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Do I need to eat dairy products in order to prevent osteoporosis?

Introduction

Osteoporosis, a condition in which minerals and other substances are lost from the bones causing them to become thinner, more porous, and more easily broken, affects about 20-25 million Americans, primarily older women. While many people believe that consuming dairy products is a required nutritional strategy for preventing osteoporosis, the truth is that this is not necessarily true. There are many plant foods that not only contain calcium but other valuable bone-health promoting nutrients that can play a valuable role in a diet aimed at preventing osteoporosis.

The role of calcium in osteoporosis

Inadequate calcium intake definitely increases risk of osteoporosis. Too little calcium causes the parathyroid hormone to stimulate certain bone cells, called osteoclasts, into breaking down bone in order to raise calcium levels in the blood.

Just as calcium deficiency increases risk of osteoporosis, calcium supplementation has been shown to help prevent it by increasing bone density. For example, studies have shown that supplementing with calcium increases bone density in perimenopausal women and slows bone degeneration in postmenopausal women by an average of 30-50%. These effects translate into a significant reduction in hip fractures.

Because a glass of cow’s milk contains about 300 milligrams of calcium, (and the Adequate Intake level for a middle-aged adult is 1,000 milligrams), cow’s milk has traditionally been marketed as a high-calcium, osteoporosis-preventing food. However, calcium is not the only nutrient involved with osteoporosis risk. Many nutrients are involved in the determination of a person’s risk of osteoporosis.

The relationship between protein intake and osteoporosis

Excess protein intake, for example, increases a person’s risk of osteoporosis. The reasons for this center around protein’s impact on the body’s acidity. Bones work their best in a slightly alkaline body, but high protein diets require the body to release more acids as a means of helping to digest the protein. When these acids are released, and the body becomes more acidic, the body then responds and tries to buffer this acidity by withdrawing alkaline minerals like calcium from the bones. In clinical research studies, raising daily protein intake from 47 to 142 grams doubles the excretion of calcium in the urine.

A glass of cow’s milk contains about 8 grams of protein. Three glasses of cow’s milk, which would provide very close to a day’s worth of calcium, would also provide 24 grams of protein. By itself, this amount would not be enough to cause problematic amounts of calcium to be removed from bone. However, in combination with other protein sources, for example, an 8-ounce chicken breast, which would contain about 56 grams of protein, and a quarter-pound hamburger, which would add another 28 grams, the day’s total would be about 108 grams - much closer to the amount in the research study that doubled calcium excretion in the urine and increased risk of osteoporosis.

The relationship between magnesium intake and osteoporosis

Another example of a nutrient that plays a role in osteoporosis is magnesium, a mineral that appears to be nearly as important as calcium in preventing problems associated with this condition. Women with osteoporosis have low bone magnesium content and other signs of magnesium deficiency, and a two-year study of magnesium supplementation in postmenopausal women has found that those receiving magnesium had a slight improvement in bone density while those receiving the placebo lost some of their bone density.

Inadequate consumption of magnesium has also been shown to decrease blood concentrations of the most active form of vitamin D (called D3). In clinical research studies, vitamin D3 has been shown to stimulate the absorption of calcium, increase bone mineral density, and reduce the risk of hip fracture. Magnesium is also required to regulate the body's levels of parathyroid hormone and calcitonin, two hormones that maintain the proper concentration of calcium in the blood.

Yet, cow’s milk, which is a very good source of calcium, is not a very good source of magnesium. One cup of cow’s milk only provides about 33 milligrams, or about 10% of the daily requirement for a middle-aged woman.

Other nutrients important for bone health

We could add a long list of nutrients to calcium, protein, and magnesium that influence the risk of osteoporosis. Other bone-health promoting nutrients include vitamin D, boron, vitamin K, vitamin C, ipriflavone, silicon, and vitamins B6, B12, and folate. Not only is cow’s milk less than ideal as food source of these nutrients, but in some cases (like vitamin C) it is nearly devoid of the nutrient altogether.

Could you get enough of all nutrients - including calcium - without consuming cow’s milk, or cow’s milk yogurt, or cow’s milk cheese? The answer is definitely “yes.” In fact, most women in the world as a whole who do not develop osteoporosis also do not consume dairy products. The foods they eat, including the World’s Healthiest Foods, are concentrated in calcium and other of the bone-health promoting nutrients noted above. Just how could you get enough calcium without consuming dairy products? Consider the example below involving a dairy-free salad.

Plant foods as sources of calcium

As previously described, calcium is a mineral found in a wide variety of foods besides dairy products. Virtually all greens contain calcium. By “greens,” we mean all the dark green leafy vegetables like spinach, chard, mustard greens and collard greens, as well as lettuces, like romaine. Shredded cabbage is also a source of calcium.

Virtually all nuts and seeds - and especially sesame seeds - contain calcium. So do most beans, including navy, pinto, kidney, and black are all calcium-containing foods. Additionally, tofu can also be an important source of calcium, particularly when the tofu has been calcium-precipitated (meaning that calcium was used to help convert the soy milk into tofu) it can provide a significant amount of calcium.

