The human body contains approximately 1.5% of its weight in calcium, with 99% stored in the bones and teeth in the form of calcium phosphate salts. The remaining calcium is found inside cells, in extracellular fluids, and in plasma. Bones undergo continuous remodeling, with calcium constantly being deposited and withdrawn to maintain skeletal integrity. Bone formation occurs only when there is an adequate supply of calcium and phosphate in the plasma. Whenever calcium levels in the plasma drop, the body compensates by releasing calcium from the bones into the plasma.
From childhood to early adulthood—around the age of 30—our body reaches its peak bone mass, meaning our bones are at their strongest. However, from the age of 35 onwards, calcium loss from bones starts to outpace calcium absorption, gradually leading to bone thinning as we age. If the body does not receive sufficient calcium, the risk of developing osteoporosis increases, especially in women after menopause and in older adults.
Besides its crucial role in bone health, calcium plays a vital role in various cellular processes. It is essential for neurotransmitter release, which enables communication between nerve cells, as well as muscle contraction, blood clotting, electrical conduction in the heart, and even weight regulation.
Calcium Loss: Factors That Affect Bone Health
Although osteoporosis risk factors include genetics, body structure, and underlying health conditions, which are beyond our control, there are still ways to reduce the risk through lifestyle choices. One of the most effective strategies is maintaining a bone–healthy diet. However, certain foods and substances can inhibit calcium absorption, such as:
- Foods high in phytic acid – Found in unprocessed rice bran, phytic acid binds to essential minerals, including calcium, forming insoluble phytates that prevent absorption and are excreted from the body.
- Foods rich in oxalic acid – Vegetables like spinach, soybeans, and cocoa contain high levels of oxalates, which reduce calcium absorption. However, they do not significantly affect calcium from other sources consumed in the same meal.
- Unesterified Long-Chain Saturated Fatty Acids – Palmitic acid, which has a melting point higher than body temperature, can bind with calcium in the intestines, forming insoluble calcium soaps that the body cannot absorb.
- Excessive Soft Drink Consumption – Phosphoric acid in carbonated drinks can disrupt the body’s calcium balance. Since most diets already provide enough phosphorus, consuming too much phosphoric acid increases the body’s demand for calcium and magnesium, potentially leading to bone demineralization.
- High-Sodium Foods – Excess sodium intake increases calcium excretion through urine, which can contribute to bone loss over time.
- Tea and Tannins – Tannins in tea can bind to calcium in the intestines, reducing its absorption.
- Certain Medications – Long-term use of corticosteroids (used for conditions such as asthma, rheumatoid arthritis, and psoriasis) and antiepileptic drugs can negatively impact bone health. These medications should be taken under medical supervision to minimize the risk of bone loss and osteoporosis.
How to Prevent Calcium Loss
- Consume Calcium-Rich Foods – Include milk, soy milk, small fish that can be eaten whole, and leafy greens such as noni leaves, piper leaves, and alfalfa (a legume rich in calcium and phytonutrients). These foods contain beneficial compounds like isoflavones, coumestans, and lignans, which support bone metabolism and may be particularly beneficial for postmenopausal women.
- Supplement vitamin D to help the calcium obtained from food be absorbed into the cells and stored in the bones more effectively. Food sources rich in vitamin D include milk, salmon, and tuna.
- In addition, older adults may need more vitamin D, especially those who stay indoors and do not go outside to get sunlight, as their skin may not be able to synthesize vitamin D efficiently.
- Engage in weight-bearing exercises to increase bone mass, such as weightlifting, running, jumping rope, and brisk walking. These exercises help increase bone density and are also a good way to build muscle, allowing older adults to walk or balance better and reduce the risk of falls.
Consuming an adequate amount of calcium-rich foods can help prevent or reduce the risk of certain health conditions. However, for maximum effectiveness, it’s important to start early—ideally before entering adulthood—and to maintain consistent intake throughout life.
