Protein is a building block for strong bones and muscles. It provides the body with a source of essential amino acids necessary for health.
It is important for young people to eat enough protein-rich foods so their bones develop and grow optimally. In seniors, protein plays a role in preserving bone and muscle. Lack of protein robs the muscles of strength, which heightens the risk of falls, and contributes to poor recovery in patients who have had a fracture.
Which foods contain protein? Lean red meat, poultry and fish, as well as eggs and dairy foods, are excellent sources of animal protein. Vegetable sources of protein include legumes (e.g. lentils, kidney beans), soya products (e.g. tofu), grains, nuts and seeds.
The currently recommended daily allowance for healthy adults is 0.8 g of protein per kilogram (kg) of body weight, per day.
Poor protein intake is often related to undernutrition. The ideal body mass index (BMI) should be between 20–25 kg/m2, and a BMI below 19 kg/m2 is a risk factor for osteoporosis.
Debunking the acid-load claim
Many people have read claims that high protein intake, including drinking milk, may cause increased calcium loss via the kidneys and therefore is bad for bone health. This claim has been disproved in many studies. Both plant and animal sources of protein promote strong bones and muscles. Milk and dairy products, as part of a balanced diet, are excellent sources of calcium, protein and other nutrients.
Other vitamins and minerals
Fruits and vegetables contain many different vitamins, minerals, antioxidants and alkaline salts - some or all of which can benefit bone health. Studies have shown higher fruit and vegetable consumption is associated with beneficial effects on bone density in elderly men and women.
Vitamin K is required for the correct mineralization of bone. Some evidence suggests low vitamin K levels lead to low bone density and increased risk of fracture in the elderly. Vitamin K sources include leafy green vegetables such as lettuce, spinach, cabbage, prunes, liver and some fermented cheeses and soya bean products.
TIP: snack on prunes, a good source of vitamin K!
Magnesium plays an important role in forming bone mineral. Magnesium deficiency is rare in most countries but the elderly are sometimes at risk of mild magnesium deficiency because magnesium absorption decreases with age. Particularly good sources of magnesium include green vegetables, legumes, nuts, seeds, unrefined grains and fish.
TIP: 50 g of almonds = up to 40% of your daily need (and contain calcium too!)
This mineral is required for bone tissue renewal and mineralization. Milder degrees of zinc deficiency have been reported in the elderly and could potentially contribute to poor bone status. Sources of zinc include lean red meat, poultry, whole grain cereals, pulses and legumes.
TIP: beans and chickpeas are good plant sources!
Some plant foods contain carotenoids, which are precursors to vitamin A. Carotenoids have been linked to improved bone health and are found in green leafy vegetables, carrots, pumpkins, red and yellow peppers, mangoes, papaya and apricots.
TIP: 50 g of raw carrots meet your daily need!
Vitamins B6 and B12, as well as folic acid, play a role in changing the amino acid homocysteine into other types of amino acids for use by the body. As high blood levels of homocysteine may be linked to lower bone density and a higher risk of hip fracture in the elderly, it is possible that B vitamins might play a protective role in osteoporosis. Research is still ongoing as to whether supplementation with these B vitamins might reduce fracture risk.
Foods that can negatively affect bone health
Caffeine and salt can increase calcium loss from the body and should not be taken in excessive amounts. A good rule of thumb is to drink calcium-containing coffee in moderation and increase calcium intake to counterbalance the potential for calcium loss.
Excessive alcohol intake is a risk factor for osteoporosis and more than two units per day can increase the risk of suffering a fragility fracture. Moderation is again the key word - up to two 120 ml glasses of wine per day do not negatively impact on bone health.
There is no firm evidence that fizzy soft drinks (e.g. cola drinks) weaken bones, but here too, it's best not to overdo it - especially as such drinks tend to 'displace' nutritious drinks like milk in the diets of children and teenagers.