Enjoy a delicious salad and support your bone health

Although none of the above non-dairy foods, all by itself, will provide a large percent of your total day’s calcium, when these foods are combined, the total calcium they provide is actually higher than the amount in an 8-ounce glass of cow’s milk. Let’s take a salad as our example. Romaine lettuce contains 20 milligrams of calcium per cup. Using 2 cups of romaine as our salad base, we start off with 40 milligrams of calcium. A half-cup of chard leaves would bump us up another 25 milligrams, to 65 total. Adding 2 ounces of tofu chunks we jump up 200 milligrams to 265 while sprinkling on 2 tablespoons of sesame seeds brings us up to 350 milligrams. To top it off, add one-third of a cup of kidney beans and we have a salad that provides a substantial 390 milligrams of calcium.

How does this amount compare to a glass of 2% cow’s milk? In terms of total calcium, it’s about 33% higher! (A glass of 2% has about 300 milligrams.) How does it compare in calories? It’s also higher here - weighing in at about 240 calories versus 120 calories for a cup of 2% cow’s milk. But at the World’s Healthiest Foods, we think this difference is unimportant. All of us can afford 120 additional calories from high-quality food! The foods included in this salad provide a rich assortment of nutrients, including those that are noted to support bone health - far more than are contained in the cow’s milk. For example, there are only 2 milligrams of vitamin C in a cup of cow’s milk. There is over 20 times this much in the romaine lettuce alone!

Practical tips

As the salad above highlights, since many of the World’s Healthiest Foods contain calcium and other important bone-promoting nutrients, we feel that meal plans concentrated in these foods can help reduce risk of osteoporosis as effectively or even more effectively than cow’s milk. While Table 1 below gives details on the calcium content of some of the World's Healthiest Foods, the article on our website about Osteoporosis goes into more detail about the condition itself as well as nutrients necessary for promoting bone health. It gives detailed examples of foods other than dairy products as well as recommended dietary suggestions that can help you to promote bone health.

Table 1

Some Calcium-Rich World's Healthiest Foods

Food Serving Calcium (mg) % DV Density Quality
Tofu, raw 4.0 oz-wt 396.9 39.7 9.3 Excellent
Sesame seeds 0.25 cup 351.0 35.1 3.5 Very good
Collard greens, boiled 1.0 cup 226.1 22.6 9.3 Excellent
Turnip greens, cooked 1.0 cup 197.3 19.7 13.9 Excellent
Soybeans, cooked 1.0 cup 175.4 17.5 1.2 -
Navy beans, cooked 1.0 cup 127.4 12.7 1.0 -
Mustard greens, boiled 1.0 cup 103.6 10.4 10.0 -
Chard, boiled 1.0 cup 101.5 10.2 5.9 Very good
Kale, fresh, boiled 1.0 cup 93.6 9.4 5.2 Very good
Almonds 0.25 cup 88.0 8.8 0.9 -
Pinto beans, cooked 1.0 cup 82.1 8.2 0.7 -
Garbonzo beans, cooked 1.0 cup 80.4 8.0 0.6 -
Green snap/string beans, boiled 1.0 cup 57.5 5.8 2.7 Good
Kidney beans, cooked 1.0 cup 49.6 5.0 0.4 Good
Celery, raw 1.0 cup 48.0 4.8 5.1 Good
Black beans, boiled 1.0 cup 46.4 4.6 0.4 -
Cabbage, raw 1.0 cup 41.8 4.2 3.8 Good
Lettuce, romaine 2.0 cup 40.3 4.0 5.2 Good

References

Agnusdei D, Crepaldi G, Isaia G, et al. A double blind, placebo-controlled trial of ipriflavone for prevention of postmenopausal spinal bone loss. Calcif Tissue Int 1997; 61: 142-147.

Brattstrom LE, Hultberg BL, Hardebo JE. Folic acid responsive postmenopausal homocysteinemia. Metabolism 1985; 34: 1073-1077.

Chestnut CH 3rd, Bell NH, Clark GS, et al. Hormone replacement therapy in postmenopausal women: urinary N-telopeptide of type I collagen monitors therapeutic effect and predicts response of bone mineral density. Am J Med 1997; 102: 29-37.

Eaton-Evans J. Osteoporosis and the role of diet. Br J Biomedical Sci 1994; 51: 358-370.

Ellis F, Holesh S, Ellis J. Incidence of osteoporosis in vegetarians and omnivores. Am J Clin Nutr 1972; 25: 55-58.

Lore F, Nuti R, Vattimo A, Caniggia A. Vitamin D metabolites in postmenopausal osteoporosis. Horm Metabol Res 1984; 16: 58.

Recker R. Calcium absorption and achlorhydria. New Engl J Med 1985; 313: 70-73 61: 391-393.

Saltman PD, Strause LG. Strause LG. The role of trace minerals in osteoporosis. J Am Coll Nutr 1993; 4: 384-389.

Vermeer C, Gijsbers BL, Cracium AM, et al. Effects of vitamin K on bone mass and bone metabolism. J Nutr 1996; 126: 1187S-1191S.

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