Stress Fractures & Calcium

Every child knows you should be eating your three sources of calcium every day if you want to grow up to be big and strong.  Where in our teenage years does this message get lost? Since when does the latest ‘sugar elimination’ diet hold more credibility than our basic nutritional knowledge? Our calcium intake is vital in our childhood and teenage years as our bones are physically growing.  What we seem to forget is that our bones are constantly requiring this calcium balance for strength in both the immediate and distant future.

Calcium is a positively charged ion (Ca 2+) and is used for endless metabolic processes in our bodies including muscle contraction, heart conduction, blood clotting and neurotransmission across our nerves synapses; an undeniably crucial processes to our bodies.  When we become nutritionally deficient in calcium it is incredibly rare that our heart, blood, nerves or muscles are effected. Our body prioritises the health of these elements over our bones.  Good news for your heart, bad news for the threat of runners’ worst fear; stress fractures.

Our bones are constantly undergoing re-mineralisation through osteoclast (bone break down) and osteoblast (bone building) activity. If you think of bone density in the same way as energy, the key is maintaining a balance between input and output to support your running and weight bearing demands.

Throwing out your calcium balance can result in one of two things. Too much calcium, called hypercalcemia or not enough; calcium deficiency. Deficiency is an issue that rests at the forefront of almost all confrontations with stress fractures. The common association is to attribute stress fractures purely to training load but all injuries are multifactorial. There is never just one cause and whilst training load can contribute, there are many individuals with underlying factors predisposing them to a greater risk. Those at danger of stress fractures regardless of training load include individuals:

• who restrict daily kilojoule intake – through restricting foods
• have low bone density
• have muscle weakness associated with the load of running e.g a lack of calf strength
• and females – hormonal effect as a result of menstrual interruption

Both low bone density and the restriction of dietary intake form a cycle with calcium deficiency. An individual who restricts their diet often won’t meet their calcium requirements and this in turn reduces their overall bone density. The rate at which their osteoblasts lay down new cells is interrupted; both a preventative measure for the effects of stress fractures acutely and osteoporosis in the long run.

Milk, leafy green vegetables, fortified juice, soybeans, peanuts and sardines are all highly absorbable forms of calcium. The daily recommendation is to be aiming for 1300mg every single day for adolescents and 1000mg for adults. Athletes should use this as a minimum to compensate for calcium loss through sweating, especially for females via hormone interaction in low iron states and with menstrual absence or irregularities.

Never forget the benefits of dietary intervention and incorporation over supplements and fad diets. Calcium supplements should only be incorporated under instruction from qualified doctors or dieticians.  Another thing to note when choosing foods high in calcium is that animal product calcium is absorbed more easily by your digestive system as it doesn’t contain chemicals such as oxalates which are found in plant material such as spinach.  Fad diets such as the Paleo diet restrict consumption of animal products.  This doesn’t mean you should restrict plant material as they have many other benefits and overall any kind of food high in calcium is a better alternative to supplement use. Use the foods and their calcium content below to make the judgement yourself as to whether you are getting enough calcium in your diet;

• 1 x 250ml glass of reduced fat milk (350mg)
• 1 x 200g tub of yoghurt (300mg)
• 1 x 30g serve of low fat cheese (300mg)
• 1 x 80g serve of broccoli/spinach/bok choy (70mg)
• 100g of raw tofu (350mg)
• 1 serve of nuts/seeds, especially almonds (50mg)
• 1 x 200ml glass of calcium fortified juice (150mg)

Combining both cheese and greens: Blanched cauliflower with kale, asparagus, broccolini, roasted chickpeas, sunflower seeds + pepitas, mint and feta.