One of the most important roles of calcium, an essential mineral, is in forming bones and teeth. The recommended daily value, or DV, for this nutrient is 1,000 mg. According to AboutCalcium.net, its absorption depends upon many factors, including age. For example, calcium absorption may be as high as 60 percent in infants and children but only 15 to 20 percent in older adults. Certain nutrients, such as vitamin D, enhance calcium absorption while others, such as iron, compete with it. Thus, it is important to consume foods from which calcium is well-absorbed.
Dairy Products
According to an article published in the Journal of Nutrition in January 1996, the calcium naturally found in dairy products is the most well absorbed and used by the body. It has been suggested in this and past research articles that this may be due to fact that lactose, or milk sugar, enhances the calcium absorption. In addition, dairy foods, such as milk and yogurt, also often contain vitamin D, which enhances calcium absorption.
Examples of dairy products which are rich in calcium include skim milk, which, according to ELook.org, provides 306 mg per 8 fluid oz., or 30 percent of the recommended daily value or DV. The calcium content of yogurt varies widely but on average, a 6 oz. container of low-fat fruited yogurt provides 258 mg of calcium, or 25 percent of the DV. Certain varieties of cheese, such as hard Parmesan, are particularly calcium-rich. A 1 oz. serving provides 331.5 mg, or 33 percent of the DV.
Soy Products
The calcium content of tofu depends on the coagulating agent used in the tofu-making process. Tofu processed with calcium sulfate versus nigari or magnesium chloride is rich in well absorbed calcium according to the Vegetarian Resource Group. Look under "ingredients" on the nutrition facts panel to see which processing agent is used. A 4 oz. serving of tofu that is processed with calcium sulfate provides 200 to 330 mg per serving -- nearly as much as a cup of milk on the upper end. Calcium-fortified soy milk is another source of well absorbed calcium, particularly as it usually fortified with vitamin D. An 8 fluid oz. serving provides 200 to 300 mg per 8 fluid oz. serving. Cooked soybeans are a calcium-rich bean. One cup provides 175mg, or 17.5 percent of the DV.
Vegetables and Fortified Juice
According to VeganHealth.org, the calcium in certain green vegetables, such as collard greens, kale and broccoli, is absorbed relatively well. However, the calcium in other leafy greens, such as Swiss chard, spinach and beet greens is not well absorbed because these vegetables are rich in oxalic acid or oxalates; natural compounds found in certain plant foods. Thus, for maximum absorption, choose more of the former. A 1/2-cup serving of cooked kale provides 90mg of calcium and cooked collard greens, 133 mg, or 13.3 percent of the DV per 1/2-cups serving. Broccoli provides approximately 100 mg of calcium per 1-cup serving, cooked. The calcium in calcium-fortified orange juice is well absorbed and one cup provides the same amount of calcium as 6 fluid oz. of milk, 250 mg or 1/4 of your daily requirement.
References
- About Calcium: Calcium Absorption
- "Journal of Nutrition"; Calcium Bioavailability from Bovine Milk and Dairy Products in Premenopausal Women using Intrinsic and Extrinsic Labeling Techniques; KP Nickel et al.; 1996
- ELook: Nutrition Facts for Nonfat Milk
- ELook: Nutrition Facts for Yogurt, Fruit, Low-Fat
- ELook: Nutrition Facts for Cheese, Parmesan, hard
- Vegetarian Resource Group: Calcium in the Vegan Diet
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