Calcium is one of the metals that are fundamental for the development of our life and is one of the easiest elements to find on the planet.
In humans many cells use calcium ion for different purposes, it is important to remember its function in nerve conduction, in cardiac or skeletal musculature and, obviously, as raw material of bone mass.
As we know it is one of the basic pillars in the prevention and treatment of osteoporosis.
Much has already been said about it and much is the controversy about possible side effects that calcium salts could produce in extraosseous tissues such as the vascular endothelium and the excretory urinary tract.
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Without pretending to enter into Byzantine polemics, we are going to provide data on why we believe it is not harmful to health, and for us, calcium is a nutrient rather than a drug, as stated by Prof. Dr. Jorge Talbot [1, 25] .
We will answer questions that arise in our daily practice:
What are the primary food sources of calcium?
The main food sources of calcium, in developed countries, are products of massive and daily use, particularly milk, yogurt and other dairy products. Convinced of the contribution of calcium beneficial to the individual; and in the intention to reach all age groups and the different physiological conditions and in light of the results of the 1999 osteoporosis risk factor survey, which clearly demonstrates the poor intake of dairy products in our population; is that the GEOSUR group decided, as a first step, to support and promote the consumption of milk and milk products [3, 4, 26].
There are other food products in the diet that provide calcium in different proportions, here we attach a table.
Calcium content in foods
(milligrams of calcium per 100 grams of food)
Cereals
- White wheat bread 38
- Whole wheat bread 65
- Toasted wheat bread 13
- Rice in paella 3
- Wheat flour 25 - 187
Vegetables
- Cooked chickpeas 35
- Cooked beans 18
- Cooked white beans 87
- Cooked beans 103
Vegetables and tubers
- Cooked artichokes 44
- Raw cress 192
- Raw lettuce 29
- Fried potato 16
- Raw tomato 11
- Fried tomato 36
Eggs
- Boiled 54
- Fried 81
- Tortilla 190
fruit
- Cherry 267
- Fresón 31
- Lemon 58
- Orange 36
- Pear 12
Nuts
- Almond and hazelnut 240
- Dried chestnut 98
- Figs 212
- Raisins and peanuts 61
Dairy products
- Cow's milk 120
- Condensed milk 290-380
- Soft cheese 350-550
- Hard cheese 800-1200
- Yogurt 145
meats
- Cattle, pigs and cattle 10
- Birds and game 20
Fish and seafood
- Fried squid 240
- Cooked hake 16
- Cooked Mussel 197
- Sardine preserves 410
- Fried flounder 93
- Fried hake 20
- Fried sardine 409
- Seafood 30 -300
Now, if we look at the calcium content of these products; and taking into account that the absorption of them is not total since the calcium coming from the dairy products is absorbed by 30% and by the fish by 20% [31]; We would have to consume large quantities, which in practice is not real. For what would be a good complement a pharmacological contribution of calcium.
Another resource is the use of foods to which calcium salts are added, which are compatible with good bioavailability for the organism. In this land are: breads, pastas, cereals, fruit juices etc.
What is the best way to get calcium?
The contribution of calcium in the diet to prevent and treat osteoporosis averages between 1000 and 1500 mg / day, hence it is necessary to interrogate dietary habits before facing a supplemental treatment of calcium [2].
In the survey conducted by GEOSUR, analyzing 256 Uruguayan women, it was shown that women with osteoporosis consumed less white meat, scarce vegetables rich in carotene (tomato and carrot) and onions. Instead they consumed more salt and products of animal origin with higher fat content. This survey shows that we must insist not only on a high intake of calcium but also other nutrients.
Surveys conducted by ANEP in children and the School of Nutrition and Dietetics of the University of the Republic showed that the majority of children and adolescents do not get to consume the daily requirements of calcium with the diet [19, 20].
After making it clear to the patient that life habits favor him in the development and maintenance of bone mass, we indicate pharmacological supplements of calcium salts [3, 4].
The majority of patients can not reach daily requirements through diet, in these cases it is recommended to supplement with pharmaceutical preparations.
What calcium salt is preferable to use?
When using a calcium supplement, it is important to know the mineral content of calcium in the salt to be used, which varies between 40% of calcium carbonate, 30% of calcium citrate and 9% of calcium biolate or gluconate .
In fact, the most commonly used salts are: carbonate and citrate, which must be administered during main meals to achieve greater absorption. It is advisable not to give doses higher than 500 mg at a time and this is because calcium is absorbed at the level of the duodenum by an active and saturable dependent vitamin D mechanism, and the rest of the absorption is carried out passively in small intestine.
The carbonate often has little adhesion by the patient to produce gastrointestinal disorders.
Citrate is the salt most used by the authors. It has, in our opinion, the advantage of being able to be administered at any time of the day, since these salts are better absorbed than carbonate, even in conditions of gastric achlorhydria.
