We have all heard the phrase ‘those bones need calcium’ and it is essential advice for all of us! An adequate intake of calcium is one of a number of factors important for acquiring bone mass and attaining peak bone mass. Diets containing insufficient amounts of calcium may lead to lower bone mineral density, which may have implications for bone health, notably risk of osteoporosis later in life. Our bones are gaining and losing minerals continuously in an ongoing process of remodeling. Calcium forms crystals on a matrix of the protein collagen. This process is called mineralization. During mineralization, as the crystals become denser, they give strength and rigidity to the bones. Most people achieve a peak bone mass by their late 20s, and dense bones best protect against age-related bone loss and fractures.
Calcium is in fact the most abundant mineral in the body. Ninety-nine percent of the body’s calcium exists in the bones and teeth. It is an integral part of bone structure and calcium found in the bones also serves as a bank from which the body can withdraw calcium to compensate for low intakes. The remaining 1% of the body’s calcium is in the body fluids, where it helps regulate blood pressure and muscle movement. Calcium is important at all life stages, and most especially during periods of linear growth, infancy, childhood and puberty, as well as pregnancy and lactation. In the blood, calcium helps to maintain normal blood pressure. Calcium is also involved in the regulation of muscle contraction, transmission of nerve impulses, secretion of hormones and activation of some enzyme reactions.
The Primary Sources of Calcium
Calcium is most commonly found in milk and milk products as well as small fish (with bones), calcium-set tofu (bean curd), legumes, spinach, Chinese cabbage, kale, and broccoli.
Bioavailability of Calcium
Calcium absorption by the body is enhanced by the presence of vitamin D and decreased in the presence of oxalic and phytic acid in foods. Thus, foods with high content of calcium that are also rich in oxalic acid (e.g., spinach, sweet potatoes, rhubarb, and beans) or phytic acid (e.g., seeds, nuts, grains) will result in a lower absorption of calcium compared to foods with no inhibitors, such as milk and milk products. Diets high in sodium or phosphorus (e.g., cola beverages) also negatively affect calcium levels in the bone.
Risks Related to Inadequate Intake of Calcium
Because calcium is critical to muscle contraction and nerve impulses, the body tightly regulates blood calcium levels. If calcium intake is low, the body will draw on calcium in the bones. Poor chronic intake in calcium results in osteomalacia, in which bones become weak owing to lack of calcium. Insufficient calcium in bones can also result from an inadequate supply of vitamin D, which is essential for absorption of calcium and its deposition in the bones. Thus, adequate calcium and vitamin D intake is vital for bone integrity and for bone growth.
Incorporate calcium into your next meal by trying the delicious recipe below…
Cheese & Spinach Penne with Walnut Crumble*
500g pack penne
2 large leeks, sliced
85g plain flour
2 tsp ready-made English mustard
good grating nutmeg
1l milk, plus a bit extra
350g pack mature cheddar, grated
4 slices French bread, diced
85g walnut piece
400g bag spinach
Heat oven to 190C/170C fan/ gas 5. Boil the pasta with the leeks for 10 mins, then drain.
Meanwhile, put the butter, flour, mustard, nutmeg and milk in a large pan with some seasoning. Gently heat, stirring all the time, until bubbling and thickened, then cook for 2 mins more, stirring frequently. Remove from the heat and stir in two-thirds of the cheese. Toss the remaining cheese with the bread and walnuts.
Cook the spinach in the microwave, or pour a kettle of boiling water over it to wilt, then squeeze out the excess water. Stir into the sauce with the pasta, leeks and some seasoning. If necessary, add a little extra milk to loosen. Divide between 2 ovenproof dishes and scatter the bread mixture on top. If eating straight away, bake for 40 mins until golden, or cool to freeze.
*Adapted from BBC Good Food