Calcium is the most common mineral in the body. It makes up around 1.5-2% of our body weight. More than 99% of calcium is stored in our bones and teeth, where it helps keep them strong.
Calcium also supports many other important jobs in the body. These include helping muscles move, nerves to send messages, the heart keep a steady rhythm, blood to clot properly and enzymes to work as they should.
Getting enough calcium helps maintain bone mineral density and reduce the risk of osteoporosis. People with osteoporosis are usually advised to get around 1,200 mg of calcium per day. If we do not get enough calcium from food, or if the body cannot absorb it properly (for example, due to digestive problems), the body will take calcium from the bones to keep vital processes working. And that is something to be avoided at all costs!
Can too much calcium be a problem?
More calcium is not always better. High intakes from supplements or fortified foods have been linked to a higher risk of heart disease in both men and women. This may be because supplements can raise calcium levels in the blood too much, which can lead to calcium building up in arteries and soft tissues.
Calcium from food does not appear to carry the same risk, which is why food sources are preferred.
Nutrients that help calcium work properly
Calcium does not work on its own. Other nutrients are needed to help the body use it correctly:
- Vitamin D helps control calcium levels in the blood
- Vitamin K2 helps guide calcium into bones and teeth instead of soft tissues
- Magnesium helps activate vitamin D and supports calcium movement in the body
Calcium and magnesium should be balanced. A common guideline is a calcium-to-magnesium ratio of about 2:1, whether from food or supplements.
Another important aspect to consider is that calcium needs adequate protein intake in order for it to be held in bone tissue. Protein provides a structure, made up mainly of collagen, which holds nutrients, including calcium, in the bone. Without enough protein, the bone mineralisation process doesn’t work so well, even if there is enough calcium in the body.
Vegans, vegetarians and lactose intolerance
People who follow a dairy-free diet may find it harder to get enough calcium. Research suggests that fracture rates are higher in vegans and people who do not consume dairy. In these cases, calcium supplements may be needed, but high doses should be avoided and supporting nutrients should be included.
For people with lactose intolerance, calcium intake may improve by:
- Having dairy with meals
- Spreading dairy intake across the day
- Choosing lower-lactose options such as yoghurt, aged cheeses or lactose-free milk
Calcium and prescription medicines
Calcium can reduce how well some medicines are absorbed. For example, people taking levothyroxine should leave at least three hours between their medication and calcium intake. This includes calcium from foods such as milk added to tea or coffee.
Food sources of calcium
Foods that naturally contain calcium include:
- Milk, cheese and yoghurt
- Tinned sardines and salmon (with bones)
- Fortified soya milk
- Tofu and tempeh
- Kale, bok choy and broccoli
- Almonds, sesame seeds and chia seeds
- Eggs, liver and sea vegetables such as kelp
Key Takeaway
Calcium intake should ideally come from whole food sources rather than supplements. Most adults should aim for approximately 1,200 mg of calcium per day. For individuals who struggle to meet their calcium needs through diet alone, supplementation may be appropriate. In these cases, no more than 500 mg should be taken per dose and total daily intake should not exceed 1,500 mg.