Find out all about calcium, including what it does, how much you need, where to find it and who might need to supplement their diet
Overview of calcium
What is calcium and what does it do?
Calcium is a mineral that’s essential for all living organisms. It’s the most abundant mineral in our body1 and is needed for:2
- maintaining healthy bones and teeth
- normal blood clotting
- controlling muscle contractions, including heartbeat
- healthy digestion
Calcium is found in milk, cheese and dairy foods, dark green vegetables and nuts. Most people will get all the calcium they need from their diet,3 but vegans or those who don’t eat dairy may be lacking.4
A calcium deficiency can lead to rickets when you’re young, and osteoporosis or brittle bone disease later in life.5
Functions of calcium
What does calcium do in the body?
Around 99% of the calcium in our bodies is stored in our bones and teeth.6 Calcium helps our bones to grow strong until the age of 20-25, when bone density reaches its peak.
After the age of about 35 years, the amount of bone tissue we have naturally starts to decrease, but calcium can help to maintain our bone density and slow down bone loss.7 Calcium also enables our blood to clot normally and regulates our muscle contractions, including our heartbeat.8
We lose calcium everyday via our skin, nails, sweat, urine and faeces. Our bodies cannot make calcium, so we need to get enough from our diets. If we don’t, our body can start leaching it from our bones.
This is fine once in a while, but if it happens on a regular basis, it could eventually lead to weak bones.9
Vitamin D is essential to help our body absorb calcium properly from food. A calcium deficiency could even occur due to low vitamin D levels.10 The government recommends everyone over the age of one gets 10mcg of vitamin D a day.11
How much calcium do I need?
The reference nutrient intake (RNI) for adults is 700mg a day – about the amount found in a glass of milk and a small portion of whitebait12 – but some groups may need more, such as breast-feeding women, post-menopausal women and those with coeliac disease.13
How much calcium do children need?
Children need increasing amounts of calcium while growing,14 especially during puberty, to build bone density.
- 0-12 months – 525mg daily
- 1-3 – 350mg daily
- 4-6 – 450mg daily
- 7-10 – 550mg daily
- 11-18 – boys 1000mg, girls 800mg daily
Which foods are the best sources of calcium?
The best food sources15 of calcium include:
- a glass of malted milk – this contains your RNI in one glass
- fish with soft bones, like sardines or whitebait
- a glass of regular, semi-skimmed or skimmed milk
- a small portion of cottage cheese
- a small pot of yoghurt
The best plant-based sources16 of calcium include:
- calcium-enriched plant milks
- green leafy veg, such as kale
- dried figs
- nuts and seeds, including almonds
- white or brown bread – white and brown flour is fortified in the UK
Who is most at risk of calcium deficiency?
You are more at risk of a calcium deficiency17 if you:
- are on a cow’s milk- or lactose-free diet
- have coeliac disease, as you may not be able to absorb nutrients properly
- are breast-feeding
- have been through the menopause – oestrogen helps protect bones, so declining levels can lead to osteoporosis
Children are at the greatest risk of developing rickets between six and 36 months because they experience rapid growth during this time, which increases their need for calcium and vitamin D. Rickets leads to soft bones and stunted growth.18
What are the symptoms of a calcium deficiency?
Symptoms of a calcium deficiency include:19
- muscle aches and cramps
- extreme fatigue
- dry, itchy skin
- brittle nails
- tooth loss
- more fractures due to weak bones
What happens if I consume too much calcium?
Getting too much calcium – more than 1,500mg a day – can lead to stomach pain and diarrhoea,20 and could even lead to developing kidney stones.21
When should I take calcium supplements?
You should be able to get all the calcium you need from your daily diet. But if you’re vegan, going through the menopause, or have been diagnosed with osteoporosis, you may want to consider a supplement.22
Should children take a calcium supplement?
Children eating a healthy, balanced diet should be getting all the calcium they need.23 If you’re worried they’re not, talk to your GP before giving them supplements.
Should women take a calcium supplement during pregnancy?
Pregnant women do not need calcium supplements as they can get all the calcium they need from their diet. However, all adults – including pregnant and breastfeeding women – need 10mcg of vitamin D a day, so should consider taking a supplement.24
What are the potential benefits of taking a calcium supplement?
After menopause, women lose more bone mass due to a decline in oestrogen. But a 2014 review of studies concluded that calcium supplements could help reduce bone loss in elderly and post-menopausal women.25
It’s also thought that a low-calcium intake could lead to a higher BMI. Chinese researchers found overweight people with low calcium levels who were given combined calcium and vitamin D supplements, lost more body fat on a calorie-controlled diet than those who didn’t take the supplement.26
Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.
Written by Nic Hopkirk on November 28, 2018
Reviewed by dietitian and nutritionist Azmina Govindji on December 19, 2018
1. Beto, J. The Role of Calcium in Human Ageing. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4337919/
2. European Commission. EU Register on nutrition and health claims. Available from: http://ec.europa.eu/food/safety/labelling_nutrition/claims/register/public/?event=register.home
3. NHS. Calcium. Available from: https://www.nhs.uk/conditions/vitamins-and-minerals/calcium/
4. British Nutrition Foundation. Dietary calcium and health. Available from: https://www.nutrition.org.uk/attachments/105_Dietary%20calcium%20and%20health.pdf
5. April Khan and Ana Gotter. Hypocalcemia (Calcium Deficiency Disease). Healthline.com. Available from: https://www.healthline.com/health/calcium-deficiency-disease
6. Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Available from: https://www.ncbi.nlm.nih.gov/books/NBK109827/
7. National Osteoporosis Society. What is osteoporosis? https://nos.org.uk/about-osteoporosis/what-is-osteoporosis/
8. As Source 3
9. National Osteoporosis Foundation. Calcium/Vitamin D. Available from: https://www.nof.org/patients/treatment/calciumvitamin-d/
10. British Nutrition Foundation. Calcium. Available from: https://www.nutrition.org.uk/nutritionscience/nutrients-food-and-ingredients/minerals-and-trace-elements.html?start=3
11. NHS. Vitamin D. Available from: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
12. The Association of UK Dieticians. Calcium Food Fact Sheet. Available from: https://www.bda.uk.com/foodfacts/Calcium.pdf
13. As above
14. NHS. Royal Surrey County Hospital. Calcium for infants and children. Available from: https://www.royalsurrey.nhs.uk/wp-content/uploads/2017/11/PIN1297_Calcium_for_infants_and_children_w.pdf
15. As Source 12
16. British Nutrition Foundation. Dairy and non-dairy sources of calcium. https://www.nutrition.org.uk/attachments/article/874/Calcium%20counts_final_20.08.18.pdf
17. Kerri-Ann Jennings, MS, RD. Calcium Supplements: Should You Take Them? Healthline.com. Available from: https://www.healthline.com/nutrition/calcium-supplements
18. Jacquelyn Cafasso. Rickets. Healthline.com. Available from: https://www.healthline.com/health/rickets
19. April Khan and Ana Gotter. Healthline. Hypocalcemia (Calcium Deficiency Disease). Available from: https://www.healthline.com/health/calcium-deficiency-disease
20. As Source 3
21. As Source 17
22. As Source 19
23. As Source 14
24. As Source 11
25. Lamy O, Burckhardt, P. Calcium revisited: part II calcium supplements and their effects. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4189255/
26. Zhu W, et al. Calcium plus vitamin D3 supplementation facilitated fat loss in overweight and obese college students with very-low calcium consumption: a randomized controlled trial. Available from: https://www.ncbi.nlm.nih.gov/pubmed/23297844