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THE DIET DETECTIVE, A COLUMN BY CHARLES STUART PLATKIN

Catch up on calcium

It keeps bones strong and blood pressure low

Saturday, March 15, 2014 - 9:15 am

Why do you need calcium?

Calcium is famous for helping to build and maintain strong bones, but it also plays a role in blood clotting, blood pressure, and muscle and nerve functioning. Calcium accounts for 1 to 2 percent of adult human body weight. More than 99 percent of total body calcium is found in the teeth and bones.

What happens if you don’t get enough?

It can result in bone deformities, muscle cramps, high blood pressure and osteoporosis, a disease characterized by fragile bones. The body will take calcium from bone to maintain the required level in the blood. It is estimated that more than 25 million adults in the United States have or are at risk of developing osteoporosis.

How much do you need?

1,000 mg for men and women ages 19-50; 1,000 mg for men and 1,200 for women ages 51- 70. Above 71, 1,200 mg for men and women

What’s the problem with dairy and calcium?

While dairy is an excellent source of calcium and protein, it can also be a source of excess calories and fat, primarily saturated fat. Even low-fat cheese should be considered a splurge food. According to the nonprofit Center for Science in the Public Interest, 1 cup of whole milk (cheese is made from milk) has 5 grams of artery-clogging saturated fat, the same amount found in one hot dog, five strips of bacon, a Snickers bar or a hamburger, and as many calories as a can of soda. Finally, a recent article in Nature Medicine (see: http://tinyurl.com/q69avb7) has found a link between l-carnitine, a nutrient found in red meat and milk products, and an increased risk of heart disease.

What about non-dairy sources of calcium?

According to Rebecca Solomon, M.S., R.D., clinical nutrition coordinator at Mount Sinai Hospital in New York City: “Generally, calcium from animal sources (such as dairy) is best absorbed, whereas that from foods high in oxalic acid (such as spinach, sweet potatoes, rhubarb, walnuts, celery, okra and beans) or phytic acid — a phosphorus compound found in unleavened bread, raw beans, seeds and nuts — is typically not well absorbed.” Oxalic acid binds calcium and makes it unavailable for absorption in the body.

According to a briefing paper from the British Nutrition Foundation, “The bioavailability of calcium from milk and milk products is in the region of 30 percent compared to 5 percent from spinach.” Soybeans and products are a notable exception. They have oxalates and phytates, yet provide a bioavailable source of calcium.

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 cups

What else affects calcium absorption?

Sodium: 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.

What are some common drugs that cause calcium loss?

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.

What about vitamin D and calcium?

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.

Charles Stuart Platkin is a nutrition and public health advocate and founder of DietDetective.com.