From the Guidelines
Calcium-rich foods are essential for maintaining strong bones, teeth, and proper muscle and nerve function, and the best sources include dairy products, leafy greens, and calcium-fortified foods, with a recommended daily intake of 1000-1200mg for most adults. The most recent and highest quality study, 1, suggests that dairy products are the main dietary sources of calcium, but it is also found in green leafy vegetables, nuts, and soya beans. Other good sources of calcium include:
- Calcium-fortified foods (plant milks, orange juice, cereals)
- Canned fish with bones (sardines, salmon)
- Tofu made with calcium sulfate
- Almonds and seeds like chia and sesame For optimal calcium absorption, it is recommended to pair these foods with vitamin D sources like fatty fish, egg yolks, or sunlight exposure, as vitamin D helps the body utilize calcium effectively 1.
The recommended dietary allowance (RDA) for calcium is 1000 mg/day for adults, and 1300 mg/day for adolescents, with an upper intake level of 2000-2500 mg per day 1. However, the most recent study, 1, suggests that athletes may require a higher intake of 1500 mg/day to optimize bone health. It is also important to note that excessive calcium intake can increase the risk of nephrolithiasis and potentially cardiovascular risk, although the findings are inconsistent and inconclusive 1.
To achieve the recommended daily intake of calcium, it is suggested to spread calcium intake throughout the day, as the body can only absorb about 500mg at once, and to limit caffeine, alcohol, and excessive salt, which can help maintain calcium levels in the body 1. Additionally, calcium supplements, such as calcium carbonate and calcium citrate, can be considered when dietary intake is inadequate, but should be used with caution due to potential side effects and interactions 1.
From the Research
Calcium-Rich Foods
- Dairy foods, such as milk, are the major source of calcium in the U.S. and provide substantial amounts of other essential nutrients 2
- Other foods rich in calcium include green leafy vegetables, legumes, and cereals, although they generally contain lower amounts of calcium per serving than dairy foods 2
- Calcium-fortified foods and beverages can also provide a significant amount of calcium 2
Bioavailability of Calcium
- The bioavailability of calcium can be affected by factors such as phytates in cereals and oxalates in spinach, which can reduce calcium absorption 2
- Calcium citrate and calcium carbonate are two common forms of calcium supplements, with calcium citrate being more easily absorbed in some cases 3, 4, 5
- A study found that a single serving of calcium carbonate powder resulted in greater absorption of total and ionized calcium compared to a single serving of calcium citrate tablets 4
Health Benefits of Calcium
- Calcium is essential for maintaining strong bones and preventing osteoporosis, with supplementation being beneficial for individuals at risk of fracture or with insufficient dietary intake 3, 6
- Calcium supplementation, particularly when combined with vitamin D, can help reduce the incidence of non-vertebral and hip fractures 3
- Other nutrients, such as vitamin K2 and magnesium, may also play a role in maintaining skeletal health, although more research is needed to confirm their efficacy 6