This is one of those topics that is pushed hard (mostly by Veg*ans) as the ultimate proof against a protein rich diet.
Their claim is that consuming a diet high in protein causes an acid balance in the blood, leaching calcium from your bones, osteoperosis blah blah blah. The only way to fix this, apparently, is to consume an alkaline diet rich in veggies and fruit, and avoid meat completely (because we all know, meat also causes cancer and heart disease! oooh noooo!)
Ok, lets assume that acidosis is real.
So if an acid balance in the blood is bad, than an alkaline balance in the blood is good, right? Carried to its logical extreme, we would want to avoid acidosis causing foods all together. Their reasoning is that cancer cells can’t survive in an alkaline environment. This is true, but neither can the other cells in your body! The extreme end of the spectrum, metabolic alkalosis, is not suitable for any cells to live. You will die. You must understand that there is a spectrum here, and at either extreme, acidosis or alkalosis, we’re in danger.
Of course, while both acidosis and alkalosis are definitely medical issues, neither are likely and neither dichotomy is the way it really works. Lucky for all of us, evolution equipped the body with a range of ways to keep blood pH in the proper range and you’re not going to outdo your acid-base metabolism by eating too much meat, dairy, grains, or anything else.
The origination of the “acidosis” argument.
The China Study, by Campbell, which has been thoroughly debunked [here], was a pretty awful epidemiological study, full of errors, statistical miscalculations, unfounded conclusions, and straight up fabrication in some instances. The study was conducted and designed to make meat the villain and defame all animal products. The main problem, however, is that correlation does not equal causation.
Anyway, here is what Campell et al concluded:
Animal protein, including that from dairy products, may leach more calcium from the bones than is ingested, said Campbell, professor of nutritional biochemistry at Cornell and director of the Cornell-China-Oxford Project, the most comprehensive project on diet and disease ever conducted.
Campbell [and other collaborators] analyzed the role of dietary calcium in bone density by following closely the diets of 800 women from five counties that have very different diets in China. … Analyses of these data suggest that increased levels of animal-based proteins, including protein from dairy products, “almost certainly contribute to a significant loss of bone calcium while vegetable-based diets clearly protect against bone loss,” Campbell reported.
Interesting. So Campell drew a conclusion and causation from his correlation. A fallacy.
Let’s now turn to the discussion over at Whole Food SOS
“But, do the summaries above match up with the data? First, let’s look at what each county was typically eating:”
“As you can see, Xianghuangqi ate a pretty shabby diet as far as whole-foods veganism is concerned: We’ve got dairy galore, beef, mutton, wheat flour, a mere smattering vegetables, and millet. Their bones should be snapping like peanut brittle! Tuoli’s not much better, what with their milk tea, animal flesh, and decided lack of green leafy veggies. More bone snappage, right?
I’ll let the paper speak for itself:
Analysis by individual for all counties combined showed that [bone mineral content] and [bone mineral density] were correlated positively with total calcium (r = 0.27-0.38, P < 0.0001), dairy calcium (r = 0.34-0.40, P < 0.0001), and to a lesser extent with nondairy calcium (r = 0.06-0.12. P = 0.001-0.100), even after age and/or body weight were adjusted for. The results strongly indicated that dietary calcium, especially from dairy sources, increased bone mass in middle-aged and elderly women by facilitating optimal peak bone mass earlier in life.
Did you catch that? Dairy calcium—far more than plant calcium—was linked with stronger bones. Moreover, the paper notes that “nondairy calcium … showed no association with bone variables after age and/or body weight were adjusted for”
Now, here’s where Campbell makes his unfounded conclusion about non-dairy animal protein (from Whole Food SOS again):
“The associations between bone mass and other nutrients, like dietary protein and phosphorous, were also examined. However, none of these nutrients showed an association with bone mass as significantly as did dietary calcium, although an inverse correlation was observed consistently for nondairy animal protein.”
“Unfortunately, that’s the only blurb in the entire paper that mentions animal protein in relation to bone mass, so we can’t see the data behind the “consistent inverse correlation.” In the context of this study, though, it makes sense: Protein has a complex relationship with bone formation, serving as a synergist when calcium intake is adequate, but as a potential antagonist when calcium intake is low. In other words, the effects of protein on bone health depend on how much calcium you’re taking in.”
Bingo. as long as you are eating properly, and not just downing protein powder as your only source of food, you will be consuming adequate calcium and fat soluble vitamins, like K2, which support proper calcium metabolism.
“In addition, if animal protein was such a bone-killer and plant protein was bone protective, we’d see vegetarians or vegans having the best outcomes in the bone department. But this just ain’t the case. At best, non-meat-eaters are equally matched with their omnivorous counterparts; at worst, they’re more prone to fracture:
- Veganism and osteoporosis: A review of the current literature.“The findings gathered consistently support the hypothesis that vegans do have lower bone mineral density than their non-vegan counterparts.”
- A Comparison of Bone Mass Measurements of Vegetarians and Omnivores. “In this review of 9 cross-sectional and 1 longitudinal study, little statistical significance between bone density and bone content was found between vegetarians and omnivores.”
- Effect of vegetarian diets on bone mineral density: a Bayesian meta-analysis.“The results suggest that vegetarian diets, particularly vegan diets, are associated with lower BMD, but the magnitude of the association is clinically insignificant.”
- Long-Term Vegetarian Diet and Bone Mineral Density in Postmenopausal Taiwanese Women. “Long-term practitioners of vegan vegetarian were found to be at a higher risk of exceeding lumbar spine fracture threshold … and of being classified as having osteopenia of the femoral neck.”
So, although the “calcium-leeching” properties of animal protein is a common battle cry in the vegan world, the research just doesn’t support it…”
There is no evidence in the real world that food changes the pH of the blood.
Also, there is a persistent myth that ketosis is dangerous: it’s not. People (including some doctors) commonly confuse it with ketoacidosis, a pathological state usually only found in uncontrolled diabetics and (rarely) raging alcoholics.
You may also like to read ths very detailed article by Chris Masterjohn regarding acid/base diets: Does meat really leach calcium from your bones?
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