Are seniors who follow the ketogenic diet at risk of calcium deficiency?
Calcium is essential for the health of bones and teeth, blood vessels, muscles, and nerves. In addition to losing too much calcium in the urine, long-term keto dieters may have acidic urine. As a result of high-fat diets, the body produces more acid, which the kidneys filter away to keep the blood pH stable, resulting in lower urine pH.
Calcium from bones is also used to soften the increase in acid production, which increases calcium loss in the urine and decreases bone density due to the lack of calcium-rich foods, including fruits, vegetables, dairy, and enriched grains. Studies in rats found that diets high in fat and low in carbohydrates reduced calcium absorption because fat formed indigestible soap with calcium. Calcium-rich urine and an acidic urine environment are major risk factors for kidney stones.
Studies suggest that between 3 – 6% of people on a long-term ketogenic diet will develop stones within two years. You should schedule regular urinalysis with your doctor if you are doing the keto diet for an extended period or often. In urine tests, you can determine whether you’re at risk of kidney stones based on pH, calcium crystals, and uric acid crystals. If you follow a long-term ketogenic diet, your doctor may prescribe potassium citrate, which decreases your risk of stones by increasing pH and easing the loss of calcium in your urine.
Sardines, salmon, spinach, and turnip greens are keto-friendly calcium-rich foods. As blood calcium is tightly controlled within a narrow range, you may need to periodically check your bone mineral density (z-score, t-score) to find out if you’re losing calcium from your bones.