What is calcium?

Calcium is the most abundant mineral in the human body and plays a crucial role in bones, teeth, muscles, nerves, and metabolism. Approximately 99% of calcium is found in the bones and teeth, where it serves as a structural and strengthening element. The remaining 1% is found in the blood, muscles, and spaces between cells, where calcium regulates vital functions such as muscle contraction, nerve conduction, and blood clotting.

Since the body cannot produce calcium itself, it must be regularly obtained through food. A balanced calcium intake is particularly important during growth phases, pregnancy, breastfeeding, and old age to maintain bone density and muscle function.

How does calcium work in the body?

1. Formation and maintenance of bones and teeth:
Calcium is the main component of the bone mineral hydroxyapatite, which gives bones their hardness and stability. Together with vitamin D, magnesium, vitamin K, and phosphorus, it supports continuous bone regeneration. Calcium is constantly exchanged between the bones and the blood in the body - a process regulated particularly by vitamin D.

2. Muscle contraction:
Calcium controls muscle contraction - including that of the heart muscle. It ensures that muscle fibers actively contract and can relax again after completing their work. A calcium deficiency therefore often leads to muscle cramps or tremors.

3. Nerve conduction:
Calcium is crucial for the transmission of electrical signals between nerve cells. It enables the release of neurotransmitters and thus communication between the brain, muscles, and organs.

4. Blood clotting:
Calcium is involved in several steps of the coagulation cascade and helps close wounds by supporting the formation of fibrin (blood clots).

5. Cell metabolism and enzyme activity:
Calcium acts as a signaling substance in cells, activates numerous enzymes, and controls hormonal processes such as the release of insulin.

6. Heart rhythm and blood pressure:
Calcium contributes to regulating the heartbeat and can help stabilize blood pressure by influencing the contraction of blood vessels.

Benefits of adequate calcium intake

  • Supports strong bones and teeth

  • Promotes muscle contraction and relaxation

  • Contributes to normal nerve function

  • Supports blood clotting and wound healing

  • Regulates heart rhythm and blood pressure

  • Helps prevent osteoporosis

  • Supports energy and enzyme metabolism

Calcium-rich foods

Animal-based sources:

  • Milk, yogurt, cheese (especially hard cheeses such as Parmesan or Emmental)

  • Sardines or salmon (with bones)

Plant-based sources:

  • Kale, broccoli, spinach, pak choi

  • Almonds, sesame, chia seeds

  • Mineral water with a high calcium content (> 150 mg/L)

  • Legumes (e.g., white beans, chickpeas)

  • Fortified plant-based milk alternatives (e.g., soy or oat drink with calcium)

Recommended daily intake

According to the German Nutrition Society (DGE):

  • Adults: 1000 mg of calcium per day

  • Adolescents (13–18 years): 1200 mg/day

  • Older adults, pregnant women, breastfeeding women: up to 1200 mg/day

Consistent intake throughout the day improves absorption.

Calcium absorption and utilization

The following nutrients are important for optimal calcium absorption:

  • Vitamin D: improves calcium absorption in the intestines and its storage in the bones

  • Vitamin K2: promotes the incorporation of calcium into bones rather than blood vessels

  • Magnesium: supports calcium metabolism and prevents muscle cramps

  • Phosphorus: acts synergistically in bone metabolism (but too much inhibits absorption)

Deficiency symptoms (hypocalcemia)

Calcium deficiency can occur due to:

  • Insufficient intake

  • Vitamin D deficiency

  • Hormonal disorders (e.g., parathyroid disease)

  • Certain medications (e.g., diuretics)

Typical symptoms:

  • Muscle cramps, tremors

  • Numbness in the hands or face

  • Brittle nails, weakened bones

  • Dental problems

  • Osteopenia or osteoporosis in cases of chronic deficiency

Overdose (hypercalcemia)

Excessive calcium intake (usually from supplements) can lead to:

  • Nausea, vomiting

  • Kidney stones

  • Calcium deposits in blood vessels lead to
    In the long term, there is an increased risk of cardiovascular disease when calcium is consumed without sufficient vitamin K2.

Conclusion

Calcium is the cornerstone of strong bones, stable muscles, properly functioning nerves, and a healthy heart. A balanced diet with dairy products, green vegetables, nuts, and calcium-rich mineral water reliably meets the daily requirement. In combination with vitamin D and K2, calcium makes a decisive contribution to bone health, performance, and overall vitality - throughout life.

Sources

  1. German Nutrition Society (DGE). (2020): Calcium – Reference values for nutrient intake.

  2. Weaver CM. (2014): Calcium supplementation: is protecting against osteoporosis counter to protecting against cardiovascular disease? Curr Osteoporos Rep, 12(2), 211–218.

  3. Heaney RP. (2009): Factors influencing the measurement of bioavailable calcium in humans. J Nutr, 139(9), 1636S–1639S.

  4. Lips P, Cashman KD, Lamberg-Allardt C, et al. (2019): Current vitamin D status in European and Middle East countries and strategies to prevent deficiency. Endocr Connect, 8(2), R55–R75.