Article Series

  1. Calcium For Bones And Teeth / Improve Absorption
  2. Vegan Foods With Calcium / Plant-based Calcium
  3. Calcium Deficiency - Causes, Symptoms, Treatment

Related Articles

Calcium For Bones And Teeth / Improve Absorption

Calcium For Bones And Teeth / Improve Absorption
Table Of Contents
  1. Functions and Effects
  2. Preventive Effects
  3. Vitamin D plays a crucial role in calcium absorption
  4. Increasing calcium absorption from food
  5. Impairment of Calcium Absorption
  6. Considerations for Vegans

Calcium is an electrolyte and essential mineral that must be consumed through diet. It is transported to the necessary areas through the blood. Calcium is the most abundant mineral in the body among all minerals. On average, the human body contains approximately 1.1 kg of calcium, mainly bound in bones and teeth 1. Bones are also the largest reservoir of calcium.

In addition to its role in bone formation, calcium is involved in numerous other functions, such as nerve impulse transmission. Therefore, there is a constant exchange of calcium between the bones, kidneys, and digestive tract in order to maintain a steady calcium level in the blood.

Functions and Effects

A small portion of the calcium present in the body, approximately 5g to 10g, is not bound to bones and teeth. It is needed by the body for various additional functions and effects, including 2 3 45 6: Calcium

  • Facilitates the release of hormones that play an important role in digestion and lipid metabolism
  • Is involved in insulin production and thus carbohydrate metabolism
  • Coordinates cellular activities
  • Controls enzyme activities
  • Is necessary for the stabilization and optimization of activity of certain proteins and enzymes
  • Aids in regeneration and muscle relaxation, which helps prevent cramping on competition days
  • Is involved in blood clotting as calcium ions enable the formation of blood clotting factors
  • Enables nerve functions (transmission of nerve impulses), transmission of hormone signals, and bone growth
  • Is an essential mineral that contributes to the release of neurotransmitters
  • Supports hair growth by stimulating hair follicles

Furthermore, calcium ions are involved in the chemical reaction that allows muscle contractions to occur (when calcium ions flow into muscle cells, the muscles contract). Without calcium, movement and thus fitness training would not be possible.

In addition, calcium is involved in the regulation of the acid-base balance. If the pH of the blood changes and becomes low (acidic), calcium is released from the bones to neutralize the pH. A low pH, for example, has negative effects on oxygen transport in the blood.

Preventive Effects

Together with vitamin D, calcium is involved in the prevention and treatment of osteoporosis 7. According to another study, vegans have lower intake of calcium and proteins, but the higher proportion of protein intake from vegetables is very beneficial for bone health and protection against osteoporosis when adequate calcium and vitamin D intake is ensured 8. According to Korean study results from 2011, a high intake of calcium from plant sources was particularly effective in reducing the risk of osteoporosis in postmenopausal women 9. Additionally, higher bone density was achieved according to the study.

A calcium-rich diet could reduce the risk of dementia, according to study results from Japan 10. Higher calcium intake led to a decreased risk of dementia and vascular dementia in the general Japanese population. However, it did not result in a reduced risk of Alzheimer's.

Higher dietary calcium intake is also associated with a reduced risk of kidney stones 11 12. Interestingly, for omnivores, the consumption of animal protein is directly associated with the risk of stone formation.

There is also evidence that calcium may have a protective effect against colorectal cancer 13.

Vitamin D plays a crucial role in calcium absorption

Vitamin D is involved in calcium absorption with its hormone-like effect. It ensures that calcium from food can be absorbed and stored in bones and teeth. For this reason, it is of utmost importance to ensure an adequate intake of vitamin D. Vitamin D can be synthesized in the skin through sun exposure during the summer months. In the winter months, it is essential to consume foods rich in vitamin D.

Other hormones involved in regulating blood calcium concentration are calcitonin (which facilitates calcium incorporation into bones and teeth) from the thyroid gland and parathyroid hormone from the parathyroid gland.

Increasing calcium absorption from food

Generally, about 30% of the calcium consumed through food is absorbed in the intestines 14.

In addition to vitamin D, which plays a significant role in calcium absorption, prebiotic foods also support calcium absorption. 15. The best prebiotics include the fibers inulin (found in chicory, artichoke, and parsnip) and fructooligosaccharides (found in asparagus, onions, garlic, and bananas) 16.

Study results suggest that dietary lysine can improve calcium absorption in the intestine and contribute to a reduced excretion of absorbed calcium through the kidneys 17. Find a list of foods that contain lysine here.

Therefore, it is advisable to maintain a balanced and varied diet to ensure the availability of all nutrients.

Impairment of Calcium Absorption

Particularly phytic acid (phytates) and oxalic acid hinder the absorption of calcium 18. They are therefore rightly referred to as calcium robbers. They chemically bind to calcium. These bonds cannot be dissolved by the body, which prevents calcium from being absorbed and eventually excreted. Phytic acid is mainly found in grains and legumes. Oxalic acid (causes tooth enamel to become dull) is abundant in spinach, beets, chard, and rhubarb, among other things. For this reason, these mentioned foods are rather poor sources of calcium. The calcium from foods with a lower oxalic acid content, such as dark green vegetables, is absorbed by the body at 50 to 70% 19. With high oxalic acid levels, as found in beans, the absorption rate drops to only 17%. If the acids are not adequately excreted by the body, kidney stones can form.

Furthermore, the mentioned foods (groups) should not be avoided, as they are rich in important nutrients. Moreover, certain preparation methods, such as cooking, sprouting seeds, and roasting the respective foods, reduce the negative effects of phytic and oxalic acids on absorbable calcium 20.

According to findings, there are no disadvantages in terms of bone density and calcium excretion in healthy individuals with increased protein intake 21. Nevertheless, it is advisable to aim for a protein intake within the range of 0.8 to about 1.6 g for athletes. For vegetarians and omnivores, it should be noted that the body loses calcium due to animal-derived protein. Animal protein contains more sulfur-containing amino acids than plant-based protein. Consequently, high amounts of animal protein lead to acidification. This is counterbalanced by the dissolution of calcium from the bones, resulting in increased calcium excretion. As a result, more calcium must be consumed to compensate for the deficiency 22. For this reason, it is often reported that vegans require slightly less calcium.

However, the same effect also occurs with excessive consumption of sodium exceeding 5 g per day, mainly through table salt. Individuals who reduce their sodium intake by 1 to 2 g per day lower their calcium requirement by 160 mg 23.

Other factors that reduce absorption rate include smoking, alcohol, and caffeine 2425.

The more calcium is consumed with a meal, the lower the absorption rate ultimately becomes 26. For example, absorption was 28.6% with a very calcium-rich meal and 64% with a meal containing the lowest amount of calcium. Therefore, calcium-rich foods should be spread across multiple meals.

Furthermore, excessive intake of phosphorus can interfere with the body's ability to use calcium 27.

Considerations for Vegans

According to studies, vegans have lower calcium levels compared to the general population. 28 29 30. To avoid calcium deficiency, it is important to ensure an adequate supply of vitamin D to the body. As mentioned earlier, vitamin D is involved in the absorption of calcium from food, so insufficient vitamin D levels can lead to a deficiency (see also causes of calcium deficiency).