Calcium supplements: when diet is enough and when it is not

Calcium is the most abundant mineral in the body. NHS inform describes it as helping to build strong bones and teeth, regulate the heartbeat and allow blood to clot so that wounds heal. A shortage over a long time can lead to rickets in children and to osteomalacia or osteoporosis in adults, according to the NHS.

Because bone is constantly being remodelled, calcium intake matters at every age. It matters most during childhood growth and, at the other end of life, when bone is being lost faster than it is replaced.

The BDA gives practical portion examples: a 200ml glass of cows milk provides 240mg, a 30g piece of Cheddar about the size of a matchbox provides 240mg, and 150g of plain yogurt also provides 240mg. For people who avoid dairy, calcium-fortified plant drinks, tinned sardines eaten with their bones, and calcium-set tofu are alternatives.

The BDA also points out that spinach, dried fruits, beans, seeds and nuts contain calcium but are also high in oxalates or phytates, which reduce how much the body absorbs. Many plant milks are not fortified, so the label is worth reading. The NHS lists dairy foods, green leafy vegetables such as curly kale and okra, fortified soya drinks and bread, and fish with edible bones as good sources, and notes that spinach is not one.

• Dairy: milk, cheese, yoghurt.

• Fish with soft edible bones, such as sardines and pilchards.

• Fortified soya or other plant drinks and fortified bread.

• Green leafy vegetables such as kale and okra.

The NHS figure of 700mg a day applies to adults of 19 and over. The BDA, which breaks needs down by life stage, gives 700mg for adults aged 19 to 55, 1250mg for breastfeeding mothers and 1200mg for postmenopausal women and men over 55.

A supplement can fill a gap when someone eats little dairy or fortified food, has a condition that limits absorption, or is being treated for bone loss. The BDA says that where intake from food is not enough, a supplement may help, but advises a discussion with a health professional before adding more than 500mg of extra calcium daily.

The NHS keeps its position simple: a varied, balanced diet should provide enough calcium, and anyone using supplements should stay within the safe limit of 1,500mg or less a day. Doctors treating osteoporosis may prescribe calcium with vitamin D alongside bone medicines, and in that setting the prescribed dose takes precedence over the general advice here.

The BDA stresses vitamin D as crucial for calcium absorption. NHS pages recommend that adults consider 10 micrograms of vitamin D a day, since it is hard to obtain enough from food alone, and describe sunlight from late March to September as another source. The NHS sets an upper limit of 100 micrograms a day for adults, because too much vitamin D over a long period can cause calcium to build up in the body and harm the bones, kidneys and heart.

Exercise also counts. The NHS recommends weight-bearing and resistance activity to improve bone density, alongside not smoking and keeping alcohol within the 14 units a week guideline.

Going over 1,500mg a day can cause stomach pain and diarrhoea, per the NHS. Calcium tablets can also affect how some other medicines are absorbed, so a pharmacist should check the timing if you take thyroid tablets, certain antibiotics or bone medicines.

People with a history of kidney stones, kidney disease or high blood calcium should not start a calcium supplement without advice from their doctor, because the choice of product and dose matters.

Bone pain, repeated fractures after minor falls, loss of height, or muscle cramps and tingling with low intake are reasons to see a GP rather than to increase supplements yourself. A GP can arrange blood tests, including vitamin D, and consider whether a bone density scan is appropriate.