The possibility of greater passive absorption makes it much more usable. The intestinal absorption of calcium varies from one person to another and decreases linearly after 50 years in women and 60 in men, making it the salt of choice for older adults [1, 5, 6, 9 , 13, 14].
It must be taken into account that the absorption of calcium depends on the amount that is ingested, if we take 1 g, 20% is absorbed, instead of the 500 mg intake, absorption increases to 30%.
It is not recommended to take calcium before going to sleep, because night rest increases bone resorption [31].
In a comparative study between calcium citrate and calcium carbonate, after supplying these salts to two groups of women with osteopenia or osteoporosis for 12 weeks, an improvement in markers of bone resorption was found in the group treated with citrate. it did not happen in the group treated with carbonate [32, 33, 34].
Vitamin D in the absorption of calcium?
Vitamin D plays an important role in the intestinal absorption of calcium and the dose / day required varies, either in prevention or treatment, age and time of year.
Although 400 ui / day is commonly recommended at 800 ui / day, there is a lot of literature that shows that in higher doses of osteoporosis, higher doses could be used weekly, monthly or quarterly (macrodoses of vitamin D) [5, 6]. , 7, 15].
The best calcium absorption depends on the gene of vitamin D receptors (VDR) [31].
In addition to experimental confirmation; in numerous clinical investigations of the beneficial effect of calcium and vitamin D on the skeleton (which we will not discuss here); the remarkable consequences of vitamin K on the carboxylation of osteocalcin are already known: this bone protein, in its carboxylated form, favors the deposit of the mineral phase in the osteoid; Vitamin K prevents hypercalciuria and post-castration osteopenia in rodents and humans. In Japan, this vitamin has been marketed since 1995 for the prevention and treatment of osteoporosis. Other vitamins with osteoprotective potential, attributed to their antioxidant properties, are E and C [24].
What can act on the absorption of calcium supplements?
Some foods such as spinach, cocoa, tea, potatoes, cereals etc. they diminish the intestinal absorption of calcium. The anti-nutrient effects are overcome with a balanced diet and sometimes calcium should be removed from these nutrients.
In turn, caffeine interferes with the absorption of calcium, an effect probably mediated by Calcitriol, (this does not contraindicate the addition of a part of coffee to the milk, since the coffee portion neutralizes only a small part of the milk) [ 28, 27].
There are works that mention that the tea would act as an antinutrient of calcium, however other studies show that the high consumption of tea is associated with higher bone mineral density and lower risk of fractures in elderly women. Tea is rich in fluoride and antioxidants [24].
Moderate alcohol consumption tends to conserve and even increase bone mass in both sexes [24], while abusive consumption produces significant bone loss, alcohol induces poor food intake, alters liver metabolism and increases excretion renal calcium and phosphorus [26, 27].
Another of the public health issues that concern us is the increase in alcohol consumption in adolescents, the time of their lives in which their greater bone mass is forming with the deleterious effect on it that this noxa causes.
Cocoa also acts by inhibiting the absorption of calcium. Its use is important because chocolate milk is much more accepted by children and adolescents than milk alone (which in general they do not like), and although less is absorbed, "it is better little than nothing".
It is recommended not to ingest fibers along with dairy products, since the phytates and oxalates they contain interfere with absorption.
The phosphoric acid contained in cola soft drinks has a demineralizing effect since phosphorus precipitates with calcium and prevents its absorption. It is for this reason that the abusive use of these beverages is not recommended [21, 22]. In a paper presented by Dr. Katherine L. Tucker. (25th Annual Meeting of the American Society for Bone and Mineral Research) reports that high consumption of cola beverages is correlated with low mineral density in the hip of female patients [22].
In our talks to the community, regarding the prevention of osteoporosis, we made it clear that the dairy snack should not be substituted for soft drinks and that the intake of these beverages should be less than 3 glasses per day [22].
The consumption of broccoli (1-3 servings per week) seems to protect against fragility fractures. Supplementation with plum, fruit rich in polyphenols and antioxidant compounds, prevents and reverses osteoporosis in the castrated rat model. In another murine model, 1 g / day of onion (but also of fennel, parsley, garlic, lettuce and other common vegetables in the human diet) increased bone mass significantly [25].
What medications alter absorption?
Calcium interferes with the absorption of iron, so it is advisable to separate iron from calcium supplements.
In turn, calcium interferes with the absorption of certain antibiotics such as tetracycline, isoniazid, aluminum-containing antacids and corticosteroids.
Another of the interferences is with the thyroid hormones that decrease calcium absorption in the order of 20%.
What happens with calcium after being absorbed?
It is important to remember that 48% of the total serum calcium is composed of free calcium (Ca ++) ion which is biologically active, 12% bound to citrate, phosphate and sulfate that is diffusible and ultrafiltrable as well as ionic calcium (Ca ++) and the remaining 40% is bound to proteins, especially to albumin.
