Soy what's new?

There's been a lot of buzz about soy products like tofu, tofurkey, soy juice and the like. Is all the ballyhoo warranted...and just what can these foods do for us that other, more traditional western foods can't? To begin with, let's get the terminology right. The juice or liquid expressed from soy beans, although often referred to as soy 'milk' is of course, not milk at all. As the old joke goes: "Did you ever try to milk a soy bean? The notion of this juice being 'milk' is largely promoted on the basis that it doesn't contain animal fat or lactose,it's of plant origin, and it contains components such as phytoestrogens that are suggested to be beneficial to health. But how does the juice compare to cow's milk in terms of its nutrient content?

Let's start with the protein. Raw soy bean contains a substance that keeps its protein from being digested in the human body...but in processing this substance is removed and we end up with a protein of relatively high quality. 'Relatively' is the key word here because the profile of essential amino acids (the building blocks of protein) still doesn't match the high quality of animal protein. The term 'high quality' refers to the amount and balance of essential amino acids in the protein under question and while the actual amount of protein in soy is impressive, the balance of its amino acids is off the mark. This isn't usually a serious problem, however, since in cultures where soy is routinely eaten, dietary patterns have developed whereby the amino acid picture is completed by other protein foods in the diet. What it's lacking specifically is sufficient quantity of sulfur-containing amino acids.

Well then, how about soy's calcium content? Soy is actually quite low in calcium, but some of the tofus (soy bean cakes) are 'set' with calcium, and many of the soy beverages have calcium added as well. Unfortunately, soy contains phytic acid, a substance that hampers the body's absorption of several minerals including iron, zinc and calcium. Because of these mineral problems there has been some concern expressed about the calcium status of children raised on soy-based drinks and the impact on bone health. In addition, some of the calcium added to the soy drinks remains as 'sludge' in the bottom of the container.

One of the popular uses of soy products has been as a way of avoiding milk protein allergy. As it turns out, research has shown that a lot of babies who develop an allergy to cow's milk proteins will also be allergic to soy-based formulas. For such infants...in fact for all infants...breast feeding is the best choice, but when that is not possible and milk/soy allergy is a concern, the only reliable alternative formulas are ones based on fully hydrolysed milk protein.

And then we have the potential role of soy foods in dealing with certain symptoms of menopause. Anything's possible, but right now the jury's still out...largely because the alleged active ingredients of soy (isoflavones) are so greatly reduced in being transformed into tofu and soy beverage. On a different topic concerning soy foods, it's often claimed that consumption of these products will lower serum cholesterol levels, but this has only been seen in people who had very high cholesterol levels to begin with.

In a nutshell then, soy foods are obviously nutritious; many cultures have thrived on them. These cultures, however, have a different set of genes and different food patterns than the typical westerner. Whether they can deliver the same nutritional wallop we've come to expect in our traditional diet remains to be seen.