FIT FOR DUTY. . .FIT FOR LIFE!

Submitted by: CAPT Maureen Leser

This “Fit for Duty. . .Fit for Life” column is the second in a series of articles designed to provide current information on bone health. This article will focus on calcium and osteoporosis.

Four out of every 10 White women age 50 or older in the United States will experience a hip, spine, or wrist fracture sometime during the remainder of their lives; 13 percent of White men in this country will suffer a similar fate. Recent statistics suggest that lifetime risk for fractures may be rising among Hispanic women1. While incidence of osteoporotic fractures among White women may be 2.6 times higher than in similarly aged African American women, there is concern that health consequences from osteoporotic fractures may be greater among African American older women2. A study of a Medicaid population suggested that postmenopausal African American women were 3 times more likely to die within 3 years of experiencing an osteoporotic fracture than postmenopausal White women3. These statistics indicate it is important for men and women of all races to follow lifestyle habits that decrease the risk of developing osteoporosis, including consuming adequate calcium.

Calcium is the most abundant mineral in the human body. More than 99 percent of total body calcium is stored in our bones and teeth; the remaining 1 percent is found in blood and soft tissues. Calcium is needed to support bone structure, to promote muscle contraction and hormone secretion, and to help send messages throughout the nervous system4.

Dietary Reference Intakes (DRIs), developed for healthy people by the Institute of Medicine (IOM) of the National Academy of Sciences, provide recommendations for calcium intake5. DRIs include Recommended Dietary Allowances (RDA), average daily intakes sufficient to meet nutrient requirements of nearly all (97-98%) healthy individuals, and Adequate Intakes (AI), which are set when there is insufficient scientific data available to establish a RDA. The recommended intake for calcium is listed as an AI. Table 1 lists the AIs for calcium for healthy people5.

Table 1: Recommended Adequate Intake for Calcium

Age	Male and Female (milligrams/day)	Pregnancy & Lactation (milligrams/day)
0 to 6 months	210	N/A*
7 to 12 months	270	N/A
1 to 3 years	500	N/A
4 to 8 years	800	N/A
9 to 13 years	1300	N/A
14 to 18 years	1300	1300
19 to 50 years	1000	1000
51+ years	1200	N/A

* N/A: Not available

 

In the U.S., milk, yogurt, and cheese are major contributors of calcium in the typical diet. However, many Americans are not consuming recommended amounts of calcium2-3 and inadequate intake of dairy foods may explain why. The U.S. Department of Agriculture's recently published My Pyramid, which provides recommendations for following the US Dietary Guidelines, encourages children over 2 years and adults to consume 2-3 servings of dairy products per day to help meet their calcium needs6.

There are, however, groups that object to recommending dairy foods as a source of calcium and question the current recommended need for calcium. They propose research on strategies to reduce calcium loss, which in turn may lower calcium requirements7. In a recent review of 37 studies, 27 were found to have no relationship between calcium or dairy intake and bone health8. Authors suggested that rather than calcium promoting strong bones, it is the vitamin D and energy content of milk that is providing bone health benefits. On the other hand, a review of 139 reports investigating the role of calcium on bone mass demonstrated positive effects of calcium on bone mass across the lifespan9.

Researchers do agree that the development of osteoporosis is influenced by many factors, and at this time most health organizations believe that dairy foods can make a significant contribution to bone health because of their calcium, vitamin D, and energy content In fact, the Food and Drug Administration, beginning in 1993, has allowed the following health claim for food labels: “adequate calcium intake throughout life is linked to reduced risk of osteoporosis through the mechanism of optimizing peak bone mass during adolescence and early adulthood and decreasing bone loss later in life"10.

For those choosing to meet their calcium needs through dairy foods:

A serving of dairy food is equal to: 1 cup (8 fl oz) of milk 8 oz of yogurt 1.5 oz of natural cheese (such as Cheddar) 2.0 oz of processed cheese (such as American)

For Special Populations

Non-fat and reduced fat dairy products that contain the same amount of calcium as regular (higher fat) dairy products are readily available for people concerned about total and saturated fat intake.

