Calcium in the diet
Calcium is by far the most abundant mineral in the body. It is largely stored in the bones, which it is an integral part. It contributes to the formation of the latter, as well as teeth, and maintaining their health. Calcium also plays a vital role in blood clotting, maintaining blood pressure and muscle contraction (including the heart).
Physiological importance of Calcium
Calcium is an important component of a healthy diet. Contrary to popular belief, these are not dairy products that represent the best source of calcium, because the proportion calcium / phosphorus ratio is not good. Milk is indeed too much phosphorus, which can lead to inadequate calcification. The body needs magnesium, silicon, vitamins A, C and D, protein and phosphorus to fully assimilate. It intervenes in the formation of bones and teeth; its deficit will affect them (osteoporosis, growth problems). Its excess leads to the appearance of kidney stones. In addition, he is involved in cellular exchanges and is, therefore, vital. His blood (serum calcium) is highly regulated to avoid fatal changes to the organization. The hormones involved in the regulation are calcitonin and parathyroid. Although the “role” of the calcitonin hormone be discussed since its increase results in no change on calcium-phosphor metabolism. It would be more accurate to consider the parathyroid and calcitriol (derivative of vitamin D) as the two main hormones phosphor- calcium metabolism. See also metabolism of calcium. Calcium is also used to regulate the pH body, it is released bones when there is an acidification of the environment caused by internal consumption produces acid (Protein, Milk …) and inadequate intake of plants which have an effect alkalizing .
The risk of colon cancer seems diminished by a diet rich in calcium. The majority of epidemiological studies indicate that people whose diet contains more calcium causes less frequently colorectal cancer. More than 25 scientific publications indicate that calcium reduces colon carcinogenesis in rodents. Finally, three controlled clinical trials show that taking a supplement of calcium carbonate (1-2 g / d) reduces the recurrence of polyps by 15 to 30% in volunteers.This suggests that calcium prevents colorectal cancer.
Presence of calcium in our food
Calcium is present in many foods commonly consumed. Dairy products are the main source of dietary calcium (over two thirds). Calcium is present in a form that is a good intestinal absorption (about 30%) and that do not urinary excretion, allowing the good bioavailability.
Other foods contain calcium: tap water, almonds, parsley, figs, watercress, soybeans, cocoa, dandelion, egg yolk, sesame seeds, spinach, fish, … (See in this regard Calcium content of foods). Calcium of plant origin, however, is most often less absorbable because it is largely insoluble irreversibly in the form of phytate (soybean) or oxalates (spinach, cocoa). Thus the absorbability of calcium in spinach would not exceed 5%.
In order to evaluate the real bioavailability, we must also take into account the dietary factors that influence the urinary loss of absorbed calcium. Thus, the simultaneous absorption of phosphorus decreases urinary excretion of calcium. In contrast, “acidic components” of the regime, such as sulfates (particularly in the mineral waters calcium sulphate), increase the calcium.
Finally, the setting of calcium absorbed from the bone (preventing osteoporosis) depends on many other factors, especially hormonal (see above).
The RDAs are 800 mg per day in adults.
Calcium in medicine
The absorption of calcium in the form of pills can increase their daily intake if it is not optimal. It is sometimes associated with taking vitamin D. It seems to be effective in the preventive treatment of osteoporosis in the elderly, by reducing the rate of fractures as well as indices of bone demineralization. The side effect is most noted constipation. However, this supplementation may be associated with an increased risk of cardiovascular disease, though this figure is still discussed.
