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Calcium is an important mineral that aids in muscle movements, nerve transmissions and the maintenance of strong bones and teeth. Depleted calcium levels can lead to bone disorders and heart problems. Although milk and other dairy products are the most abundant sources of calcium, leafy greens such as spinach also contain high calcium content. However, the calcium bioavailability -- the amount of absorbable calcium -- in raw spinach is relatively poor.
Spinach: High Calcium, Low Availability
The average adult needs about 1,000 milligrams of calcium daily, according to the Office of Dietary Supplements 1. Raw spinach has low calcium bioavailability due to high amounts of oxalic acid, which binds with the calcium found in spinach, thus reducing its digestibility. Spinach does not deplete other dietary sources of calcium such as yogurt, cheese and milk 1. However, relying on spinach for calcium can lead to low levels of the mineral in the blood, which may cause bone development issues or an increased risk of osteoporosis. One cup of cooked spinach contains 245 milligrams of calcium, but the body can only absorb about 5 percent --12 milligrams -- while the body can absorb 30 percent of milk’s calcium content.
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Don't let spinach's low calcium bioavailability keep you from eating it. It's rich in fiber, protein, vitamins A, C, E, K, thiamine, riboflavin, folate and several minerals. In addition to one or two daily servings of high-calcium dairy foods, such as Greek yogurt and milk, cooked spinach, broccoli and other leafy green vegetables can add to your daily calcium intake.
- Don't let spinach's low calcium bioavailability keep you from eating it.
- In addition to one or two daily servings of high-calcium dairy foods, such as Greek yogurt and milk, cooked spinach, broccoli and other leafy green vegetables can add to your daily calcium intake.
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- Office of Dietary Supplements: Calcium
- USDA National Nutrient Database: Spinach, Raw
- USDA National Nutrient Database: Spinach, Cooked, Boiled, Drained, Without Salt
- Bolland, MJ, et. al. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health Initiative limited access dataset and meta-analysis. BMJ. 2011 Apr 19;342:d2040. DOI: 10.1136/bmj.d2040
- Reid IR. The roles of calcium and vitamin D in the prevention of osteoporosis. Endocrinol Metab Clin North Am. 27: 389-398. DOI:10.1016/s0889-8529(05)70011-6
- Chen M, Pan A, Malik VS, Hu FB. Effects of dairy intake on body weight and fat: a meta-analysis of randomized controlled trials. The American Journal of Clinical Nutrition. 2012;96(4):735-747. DOI:10.3945/ajcn.112.037119
- Williams V, Rawat A, Vignesh P, Shandilya JK, Gupta A, Singh S. Fc-gamma receptor expression profile in a North-Indian cohort of pediatric-onset systemic lupus erythematosus: An observational study. Int J Rheum Dis. 2019;22(3):449-457. doi: 10.6061/clinics/2012(07)22
- Reid IR, Birstow SM, Bolland MJ. Calcium and Cardiovascular Disease. Endocrinol Metab (Seoul). 2017;32(3):339-349. doi: 10.3803/EnM.2017.32.3.339
- MedlinePlus Medical Encyclopedia, "Milk-alkali syndrome"
- Bolland MJ, Grey A, Avenell A, Gamble GD, Reid IR. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women’s Health Initiative limited access dataset and meta-analysis. BMJ. d2040-d2040. DOI:10.1136/bmj.d2040
- Chan Soo Shin, et. al. Endocrinol Metab (Seoul). 30(1): 27–34. DOI: 10.3803/EnM.2015.30.1.27
- Linus Pauling Institute. Calcium.
- National Institute of Health Office of Dietary Supplements. Calcium.
- Weingarten MAMA, Zalmanovici Trestioreanu A, Yaphe J. Dietary calcium supplementation for preventing colorectal cancer and adenomatous polyps. Cochrane Database of Systematic Reviews 2008, Issue 1. Art. No.: CD003548. DOI: 10.1002/14651858.CD003548.pub4
- Zemel, MB et. al. Calcium and dairy acceleration of weight and fat loss during energy restriction in obese adults. Obes Res. 2004 Apr;12(4):582-90. DOI: 10.1038/oby.2004.67
Joseph Ng has a Bachelor of Science in Sport and Exercise Science and is an advanced level 3 accredited personal trainer. He also has a diploma in nutrition and health.