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Do You Need a Calcium Supplement? The 700 mg Question Answered
Most adults in the UK do not need a calcium supplement, because the reference intake of 700 mg a day is reachable from ordinary food; a supplement is for the gap between what you eat and 700 mg, not a replacement for the total. The gap is real for some people: people who avoid dairy without fortified alternatives, teenage girls and women on the low intakes the National Diet and Nutrition Survey keeps finding, and older adults eating less than they used to.1, 2 The evidence sets the limits: calcium from food and from supplements raises bone density by the same one to two per cent, which then plateaus; calcium with vitamin D modestly reduces hip fractures, mainly in care-home residents; and the question of whether high-dose tablets affect the heart is unsettled.3, 4, 5, 6
- UK need: 700 mg a day for adults, not the 1,000 to 1,200 mg quoted on American sites
- Food first: a glass of milk, a pot of yoghurt and a matchbox of cheese get most people there
- A supplement is for the gap: 300 to 500 mg a day; absorption falls above about 500 mg in one dose
- Ask first: kidney stones, a high blood calcium, parathyroid or kidney disease, thyroid medicine
How much calcium do you need in the UK?
Adults need 700 mg of calcium a day, the UK reference nutrient intake; 11 to 18 year olds need 800 to 1,000 mg, and breastfeeding adds 550 mg.1 The 1,000 to 1,200 mg figures in most search results are the American recommendations, and menopause does not change the UK figure. Count a typical day in UK portions:
| Food, UK portion | Calcium, approximate |
|---|---|
| Semi-skimmed milk, 200 ml glass | 240 mg |
| Plain yoghurt, 150 g pot | 240 mg |
| Cheddar, 30 g (a matchbox) | 220 mg |
| Fortified soya or oat milk, 200 ml | 240 mg (check the label) |
| Calcium-set tofu, 100 g | 350 mg |
| Tinned sardines eaten with the bones, 100 g | 400 mg |
| Kale, 80 g cooked | 120 mg |
| White or brown bread, 2 slices (UK flour is fortified) | 120 mg |
| Almonds, 30 g handful | 70 mg |
Two dairy portions and two slices of toast reach 700 mg; a day with no dairy and no fortified alternative often lands at 300 to 400 mg, which is where the gap appears. Foods high in calcium has the full UK list.
Who is most likely to be short of calcium?
The National Diet and Nutrition Survey finds intakes below the lower reference nutrient intake in a sizeable minority of girls aged 11 to 18 and a smaller share of women aged 19 to 64; men are rarely short.2 Beyond the averages: people who have cut out dairy without fortified plant milk, calcium-set tofu or tinned fish; older adults with smaller appetites, especially in care; and people a doctor has told to raise their intake after a fracture or a bone scan. If your count lands under 700 mg, the shortfall is what a supplement is for. If it is already there, more adds nothing to bone; a low intake has no symptoms to warn you, which what are the signs of low calcium explains.3
Do calcium supplements strengthen bones?
Modestly, and no more than food calcium does. A 2015 review of 59 trials found that raising calcium intake, from food or from tablets, increased bone density by 0.7 to 1.8 per cent in the first year with no further gain after that.3 The companion review of 26 fracture trials found supplements reduced total fractures by about 11 per cent, but the lowest-bias trials showed no effect, and calcium alone has little evidence for hip fracture.4 The clear result belongs to calcium plus vitamin D in frail older people: in a French trial of 3,270 care-home residents, 1,200 mg of calcium with 20 micrograms of vitamin D cut hip fractures by 43 per cent in 18 months, and the Cochrane review found the combination reduced hip fractures by 16 per cent, about one fewer per 1,000 older adults living at home each year and nine fewer per 1,000 in institutions.5, 6 Bone density itself responds more to loading exercise than to any tablet, which can you rebuild bone density sets out; the Wellgard joint health guide covers the joints.
Are calcium supplements bad for your heart?
Unresolved: a question was raised about high-dose tablets, later analyses did not confirm it, and food calcium has never been implicated. In 2010 a meta-analysis of 15 trials found 31 per cent more heart attacks in people taking calcium supplements of 500 mg or more without vitamin D.8 Later analyses used verified hospital records: an 18-trial collaboration covering 63,563 women found no increase in coronary events or deaths, and a 2016 review commissioned by the US National Osteoporosis Foundation concluded that calcium with or without vitamin D, at total intakes up to 2,000 to 2,500 mg, is not linked to cardiovascular disease in generally healthy adults.9, 10 The Royal Osteoporosis Society's position is that there is not enough evidence to prove supplements raise cardiovascular risk. None of this is a reason to avoid calcium. It is a reason to take the amount you are short of.
Why is calcium "no longer recommended"?
