Connie Weaver, PhD, Distinguished Professor of Food and Nutrition at Purdue University reported in her 2001 book chapter "Calcium," in Present Knowledge in Nutrition:
absorption from milk and other dairy products is about 32%, whereas
calcium absorption from vegetables ranges from about 5% in spinach to
more than 60% in some brassica vegetables such as broccoli. However,
the high bioavailability of calcium from some vegetables cannot
overcome their low calcium content. One would have to consume 2 1/4
cups of broccoli to obtain the same amount of calcium absorbed from one
cup of milk."
Frank Greer, MD, Professor of Pediatrics at the University of Wisconsin-Madison School of Medicine and Nancy Krebs, MD, Professor of Pediatrics at the University of Colorado Health Sciences Center wrote in their Feb. 2006 paper "Optimizing Bone Health and Calcium Intakes of Infants, Children, and Adolescents," Pediatrics:
"The largest source of dietary calcium for most persons is milk and other dairy products, which accounts for 72% of the calcium in the US food supply. Sixty-five percent of the dietary calcium intake in children in the United States is supplied by dairy products. Drinking three 8-oz glasses of milk per day will achieve the recommended adequate intake of calcium in children 4 to 8 years of age, and four 8- to 10-oz glasses of milk will provide the adequate calcium intake for adolescents... It is important to note that there is relatively little difference in the calcium content of reduced-fat dairy products compared with whole milk–derived products...
Most vegetables contain calcium, although at relatively low density. Thus, large servings are needed to equal the total intake achieved with typical servings of dairy products... Calcium supplements are another alternative source, but these products do not offer the benefits of other associated nutrients, and compliance may be a problem."
The National Institute of Child Health and Human Development (NICHD) stated in its Mar. 13, 2006 publication for the Milk Matters campaign titled "Building Strong Bones: Calcium Information for Health Care Providers," available on its website:
the degree to which the intestinal system absorbs calcium, depends on
the overall level of calcium in a food and the type of food being
consumed. Calcium in foods such as milk and milk products is highly
bioavailable, meaning that it is easily absorbed...
calcium in foods high in oxalic acid (such as spinach, sweet potatoes,
and beans) or phytic acid (such as unleavened bread, raw beans, seeds,
and nuts) may be poorly absorbed. Oxalates in particular are strong
inhibitors of calcium absorption. As a result, additional servings of
certain calcium-rich foods are needed to compensate for their low
bioavailability is one of the reasons that the NICHD describes low-fat
and fat-free milk and milk products as the best dietary source of
The American Council on Science and Health discussed calcium in its June 2001 publication "The Role of Milk in Your Diet," published on its website:
foods in the 'milk, yogurt, and cheese' food group are rich in calcium.
So if you include enough foods from this group in your daily diet, you
are assured of getting a reliable source of calcium every day. In the
other food groups, however, only a few of the many possible choices are
high in calcium. For example, only a few vegetables (such as spinach,
collard greens, and broccoli) are calcium-rich; most other vegetables
(including such favorites as potatoes, tomatoes, lettuce, corn, and
carrots) are not. In addition, the calcium in dairy products is better
absorbed from the digestive tract than the calcium from some other
sources... Milk and dairy products are good sources of many nutrients,
and they are the best food source of the mineral calcium."
Stephen Walsh, Science Coordinator for the International Vegetarian Union, wrote in his article "Beyond Dairy and Calcium: The Truth About Diet and Bone Health," published on www.vegsource.com (accessed Apr. 26, 2007):
"Dairy products are not the best source
of calcium as they cause calcium losses at the same time as increasing
calcium intake. A third of the calcium absorbed from milk and more than
two thirds of the calcium absorbed from cheese is wasted this way. In
contrast, low oxalate green leafy vegetables such as kale and spring
greens provide plenty of well absorbed calcium while at the same time
reducing calcium losses. Calcium supplements lie in between in terms of
their effect of retained calcium."
Amy Joy Lanou, PhD, Senior Nutrition Scientist at the Physician's Committee for Responsible Medicine explained in her March 2005 paper "Calcium, Dairy Products, and Bone Health in Children and Young Adults: A Reevaluation of the Evidence," in Pediatrics:
products contain nutrients, including protein, sodium, and, in some
cases, supplemental vitamin D, all of which influence calcium balance
and bone mineralization and alter or negate the effect of dairy calcium
in the body’s mineral economy. Animal protein and sodium, in
particular, tend to increase calcium excretion...
found no evidence to support the notion that milk is a preferred source
of calcium... Although milk and other dairy products are reliable
sources of calcium, many factors affect the availability and retention
of the calcium from these products. For example, the calcium in dairy
products is not as well absorbed as that in many dark green leafy
vegetables but has an absorption fraction similar to that of calcium
supplements, calcium-enriched beverages, calcium-set tofu, sweet
potatoes, and beans. Dairy products... clearly increase the urinary
excretion of calcium as a result of their increased sodium,
sulfur-containing amino acid, and phosphorus content."
The Harvard University School of Public Health (HSPH) reported in its Dec. 13, 2004 article "Calcium and Milk," published on the HSPH website:
"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...
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... Many dairy products are high in saturated fats, and a high saturated fat intake is a risk factor for heart disease...
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... 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."
The Physicians Committee for Social Responsibility stated in its publication "Understanding Lactose Intolerance," available on its website (aaccessed Apr. 26, 2007):
"Calcium is readily available in sources other than dairy products. Green leafy vegetables, such as broccoli, kale, and collards, are rich in readily absorbable calcium. Many green vegetables have absorption rates of more than 50 percent, compared with about 32 percent for milk...
Green leafy vegetables, beans, calcium-fortified soymilk, and calcium-fortified 100-percent juices are good calcium sources with advantages that dairy products lack. They are excellent sources of phytochemicals and antioxidants, while containing little fat, no cholesterol, and no animal proteins."