Calcium loss from bone causes osteoporosis which is particularly prevalent in postmenopausal women. In a comparative study between 1 600 ovo-lacto-vegetarians and omnivorous women in Michigan USA it was found that the vegetarians had only 18% loss of bone mineral by age 80, whereas closely paired omnivores had 35% loss of bone mineral.60 High-protein diets cause calcium loss in the urine,61 and evidence suggests that the rates of osteoporosis are higher in Western countries than in developing countries where diets tend to be vegetarian. The higher rate of calcium excretion may also be a reason for the observed higher incidence of kidney stones in affluent Western societies than in vegetarian or semi-vegetarian societies.
In a study carried out on merino rams, in which fifty weaned (100 day old) rams were divided into five groups of ten and fed diets containing either 20% plant protein (gluten-grain) or a mixed ration consisting of 12% plant and 8% animal protein (fishmeal and bloodmeal as is standard practice in the animal husbandry industry) it was shown that the addition of animal protein to the diet severely compromised bone development, although weight gain and food consumption did not differ significantly between the two groups.,62,63,64 Increased protein consumption enhanced calciuresis and resulted in significant limb skewness. The limb skewness could not be ascribed to osteopenic bones and compared with animals consuming lower protein rations, the bone mineral density (BMD) and vertebral trabecular bone volume (TBV) of animals fed high protein diets were significantly increased. In animals consuming higher protein diets, skeletal radiology and quantitative bone histology revealed no evidence of bone turnover as would be expected in animals which are in negative calcium balance. The ratio of Calcium:Phosphorus in the bone was inversely correlated with increased protein intake and resulted from an increase in phosphorus content of bone while the amount of bone calcium was unaffected. Bone density was thus not a good indicator of bone strength, as sheep with the highest BMD were worst affected by limb deformity.
A comparison between those sheep receiving the highest protein rations (20% plant protein vs. 20% protein of which 12% was of plant origin and 8% of animal origin) showed that the addition of animal protein significantly impaired bone development. The group receiving animal protein showed a significant increase in calciuresis (figure 5.7 a), had a higher BMD (fig.5.7b), increased limb deformity (fig. 5.7c) and had a lower calcium to phosphorus ratio (fig. 5.7d) than those receiving plant proteins. This study shows, that the common practice of measuring BMD as an indicator of bone strength and the risk in terms of osteoporosis, is not necessarily sound. Other factors, such as qualitative micro-architectural abnormalities, and not mere bone loss, may underlie the skeletal deformities induced by increased protein consumption, particularly animal proteins.
Figure 5.7. Change in parameters reflecting bone mineral status in merino rams fed diets containing only plant proteins (20% plant protein) and mixed proteins (12% plant and 8% animal). Units for deformity are arbitrary units in which 50 represents normal straight legs and 100 would represents legs bent at a 90° angle. (From reference 64).
Preliminary results in follow up studies on rats, rabbits and vervet monkeys, using the milk protein casein as animal protein source, and comparing it with plant protein (soya), show the same trend in all the groups studied. In our modern society the notion exists that dairy products are essential for maintenance of calcium levels and prevention of osteoporosis. Vegan diets are often criticized on the grounds that they will lead to severe calcium depletion. In fact there is no evidence that this is the case and if anything, the reverse is true, as indicated by current research findings. Moreover, osteoporosis is more prevalent in Western countries where an abundance of milk is consumed than in countries where vegan diets are more common.28 There is also no clear evidence that dietary calcium supplementation will slow the rate of bone loss in postmenopausal women, a position also held by the US department of Health and Human services.65
Osteoporosis
Calcium loss from bone causes osteoporosis which is particularly prevalent in postmenopausal women. In a comparative study between 1 600 ovo-lacto-vegetarians and omnivorous women in Michigan USA it was found that the vegetarians had only 18% loss of bone mineral by age 80, whereas closely paired omnivores had 35% loss of bone mineral.60 High-protein diets cause calcium loss in the urine,61 and evidence suggests that the rates of osteoporosis are higher in Western countries than in developing countries where diets tend to be vegetarian. The higher rate of calcium excretion may also be a reason for the observed higher incidence of kidney stones in affluent Western societies than in vegetarian or semi-vegetarian societies.
In a study carried out on merino rams, in which fifty weaned (100 day old) rams were divided into five groups of ten and fed diets containing either 20% plant protein (gluten-grain) or a mixed ration consisting of 12% plant and 8% animal protein (fishmeal and bloodmeal as is standard practice in the animal husbandry industry) it was shown that the addition of animal protein to the diet severely compromised bone development, although weight gain and food consumption did not differ significantly between the two groups.,62,63,64 Increased protein consumption enhanced calciuresis and resulted in significant limb skewness. The limb skewness could not be ascribed to osteopenic bones and compared with animals consuming lower protein rations, the bone mineral density (BMD) and vertebral trabecular bone volume (TBV) of animals fed high protein diets were significantly increased. In animals consuming higher protein diets, skeletal radiology and quantitative bone histology revealed no evidence of bone turnover as would be expected in animals which are in negative calcium balance. The ratio of Calcium:Phosphorus in the bone was inversely correlated with increased protein intake and resulted from an increase in phosphorus content of bone while the amount of bone calcium was unaffected. Bone density was thus not a good indicator of bone strength, as sheep with the highest BMD were worst affected by limb deformity.
A comparison between those sheep receiving the highest protein rations (20% plant protein vs. 20% protein of which 12% was of plant origin and 8% of animal origin) showed that the addition of animal protein significantly impaired bone development. The group receiving animal protein showed a significant increase in calciuresis (figure 5.7 a), had a higher BMD (fig.5.7b), increased limb deformity (fig. 5.7c) and had a lower calcium to phosphorus ratio (fig. 5.7d) than those receiving plant proteins. This study shows, that the common practice of measuring BMD as an indicator of bone strength and the risk in terms of osteoporosis, is not necessarily sound. Other factors, such as qualitative micro-architectural abnormalities, and not mere bone loss, may underlie the skeletal deformities induced by increased protein consumption, particularly animal proteins.
Figure 5.7. Change in parameters reflecting bone mineral status in merino rams fed diets containing only plant proteins (20% plant protein) and mixed proteins (12% plant and 8% animal). Units for deformity are arbitrary units in which 50 represents normal straight legs and 100 would represents legs bent at a 90° angle. (From reference 64).
Preliminary results in follow up studies on rats, rabbits and vervet monkeys, using the milk protein casein as animal protein source, and comparing it with plant protein (soya), show the same trend in all the groups studied. In our modern society the notion exists that dairy products are essential for maintenance of calcium levels and prevention of osteoporosis. Vegan diets are often criticized on the grounds that they will lead to severe calcium depletion. In fact there is no evidence that this is the case and if anything, the reverse is true, as indicated by current research findings. Moreover, osteoporosis is more prevalent in Western countries where an abundance of milk is consumed than in countries where vegan diets are more common.28 There is also no clear evidence that dietary calcium supplementation will slow the rate of bone loss in postmenopausal women, a position also held by the US department of Health and Human services.65