99% of body fat is contained in bones. The remaining 1% of calcium in the human body is essential for many vital functions of the body - blood clotting, cardiac and muscular activity, blood pressure, transmission of the nervous muscle, many enzymes, etc. The calcium content of the blood must remain constant. Even its slight change can cause problems, such as increased nervous system irritation or even cardiac arrest.
Calcium is continuously excreted from the body - urine, faeces, sweat. If the supply is inadequate, the body will use calcium as the source of bone to retain its contents and ensure life functions. Therefore, consumption of calcium is so important.
"Since the body does not produce calcium itself, it must be supplied with nutrition. The richest calcium foods are milk and dairy products. Other foods like sardines (with bones), some fruits or vegetables (cabbage, nuts, almonds) and some mineral water also contain calcium, but in a much smaller amount. However, due to its absorption and bioavailability, all calcium sources are not equivalent, as explained below, " explains Ing. Jiří Kopáček, CSc., Chairman of the Czech-Moravian Dairy Association.
How is calcium absorbed?
Calcium must be delivered to our body in a soluble form so that it can be absorbed in it. It should be remembered that this process decreases with age and on the contrary it increases in some physiological states (pregnancy, adolescence, etc.).
"In order for calcium to be absorbed in the body, it must be supplied in a soluble form, which is about one-third of milk calcium in dairy products. The remaining part is easily released in the stomach and duodenum. Calcium absorption also contributes to the milk containing phosphopeptides and lactose, which also promotes the absorption of calcium in the lower intestine, especially in the case of vitamin D deficiency, " explains the expert.
Most plant sources, with the exception of curly cabbage, contain substances that cause calcium to be insoluble and therefore poorly absorbable:
• Phytates, such as pastries, cereals, soybeans, legumes,
• Oxalates, such as spinach, rhubarb, cress, sorrel,
• Tannins, such as tea
The calcium content in humans is very different for individual foods: milk 32.4%, cheese 32.8%, yogurt 25%, spinach and cress 5-13%, curly 29-32% cabbage, soybean enriched 23.7%, calcium mineral water 32.3%.
Are all calcium sources equal?
When comparing individual sources, the calcium content, its absorbability and so-called bioavailability must be taken into account.
"Although calcium contained in cabbage is absorbed just as well as calcium contained in milk, cabbage is not so rich in calcium. One liter of milk contains approximately 1200 mg of calcium, while 1 kg of cabbage (cooked) only about 300 mg. So, to get 300 mg of calcium, we have to drink a cup of milk, which is real, or eat nearly a kilo of cabbage. However, this amount is practically unrealistic from the practical point of view, " explains Ing. A bumper.
Once calcium is absorbed in the intestine, it must remain in the bones and must not be excreted in the urine. Therefore, we have to distinguish between absorption (in the intestine) and real bioavailability (for bones). Dairy calcium has a very good bioavailability.
"In addition, milk calcium utilizes the" main daily diet effect, "which is a distributed and prolonged absorption due to delayed intestinal emptying, which has a beneficial effect on its absorption and bone retention, but this does not apply to other calcium sources that are taken off main daily meals. continues the chairman of the Czech-Moravian Dairy Association.
What is the recommended nutritional supply of calcium?
Daily calcium intake in European or American diet is between 600-1200 mg. Only 5 - 50% of these are absorbed. Approximately 50-70% of total daily consumption is covered by milk and dairy products.
In most cases, the following recommended daily allowances are given:
- 500 mg in children aged 1 - 3 years
- 700 mg in children aged 4-6 years
- 900 mg in children for 7 - 9 years
- 1200 mg in youngsters between 10 and 19 years of age
- 900 mg for pregnant and lactating women
- 1200 mg for women over 55 years and for men over 65 years.
"Metabolism experts agree that the use of calcium in milk and dairy products is high. Milk does not contain substances that bind calcium to non-absorbable matter, making it impossible to use, and on the contrary contains lactose and some amino acids that increase calcium utilization. To meet the calcium needs, we should eat 3 servings of dairy products daily, eg one glass of milk + one yogurt + a piece of cheese (50-100 grams), " adds Ing. Jiří Kopáček, CSc.
Equivalence of calcium sources
(source: Y.Soustre - CERIN, Nr.9 / 2004)
300 mg of calcium can be obtained, for example, from the following sources:
3 kg of oranges
2 yoghurts
5 baguettes
¼ liter of milk
1 cabbage weighing about 850g
30 g of hard cheese, such as emmental
40 g of blue cheese
300 g of cottage cheese or fresh cheese
4 kg of beef
120 g of almonds
80 g of sardines with bones
2.5 l of orange juice
10 plates of soy sprouts
Source: tz, edited editorially