Nowadays, more and more Chinese people are focusing on calcium supplementation, a trend often called "nationwide calcium supplementation." In daily life, people not only eat calcium-rich foods but also take calcium supplements. However, some worry: could such high calcium intake increase the risk of developing stones? Experts have answered: there is a risk, and caution is needed, but as long as calcium is supplemented scientifically, this danger can be avoided.
Excessive Calcium Intake May Increase Risk of Kidney Stones
Calcium, often called the "element of life," plays vital physiological roles throughout all stages of human growth and development. It is an essential element for ensuring health and longevity. While calcium supplementation is necessary throughout one's lifetime, moderation is key.
China's Dietary Reference Intakes (DRI) specify that the tolerable upper intake level (UL) for adults is 2000mg daily—not the recommended standard intake. Generally, the recommended daily intake for adults is 800mg, with at least 500mg coming from dietary sources. The closer calcium intake approaches the UL, the greater the risk to health.
Excessive calcium intake may interfere with the absorption and utilization of other trace elements in the body and may also lead to various types of stone diseases. Experts point out that calcium is not easily absorbed by the human body. Particularly when calcium combines with foods containing oxalic acid, a chemical reaction occurs, forming calcium oxalate stones. Once stones form, they can deposit and cause damage within the body.
Calcium Supplements Increase Stone Risk
Additionally, the principle "dietary supplementation is preferable to medicinal supplementation" applies to calcium intake. Studies indicate that taking calcium supplements may elevate kidney stone risk by 20%, whereas calcium from natural foods reduces this risk by approximately one-third.
This is because calcium from natural foods binds with oxalate in the diet, reducing its absorption and thereby preventing kidney stones—an effect not achieved by supplements. Fundamentally, lower oxalate intake lowers kidney stone risk. Thus, supplementing calcium while avoiding excessive oxalate intake mitigates this risk.
How to Supplement Calcium Scientifically and Effectively?
(1) Ensure adequate vitamin D intake. Vitamin D is essential for calcium transport within the body. Through a series of complex conversions, vitamin D regulates calcium and phosphorus metabolism, thereby promoting bone formation. Foods rich in vitamin D include cod liver oil, animal liver, eggs, and meat. Additionally, encourage children to engage in outdoor activities and get sunlight exposure to promote vitamin D synthesis in the body.
(2) Maintain calcium-phosphorus balance. Calcium and phosphorus are closely linked, but excessive phosphorus intake can impair calcium absorption. Aim for a calcium-to-phosphorus ratio of 1:1.2 to 1:1.5. Focus particularly on calcium supplementation, as phosphorus is widely present in natural foods.
(3)The daily diet of Chinese residents is primarily plant-based, containing higher levels of oxalic acid, phytic acid, and fiber. These substances bind with calcium to form insoluble compounds, thereby impairing calcium absorption. To minimize this binding, blanch leafy greens high in oxalic acid in boiling water first. This process dissolves oxalic acid, phytic acid, and similar compounds into the water, reducing their concentration in the food.
(4) Excessive dietary fat intake causes fats to bind with calcium, forming calcium soap through a process called saponification. This substance is excreted in feces, leading to calcium loss. Therefore, high-fat foods should be limited in daily diets.
(5) Calcium is insoluble in alkaline environments, reducing its absorption and utilization rate. Conversely, acidic environments keep calcium dissolved, facilitating absorption. Vitamin C and citric acid lower intestinal pH, promoting calcium absorption in the gut.