It never was recommended for everyone. UK guidance has always been food first, with a supplement where food falls short or where a doctor prescribes calcium and vitamin D as part of osteoporosis care. What changed after 2010 was the habit of handing 1,000 to 1,200 mg tablets to people already eating enough, the dose range the heart question concerned.3, 8
How to take a calcium supplement
Size the dose to the gap, keep it to 500 mg or less at a time, and keep it away from certain medicines. Absorption is a fraction of the dose and the fraction falls as the dose rises, so 500 mg taken twice is absorbed better than 1,000 mg taken once.11 Calcium carbonate is best with a meal; calcium citrate absorbs with or without food and suits people on acid-reducing medicines. Calcium binds to levothyroxine, iron, zinc, some antibiotics and bisphosphonates in the gut, so leave two to four hours between them. Do not take more than 1,500 mg a day from supplements; above that the NHS lists stomach pain and diarrhoea.1
Why take calcium with vitamin D?
Because vitamin D contributes to the normal absorption and utilisation of calcium and phosphorus; without enough of it part of the calcium you eat is wasted, and the fracture trials that worked paired the two.5, 6 The NHS advises 10 micrograms of vitamin D a day for everyone in autumn and winter, and no more than 100 micrograms a day from all products.12 Vitamin K has its own bone wording: vitamin D3 and K2 covers the pairing and what foods are high in vitamin K2 the food sources. Wellgard's Vegan Calcium Gummies with Vitamin D3 and Phosphorus supply 400 mg of calcium and 7.5 micrograms of vitamin D3 per two gummies: a dose sized for the gap between a low-calcium day and 700 mg, under the 500 mg per-dose absorption ceiling; calcium is needed for the maintenance of normal bones and teeth, and vitamin D contributes to the maintenance of normal bones and to the normal absorption of calcium. For children aged 4 to 14, the Kids Calcium & D3 Gummies give 200 mg of calcium and 3.75 micrograms of vitamin D3 in one gummy; vitamin D is needed for normal growth and development of bone in children.
Side effects of calcium supplements
Constipation and bloating are the common ones, more with carbonate than citrate, and they ease with a smaller dose taken with food. Kidney stones rose by 17 per cent in the Women's Health Initiative at 1,000 mg a day on top of diet, the main reason to supplement only the gap.7 Ask your GP before starting calcium if you have had kidney stones, a high blood calcium, parathyroid disease, sarcoidosis or kidney disease, or take a thyroid medicine or a bisphosphonate, so the timing can be arranged.
Frequently asked questions
Who should not take calcium supplements?
People with a high blood calcium, hyperparathyroidism, sarcoidosis, kidney disease or a history of kidney stones, unless a doctor has told them to; and anyone already reaching 700 mg from food.3
Is it bad to take calcium every day?
Not at a dose that fills your gap: the NHS says 1,500 mg or less a day from supplements is unlikely to cause harm.1
What are the signs of too much calcium?
From supplements alone, constipation and occasionally kidney stones. A high blood calcium, which almost never comes from a supplement at label doses, causes thirst, frequent urination, nausea, tiredness and confusion and needs a GP blood test; the usual cause is the parathyroid glands.
Which food is highest in calcium?
Tinned sardines with the bones, calcium-set tofu, milk, yoghurt and hard cheese; among fruit, dried figs lead at about 75 mg in 30 g, but no fruit is a major source. The full UK list is in the foods high in calcium guide linked above.
Is calcium good for your heart?
No heart benefit is claimed for calcium; the question runs the other way, and the most recent reviews with verified outcomes found no increase in risk at total intakes up to 2,000 to 2,500 mg a day.9, 10
Sources
- NHS. Calcium: vitamins and minerals. nhs.uk.
- Public Health England and the Food Standards Agency. National Diet and Nutrition Survey. gov.uk.
- Tai V, et al. Calcium intake and bone mineral density: systematic review and meta-analysis. BMJ, 2015. PubMed 26420598.
- Bolland MJ, et al. Calcium intake and risk of fracture: systematic review. BMJ, 2015. PubMed 26420387.
- Chapuy MC, et al. Vitamin D3 and calcium to prevent hip fractures in elderly women. New England Journal of Medicine, 1992. PubMed 1331788.
- Avenell A, et al. Vitamin D and vitamin D analogues for preventing fractures in post-menopausal women and older men. Cochrane Database of Systematic Reviews, 2014. PubMed 24729336.
- Jackson RD, et al. Calcium plus vitamin D supplementation and the risk of fractures. New England Journal of Medicine, 2006. PubMed 16481635.
- Bolland MJ, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ, 2010. PubMed 20671013.
- Lewis JR, et al. Calcium supplementation and verified coronary heart disease hospitalization and death in postmenopausal women: a collaborative meta-analysis. Journal of Bone and Mineral Research, 2015. PubMed 25042841.
- Chung M, et al. Calcium intake and cardiovascular disease risk: an updated systematic review and meta-analysis. Annals of Internal Medicine, 2016. PubMed 27776363.
- Harvey JA, et al. Dose dependency of calcium absorption: a comparison of calcium carbonate and calcium citrate. Journal of Bone and Mineral Research, 1988. PubMed 3213620.
- NHS. Vitamin D: vitamins and minerals. nhs.uk.
This article is general information, not medical advice. If you have osteoporosis, a fracture after a minor fall, kidney stones, a high blood calcium or a parathyroid condition, follow your doctor's advice on calcium and vitamin D.