Reduced lactose milk and milk products are available for individuals with lactose intolerance, who experience symptoms such as bloating and diarrhea because they cannot completely digest the milk sugar lactose. Pills and drops that help digest lactose in milk are available without a prescription.

People who avoid all animal products because they are vegan or lactose intolerant can meet their calcium needs from alternative calcium sources such as Chinese cabbage, kale, and broccoli1,4,5,11. Most grains are not high in calcium (unless fortified), but they contribute calcium to the diet when they are consumed frequently. Additionally, a variety of calcium-fortified foods including fruit juices, fruit drinks, tofu, and cereals are now sold in grocery stores.

While alternative calcium sources such as kale are important for vegans and others who choose to avoid dairy foods, the calcium in these foods is generally not as well absorbed. The Office of Dietary Supplements, National Institutes of Health, states that when portions are adjusted for calcium absorption, one would need to consume the following equivalents to obtain an equal amount of calcium4:

8 fluid ounces of milk OR 1 cup yogurt OR 1 ½ ounces of Cheddar Cheese 8 fluid ounces milk OR 1 ½ cups cooked kale OR 2 ¼ cups cooked broccoli OR 8 cups cooked spinach

Table 2 lists a variety of food sources of calcium, but does not address absorption of the various foods.

Table 2: Calcium Content of a Variety of Foods4, 12

FOOD	Calcium (mg)	% DV*
Yogurt, plain, low fat, 8 oz.	448	45
Yogurt, fruit, low fat, 8 oz.	338	34
Mozzarella, part skim 1 ½ oz.	333	33
Sardines, canned in oil, with bones, 3 oz.	324	32
Cheddar cheese, 1 ½ oz shredded	306	30
Milk, non-fat, 2%, 3.25%, buttermilk, and lactose reduced, 8 fl oz	276-300	30
Salmon, pink, canned, solids with bone, 3 oz.	181	18
Tofu, soft, made w/calcium sulfate, ½ cup of ½ inch cubes**	138	14
Cottage cheese, 1% milk fat, 1 cup unpacked	138	14
Ready to eat cereal, calcium fortified, 1 cup	100-1000	10-100
Turnip greens, boiled, ½ cup	125	12
Soy or Rice beverage, calcium fortified, 8 fl oz.	80 - 500	8 to 50
Chinese cabbage, raw, shredded, 1 cup	59	6
Broccoli, raw, chopped, ½ cup	35	4
Tortilla, corn, ready to bake/fry, 1 (24 grams)	19	2
Bread, white or whole wheat, 1 slice	20 - 30	2

 

*DV=Daily Value. DVs were developed to help consumers determine if a typical serving of a food contains a lot or a little of a specific nutrient. The DV for calcium is based on 1,000 mg. The percent DV (% DV) listed on the Nutrition Facts panel of food labels tells you what percentage of the DV is provided in one serving. A food providing 5% of the DV or less is considered a low source while a food that provides 10-19% of the DV is a good source and a food that provides 20% of the DV or more is high in that nutrient. For foods not listed in this table, please refer to the U.S. Department of Agriculture's Nutrient Database Web site: http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl.

** Calcium values are only for tofu processed with a calcium salt. Tofu processed with a non-calcium salt will not contain significant amounts of calcium.

 

Helpful hints for meeting your calcium needs

Use milk or a calcium fortified unflavored soy or rice beverage instead of water in recipes such as pancakes, mashed potatoes, pudding, and instant, hot breakfast cereals. For a great breakfast, blend yogurt and fruit into a fruit smoothie. Sprinkle grated cheese on salad, soup, or pasta. Choose calcium fortified soy or rice beverage or milk instead of carbonated soft drinks for meals and/or snacks. Serve raw fruits and vegetables with a yogurt based dip. Create a vegetable stir-fry and toss in diced calcium-set tofu. Enjoy a parfait with fruit and yogurt. Complement your diet with calcium-fortified foods such as certain cereals, orange juice and soy beverages. Keep portable, calcium-rich foods on hand for snacks on the run, such as string cheese or individual pudding cups with calcium added. Serve non-milk sources of calcium, such as broccoli or orange juice with added calcium

Calcium Supplements

It is best to obtain recommended amounts of calcium from food, but there may be times when supplements can help meet calcium needs. Calcium carbonate and calcium citrate are common forms of calcium supplements4. They are both well absorbed by healthy people, but calcium citrate is better absorbed by people with less stomach acid. Because calcium carbonate contains 40% calcium while calcium citrate contains 21% calcium, you will obtain more calcium from the same dose of calcium carbonate as calcium citrate supplement.

