Table #3 brings with it a slightly different message when the protein
contribution from the soy nuts and steak are the same, and more
commonly consumed vegetarian protein sources are included:
Sulfur-containing amino acid content of
some food servings
Methionine and Cysteine (mg)
2. The nutritionists at the Dairy Bureau quote Dr. Robert Heaney
in concluding this discussion of protein and sulfur-containing amino
acids. The quote is as follows:
"This effect of protein on the calcium economy is sometimes interpreted
as bad, especially in the popular press. Whereas too much protein
may be harmful, nutritionists readily recognize that this phenomenon
is simply an instance of nutrient-nutrient interaction. Whether
harm results will depend on the basic adequacy of the dietary calcium.
Simply put, this interaction means that the efficiency of calcium
conservation is influenced by the level of protein intake. At high
calcium intakes, the effect of protein can easily be offset by improved
absorption efficiency. However, at low calcium intakes the degree
of adjustment possible is usually not sufficient to compensate for
the protein-induced calcium loss."
This quote is an important one, and we do not disagree with this
position, particularly when it is applied to people consuming a
typical North American diet. However, it also implies that for those
who consume less protein, total calcium requirements may be somewhat
lower. Let's look at a few more quotes from the same commentary
by Dr. Heaney1:
"There seems to be a sense that whereas pure protein undoubtedly
increases urinary calcium loss, other nutrients ingested with protein
in natural foods effectively neutralize that negative effect. Is
"Urinary calcium content rises as protein intake increase. This
effect has been documented in several different study designs for
more than 70 years. The data show quite remarkable reproducibility
over this period and across the different designs. The net effect
is such that, if protein intake is doubled without changing intake
of other nutrients, urinary calcium content increase by about 50%."
"This much seems clear; however, the issue is complicated by the
fact that, except in nutrition research studies, few people ingest
protein as an isolated nutrient. Protein is typically ingested as
meat, cereals, beans or dairy products, all of which contain other
nutrients, most notably phosphorus. Phosphorus is well known to
decrease urinary calcium loss. Precisely for this reason, phosphorus
supplements are part of the management of patients with recurrent
renal stones; also, for the same reason, it is commonly believed
that the hypocalciuric effect of the coingested phosphorus offsets
the hypercalciuric effect of the protein. Indeed, the phosphorus
in these food protein sources does lower urinary calcium.
However, that does not mean that coingested phosphorus offsets
the negative effect of protein on calcium balance. What is less
well recognized is that, in addition to its effect on the kidney,
phosphorus increases the calcium content of the digestive secretions
and, hence, increases endogenous calcium loss through the gut. In
more than 500 individual studies, using a parenteral calcium tracer
(unpublished observations), my colleagues and I have found that
endogenous fecal calcium increases with phosphorus intake. Furthermore,
this increase is of about the same magnitude as the concurrent decrease
in urinary calcium...
Although the studies of Spencer and colleagues are commonly
cited to the contrary, the shift of calcium excretion from kidney
to gut is shown in their published reports on this topic and (although
not explicitly commented on) in their study of the effect of a phosphorus
supplement on calcium balance. At low, normal, and high calcium
intakes they found the expected decrease in urinary calcium with
phosphorus supplementation. Nevertheless, the phosphorus supplement
did not alter overall calcium balance. Thus, when protein is ingested
as meat, urinary calcium falls without a change in balance. This
means that there must be an increase in fecal calcium."
"Lest these considerations seem too theoretical, it is worth noting
that the calcium-wasting effect of dietary protein has been found
in free-living women in at least two large observational studies
in which all nutrients were ingested as natural foods. One of the
two, which used calcium tracers, showed a rise in endogenous fecal
calcium with increasing phosphorus intake, as did one controlled
trial involving direct phosphorus supplementation."
1. Heaney, R. Protein intake and the calcium economy. J.Am.Diet.Assoc.
1. "Protein does not induce calcium loss from the skeleton unless
protein intake is well above RNI with concomitantly low calcium
intake. Those who comply with the recommendation for dairy products
in Canada's Food Guide to Healthy Eating do not have to worry about
their protein levels being too high."
