Calcium is an important mineral in the human body, 99% of which is found in bones and teeth, with the remaining 1% distributed in the blood, nerves, and various soft tissues. In skeletal tissues, calcium ions and phosphorus form hydroxyl phosphate lime crystals that are deposited on a matrix of collagen and maintain the solidity of the bone.
When the body is deficient in calcium, on the one hand, the lack of raw materials to form bone leads to an intensification of bone metabolism in the direction of osteolysis; on the other hand, a drop in blood calcium to a threshold will lead to hyperparathyroidism (parathyroid hormone can raise blood calcium), increasing bone resorption and freeing calcium from bone tissue into the blood. Both factors can lead to a decrease in bone mass per unit volume, so calcium deficiency is an important cause of osteoporosis.
Whether it is primary osteoporosis (including postmenopausal, senile and idiopathic) or secondary to various other diseases or medications, calcium supplementation can reduce bone loss and is a basic adjunctive treatment.
However, in clinical work, calcium supplementation therapy may not be reasonably standardized. So, what do we need to pay attention to for reasonable and standardized calcium supplementation?
Note 1: Calcium supplements should be selected reasonably
Case: Female patient, 50 years old, with a history of kidney stones, was given calcium supplementation for “postmenopausal osteoporosis”, and calcium tablets were used for calcium supplementation.
Ans: Based on the physiological and biochemical functions and pharmacological effects of calcium, the preparation with calcium salts as the main component is called calcium agent.
There are many kinds of calcium preparations, which can be divided into inorganic calcium and organic acid calcium according to their composition. Inorganic calcium mainly includes calcium oxide, calcium carbonate, calcium hydrogen phosphate, calcium chloride, calcium hydroxide and so on. Organic calcium acids mainly include calcium gluconate, calcium lactate, calcium citrate, calcium citrate, etc.
Inorganic calcium has higher calcium content, but most of them have low solubility and great gastrointestinal tract irritation; organic acid calcium generally has better body solubility, but low calcium content.
When choosing calcium, the characteristics of the population and the combined diseases should be taken into account. For example, a few points.
Note that.
1. people who lack stomach acid basically do not absorb inorganic calcium; elderly people often have reduced stomach acid secretion; therefore, it is recommended that people older than 65 years old and lacking stomach acid take organic acid calcium such as calcium citrate; calcium supplements for the general population are elected with high calcium content inorganic calcium such as calcium carbonate;
2. Patients with hypoparathyroidism and chronic renal failure, often combined with hyperphosphatemia, should not use calcium containing phosphorus (calcium hydrogen phosphate), calcium carbonate, calcium citrate, calcium acetate should be used, not only for calcium supplementation, but also as a phosphorus binding agent for hyperphosphatemia, in order to reduce blood phosphorus concentration;
3. calcium citrate increases intestinal aluminum absorption, and is prohibited for those taking aluminum;
4. Calcium gluconate is not suitable for diabetic patients. 5;
5. Calcium acetate tends to increase blood pressure and is not suitable for patients with hypertension and cardiac insufficiency.
Long-term use of general calcium supplements, such as calcium carbonate in cases, can cause elevated blood and urine calcium concentrations, which can increase the risk of urinary calcium oxalate crystals and stone formation, especially in patients with a history of urinary stones.
Calcium citrate has a strong complexation of calcium, and when the concentration of citrate is increased, it can combine to replace calcium oxalate, free calcium ions and calcium phosphate salts, thus forming a complex that is easily soluble in water and inhibiting calcium oxalate supersaturation to precipitate crystals and form stones. Calcium citrate is recommended for patients with urinary stones.
Note 2: The dosage and usage are important
Case: The patient was 68 years old and took 600 mg of calcium carbonate in the morning and evening for primary osteoporosis.
Analysis: The recommended daily calcium intake of 800 mg for adults by the Chinese Nutrition Society is the appropriate dose to obtain the ideal bone peak and maintain bone health.
For postmenopausal women and the elderly, the recommended daily calcium intake is 1000 mg. The current dietary nutrition survey shows that the average daily calcium intake of the elderly in China is about 400 mg, so the average daily amount of elemental calcium supplementation for postmenopausal women and the elderly should be 500-600 mg (e.g., calcium carbonate contains 600 mg of elemental calcium per tablet).
Before determining the dose, the patient’s blood calcium and urine calcium levels should also be measured and considered in conjunction with the patient’s dietary calcium intake to prevent the occurrence of hypercalcemia (as in the case), which increases the risk of kidney stones and cardiovascular disease. The maximum permissible daily intake of calcium for adults in China is 2000 mg.
After calcium supplementation, it is recommended to test blood and urine calcium concentrations every 3 months, and to discontinue the drug if hypercalcemia occurs, and to reduce the calcium dose if urine calcium increases.
A large dose of calcium in one dose is not as well absorbed as a divided dose. The commonly used calcium carbonate is better absorbed in an acidic environment, and when taken with food, the stimulation of food increases the secretion of gastric acid, which increases the efficiency of calcium absorption.
If the elderly are not in a position to take organic calcium, calcium carbonate can be taken in this way. Organic calcium does not need to be activated by gastric acid and does not need to be taken with food. Also note that vegetables containing more oxalic acid (spinach, amaranth) reduce the absorption of calcium and avoid using with calcium supplements as much as possible.
Note three: “golden partner” can not be missing
Case: Male patient, 70 years old, with chronic nephritis and osteoporosis, was given only calcium carbonate vitamin D chewable tablets orally.
Analysis: Vitamin D promotes calcium absorption, is beneficial for bone health, maintains muscle strength, enhances body balance, reduces falls, and lowers the risk of fractures. Vitamin D deficiency can lead to secondary hyperparathyroidism and increase bone resorption, which can cause or worsen osteoporosis. Along with calcium supplementation, vitamin D is indispensable as the “golden partner” and basic treatment.
Although some calcium supplements include vitamin D (e.g. cases), the dose is far from adequate. The relevant guidelines in China recommend a dose of 800-1200 IU/d for the treatment of osteoporosis with regular vitamin D.
Regular vitamin D is converted to active vitamin D in order to be effective, so substitute active vitamin D supplementation, including α-osteotriol (0.25-1.0 μg daily) or osteopontin (0.25-0.5 μg daily).
Osteoporosis secondary to renal failure is due to reduced active vitamin D synthesis, but only osteotriol should be supplemented because α-osteotriol requires activation of renal 1-alpha hydroxylase, which is reduced in patients with renal failure.
Blood and urine calcium should also be monitored once every 3 months when calcium and vitamin D are used together clinically, and dose adjustments should be made as appropriate. It is recommended that serum 25-hydroxyvitamin D concentrations (reflecting vitamin D nutritional status for better supplementation) equal to or above 30 ng/mL (75 nmol/L) be measured as appropriate in hospitals where available to reduce the risk of falls and fractures.