According to the Linus Pauling Institute at Oregon State University, to get the same level of calcium as in one 8-ounce glass of milk (300 mg calcium) you would need:
•Pinto beans: 8 servings, or 4 cooked cups.
•White beans: 4 servings, or 2 cooked cups.
•Kale: 3 servings, or 1 1/2 cooked cups.
•Broccoli: 4.5 servings, or 2 1/2 cooked cups
•Spinach: 16.5 servings, or 8 1/4 cooked cups
•Bok choy: 2.3 servings, or 1 1/4 cooked cups
•Rhubarb: 9.5 servings, or 4 3/4 cooked cupsSodium: Sodium intake increases urinary excretion of calcium in addition to increasing risk of high blood pressure. According to research reported in the American Journal of Clinical Nutrition (http://tinyurl.com/psofzmk): “Urinary calcium losses account for 50 percent of the variability in calcium retention. Of the nutritional factors thought to influence urinary calcium losses (protein, caffeine, and sodium intake), sodium appears to be the most important.”
Protein: High protein intake increases calcium excretion, but recent research suggests that it also increases intestinal calcium absorption, so it's a wash, says Deb Askine, R.D., L.D.N., a nutritionist at Stella Maris of Mercy Medical Center in Baltimore.
Caffeine: According to the National Institutes of Health, Office of Dietary Supplements: “This stimulant in coffee and tea can modestly increase calcium excretion and reduce absorption. One cup of regular brewed coffee, for example, causes a loss of only 2-3 mg of calcium. Moderate caffeine consumption (1 cup of coffee or 2 cups of tea per day) in young women has no negative effects on bone.”
Alcohol: According to the National Institutes of Health, Office of Dietary Supplements: “Alcohol intake can affect calcium status by reducing its absorption and by inhibiting enzymes in the liver that help convert vitamin D to its active form. However, the amount of alcohol required to affect calcium status … is unknown.”
Fruit and vegetables: According to the National Institutes of Health, Office of Dietary Supplements: “Metabolic acids produced by diets high in protein and cereal grains increase calcium excretion. Fruits and vegetables, when metabolized, shift the acid/base balance of the body towards the alkaline by producing bicarbonate, which reduces calcium excretion. However, it is unclear if consuming more fruits and vegetables affects bone mineral density.”
Tannins: These acidic compounds in tea and red wine inhibit the absorption of calcium, says Solomon.According to Mount Sinai's Solomon: “Glucocorticoids (such as prednisone) and lithium have both been shown to cause bone loss or osteopenia. Chronic anticonvulsant drug use can lower bone mineral density, as can medroxyprogesterone, heparin, and thyroxine.”
Both aluminum- and magnesium-containing antacids increase urinary calcium excretion. Mineral oil and stimulant laxatives decrease calcium absorption as well, says Askine.The Recommended Dietary Allowances for vitamin D are 600 IU for those 19-70 years old and 800 IU's for 71 years old or more. According to the National Institutes of Health, Office of Dietary Supplements: “Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and to prevent hypocalcemic tetany (muscular spasms caused by low calcium in blood). It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts.”
“Vitamin D-rich foods include: egg yolks, saltwater fish, and liver. We also synthesize vitamin D when our bodies are exposed to sunlight,” says Solomon.