Calcium is well-known for building strong bones and teeth, but this essential mineral does much more. It plays a critical role in blood clotting, muscle function, nerve transmission, and maintaining a healthy heartbeat. While 99% of the body’s calcium is stored in bones, the remaining 1% is vital for these other functions and circulates in the blood and soft tissues. Ensuring you get enough calcium from What Food Has Calcium is crucial for overall health.
The body is remarkably efficient at maintaining calcium balance. When blood calcium levels dip too low, the parathyroid hormone (PTH) signals bones to release calcium. PTH also activates vitamin D to enhance calcium absorption in the intestines and signals the kidneys to conserve calcium. Conversely, when calcium levels are sufficient, calcitonin, another hormone, reduces blood calcium by halting calcium release from bones and increasing kidney excretion.
We obtain calcium in two primary ways: through consuming food that has calcium or calcium supplements, and by drawing upon the calcium reserves in our bones. If dietary intake is insufficient, the body will resort to taking calcium from bones. Ideally, this borrowed calcium is replenished later, but this isn’t always guaranteed and can’t always be fixed simply by increasing calcium intake later on.
top view wooden board with various cheese, nuts, broccoli, canned fish, and jug of milk
Recommended Daily Calcium Intake
The amount of calcium you need daily varies based on age and sex. Here are the Recommended Dietary Allowances (RDAs) for calcium:
- Women 19-50 years: 1,000 mg daily
- Women 51+ years: 1,200 mg daily
- Pregnant and lactating women: 1,000 mg daily
- Men 19-70 years: 1,000 mg daily
- Men 71+ years: 1,200 mg daily [1]
Calcium and Your Health: Beyond Strong Bones
Calcium’s impact extends far beyond bone health. Let’s explore its role in various aspects of health:
Calcium for Blood Pressure Regulation
Several studies have investigated the link between calcium intake and blood pressure. Some research suggests that adequate calcium, from both food sources with calcium and supplements, might contribute to lowering high blood pressure. However, due to limitations in study designs, current evidence isn’t strong enough to recommend increasing calcium intake beyond the RDA solely for treating hypertension. [2] More extensive research is needed to confirm if increasing calcium intake can effectively lower blood pressure.
Calcium and Cardiovascular Health: What to Know
There’s been some debate about calcium supplements and heart health. Some studies raised concerns about calcium supplements potentially increasing the risk of cardiovascular events. The theory is that high doses of supplements might lead to hypercalcemia (excess calcium in the blood), potentially causing blood clots or artery hardening. However, a comprehensive review by the National Osteoporosis Foundation and the American Society for Preventive Cardiology concluded that calcium from food that contains calcium or supplements has no proven harmful or beneficial relationship with cardiovascular disease in healthy adults. The key recommendation is to stay within the safe Upper Limit for calcium intake, which is 2,000-2,500 mg daily from all sources. [3]
Calcium’s Vital Role in Bone Health
Calcium is undeniably essential for bone health. Bones are dynamic, living tissue constantly undergoing remodeling – a process of breakdown and rebuilding. Osteoblasts build new bone, while osteoclasts break down old bone when calcium is needed elsewhere. In youth, bone formation outpaces breakdown, leading to peak bone mass around age 30. After that, bone breakdown gradually exceeds formation, potentially leading to bone loss. Adequate calcium intake throughout life, from calcium rich foods, can help slow down this bone loss, though it won’t entirely prevent it. [4] Calcium absorption also decreases with age, so simply increasing intake later in life might not fully compensate for bone loss.
Studies on calcium and bone density in postmenopausal women have yielded mixed results, possibly due to variations in study design, such as focusing only on supplements and not total calcium intake, or not accounting for hormone replacement therapy or vitamin D intake. However, some larger trials indicate that higher calcium intake (often through supplements) may improve bone density and slightly reduce hip fracture risk, especially in frail elderly individuals. [5, 6] Interestingly, a 2018 review found that calcium and vitamin D supplements didn’t reduce fracture risk in healthy postmenopausal women without osteoporosis or vitamin D deficiency. [7]
Calcium and Colorectal Cancer: Potential Protective Effects
Long-term observational studies suggest a protective role of high calcium intake against colorectal cancer. [8] However, clinical trials using calcium supplements have shown inconsistent results, possibly due to their relatively short duration compared to the slow development of colorectal cancer.
- A review of two trials found that 1,200 mg of daily calcium reduced new colorectal adenomas (precancerous tumors) by 26% over 4 years. [9]
- However, a large trial in postmenopausal women found no difference in colorectal cancer incidence between those taking calcium and vitamin D supplements and those taking a placebo over 7-11 years. [8, 10] It’s worth noting that the women in this study already had high calcium intake, so supplements might not have made a significant difference.
