It is widely accepted in popular belief that animal products are the ideal source for maintaining bone health. However, a study published in the US Journal of Nutrition found that populations consuming large amounts of calcium and protein from animal sources had a higher rate of hip fractures (Hegsted, 1986).
Myth: dairy products are the only good source of calcium.
Calcium is the most abundant mineral in the human body, accounting for up to 2% of body weight. Approximately 99% of this is stored in bones and teeth. The remaining 1% is found mainly in soft tissues and blood.
The importance of calcium in the body
Calcium contributes to more than just strong bones; it is essential for the proper functioning of muscles and nerve impulses, and plays a key role in various cellular processes, including blood clotting and the activation of certain enzymes. Requirements vary depending on age and physiological status: an infant under six months of age needs 200 mg per day, whereas a growing child or pregnant woman needs around 1,300 mg per day.
Calcium is absorbed into the body in two ways: active transport, which pumps calcium ions into cells, and passive diffusion, which relies on the natural movement of calcium through the intestinal walls.
Sources of calcium and their effectiveness
The most popular sources of calcium are dairy products. However, these are not the only or most effective sources. Vegetables (especially green leafy vegetables), seeds, and grains are a well-balanced source of calcium.
While it is tempting to focus solely on the amount of calcium present in various foods, it is important to consider not just the quantity, but also the bioavailability of calcium when comparing animal-based and plant-based sources.
According to the US Agricultural Research Service, 100 g of whole milk contains 127 mg of calcium, 2.32 g of saturated fatty acids, and 14 mg of cholesterol. By contrast, 100 g of dried figs contain more calcium (162 mg), much less saturated fat (0.14 g) and no cholesterol (SR Legacy, 2018). Figs are also rich in vitamins and contain all the essential amino acids, the “building blocks” of protein in our bodies.
In terms of bioavailability, studies show that if a person drinks a cup of milk containing 300 mg of calcium, their body will only absorb around 30% of it. By contrast, from a serving of Chinese cabbage containing 160 mg of calcium, around 80 mg is used—50%.
Factors influencing calcium absorption
The bioavailability of calcium is influenced by many factors. For example, certain substances, such as oxalates and phytates, can hinder calcium absorption in the body. Spinach is rich in calcium (up to 260 mg per serving), but the oxalates it contains limit calcium absorption to 5%. The total amount of calcium consumed by a person also influences bioavailability. A meta-analysis published by the US National Center for Biotechnology Information shows that taking calcium supplements without medical advice increases the risk of heart attack by 30% (Bolland, Avenell et al., 2010). Additionally, calcium absorption tends to decrease exponentially as intake increases (Shkembi & Huppertz, 2021). In short, if we consume too much calcium at once, our bodies will not absorb it very well; however, when calcium is taken in small, consistent doses, it is absorbed more efficiently.
Smoking decreases calcium absorption, reduces bone formation (osteogenesis), and intensifies bone degradation. It also disrupts hormonal balance. High protein and salt (sodium) intake is associated with increased calcium excretion in urine. However, based on current data, changes to daily calcium intake according to protein and salt consumption are not recommended (Standing Committee 1997: 71–145).
In conclusion, although dairy products are a recognised source of calcium, they are not the only or most effective option. Plant-based foods provide calcium and other essential nutrients. To ensure we benefit from a wide range of vitamins, minerals, and essential amino acids, it is essential to diversify our diet. Let’s replace the old myth with a new understanding: calcium is abundant in many foods, not just dairy products, and a balanced diet is the key to optimal health.
Bibliography
- Al-Bashaireh, A. M., Haddad, L. G. et al. (2018), “The effect of tobacco smoking on bone mass: An overview of pathophysiologic mechanisms,” in Journal of Osteoporosis, vol. 2018, art. no. 1206235.
- Bolland, M. J., Avenell, A., et al. (2010), “Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: Meta-analysis,” in BMJ, vol. 341, art. no. c3691.
- Dan, N., and Dan, V. (2021), “Dietoterapie și nutriţie bazată pe alimente vegetale integrale” (“Diet Therapy and Nutrition Based on Whole Plant Foods”), vol. 1, Viaţă și Sănătate, Pantelimon.
- Hegsted, D. M. (1986), “Calcium and osteoporosis,” in The Journal of Nutrition, vol. 116, no. 11, pp. 2316–2319.
- Shkembi, B., and Huppertz, T. (2022), “Calcium absorption from food products: Food matrix effects,” in Nutrients, vol. 14, no. 1, art. no. 180.
- SR Legacy (2018) – USDA National Nutrient Database for Standard Reference (SR) Legacy, published in 2018, available at https://fdc.nal.usda.gov/fdc-app.html#.
- Standing Committee (1997) – Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine (1997), Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride, National Academies Press, Washington, D.C.