated with an increased risk of fractures(10). In terms of bone health, it is better not to be at the lower end of the healthy body mass index range.
References
- Tenti, S., Correale, P., Cheleschi, S. et al. (2020). “Aromatase Inhibitors—Induced Musculoskeletal Disorders: Current Knowledge on Clinical and Molecular Aspects”, International Journal of Molecular Sciences, 21(16), 5625. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7460580/
- Chang, X., Xu, S. and Zhang, H. (2022). “Regulation of bone health through physical exercise: Mechanisms and types”, Frontiers in Endocrinology, 13: 1029475. Available at https://www.frontiersin.org/articles/10.3389/fendo.2022.1029475/full#h6
- Khazai, N., Judd, S.E. and Tangpricha, V. (2008). “Calcium and Vitamin D: Skeletal and Extraskeletal Health”, Current Rheumatology Reports, 10(2), pp110-117. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2669834/
- Ling, Y., Xu, F., Xia, X. et al. (2021). “Vitamin D supplementation reduces the risk of fall in the vitamin D deficient elderly: An updated meta-analysis”, Clinical Nutrition, 40(11), pp5531-5537. Available at https://pubmed.ncbi.nlm.nih.gov/34656949/
- Bolton-Smith, C., McMurdo, M.E.T., Paterson, C.R. et al. (2009). “Two-Year Randomized Controlled Trial of Vitamin K1 (Phylloquinone) and Vitamin D3 Plus Calcium on the Bone Health of Older Women”, Journal of Bone and Mineral Research, 22(4), pp509-519. Available at https://asbmr.onlinelibrary.wiley.com/doi/full/10.1359/jbmr.070116
- Ciosek, Z., Kot, K., Kosik-Bogacka, D. et al. (2021). “The Effects of Calcium, Magnesium, Phosphorus, Fluoride, and Lead on Bone Tissue”, Biomolecules, 11(4), 506. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8066206/
- Tucker, K.L. (2009). “Osteoporosis prevention and nutrition”, Current Osteoporosis Reports, 7(4), pp111-117. Available at https://pubmed.ncbi.nlm.nih.gov/19968914/
- Høstmark, A.T., Søgaard, A.J., Alvær, K. et al. (2011). “The Oslo Health Study: A Dietary Index Estimating Frequent Intake of Soft Drinks and Rare Intake of Fruit and Vegetables Is Negatively Associated with Bone Mineral Density”, Journal of Osteoporosis, 2011:102686. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3135045/
- Livshits, G. and Kalinkivich, A. (2022). “Targeting chronic inflammation as a potential adjuvant therapy for osteoporosis”, Life Sciences, 306:120847. Available at https://pubmed.ncbi.nlm.nih.gov/35908619/
- Stránský, M. and Ryšavá, L. (2009). “Nutrition as prevention and treatment of osteoporosis”, Physiological Research, 58 Suppl 1, S7-S11. Available at http://www.biomed.cas.cz/physiolres/pdf/58%20Suppl%201/58_S7.pdf