A diet rich in calcium and dairy products is recommended to support bone growth and development. The irony is, many nations with food supplies abundant in this nutrient have high rates of hip fractures - an indicator of osteoporosis and poor bone health.
Osteoporosis is a progressive bone disease characterised by reduced bone mass and brittleness. The Ministry of Health recommends Kiwis consume 1000 to 1300mg of calcium a day to help keep bones strong - that's about 3 cups of milk.
Western countries have adapted their food supply to ensure everyone has access to ample amounts of dairy like milk, cheese and yoghurt. Calcium also comes from a variety of milk alternatives and smaller amounts from some vegetables and nuts.
The problem is: the same countries continue to experience high rates of hip fractures and osteoporosis.
This trend was raised in a review nearly 30 years ago that also compared the available calcium in the food supply of 10 nations against rates of hip fractures.
It suggests various dietary and physiological mechanisms that not only harm our bones, but also protect them. Twenty-six years later, a systematic review of hip fracture incidence and probability of fracture worldwide from 1950 to 2011 again showed high rates in many Western countries.
Strangely, countries where milk and diary products are rare (like Nigeria, Tunisia and Morocco) appear to have perfectly good bone health.
What many nations with poor bone health have in common is their Westernised diet and lifestyle - packed full of processed, refined and convenience foods. While rich in dairy, these diets interfere with the body's metabolism of calcium. As a result, requirements for this nutrient increase and the food industry react by flooding the market with calcium rich products.
Six factors that could be bad for bone health:
1. Soft drink
While some fizzy drinks contain caffeine, there are a couple other reasons they could be bad for your bones. They're high in phosphorus, an essential component for bone health. But when consumed in excessive amounts, it can interfere with calcium absorption. Also, soft drinks often replace more nutritious options like milk. This means you're filling up on calories, but with none of the goodness from calcium or protein to strengthen your bones
Our hectic lives support sipping coffee to stay focused during the day or for a pep up at night. The problem is, too much caffeine can pull calcium from the bone and excrete it in urine. The effect may be relatively small, but if you're not getting enough calcium you may be placing yourself at risk.
A diet with low alcohol consumption is fine - that's one drink a day for women and up to two for men - with a couple alcohol free days a week. If you want to see the short term effects of too much heavy drinking, head down to your local A&E department on a Sunday morning.
Salt is more common that caffeine in the Western diet. If you haven't already been convinced to cut back on sodium for general health and wellbeing, then you may want to reconsider. The more salt we consume, the more calcium we shed in urine and sweat. Remember that salt is hidden in most processed foods - nearly everything you find in a packet, tin or jar.
Moving is essential for bone health. A sedentary lifestyle doesn't allow bones to remodel, adapt and grow stronger. Exercise that places force on your bones like jogging, walking and playing sport are great ways the keep your bones strong. Plus, by getting out into the sun your body will naturally produce vitamin D, an essential nutrient to effectively metabolise calcium.
6. Too much protein
Protein's important for building strong healthy bones, but too much can cause calcium to be excreted in the urine. A diet high in protein and low in fruit and vegetables makes an acidic environment that draws calcium from the bone to act as a buffering agent. Different foods have different acid producing effects. However, you don't need to worry if you're eating a balanced diet with one to two of protein packed foods a day.
Dave Shaw is a New Zealand registered dietitian and nutritionist. Follow him on Twitter.