Despite mixed trial results, the World Cancer Research Fund and the American Institute for Cancer Research concluded that there is strong evidence that calcium supplements (over 200mg daily) and high-calcium dairy foods likely reduce colorectal cancer risk. [11] This could be due to calcium binding to toxic substances in the colon and inhibiting tumor cell growth. Certain bacteria in dairy foods might also offer protection. [12]
Calcium and Kidney Stones: Debunking a Myth
Contrary to older advice, limiting calcium intake is now known to increase the risk of kidney stones. Studies like the Women’s Health Initiative and the Nurses’ Health Study found that higher intake of foods with calcium actually decreased kidney stone risk in women. However, calcium supplements, in pill form, were found to increase risk. [13, 14] Dairy foods high in calcium seem particularly protective against kidney stones. Skim milk and cottage cheese have shown the greatest benefit. It’s believed that calcium-rich foods reduce stone formation by decreasing oxalate absorption (oxalates are a component of calcium-oxalate stones). Other components in dairy might also contribute to this protective effect. [15]
What Food Has Calcium? Discovering Calcium-Rich Sources
Calcium is abundant in various foods beyond just dairy. Fruits, leafy green vegetables, beans, nuts, and some starchy vegetables are also valuable sources. To effectively increase your calcium intake, focus on incorporating a variety of these foods that are high in calcium into your daily diet.
Dairy Products: Classic Calcium Sources
Dairy products like milk, cheese, and yogurt are well-known for their high calcium content. They are also a good source of protein and vitamin D, which aids calcium absorption.
- Milk: One cup of milk provides around 300mg of calcium.
- Cheese: The calcium content varies by type, but hard cheeses like cheddar and parmesan are particularly rich in calcium.
- Yogurt: Plain yogurt is a good source of calcium, and Greek yogurt also contributes significantly.
Leafy Green Vegetables: Plant-Based Calcium Powerhouses
Certain leafy greens are surprisingly good sources of calcium.
- Collard greens: Cooked collard greens are an excellent plant-based source of calcium.
- Kale: Kale offers a decent amount of calcium per serving.
- Bok choy: As mentioned earlier, bok choy has a high bioavailability of calcium.
While spinach has a high calcium content, its bioavailability is low due to oxalates. Therefore, it’s best to rely on other leafy greens for calcium.
Nuts and Seeds: Calcium in Small Packages
Nuts and seeds can contribute to your daily calcium intake.
- Almonds: Almonds are a good source of calcium and healthy fats.
- Chia seeds: Chia seeds offer a small amount of calcium along with fiber and omega-3 fatty acids.
- Sesame seeds: Sesame seeds and tahini (sesame seed paste) contain calcium.
Fortified Foods: Boosting Calcium Intake
Many foods are fortified with calcium, making them convenient sources.
- Fortified plant-based milks: Almond milk, soy milk, and oat milk are often fortified with calcium to match the levels in cow’s milk.
- Fortified orange juice: Some brands of orange juice are fortified with calcium and vitamin D.
- Fortified cereals: Certain breakfast cereals are fortified with calcium and other vitamins and minerals.
- Calcium-set tofu: Tofu set with calcium sulfate is a good source of calcium.
Other Food Sources of Calcium
- Canned fish with bones: Sardines and canned salmon with edible bones are excellent sources of calcium.
- Beans and lentils: These legumes provide some calcium along with fiber and protein.
- Broccoli: Broccoli, like other cruciferous vegetables, offers a modest amount of calcium.
Understanding Calcium Bioavailability
It’s important to consider calcium bioavailability, which is the proportion of calcium in food that the body actually absorbs and utilizes. Dairy products have about 30% calcium bioavailability. Certain plant foods, like bok choy, have higher bioavailability (around 50%) even if they contain less total calcium than dairy. Factors like oxalates and phytates in some plant foods can reduce calcium bioavailability. For example, spinach, despite its high calcium content, has low bioavailability due to oxalates.
To maximize calcium absorption:
- Consume a variety of calcium-rich foods: This helps to offset any bioavailability limitations from specific foods.
- Space out calcium intake: Taking smaller doses of calcium throughout the day is more effective than consuming a large amount at once, especially from supplements.
- Consider food combinations: Avoid consuming calcium-rich foods with large amounts of foods high in oxalates or phytates in the same meal.
Calcium Deficiency and Toxicity: Recognizing Imbalances
Calcium Deficiency (Hypocalcemia)
Short-term calcium deficiency is usually asymptomatic because the body draws calcium from bones to maintain blood calcium levels. However, prolonged insufficient calcium intake can lead to more serious issues. Hypocalcemia, a severe calcium deficiency, is often caused by underlying medical conditions or medications rather than simply low dietary intake.
Symptoms of hypocalcemia may include:
- Muscle cramps or weakness
- Numbness or tingling in fingers
- Abnormal heart rate
- Poor appetite
Long-term calcium deficiency can contribute to osteopenia (early bone loss) and osteoporosis. Individuals at higher risk of deficiency include postmenopausal women, women with amenorrhea, and those with milk allergy or lactose intolerance.
