What is calcium?

Calcium is the most abundant mineral in the body. It is required for vascular contraction and vasodilation, muscle function, nerve transmission, intracellular signalling and hormonal secretion. However, less than 1% of total body calcium is used to support these functions.

The calcium in our blood is very tightly regulation and doesn’t fluctuate with changes in dietary intake. Instead, the body uses bone tissue as a reserve and source of calcium to maintain constant concentrations of calcium in blood, muscle and intercellular fluids. The remaining 99% of the body’s calcium is stored in bones and teeth, where it provides structural support and function1.

How much do I need?

For adults 19 – 50 years old, Health Canada recommends 1000 mg/day of calcium.

For men 51 – 70 years old, Health Canada recommends 1000 mg/day of calcium.

For women 51 – 70 years old, Health Canada recommends 1200 mg/day of calcium.

For adults older than 70, Health Canada recommends 1200 mg/day of calcium2.

Why do I need calcium?

According to the National Health and Nutrition Examination Survey, females are less likely than males to get adequate amounts of calcium from food [1]. Based on food intakes only, adult men have a prevalence of inadequate intakes ranging from 27-80% and adult women have a prevalence of inadequate intakes ranging from 48-87% depending on the age group2.

Inadequate intakes of dietary calcium cause no obvious symptoms in the short-term. However, over the long term, inadequate calcium intake causes osteopenia which can progress to osteoporosis, a disorder characterized by porous and fragile bones. Osteoporosis is associated with fracturs of the hip, vertebrae, wrist, pelvis, ribs and other bones.

Our bones increase in size and mass, reaching their peak at around age 30. The greater our peak bone mass, the longer we can delay serious bone loss, which is inevitable with aging1.

Factors that Affect Calcium Absorption

Amount consumed – calcium absorption decreases, and intake increases

Age and life stage – net calcium absorption is highest in infants and young children and decreases to 15-20% in adulthood and continues to decrease as we age

Vitamin D intake – vitamin D improves calcium absorption. See last week’s nutrition tip for more information about vitamin D!

Other components in food – phytic and oxalic acid which are found naturally in some plants can bind to calcium and inhibit its absorption. Eating a variety of foods ensures that these interactions have little or no nutritional consequence1.

Factors that Affect Calcium Excretion

Sodium and protein intakes – high sodium and/or protein intake increases urinary calcium excretion. However, research suggests that high protein intake also increases intestinal calcium absorption, which offsets the calcium excretion.

Caffeine intake – caffeine is a stimulate that can increase calcium excretion and reduce absorption.

Alcohol intake – alcohol intake can reduce calcium absorption and inhibits enzymes in the liver from converting vitamin D to its active form. However, the amount of alcohol required to affect calcium status is unknown, so just be mindful of your intake – everything in moderation!1

How do I get enough calcium?

Calcium is found in many foods. One of the best ways to get the recommended amounts of calcium is by eating a variety of foods, including:

  • fortified plant-based beverages
  • dark green vegetables (eg. broccoli, kale, and spinach)
  • tofu
  • fortified orange juice
  • chia seeds

For non-vegans:

  • dairy products (eg. milk, yogurt, cheese)
  • fish with soft bones that are eaten (eg. canned salmon or sardines)1,2

Should I be taking a calcium supplement?

The percentage of calcium absorbed depends on the total amount of elemental calcium consumed at one time, as the amount increases, the percentage absorption decreases. Calcium absorption is highest in doses of less than or equal to 500 mg1.

Data on calcium intakes from food and supplement sources combined showed that supplement use did not significantly affect the prevalence of inadequate calcium intakes in most age and gender groups, except for women over the age of 502.

Getting too much calcium can cause constipation and may interfere with the body’s ability to absorb iron and zine. Too much calcium can also increase the risk of kidney stones. Excess intake of calcium is usually from the use of calcium supplements3, so if you are concerned about your calcium status and are wondering if a calcium supplement is suitable for your needs, consult your physician.


  1. National Institutes of Health – Office of Dietary Supplements. (2020, March 26). Calcium. Retrieved from https://ods-od-nih-gov.subzero.lib.uoguelph.ca/factsheets/Calcium-HealthProfessional/
  2. Health Canada. (2019, July 10). Vitamin D and Calcium: Updated Dietary Reference Intakes. Retrieved from https://www.canada.ca/en/health-canada/services/food-nutrition/healthy-eating/vitamins-minerals/vitamin-calcium-updated-dietary-reference-intakes-nutrition.html#a7
  3. National Institutes of Health – Office of Dietary Supplements. (2019, December 6). Calcium Factsheet for Consumers. Retrieved from https://ods-od-nih-gov.subzero.lib.uoguelph.ca/factsheets/Calcium-Consumer/

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