The Essential Role of Calcium and Phosphorus
“Let’s first remember that calcium is the star mineral for strong bones, as it ensures our bones’ mechanical resistance and participates in the continual renewal of bone tissue,” says Raphaël Gruman.
Nearly 98% of the body’s calcium reserves are stored in our bones. Every day, the body takes a small amount for other vital processes—muscle contraction, blood clotting, nerve transmission—and it needs to be replenished through our diet.
Phosphorus joins forces with calcium to form hydroxyapatite crystals, which give bones their structure and strength. But for everything to run smoothly, the calcium-to-phosphorus ratio should ideally stay near 1:1.
Too much phosphorus in the diet leads the body to pull calcium out of bones to compensate, weakening the skeleton. Maintaining a balanced intake of calcium (from dairy, mineral waters, and plant foods) and phosphorus (in meat, fish, eggs) is essential for a solid bone structure and a stable metabolism.
The Surprising Foods That May Undermine Your Bones
- Salt: When consumed in excess, salt increases the rate at which calcium is excreted in urine, reducing the amount available in the body.
“Without going overboard with a strict low-sodium diet, it’s important to limit processed dishes, deli meats, cheeses, and go easy on table salt,” our expert suggests.
- Alcohol: Alcohol is also involved in bone demineralization. When consumed in excess, it interferes with the formation of osteoblasts (the bone-building cells) and worsens bone loss.
- Caffeine: Too much caffeine can boost the loss of calcium via urine. It’s recommended not to exceed three cups of coffee per day.
- Phytates and Oxalates: These so-called “antinutritional factors” can bind to dietary calcium, interfering with its absorption. Phytates are found in whole grains, legumes, seeds and nuts, while oxalates are present in spinach, rhubarb, beets, cocoa, black tea, and almonds.
Should You Ditch Whole Grains and Veggies?
Here’s a plot twist: those same whole grains and veggies loaded with phytates and oxalates also deliver valuable fiber, vitamins, minerals, and antioxidants. It would be a shame to miss out.
“These foods shouldn’t be banned, but eaten as part of a varied diet, making sure they don’t become your main source of fiber or vegetables,” the nutritionist continues.
One practical tip is to avoid eating calcium-rich foods at the same time as foods high in oxalates or phytates, to limit their impact on calcium absorption. Sometimes, who you invite to the dinner table makes all the difference.
The Best Sources of Calcium—and How to Make It Count
Dairy—milk, cheese, yogurt—remains a prime and easily absorbed source of calcium, making it a powerful ally against osteoporosis, provided it’s part of a balanced diet, and especially paired with enough vitamin D.
“Dairy calcium is highly bioavailable (about 30–35% absorbed), but remember that calcium can’t attach to bones without vitamin D. That’s why a vitamin D supplement during the winter, when sunlight is scarce, is important for everyone,” insists Raphaël Gruman.
Some groups, like children, seniors, and post-menopausal women, who have higher calcium needs or a greater risk of deficiency, benefit from year-round vitamin D supplementation.
“It may also be smart to choose milk and dairy products fortified with vitamin D, which are easier to find these days,” adds our expert.
Several mineral waters are especially rich in calcium and can be a helpful alternative for those who struggle to meet their needs through food alone. Water is considered “calcium-rich” if it contains more than 150 mg of calcium per liter. Examples include the French brands Hépar (550 mg/L), Contrex (460 mg/L), Courmayeur (570 mg/L), Talians (290 mg/L), and Vittel (240 mg/L).
“Calcium absorption from mineral water is roughly the same as from dairy, especially if the water contains bicarbonates (i.e., sparkling water). However, high-calcium still (non-sparkling) waters actually have more than twice the calcium of sparkling ones, making them at least as beneficial,” specifies Gruman.
In practice, drinking half a liter (about 17 fluid ounces) per day of one of these waters will meet around 25–30% of an adult’s daily needs.
“These calcium-rich waters are especially beneficial for people who are lactose-intolerant or vegan and consume little or no dairy,” the nutritionist points out.
Don’t Forget Movement: Bones Love a Workout
Remember, bone is living tissue—it regenerates and grows stronger under mechanical strain. Every impact and every bit of muscle strain prompts bone cells (osteoblasts) to produce ossein, helping to fortify our skeleton. Moderate-impact activities like brisk walking, dancing, hiking, stair climbing, and energetic group fitness classes are even more beneficial to bone density than low-impact activities like swimming or cycling, which stimulate osteoblasts less. In other words: keep moving, your bones will thank you!
