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Our assessment

The evidence shows that calcium is a critical mineral for bone health, but the data on supplementation requires careful consideration. For you, the key is balancing adequate intake with potential risks. The National Institutes of Health Office of Dietary Supplements (NIH ODS) confirms calcium supports bone mineralization and neuromuscular relaxation. However, some research suggests high calcium intakes might increase the risk of heart disease and prostate cancer [NIH ODS].

How it works

Think of calcium as a structural building block for your bones and a signaling molecule for your nerves and muscles. It supports bone density and mineral deposition, making your skeleton strong. It also helps your muscles relax and your nerves send signals properly [NIH ODS].

Safety profile

Safety data is critical here. The FDA has received a total of 592,059 adverse event reports across all supplements, though specific reports for calcium alone are not isolated in this data. The NIH ODS warns that high levels of calcium in the blood and urine can cause poor muscle tone, poor kidney function, low phosphate levels, constipation, nausea, weight loss, extreme tiredness, frequent need to urinate, abnormal heart rhythms, and a high risk of death from heart disease [NIH ODS] [FDA data]. Additionally, calcium can reduce the absorption of several medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS].

Our recommendation

Our recommendation: Only take calcium supplements if you cannot meet your needs through diet. If you do supplement, stick to the RDA (1,000 mg for most adults, 1,200 mg for women over 50 and men over 70). Avoid exceeding 2,000 mg per day from all sources, as the risks increase significantly above this level. Always take calcium with food and separate it from thyroid medication or antibiotics by at least 2 hours. The best approach is to get your calcium from food first—dairy, fortified plant milks, and leafy greens are excellent sources [NIH ODS].

Supplement labels contain several key sections regulated by the FDA:

• Serving Size — The recommended amount per dose. Always check this — some products require multiple capsules per serving.
• Amount Per Serving — Shows the quantity of each nutrient in the product, typically in IU (International Units), mg (milligrams), or mcg (micrograms).
• % Daily Value (%DV) — Indicates how much a nutrient in a serving contributes to a daily diet. 5% DV or less is low; 20% DV or more is high.
• Other Ingredients — Lists inactive ingredients like fillers, binders, and capsule materials (e.g., gelatin, cellulose, magnesium stearate).
• Suggested Use — The manufacturer's recommended directions for taking the supplement, including timing and dosage.

Source: FDA Dietary Supplement Labeling Guide