Everyone understands that calcium is essential for building and maintaining healthy bones. Calcium is used by our bone producing cells (osteoblasts) to formulate new bone. However most people aren't aware of the role calcium plays in maintaining our body balance (homeostasis) in everyday life. A small amount of calcium is absorbed into the blood and used for the healthy functioning of the heart, muscles, blood and nerves.
Close to 99% of our calcium is stored in our bones. However we do gradually lose calcium through the skin, kidney and bowels from excretion. Your bones act like a calcium bank. If there is not enough calcium in your diet your body will take what is needed from your bones for use in other parts of the body. If this happens your bone density (bone strength) will gradually decline and you may be at risk of developing osteoporosis.
Osteoporosis (meaning 'porous bones')
is a condition that causes bones to become thin, weak and fragile. As a result, even a minor bump or accident can cause a fracture (broken bone). Fractures due to osteoporosis can result in chronic pain, disability, loss of independence and premature death.
Peak Bone Mass (PBM)
The best chance we have of avoiding Osteoporosis is to build up a really large calcium bank (strong bones) while we are young. Childhood and young adulthood are the bone building years. Bone mass increases by about sevenfold from birth to puberty and a further threefold during adolescence and then remains stable until about age 50 in men and until the menopause in women.
During the adolescent growth spurt, the required calcium retention is two to three times higher than that required for the development of peak bone mass (PBM) which occurs at the same time as maximum height. PBM is the greatest amount of bone an individual can attain. Children and adolescents who have higher PBM reduce their risk of osteoporosis later in life.
Calcium deficiency in young people can account for 5-10 percent lower peak bone mass and can significantly increase a person’s risk for hip fracture in later life.
Menopause and Calcium
Calcium balance deteriorates for women at menopause when there is a decline in intestinal calcium absorption and/or an increase in urinary calcium excretion. In post menopausal women, there is evidence that a high calcium intake will slow the rate of bone loss and may reduce the risk of fracture.
Calcium needs vary throughout life
The recommended dietary intake of calcium is different for people of different ages and life stages.
Age and life stage Recommended dietary intake of calcium (mg/day)
Babies 0–6 months – breastfed approx. 210 mg
Babies 0–6 months – formula fed approx. 350 mg
Babies 7–12 months 270 mg
Children 1–3 years 500 mg
Children 4–8 years 700 mg
Children 9–11 years 1,000 mg
Adolescents 12–18 years (including pregnant
and breastfeeding young women) 1,300 mg
Women 19–50 (including pregnant and
breastfeeding women) 1,000 mg
Women 51–70 1,300 mg
Men 19–70 1,000 mg
Adults over 70 1,300 mg
Calcium and food
The best way to achieve recommended calcium intake is to eat a diet rich in calcium. Calcium content in food varies so it is important to consume ‘calcium rich’ foods. Half of all Australian adults do not achieve their daily recommended intake of calcium. It is easy to add calcium to your diet by focusing on food groups which contain higher levels of calcium.
Food type Examples Calcium range (mg per serve)
Dairy Milk, cheese, yogurt 150 – 305 mg per serve
Seafood Trout, snapper, mussels, oysters, prawns,
canned sardines or salmon 35 – 300 mg per serve Vegetables Cucumber, kale, silverbeat, chinese
cabbage, broccoli rocket, watercress,
bok choy, leeks 59 - 250 mg per serve
Nuts & seed Almonds, brazil nuts, hazelnuts, walnuts,
sesame seeds, tahini paste 28 – 75 mg per serve
Fruits Orange, strawberries, figs, kiwi fruit, dates 16 - 95 mg per serve
Other Eggs, calcium-set tofu, canned chickpeas
or soybean 21 – 105 mg per serve
Meat Pork chop, chicken 21 – 105 mg per serve
Click on the file below to see a more extensive table of calcium content in food.
Do we absorb all the calcium we eat?
Not all the calcium we consume is absorbed. A small amount of calcium will be lost and excreted from the body which is normal. This is factored into the recommended intake for your age. Other factors can impact calcium absorption and should be discussed with your doctor, for example:
Low vitamin D levels
Excessive caffeine and alcohol intake
Certain medical conditions (for example coeliac disease, kidney disease)
It is much better to get calcium from foods (which also provide other nutrients) than from calcium supplements. But if you have difficulty eating enough foods rich in calcium, you might need to consider a calcium supplement, especially if you are at risk of developing osteoporosis. Before taking supplements, it’s best to discuss this with your doctor or other registered healthcare professional. If you do take calcium supplements, make sure you don’t take more than the amount recommended on the bottle. Too much calcium may cause gastrointestinal upsets such as bloating and constipation and, rarely, other complications such as kidney stones.
Lifestyle can affect bone strength
Some of the factors that can reduce calcium in your bones and lower your bone density (weaken your bones) include:
more than six drinks per day of caffeine-containing drinks – for example, coffee, cola and energy drinks (and, to a lesser extent, tea)
excessive alcohol intake
very low body weight
very high intakes of fibre (more than 50 g per day, from wheat bran)
low levels of physical activity
low levels of vitamin D – people who are housebound or cover their bodies completely when they are outside are at increased risk
Diagnosed osteoporosis and calcium.
For people with diagnosed osteoporosis calcium alone is not sufficient, osteoporosis medication is generally required as directed by your doctor. It is common practice for doctors to prescribe calcium supplementation to accompany osteoporosis medication. Adequate calcium intake throughout adult life helps support bone health but may not prevent osteoporosis as other factors can negatively impact your bone health.