Calcium citrate malate is often used to fortify juices, and is also well absorbed. Other forms of calcium in supplements or fortified foods are calcium gluconate, lactate, and phosphate. Coral calcium is a calcium supplement that includes small amounts of minerals such as magnesium. Absorption from supplements is best when doses of 500 mg or less are taken because the percent of calcium absorbed decreases with larger amounts. Therefore, someone advised by their physician to take 1000 mg of calcium in supplement form per day should take it as 500 mg twice a day instead of 1000 mg calcium at one time. A comparison of the calcium content of various calcium supplements is provided below4:

 

Product	Percent Elemental Calcium	Amount of Calcium(mg) in a 500 mg dose
Calcium Carbonate	40%	200
Tricalcium Phosphate	30%	150
Calcium Citrate	21%	105
Calcium Lactate	13%	65
Calcium Gluconate	9%	45

 

It is important to remember that the IOM has recommended that healthy people limit their total calcium intake per day to 2,500 milligrams per day5. If you are already consuming three servings of dairy foods daily, as recommended for people 2 years of age and older, you are consuming about 900 milligrams of calcium. Smaller amounts of calcium will be obtained from other foods such as grains, and some fortified foods can provide substantial amounts of calcium. Healthy people who are meeting their needs from diet do not need to take a calcium supplement and may be at risk of consuming too much calcium. Recommended intakes developed by the IOM refer to healthy people; physicians may recommend that a person consume additional calcium for a specific health problem.

Next: Vitamin D and Osteoporosis

U.S. Department of Health and Human Services. Bone Health and Osteoporosis: A Report of the Surgeon General. Rockville, MD: Public Health Service, Office of the Surgeon General, 2004. http://www.surgeongeneral.gov/library/bonehealth/content.html. Woodson GC. Risk factors for osteoporosis in postmenopausal African American women. Current Medical Research and Opinions 2004;24:1681-7. Kotzan JA, Martin JC, Reeves JH, Wade W. The impact of race and fractures on mortality in a postmenopausal Medicaid population. Clin Ther 1999;21:1988-2000. Office of Dietary Supplements, National Institutes of Health. Dietary Supplement Fact Sheet: Calcium. 4/2005. Food and Nutrition Board, Institute of Medicine. Calcium. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, D.C.: National Academy Press; 1997:71-145. (National Academy Press). http://www.mypyramid.gov/ Weinsier RL and Krumdieck CL. Dairy foods and bone health: examination of the evidence. Am J Clin Nutr. 2000 Sep;72(3):681-9. Lanou AJ, Berkow SE, Barnard ND. Calcium, dairy products, and bone health in children and young adults: a reevaluation of the evidence. Pediatrics. 2005 Mar;115(3):736-43]. Heaney RP. Calcium, dairy products and osteoporosis. J Am Coll Nutr. 2000;19(2 Suppl):83S- 99S. (PubMed). U.S. Food and Drug Administration. Center for Food Safety and Applied Nutrition. A Food Labeling Guide. September 1994 (editorial revisions June 1999 and November 2000). Weaver CM, Proulx WR, Heaney R. Choices for achieving adequate dietary calcium with a vegetarian diet. Am J Clin Nutr. 1999;70(3 Suppl):543S-548S. (PubMed). U.S. Department of Agriculture ARS. USDA Nutrient Database for Standard Reference Release 17. Nutrient Data Laboratory Home Page. 2004. http://www.nal.usda.gov/fnic/foodcomp. Additional Resource: Nutrition and Osteoporosis. Available online at http://lancaster.unl.edu/food/osteoporosis.htm.

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