We all know that calcium is important for healthy bones (1, 2); however this is a simplistic statement. Having too much calcium is unlikely to increase bone mass; in fact, studies have shown that increasing calcium can be detrimental, leading to deposition in soft tissues where it has been linked to atherosclerosis (3).
Calcium intake in young children builds up a healthy reserve of calcium; however, calcium is not the only factor in bone growth and strength. No one single substance, food, vitamin or mineral can produce strong, healthy bones. Nutrients are required in combination to develop the complex matrix of bone. Magnesium, vitamins K and D are also equally important in preventing calcium loss from the body and building strong bones.
Food sources of calcium are dairy, tinned salmon, sardines, broad beans, almonds, tofu, green leafy vegetables (e.g. kale, pak choi, cabbage and broccoli) as well as fortified foods, such as alternative milks. Calcium is well absorbed from dairy foods, and dairy also contains magnesium and vitamin D, which are also required for healthy bones. It is recommended to get calcium from foods, as these contain other compounds which help with calcium absorption.
Some people are concerned about health problems associated with dairy. For those who are allergic or intolerant, it might be best to eat vegan sources of calcium and take a calcium supplement. Any such supplement should also contain vitamin D to help with proper calcium absorption.However, before taking a calcium supplement, you are recommended to speak to your medical practitioner.
Calcium loss accelerates during the menopause, and many women become osteopenic (lowered bone density) Omega 3 fatty acids are important at this time to increase calcium absorption and reduce calcium loss. Omega-3 fatty acids are found in oily fish as well as walnuts, flaxseeds and chia seeds.
Some foods (containing oxalates) reduce absorption of calcium, but by eating a wide variety of food this effect matters little. Vegetarians may need to take care if they are eating a lot of oxalate containing foods.
The take home message is to eat a wide variety of foods, and if you are thinking of excluding a food group, such as dairy, to think carefully about how you are going to get your calcium.
Lanou, AJ, Berkow, SE & Barnard, ND (2005). Calcium, dairy products and bone health in children and young afults: A re-evaluation of the evidence. Pediatrics March 2005: 115(3)
Sato, Y, et al. (2015) Greater milk intake is associated with lower bone turnover, higher bone density, and higher bone microarchitecture index in a population of elderly Japanese men with relatively low dietary calcium intake: Fujiwara-kyo Osteoporosis Risk in Men (FORMEN) Study. Osteoporos Int. 2015 May;26(5):1585-94. doi: 10.1007/s00198-015-3032-2. Epub 2015 Jan 28.
Ilich J & Kerstetter J E (2000) - Nutrition in Bone Health Revisited: A Story Beyond Calcium. Journal of the American College of Nutrition, 9, 6, 715-7137.