The Problems with Using Animals to Study Osteoporosis
In Turner’s comprehensive review of research that uses animals to study osteoporosis, he states, “Animal models for [osteoporosis and osteopenia] have more than just a few differences from humans and there are many animal model studies that are not yet adequately validated by corresponding data from human patients.”5 This statement is the conclusion of a man who works with sheep models of osteoporosis for a living. Moreover, in discussing osteoporosis in postmenopausal women, who suffer the vast majority of cases of the disease, Turner admits, “There is no animal model that exactly mimics the condition of postmenopausal osteoporosis and one must know the limitations of the different animal models.”6
A look at the bone physiology of the animals most commonly used to study osteoporosis shows why Turner and others consider them to be inappropriate models for women.
Rodents
Rats and mice are by far the most commonly used animals in osteoporosis research. As Turner puts it, they are used primarily because “they are inexpensive, easy to house, and the general public is accustomed to the role of rodents in research.”7 None of these “advantages,” however, says anything about the scientific validity of using mice and rats. In discussing the merits of the model, Turner is less than flattering. He writes, “In a study that compared bone composition, density and quality in bone samples derived from seven vertebrates that are commonly used in bone research: human, dog, pig, cow, sheep, chicken, and rat, large interspecies differences were observed. Of all species included in the biochemical analysis, rat bone was most different ….”8 The animal most often used in osteoporosis research has bones that are radically different from human bones—more so than any other animal measured! This is common in vivisection: The “models” that are the cheapest and easiest to use are studied, regardless of the fact that their study lacks scientific value and validation.
The problems associated with using mice and rats in these studies don’t end with the vast differences in bone composition between animals and humans. Although rodents who have had their ovaries cut out are the standard postmenopausal model, Turner notes that “[r]odents do not experience a natural menopause.”9 In response to a study by C.M. Vanin et al. that appeared in the American Journal of Obstetrics and Gynecology regarding the effects of ovary removal on the bones of rats, Turner writes that rodents’ bones “showed an increased flexibility, unlike the brittleness seen in osteopenic women.”10 Turner quotes from the Vanin et al. article, which concluded that “the rat model may therefore not be appropriate for comparison of mechanical properties with the human.”11 There are too many significant physiological differences between rats and humans to list here, but researchers who use mice and rats to study osteoporosis are clearly wasting money and doing little to advance the medical knowledge about women’s health.
Dogs
Dogs have been particularly popular in the cruelest forms of osteoporosis experiments: bone fracture studies and immobilization studies. But the dog “model” of osteoporosis is seriously flawed. One of the key problems is that dogs cannot model postmenopausal women—the primary group afflicted by osteoporosis. Loss of estrogen does not cause bone loss in dogs even though it is the primary factor in bone loss investigated in women’s health research. In fact, Turner quotes from a major study of ovariectomized dogs by V. Shen et al. in Bone, which concluded, “The lack of sizeable responses in histomorphometric, bone mass, and biochemical parameters may limit the utility of dogs for the study of cancellous bone loss in ovarian-dysfunction osteoporosis.”12
We should hardly be surprised that canine bone strength is not dependent on hormones as human bone strength is because many spayed dogs (and cats) live to a ripe old age without suffering any bone problems. The reason for this difference is that there are vast dissimilarities between human and canine hormonal systems. Dogs have naturally low amounts of circulating estrogen, and unlike human women, who ovulate monthly, female dogs only ovulate twice a year. As a result of these differences, spontaneous fractures in dogs are almost unheard of. Dogs simply do not suffer from anything like osteoporosis, and vivisectors have found it impossible to even induce such a condition in canines.13
Primates
When other animal models fail, researchers often turn to primates, as they have in osteoporosis research, arguing that primates undergo natural menopause and are more similar to humans than dogs and rodents are. There is nothing natural, however, about most studies of osteoporosis that use primates. For one thing, primates are not considered menopausal until their late 20s. It is almost impossible to obtain a group of postmenopausal primates, making such studies more expensive, difficult, and unwieldy than running clinical trials on humans. Consequently, researchers typically resort to the standard shoddy method of inducing bone loss, which is to cut out female monkeys’ ovaries. Again, we see all the same problems that using artificially induced models cause. Furthermore, the long lifespan of primates means that physically immature animals are sometimes used in studies that require fully developed bodies. For example, it takes about a decade for primates to develop their peak bone mass, but most studies use ovariectomized monkeys aged 4 to 7 years.14 In other words, vivisectors use juvenile monkeys to study a disease that affects elderly women! Jee and Yao summarized, “[W]e find that the information generated from skeletal studies of nonhuman primates has been most disappointing and recommend that these expensive skeletal studies be curtailed unless it is required by a regulatory agency for safety studies.”15
Animal Studies are Misleading >>
5. Turner 76.
6. Turner 76.
7. Turner 69.
8. Turner 68.
9. Turner 69.
10. Turner 69.
11. Turner 69.
12. Turner 68.
13. Turner 68.
14. Turner 67.
15. Jee and Yao 193.