Once again, the Dairy Bureau nutritionists are missing the point.
Vegans and near-vegans do not consume 2-4 servings of dairy foods
a day -- they wish to avoid or minimize their intake of dairy. If
we are to be of any real assistance to this population we must provide
them with advice that fits within their value system. Telling them
to comply with Canada's Food Guide to Healthy Eating and consume
2-4 servings of dairy foods a day is demonstrating a complete lack
of regard for their convictions and will be ineffective.
1. "Since their table fails to conform to standard servings in
Canada, it positions plants as being equal to or better than dairy
products as calcium sources. This is misleading. In addition since
calcium does not occur naturally in tofu, the calcium content varies
and the high levels cited here may be misleading, if not inaccurate.
According to data provided by Weaver and Plawecki (1994), some of
the calcium values claimed in Becoming Vegetarian are incorrect
and not based on bioavailability."
We do not position plants as being better than dairy products as
calcium sources. To the contrary. We need only consume 1/2 cup of
milk to get the same amount of calcium as one would get from a full
cup of calcium-rich vegetables.
To say that calcium does not occur naturally in tofu is simply
untrue. Soybeans do contain calcium naturally, however, one way
of processing tofu is using calcium sulfate which adds even more
calcium to the tofu. Our nutrient values came from USDA handbook
#8, as did the values for the other foods listed in the table. We
did make a note at the end of the table stating that the calcium
content of tofu can vary in different areas, and we advised people
to check with local suppliers.
Our calcium values in this table are not based on bioavailability
because no nutrition composition tables list the content of nutrients
based on bioavailability. Unfortunately, this type of information
is available for a relativity small number of foods.
For the record, Dr. Connie Weaver of Purdue University was consulted
several times when we wrote this chapter and she was a reviewer
for this particular section of the chapter.
1. "The fact that forty vegan Israelis may have had adequate calcium
intakes is far from a convincing argument for Canadians to give
Our critics have, once again, misrepresented our work and lead
the reader to believing that we said something that bares no resemblance
to what we actually stated. We used the example of vegan Israelis
because it assesses the calcium intake of a relatively large population
of vegans. We at no time stated or even implied that this is a valid
reason for Canadians to give up dairy products. In the chapter,
Without Dairy, we are not addressing the average Canadian who consumes
an animal-centered diet, but rather the individual who consumes
a plant-centered diet including little, if any dairy products. While
it may be easier for these individuals to meet calcium, vitamin
D and riboflavin needs with dairy products, this is simply not an
option for some people. Thus, it becomes very important that these
individuals receive accurate information so that they can insure
their nutrient needs are met. Becoming Vegetarian is one of the
first resources that has provided comprehensive and reliable guidelines
for this group of people.
2. "A low calcium intake in the children of vegans is a cause for
major concern - they probably have difficulty meeting their calcium
requirement without supplementation."
Here's what Health Canada's Nutrition Recommendations has to say:
"Beyond weaning age, children and adults of various countries and
food cultures subsist on diets differing markedly in calcium content.
These differences in calcium intake, which are due mainly to the
relative strengths of the dairy industry, have not been demonstrated
to have any consequences for nutritional health."
While it is possible that vegan children may require less calcium
than omnivorous children, we took a cautious approach and advised
that they aim for the current recommended nutrient intakes in Canada.
Getting this amount of calcium can be a challenge, particularly
if the diet is modeled after the standard North American diet and
includes a lot of processed foods. That having been said, the solution
would be relatively simple -- fortify non-dairy beverages with calcium
and vitamin D as is done in many other countries, including the
3. "Not according to recent research on kidney stones! High dietary
calcium intakes used to be implicated in raising the risk of kidney
stone formation. As a result, people with calcium-containing stones
were often advised to decrease their calcium consumption." [referring
to a statement about avoiding intakes above the recommended levels
for those predisposed to kidney stones.]
Our critics, once again, quoted us out of context. This quote appeared
in a section titled "Calcium Supplements" and we were discussing
the potential negative effects of using calcium supplements above
recommended levels. We made no mention of dietary calcium intake
in reference to kidney stones.
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