Guide to Calcium

Calcium is an important structural mineral and 99 per cent of the dietary calcium you absorb goes straight into your bones and teeth. The other 1 per cent plays a crucial role in blood clotting, muscle contraction, nerve conduction and the production of energy.

Calcium is only absorbed from your diet if sufficient vitamin D is present. As blood calcium levels are tightly regulated, lack of calcium (or vitamin D) means your blood levels are replenished by leaching calcium from your bone stores. Good intakes of calcium and vitamin D are therefore vital throughout life to build strong bones and help prevent brittle bone disease (osteoporosis) in later life.

Dr Sarah Brewer

What Does Calcium Do?

Calcium combines with phosphate to make the mineral, hydroxyapatite, which gives bone and tooth enamel its strength.


An estimated 30% of all postmenopausal women have osteoporosis and at least 40% of them will suffer one or more fragility fractures. Good dietary intakes of calcium, and calcium supplements helps to prevent bone loss in older people and protect against osteoporotic bone fractures i. The results from 8 studies, involving almost 31,000 people, showed that taking calcium plus vitamin D supplements reduced the risk of any fracture by 15%, and the risk of hip fracture by 30%. Calcium supplements are therefore a good idea for middle-aged and older adults, including postmenopausal women. ii

Blood Pressure

Calcium helps to regulate blood pressure through effects on blood vessel contraction and dilation, and poor intakes of calcium are linked with high blood pressure and stroke. The results of 40 studies, involving 2,492 people, show that taking calcium supplements (at an average daily dose of 1200 mg) reduced blood pressure by a small but significant amount of 1.86/0.99 mmHg overall. In those with low calcium intakes, however, supplements have a greater effect, reducing blood pressure by an average of 2.63/1.30 mmHg.iii

Getting Calcium From Your Diet

Dietary sources of calcium include milk and dairy products, eggs, green leafy vegetables especially broccoli (but not spinach, whose oxalate content reduces its bioavailability), tinned salmon (including the bones), nuts and seeds, pulses and bread made from fortified flour. It is relatively easy to increase calcium intake by drinking an extra pint of skimmed or semi-skimmed milk per day, which contains 720mg calcium per pint. The calcium found in milk is in the readily absorbable form of calcium lactate.

Correct Dosage

The EU RDA for calcium is 800 mg per day. The upper safe level for long-term use from supplements is suggested as 1500mg.

Supplements supplying calcium carbonate are best taken with meals to boost absorption.


According to the National Osteoporosis Foundation and the American Society for Preventive cardiology, calcium supplements (with or without vitamin D) have no harmful effects on the risk for cardiovascular and cerebrovascular disease in generally healthy adults if calcium intake (from food plus supplements) does not exceed a tolerable upper level of 2000 mg per day, and should be considered safe from a cardiovascular standpoint iv, v

People with a tendency to kidney stones should seek advice before taking calcium supplements. Drinking plenty of water may help to reduce any risk of kidney stones. vi

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn’t possible supplements can help. This article isn’t intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.





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