Should you get calcium from milk?
When most people in the United States think of calcium, they immediately think of milk. But should this be so? Milk is actually only one of many sources of calcium, and there are some important reasons why milk may not be the best source for everyone. These include:
* Lactose intolerance
Many people have some degree of lactose intolerance. For them, eating or drinking dairy products causes problems like cramping, bloating, gas, and diarrhea. These symptoms can range from mild to severe. Certain groups are much more likely to have lactose intolerance. For example, 90 percent of Asians, 70 percent of blacks and Native Americans, and 50 percent of Hispanics are lactose-intolerant, compared to only about 15 percent of people of Northern European descent.
One alternative for those who are lactose intolerant but who still enjoy consuming dairy products is to take a pill containing enzymes that digest milk sugar along with the dairy product, or to consume milk that has the lactase enzyme added to it.
* High saturated fat content
Many dairy products are high in saturated fats, and a high saturated fat intake is a risk factor for heart disease. And while it's true that most dairy products are now available in fat-reduced or nonfat options, the saturated fat that's removed from dairy products is inevitably consumed by someone, often in the form of premium ice cream, butter, or baked goods.
Strangely, it's often the same people who purchase these higher-fat products who also purchase the low-fat dairy products, so it's not clear that they're making great strides in cutting back on their saturated fat consumption. For more information on dietary fats, click here.
* Possible increased risk of ovarian cancer
High levels of galactose, a sugar released by the digestion of lactose in milk, have been studied as possibly damaging to the ovaries and leading to ovarian cancer. Although such associations have not been reported in all studies, there may be potential harm in consuming high amounts of dairy products.(9, 10)
* Possible increased risk of prostate cancer
A diet high in calcium has been implicated as a potential risk factor for prostate cancer. In a Harvard study of male health professionals, men who drank two or more glasses of milk a day were almost twice as likely to develop advanced prostate cancer as those who didn't drink milk at all.(11) Moreover, the association appears to be with calcium itself, rather than with dairy products in general.
Clearly, although more research is needed, we cannot be confident that high milk intake is safe.
The bottom line-recommendations for calcium intake and bone health
Adequate, lifelong dietary calcium intake is necessary to reduce the risk of osteoporosis. Consuming adequate calcium and vitamin D and performing regular, weight-bearing exercise are also important to build maximum bone density and strength. After age 30, these factors help slow bone loss, although they cannot completely prevent bone loss due to aging.
Milk and dairy products are a convenient source of calcium for many people. They are also a good source of protein and are fortified with vitamins D and A. At this time, however, the optimal intake of calcium as well as the optimal sources of calcium, are not clear. As noted earlier, the National Academy of Sciences currently recommends that people ages 19-50 consume 1,000 mg of calcium per day, and that those age 50 or over get 1,200 mg per day. Reaching 1200 mg per day would usually require drinking two to three glasses of milk per day over and above an overall healthy diet.
However, these recommendations are based on very short-term studies, and are likely to be higher than what people really need. Currently, there's no good evidence that consuming more than one serving of milk per day in addition to a reasonable diet (which typically provides about 300 milligrams of calcium per day from nondairy sources) will reduce fracture risk. Because of unresolved concerns about the risk of ovarian and prostate cancer, it may be prudent to avoid higher intakes of dairy products.
At moderate levels, though, consumption of calcium and dairy products has benefits beyond bone health, including possibly lowering the risk of high blood pressure and colon cancer.(12-14) While the blood pressure benefits appear fairly small, the protection against colon cancer seems somewhat larger, and most of the latter benefit comes from having just one glass of milk per day. Getting more than this doesn't seem to lower risk any further.
For individuals who are unable to digest - or who dislike - dairy products and for those who simply prefer not to consume large amounts of such foods, other options are available. Calcium can also be found in dark green leafy vegetables, such as kale and collard greens, and in dried beans and legumes.
