1. What are the effects of calcium on the human body?
Calcium is the main component that makes up bones and teeth and is very important for the growth and development of bones.
In fact, the role of calcium is far more than this, it can maintain the normal excitability of neuromusculars, participate in the coagulation process, activate the activity of a variety of enzymes, regulate hormone secretion, affect the rhythm of the heartbeat, reduce the permeability of capillaries ...
Once the body is deficient in calcium, not only the growth of bones and teeth will be affected, resulting in rickets in children (called "osteochondrosis" in adults) and osteoporosis, but also seriously affect the functional activity of muscles, nerves, hearts and brains. Therefore, the problem of calcium nutrition needs to be paid attention to and paid attention to by everyone.
2. Mechanism of regulation of blood calcium
The amount of calcium in normal adults is about 1200 grams, which is 2% of body weight. Of these, 99% of calcium is present in the bones, and the remaining 1% of calcium is found in the blood and soft tissues in two forms: "free calcium (i.e., ionic calcium)" and "calcium-binding (mainly calcium-binding to albumin-binding proteins)".
Combined calcium and ionic calcium can be converted into each other, and the physiological effect can be exerted after combining calcium into ionized calcium.
Under normal circumstances, the blood calcium concentration is maintained in a narrow range of 2.25 to 2.75 mmol/L, and the reason why blood calcium can remain relatively stable is the result of the synergy between the "bone calcium bank" and the "calcium regulator hormone".
Calcium-regulating hormones mainly include:
1. Parathyroid hormone (PTH): enhance osteoclast activity, dissolve bone calcium in and out of the blood, and increase blood calcium;
2. Calcitonin (CT): promote the deposition of blood calcium in the bone, reduce blood calcium;
3. Active vitamin D3 [i.e. 1,25(OH)2D3]: Promotes intestinal calcium absorption. Regulated by calcium-regulating hormones, when the blood calcium is reduced, the calcium in the bones is mobilized into the blood; when the blood calcium is increased, the calcium in the blood is deposited into the bones, so that the blood calcium concentration can remain relatively stable.
Three. Does normal blood calcium mean that there is no calcium deficiency?
Bones are the largest calcium storehouse in the human body, and most of the calcium in the body is stored in the bones (i.e., "bone calcium"), and the calcium in the blood (i.e., "blood calcium") is less than 1% of the total calcium of the whole body. We usually say that the body is deficient in calcium, generally referring to the lack of calcium in the bones.
In synergy with calcium-regulating hormones, a dynamic balance is maintained between blood calcium and bone calcium. When blood calcium is reduced, calcium in the bones is mobilized to release into the blood, so that the blood calcium is elevated, so even if the patient has bone calcium deficiency, the blood calcium test is often still normal, in other words, normal blood calcium does not mean that the body is not deficient in calcium.
Four. What are the factors that affect calcium absorption?
Active absorption of calcium is influenced by factors such as dietary composition, the nutritional status of calcium and vitamin D in the body, and the physiological condition of the body. Calcium absorption averages around 30% (20 to 60%), with vitamin D being the most helpful for calcium absorption, particularly active vitamin D [1,25(OH)2-D3].
In addition, substances that lower the intestinal pH or increase calcium solubility can promote calcium absorption.
In addition, the absorption of calcium is also related to the physiological condition of the body. Due to the increased demand of infants, young children, pregnant women, and nursing mothers, calcium absorption rate is much higher than that of adult men. With the increase of age, the calcium absorption rate gradually decreases, and the calcium absorption rate of the elderly over 60 years old decreases significantly, generally around 20%.
Five. What is the daily calcium requirement?
The recommended intake of calcium varies for people of different ages, and the following table is the reference value for the appropriate daily intake of calcium (mg/day) for Chinese residents:
According to the survey, the daily dietary calcium of mainland residents is about 400 mg, which is still 500 to 600 mg away from the recommended intake.
Six. Is calcium supplementation more and more good?
Calcium deficiency is harmful, but calcium supplementation is not more. Long-term overdose of calcium may lead to adverse reactions such as hypercalcemia, kidney stones, ectopic calcification, mood abnormalities, and muscle pain.
A growing body of research has found that calcium excess also increases the risk of myocardial infarction and stroke. Researchers believe that if the body lacks enough vitamin D to help absorb, excess calcium is deposited in the blood vessel wall rather than the bone, and over time, it will form arteriosclerotic plaques, increasing the risk of cardiovascular and cerebrovascular diseases.
In addition, a high-calcium diet interferes with the bioavailability of other minerals (e.g., zinc, iron).
Therefore, calcium supplementation is not as much as possible, and the total daily intake of calcium should not exceed 2000 mg.
Seven. Classification of calcium agents
Calcium agents are mainly divided into three categories: inorganic calcium, organic calcium and biological calcium.
1. Inorganic calcium
Mainly including calcium carbonate, calcium chloride, calcium bisphosphate, etc., the most commonly used is calcium carbonate, which has a higher calcium content, but low water solubility, and must be dissociated into calcium ions under the action of gastric acid to be absorbed by the human body, so it is advisable to take it when the stomach acid is sufficient after a meal.
Side effects are easy to cause stomach discomfort, constipation and other adverse reactions, not suitable for the elderly with insufficient gastric acid secretion and poor gastrointestinal tolerance.
2. Organic calcium
Common calcium gluconate, calcium lactate, amino acid chelated calcium, calcium acetate, calcium citrate (calcium citrate), etc., organic calcium calcium content is relatively low, but good water solubility, small stimulation to the gastrointestinal tract, and does not require gastric acid participation, more suitable for the elderly.
calcium gluconate:
The calcium content is low (9.3%), but the taste is good, mostly liquid preparations, suitable for infants and young children. Because its metabolites contain glucose, it is used with caution in diabetic patients.
Calcium acetate:
With a calcium content of 25.34%, it is a phosphorus binder that reduces phosphorus absorption and is suitable for patients with chronic kidney disease hyperphosphatemia.
Calcium ammonia phosphate:
Calcium content is relatively high, about 23.3%, but tablet disintegration and absorption difficulties, due to the high phosphorus content, not suitable for chronic renal insufficiency.
Calcium citrate (calcium citrate):
Calcium content 21%. There are ordinary tablets, effervescent tablets and other dosage forms, good absorption, bloating, constipation and other gastrointestinal adverse reactions are small, especially suitable for children and the elderly.
Calcium chelated amino acids:
Belonging to the chelate of amino acids and calcium, the calcium content is about 20%, characterized by high solubility, good absorption, and does not require vitamin D participation, it itself is neutral pH, no irritation to the intestine, more suitable for the elderly calcium supplementation.
3. Biocalcium
It is generally made of calcium-rich animal bones, fish bones, shells, etc., of which calcium has a high degree of ionization and is easily absorbed and utilized by the body. However, due to the heavy metal enrichment effect of organisms, long-term use of biological calcium may have a risk of heavy metal poisoning.
Starter | Endocrine time
Planning | Dai Dongjun
Caption | Stand cool Heero