Osteoporosis: three notes on calcium supplementation
Calcium is an important mineral in the human body, 99% of which is found in bones and teeth, while the remaining 1% is distributed in blood, nerves and various soft tissues. In the skeletal tissue, calcium ions and phosphorus form hydroxyl phosphate lime crystals deposited on the collagen matrix, maintaining 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 chosen reasonably
Case: Female patient, 50 years old, with a history of kidney stones, was given calcium supplementation for “postmenopausal osteoporosis”.
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 supplements, the characteristics of the population and the combined diseases should be taken into account. For example.
1, people who lack stomach acid basically do not absorb inorganic calcium, and the elderly often have reduced stomach acid secretion, so it is recommended that people older than 65 years old and lacking stomach acid take organic acid calcium such as calcium citrate, and the calcium supplement for the general population is elected inorganic calcium with high calcium content such as calcium carbonate;
2, hypoparathyroidism and chronic renal failure patients, often combined with hyperphosphatemia, can not use calcium containing phosphorus (calcium hydrogen phosphate), calcium carbonate, calcium citrate, calcium acetate should be used, not only to supplement calcium, but also as a phosphorus binding agent for hyperphosphatemia, in order to reduce blood phosphorus concentration;
3, calcium citrate increases intestinal aluminum absorption, taking aluminum is prohibited;
4.Calcium gluconate is not suitable for diabetic patients;
5, calcium acetate is likely to increase blood pressure, not suitable for patients with hypertension and cardiac insufficiency.
Long-term use of general calcium supplements, such as calcium carbonate in cases, can cause an increase in blood calcium and urine calcium concentrations, which can increase the risk of urinary calcium oxalate crystals and stone formation, and is particularly serious 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 water-soluble complex 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.
The recommended daily intake of calcium for adults is 800 mg, which is the appropriate dose to obtain the ideal bone peak and maintain bone health. The average daily amount of elemental calcium supplementation for postmenopausal women and the elderly is 500-600 mg (e.g., calcium carbonate contains 600 mg of elemental calcium per tablet).
Before determining the dose, the patient’s blood and urine calcium levels should also be measured and considered in conjunction with the patient’s dietary calcium intake to prevent the development 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 a single dose is not as well absorbed as a divided dose. The commonly used calcium carbonate is better absorbed in an acidic environment, and when calcium carbonate is taken with food, the stimulation of food increases the secretion of gastric acid, which can increase the absorption efficiency of calcium. Organic calcium does not need to be activated by gastric acid, so it is not necessary to take it 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” is not 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. Our guidelines recommend a dose of 800-1200 IU/d for the treatment of osteoporosis, and the conversion of vitamin D to active vitamin D is the only way to make it work, so substitute active vitamin D supplementation, including alpha-skeletriol (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 can be supplemented because α-osteotriol requires renal activation and this activating enzyme is reduced in patients with renal failure.
Clinical co-administration of calcium and vitamin D preparations should also be monitored once every 3 months for blood and urine calcium, 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.