Calcium is also found in spinach and chard, but these vegetables contain oxalic acid, which combines with the calcium to form calcium oxalate, a chemical salt that makes the calcium less available to the body. A variety of calcium-fortified foods, such as orange juice, are now on the market.
Calcium (and vitamin D) can also be ingested as a supplement. Antacids contain calcium as well. However, men may want to avoid calcium supplements for men because of questions about possible risks of prostate cancer.
An extensive list of the calcium content of foods is available online from the U.S. Department of Agriculture. These foods are good sources of calcium:
Food Amount Calcium
Yogurt, plain, low fat 8 oz
415
Collards, frozen, boiled 1 cup
357
Skim milk 1 cup
306
Spinach, frozen, boiled 1 cup
291
Yogurt, plain, whole milk 8 oz
275
Cheese food, pasteurized American 1 oz
162
Cottage cheese, 1% milk fat 1 cup
138
Baked beans, canned 1 cup
154
Iceberg lettuce 1 head
97
Canned salmon 3 oz
181
Oranges 1 cup
72
Trail mix (nuts, seeds, chocolate chips) 1 cup
159
Almonds 1 oz (24 nuts)
70
Blackeye peas, boiled 1 cup
211
Green peas, boiled 1 cup
94
References
1. Osteoporosis facts. National Osteoporosis Foundation.
2. Owusu W, Willett WC, Feskanich D, Ascherio A, Spiegelman D, Colditz GA. Calcium intake and the incidence of forearm and hip fractures among men. J Nutr 1997; 127:1782-7.
3. Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Milk, dietary calcium, and bone fractures in women: a 12-year prospective study. Am J Public Health 1997; 87:992-7.
4. Papadimitropoulos E, Wells G, Shea B, et al. Meta-analyses of therapies for postmenopausal osteoporosis. VIII: Meta-analysis of the efficacy of vitamin D treatment in preventing osteoporosis in postmenopausal women. Endocr Rev 2002; 23:560-9.
5. Bischoff-Ferrari HA, Dawson-Hughes B, Willett WC, et al. Effect of Vitamin D on falls: a meta-analysis. JAMA 2004; 291:1999-2006.
6. Weber P. Vitamin K and bone health. Nutrition 2001; 17:880-7.
7. Booth SL, Broe KE, Gagnon DR, et al. Vitamin K intake and bone mineral density in women and men. Am J Clin Nutr 2003; 77:512-6.
8. Manson JE, Hsia J, Johnson KC, et al. Estrogen plus progestin and the risk of coronary heart disease. N Engl J Med 2003; 349:523-34.
9. Cramer DW. Lactase persistence and milk consumption as determinants of ovarian cancer risk. Am J Epidemiol 1989; 130:904-10.
10. Cramer DW, Harlow BL, Willett WC, et al. Galactose consumption and metabolism in relation to the risk of ovarian cancer. Lancet 1989; 2:66-71.
11. Giovannucci E, Rimm EB, Wolk A, et al. Calcium and fructose intake in relation to risk of prostate cancer. Cancer Res 1998; 58:442-447.
12. Martinez ME, Willett WC. Calcium, vitamin D, and colorectal cancer: a review of the epidemiologic evidence. Cancer Epidemiol Biomarkers Prev 1998; 7:163-8.
13. Hyman J, Baron JA, Dain BJ, et al. Dietary and supplemental calcium and the recurrence of colorectal adenomas. Cancer Epidemiol Biomarkers Prev 1998; 7:291-5.
14. Cappuccio FP, Elliott P, Allender PS, Pryer J, Follman DA, Cutler JA. Epidemiologic association between dietary calcium intake and blood pressure: a meta-analysis of published data. Am J Epidemiol 1995; 142:935-45.
The aim of the Harvard School of Public Health Nutrition Source is to provide timely information on diet and nutrition for clinicians, allied health professionals, and the public. The contents of this Web site are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. The information does not mention brand names, nor does it endorse any particular products.
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