Calcium Toxicity (Hypercalcemia)
Excessive calcium in the blood, or hypercalcemia, is usually caused by high-dose calcium supplements, certain medical conditions, or medications. The Upper Limit for calcium intake is 2,500 mg daily (2,000 mg for those over 50). Exceeding this limit, especially from supplements, can increase the risk of kidney stones, prostate cancer, constipation, and potentially cardiovascular issues in susceptible individuals.
Symptoms of hypercalcemia can include:
- Weakness, fatigue
- Nausea, vomiting
- Shortness of breath
- Chest pain
- Heart palpitations, irregular heart rate
Factors Affecting Calcium Needs
Certain factors can influence your calcium needs or absorption:
- Corticosteroids (e.g., prednisone): These medications can decrease calcium absorption and increase excretion.
- Excess sodium: High sodium intake can increase calcium excretion.
- Phosphoric acid (in dark cola sodas): Excessive intake may affect calcium balance.
- Excess alcohol: Can interfere with calcium absorption and bone health.
- Oxalates and Phytates: These “anti-nutrients” in some plant foods can reduce calcium bioavailability.
Conclusion: Prioritizing Calcium-Rich Foods for Optimal Health
Calcium is an indispensable mineral for numerous bodily functions, not just bone health. Ensuring adequate calcium intake through a diverse diet rich in food sources of calcium is crucial for maintaining overall well-being. By understanding what food has calcium and incorporating these foods into your daily meals, you can support strong bones, healthy muscles and nerves, and contribute to long-term health. Focus on a balanced approach, prioritizing calcium-rich foods and consulting with healthcare professionals for personalized dietary advice, especially if you have specific health concerns or are considering calcium supplements.
References
[1] National Institutes of Health. Calcium Fact Sheet for Consumers. https://ods.od.nih.gov/factsheets/Calcium-Consumer/
[2] Dickinson HO, Nicolson DJ, Campbell F, Beyer FR, Mason J. Calcium supplementation for the management of primary hypertension in adults. Cochrane Database Syst Rev. 2006;(3):CD004639.
[3] Kopecky SL, Bauer DC, Gulati M, et al. Lack of evidence linking calcium with or without vitamin D supplementation to cardiovascular disease in generally healthy adults: a clinical guideline from the National Osteoporosis Foundation and the American Society for Preventive Cardiology. Ann Intern Med. 2016;165(12):867-868.
[4] NIH Consensus Development Panel on Osteoporosis Prevention, Diagnosis, and Therapy. Osteoporosis prevention, diagnosis, and therapy. JAMA. 2001;285(6):785-795.
[5] Dawson-Hughes B, Harris SS, Krall EA, Dallal GE, Falconer G, Green CL. Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older. N Engl J Med. 1997;337(10):670-676.
[6] Chapuy MC, Pamphile R, Vergnaud P, et al. Vitamin D3 and calcium to prevent hip fractures in elderly women. N Engl J Med. 1992;327(23):1637-1642.
[7] U.S. Preventive Services Task Force. Vitamin D and Calcium Supplementation to Prevent Fractures: U.S. Preventive Services Task Force Recommendation Statement. JAMA. 2018;319(15):1592-1599.
[8] কমিটির T, Baron JA, Sandler RS, et al. Calcium and vitamin D supplementation and risk of colorectal cancer. N Engl J Med. 2006;354(7):684-696.
[9] Benamouzig R, De Léotoing L, Maillard I, et al. Calcium and prevention of colorectal adenomas: a systematic review and meta-analysis. Gut. 2003;52(1):1-7.
[10] কমিটির T, Cauley JA, LeBoff MS, et al. Calcium and vitamin D supplementation and colorectal cancer incidence and mortality: 11-year follow-up of the women’s health initiative randomized trial. Cancer Epidemiol Biomarkers Prev. 2011;20(7):1309-1314.
[11] World Cancer Research Fund/American Institute for Cancer Research. Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. Washington DC: AICR, 2007.
[12] Larsson SC, Bergkvist L, Wolk A. Milk and dairy products consumption and risk of colorectal cancer: a meta-analysis of prospective studies. Am J Clin Nutr. 2004;80(1):165-173.
[13] Curhan GC, Willett WC, Rimm EB, Stampfer MJ. A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones. N Engl J Med. 1993;328(12):833-838.
[14] Jackson RD, LaCroix AZ, Gass M, et al. Calcium plus vitamin D supplementation and the risk of fractures. N Engl J Med. 2006;354(7):669-683.
[15] Curhan GC, Willett WC, Speizer FE, Stampfer MJ. Comparison of dietary calcium with supplemental calcium and other nutrients as factors affecting the risk of kidney stones in women. Ann Intern Med. 1997;126(7):497-504.
Last reviewed March 2023
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