Recall that about 1% of skeletal calcium (500-700 mg) is interchangeable, the rest is more stable and is removed slowly.
In turn, the three hormones that fundamentally handle calcium homeostasis are: calcitriol, which is the active metabolite of vitamin D that promotes the absorption of calcium from the intestine, has an important effect on the mineralization of bone and inhibits the PTH. Paradoxically, in very high doses, it can divert small amounts of calcium from the bone to the extracellular space.
PTH, in turn, stimulates the renal activation of vitamin D and increases bone resorption in hypocalcemic states.
Calcitonin is a hormone synthesized by thyroid C cells and decreases calcemia because it inhibits the mobilization of calcium from the bone.
At the same time, the diffusible calcium calculates that about 9,000 mg per day are filtered through the glomeruli and that the tubules reabsorb 98% of the ultrafiltered calcium.
It is known that after an intake of 1000 mg of calcium, the kidney excretes 250 mg in women and 300 mg in men. Major urinary excretions pose a hypercalciuria that is often corrected with small doses of thiazides or indapamide. Remember that diets rich in protein and salt and the use of diuretics, except those mentioned, are associated with elevated calciurias [1, 7].
What is the role of calcium in patients with renal lithiasis?
Currently there are works that clearly show that patients with kidney stones that have a decreased calcium intake increase the chances of having an increase in their kidney stones. So the best way to prevent lithiasis would be with high calcium doses. There is evidence that calcium citrate salts, as well as carbonate salts, inhibit the precipitation of calcium in the urine (protective factor) [8].
Urinary stones are, in general, carbonate or oxalate and not citrate (where Coke is).
Why calcium is deposited in soft tissues?
Calcium is deposited in damaged or dead tissues, by changes in Ph at the tissue level.
It is the example of a calcification of the shoulder ligaments in calcified periarthritis or enthesopathies.
At breast level in calcified tissues in mammograms that can often correspond to neoplasms, only because there is tissue damage caused by the neoplasm.
In turn, many times the role of calcium in vascular atheromatosis arises, what calcium does in fact is seal the atheroma plaque, something like healing what is a primary endothelial lesion. We must reaffirm that, under normal conditions, calcium is not deposited [2].
Calcium and obesity
There are several published studies where there is no direct relationship between calcium and obesity, however it has been shown in experimental models of obese mice that low calcium diets lead to an increase in intracellular calcium concentrations, which acts to promote deposit of body fat, reducing lipolysis and thermogenesis.
Diets high in calcium reverse this trend . Calcium in the form of dairy products would be more effective than elemental [16,17].
The calciotrophic hormones, the parathyroid hormone (PTH) and the 1,25 dihydroxyvitamin D promote the influx of calcium to the adipose cell, mediating lipogenesis.
A low intake of calcium increases these hormones and, therefore, the deposit of lipids. There are repeated observations of a high BMI in subjects with elevated parathyroid hormone [16, 17, 18, 23].
The impact of calcium intake on weight loss, or the prevention of weight gain, is controversial. Riggs et al. have shown; in a wide range of ages, from Caucasians to African-Americans of both sexes; the relationship between calcium and obesity .
Calcium, taking these results into account, could play a role in reducing the incidence of obesity and the predominance of insulin resistance syndrome [16, 17, 18, 23].
What are the adverse effects of calcium?
Digestive intolerance, especially constipation and meteorism.
Hypercalciuria can be observed in patients with a previous history of renal lithiasis, or in the concomitant use of Calcitriol.
Paradoxically, hypercalciuria caused by increased bone resorption gives way with calcium replacement therapy [25].
With this work we have tried, as a summary, to highlight our experience with the use of calcium salts, both in the prevention and treatment of osteoporosis. We have tried to show that treatment with calcium, except digestive intolerances such as flatulence or constipation, does not cause major problems even in the case of nephrolithiasis.
We also remember that calcium, despite the contribution of calcium, is a very stable value, that if it is altered we must look for a secondary cause (hyperparathyroidism, renal failure, myeloma, etc.).
Finally, the positive effect in a calcium treatment depends on the proper salt, the appropriate time and the appropriate dose for each particular circumstance.
Remember that prevention measures should be applied in all stages of life, and that according to the data provided by GEOSUR studies it is convenient to reduce dietary proteins, especially meats with higher fat content, decrease coffee consumption , salt, tobacco and increase the consumption of certain vegetables, especially onions, tomatoes and carrots; with this we will have changed the dietary pattern of calcium utilization, increasing its absorption and decreasing its elimination. This translates into greater health in general and bone in particular. If in addition we do muscle strengthening exercises appropriate for the age and situation, it can even improve and in some cases even revert bone fragility [2, 3, 4].