The authors’ Rebuttal
...to the Dairy Farmers of Canada Response
to Becoming Vegetarian
1996

Parts: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8
(Part 6)

Page 29

1. "But, being vegetarian does not necessarily mean one's intake of sulfur-containing amino acids will be low. For example, a serving of dry roasted soy beans contains substantially more methionine and cysteine than a serving of flank steak or one of milk."

The Dairy Bureau nutritionists left out a few details. First, studies show that vegetarian diets are lower in total protein than omnivorous diets. In addition, sulfur-containing amino acids are generally higher in omnivorous diets, even when total protein is held constant. It is interesting that our critics selected soy nuts as the plant foods with which to compare the steak and milk. Soy nuts are a highly concentrated source of protein -- 34 mg per 1/2 cup. This is hardly typical of most vegetarian protein sources, even most soy foods. A serving of beans (1 cup-most types) provides approximately 14 g of protein (364 mg of methionine and cysteine) and a serving of medium tofu (1/2 cup) provides 10 g of protein ( 267 mg of methionine and cysteine). Had our critics used a serving of flank steak that supplied 34 mg of protein (just under 5 ounces) , they would have found that the total methionine and cysteine contribution was 1669 mg.

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:

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 that true?"

"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. 1993: Vol.93;No.11:1259-1260.

Page 31

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.

Page 32

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.

Page 33

1. "The fact that forty vegan Israelis may have had adequate calcium intakes is far from a convincing argument for Canadians to give up milk!"

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 U.S.

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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