Last week, we published a very controversial post (that was our intention) about the importance of consuming calcium to prevent the formation of calcium oxalate stones. And despite the clinical evidence provided, and the fact that normal calcium consumption has been recommended for years in this patient group by the European Association of Urology, many readers resisted considering it because, according to them, "my doctor has always recommended that I eliminate calcium from my diet to avoid stones." If you haven't read the post, you can do so here. We hope it helps you break the false myth that calcium is bad for your kidneys.
In this new post, we will continue discussing the importance of calcium consumption in another group of patients who also tend to form calcium oxalate kidney stones: patients with osteoporosis. If you have osteoporosis, keep reading because this is relevant to you.
What is osteoporosis?
The word osteoporosis means “porous bone.”
Osteoporosis is a skeletal disease that occurs when the body produces too little new bone, loses too much old bone, or both simultaneously. The result of this disease is that bones become more porous, lose bone mass, weaken, and become more fragile. Becoming more fragile increases the risk of fracture with a simple fall or even a sneeze. The bones most prone to fracture are the hip, spine, and wrist.
Osteoporosis is one of the main public health problems worldwide, particularly affecting older women.
Why does osteoporosis affect women more than men?
It is estimated that osteoporosis affects more than 200 million women worldwide.
Women are believed to be more prone to osteoporosis because they tend to have smaller, thinner, and less dense bones than men. This is also because their bodies draw on calcium reserves in the bone during pregnancy and lactation, further reducing their bone mass, and because after menopause, the drop in estrogen production also alters their bone metabolism.
How is osteoporosis treated?
The best treatment for osteoporosis is prevention. General preventive measures include increasing dietary calcium intake, reducing tobacco or alcohol consumption, and increasing physical exercise.
When the above measures are not enough, calcium and vitamin D supplements are usually recommended. The ingested calcium helps new bone formation, while vitamin D facilitates calcium absorption in the intestine to ensure it reaches the bones. The commonly recommended amounts are 1,000 mg of calcium and 800 IU of vitamin D.
When bone density is very low and there is a high risk of fracture, medications such as oral bisphosphonates, injected denosumab, hormone replacement therapy, among others, are often recommended. All of these have side effects that should be evaluated by a specialist doctor. Before starting any of these treatments, talk to your rheumatologist.
And what does osteoporosis have to do with kidney stones?
As we have mentioned, some osteoporosis patients lose too much old bone through a process known as bone resorption. This bone resorption can elevate calcium levels in the blood and subsequently in the urine, thereby increasing the risk of forming calcium oxalate or calcium phosphate stones.
To counteract the loss of old bone, rheumatologists try to increase new bone production, and to achieve this, they recommend taking calcium and vitamin D supplements. But by doing so, they further elevate calcium levels in the blood and urine, potentially increasing the risk of forming stones.
So far, so good, because you are treating your osteoporosis. The problem arises when you end up forming a calcium oxalate stone and need surgery by a urologist. At that point, the urologist recommends that you stop taking calcium and vitamin D supplements if you don't want to form another stone. And you wonder: "Seriously? But my rheumatologist recommended it for my osteoporosis! And now who should I listen to, my urologist or my rheumatologist? I'm torn!"
So what do I do? Should I stop consuming the calcium I need for my osteoporosis if I want to prevent future stones?
Although it seems like a joke, this question is very common in consultations and generates a lot of confusion among patients. That's why we will try to answer it with clinical evidence.
The answer is NO. You should not stop taking your calcium and vitamin D supplements. In fact, a systematic review published in the prestigious journal Clinical and Experimental Rheumatology (Candelas, Martínez-López, Rosario, Carmona, & Loza, 2012), which analyzed 10 different studies with more than 8,000 osteoporosis patients who took calcium and vitamin D supplements, concluded that these supplements do not significantly increase the risk of forming kidney stones.
Instead of stopping calcium and vitamin D, make sure to follow these general preventive measures to prevent calcium oxalate stones:
1. Increase your water intake (+2.5 L per day)
2. Moderate your animal protein intake (meat, fish, eggs, etc.)
3. Moderate your sodium intake (salt, processed food, snacks, etc.)
4. Moderate your intake of oxalate-rich foods (tea, chocolate, spinach, etc.)
5. Maintain a normal calcium intake (1,000 mg per day)
6. And supplement with phytate to inhibit calcium oxalate crystallization in the urine.
Why is phytate good for preventing osteoporosis and calcium oxalate stones?
We have already discussed in many other posts on this Blog the importance of phytate as an inhibitor of calcium oxalate crystallization in urine and all the clinical evidence supporting its efficacy in preventing stone formation. That is why we designed a product with phytate called Lit-Control® pH Balance which you can buy here.
But phytate has also shown benefits in patients with osteoporosis.
In an initial study (López-González A. A., et al., 2008) with almost 2,000 volunteers interviewed about their dietary habits, the authors found a correlation between phytate deficiency in the diet and low bone density in individuals, suggesting that phytate could act as a protector against osteoporosis. These results were confirmed years later in a second study in postmenopausal women with osteoporosis in Mallorca (López-González Á. A., et al., 2011).
Later, the same research team conducted an interesting study to explain how phytate acted to prevent osteoporosis. According to the authors (Sanchis, et al., 2021), phytate's ability to adhere to the surface of crystals to prevent them from growing (inhibitor) also prevents these crystals from dissolving. Therefore, when phytate is administered to osteoporosis patients, old bone loss (bone resorption) is reduced similarly to how bisphosphonates do, but without their side effects. That's great, isn't it?
Finally, this year an article (Guimerà, et al., 2022) was published demonstrating that consuming 300 mg of phytate can simultaneously reduce urinary calcium (risk of forming kidney stones) and reduce bone resorption (risk of osteoporosis due to old bone loss).
In conclusion
Calcium is good for your body. Consume calcium-rich foods like milk to prevent osteoporosis. If necessary, supplement your diet with calcium and vitamin D to increase new bone production, and take phytate supplements to reduce old bone loss. Remember that by consuming phytate, you will not only be preventing osteoporosis but also the possible formation of kidney stones.
References
Candelas, G., Martínez-López, J. A., Rosario, M. P., Carmona, L., & Loza, E. (2012). Calcium supplementation and kidney stone risk in osteoporosis: a systematic literature review. Clinical and Experimental Rheumatology.
Guimerà, J., Martínez, A., Bauza, J. L., Sanchís, P., Pieras, E., & Grases, F. (2022). Effect of phytate on hypercalciuria secondary to bone resorption in patients with urinary stones: pilot study. Urolithiasis.
López-González, Á. A., Grases, F., Marí, B., Vicente-Herrero, M. T., Costa-Bauzà, A., & Monroy, N. (2011). The influence of consumption of phytate on the bone mass in posmenopausal women of Mallorca. Reumatología Clínica.
López-González, A. A., Grases, F., Roca, P., Mari, B., Vicente-Herrero, M. T., & Costa-Bauzá, A. (2008). Phytate (myo-inositol hexaphosphate) and risk factors for osteoporosis. Journal of Medicinal Food.
Sanchis, P., López-González, Á. A., Costa-Bauzà, A., Busquets-Cortés, C., Riutord, P., Calvo, P., & Grases, F. (2021). Understanding the Protective Effect of Phytate in Bone Decalcification Related-Diseases. Nutrients.
