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Calcium: The protagonist in bone health..and more

by Katia Annousi, Dietitian & Nutritionist, QMU

16 May 2024 • 0 min read

Calcium is a mineral that is not produced in the body, which is why diet is the main source of calcium and plays an important role in bone and dental health. Calcium is the mineral that helps maintain muscle function, blood clotting and other body processes. 99% of the calcium in the body is stored in the bones which act as a calcium reservoir from which the body draws to keep itself in balance. The body also needs vitamin D to absorb and maintain calcium levels. Vitamin K, vitamin C, magnesium, phosphorus, manganese and boron are other important nutrients for bone health.

What is the role of calcium?

  • Formation & durability of bones and teeth
  • Maintenance of body strength
  • Muscle movement
  • Function of various metabolic enzymes
  • Transmission of nerve messages between the brain
  • Normal blood vessel contraction
  • Prevention of bone density reduction and thus protection against fractures or osteopenia/osteoporosis
  • Treating symptoms of premenstrual syndrome (PMS)
Bone density increases until 25 to 30 years of life, and then gradually decreases as we age. More calcium is required during periods of growth in adolescence and young adulthood to achieve peak bone mass levels and limit bone loss later on. There is an inverse relationship between calcium intake and calcium absorption. Calcium absorption from food is about 45% at intakes of 200 mg/day, but only 15% when intakes are greater than 2,000 mg/day.

What is the recommended daily calcium intake?

  • 0-6 months: 200 mg
  • 7-12 months: 260 mg
  • 1-3 years of age: 700 mg
  • 4-8 years: 1,000 mg
  • 9-18 years: 1,300 mg
  • 19-50 years: 1,000 mg
  • Men 51-70 years old: 1,000 mg
  • Women 51-70 years old: 1,200 mg
  • 70 years & over: 1,200 mg
  • Pregnancy (14-18 years): 1,300 mg
  • Pregnancy (19-50 years old): 1,000 mg
Calcium absorption varies depending on the type of food. The absorption of calcium from dairy products and fortified foods is about 30%. Certain compounds in plants (e.g. oxalic acid, phytic acid) can reduce calcium absorption. As a result, calcium absorption is only 5% from spinach, while it is much higher from milk (27%).

What side-effects can insufficient calcium intake cause?

  1. Decrease in bone strength which can lead to osteoporosis, which is characterized by brittle bones and increased risk of falls & fractures.
  2. Increased rachitis prevalance in children and other bone disorders in adults, although these disorders are more commonly caused by vitamin D deficiency, combined with calcium deficiency.
  3. Hypocalcemia: when serum calcium level are less than 8.5 mg/dL. It is usually the result of vitamin D or magnesium deficiency, decreased production of parathyroid hormone, leading to hypoparathyroidism, and decreased bone absorption of calcium.

Which foods are rich in calcium?

  • Yoghurt: 1 cup 150g, 210 mg
  • Cheddar cheese, 30g, 216 mg
  • Parmesan cheese, 50g, 600mg
  • Sardines (on the bone), salmon
  • Fortified vegetable milk substitutes (soy milk)
  • Nuts and seeds
  • Broccoli
  • Tofu
  • Cabbage
  • Pulses (beans)
  • Fortified juices and cereals
  • Cornmeal and corn tortillas

Are there any calcium-rich fruits?

  • Figs (fresh & dried)
  • Papaya
  • Oranges

Who is at risk of calcium deficiency?

  • Women after menopause. Menopause leads to loss of bone density because decreased estrogen production makes it difficult for bones to absorb calcium and increases calcium loss in urine. On average, women lose about 1% of their bone mineral density (BMD) annually after menopause. Over time, these changes lead to reduced bone mass and brittle bones.
  • People who avoid dairy products. People with lactose intolerance and those who avoid eating dairy products (including vegans) have a higher risk of inadequate calcium intake, because dairy products are rich sources of calcium.
  • Bulimia, anorexia and certain other eating disorders
  • Magnesium overconsumption
  • Long-term use of laxatives
  • Kidney failure
  • Pancreatitis
  • Vitamin D deficiency

Health risks from excessive calcium intake:

  • Reduced muscle tone
  • Kidney failure
  • Hypophosphatemia
  • Constipation
  • Nausea
  • Weight loss
  • Fatigue
  • Polyuria
  • Heart arrhythmias
  • Higher risk of cardiovascular mortality

Calcium is essential in maintaining healthy bones and teeth, while helping to manage blood pressure and healthy functioning of the metabolism, which is vital for energy production. In addition, it plays a key role in the process of cell division and also affects the digestive system. Calcium intake will also be useful for anyone who has problems with blood clotting, as it helps to optimize it.

Scientific References

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Bakaloudi DR, Halloran A, Rippin HL, Oikonomidou AC, Dardavesis TI, Williams J, et al. (2021). Intake and adequacy of the vegan diet. A systematic review of the evidence. Clin Nutr ;40:3503-21.

Bristow SM, Horne AM, Gamble GD, Mihov B, Stewart A, Reid IR. (2019). Dietary calcium intake and bone loss over 6 years in osteopenic postmenopausal women. J Clin Endocrinol Metab ;104:3576-84.

Crandall CJ, Aragaki AK, LeBoff MS, Li W, Wactawski-Wende J, Cauley JA, et al. (2016) Calcium plus vitamin D supplementation and height loss: findings from the Women’s Health Initiative Calcium and Vitamin D clinical trial. Menopause ;23:1277-86.

Gallagher JC, Yalamanchili V, Smith LM. (2012). The effect of vitamin D on calcium absorption in older women. J Clin Endocrinol Metab ;97:3550-6.

Yao X, Hu J, Kong X, Zhu Z. (2020). Association between Dietary calcium intake and bone mineral density in older adults. Ecol Food Nutr :1-12

Wikoff D, Welsh BT, Henderson R, Brorby GP, Britt J, Myers E, et al. (2017). Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food Chem Toxicol ;109:585-648.