On one hand, there are multiple, large observational studies out of Asia which show a statistically significant association between higher intakes of natural soy foods and lower risk of developing breast cancer among (mostly post-menopausal) women.  And even those Asian studies which don’t support this association have not shown that eating more traditional soy foods ever increases the risk of breast cancer.  American studies have, by and large, failed to show a similar association, but most researchers chalk this up to the fact that even “high” intakes of soy in the U.S. are lower than the lowest intakes in Asia, meaning that American women are likely not eating enough of the natural phytochemicals in soy called isoflavones that have been credited with its potentially protective effect against breast cancer.  Furthermore, most of the soy eaten in the U.S. is not in the form of traditional, whole-r foods like tofu, miso, tempeh and natto like it is in Asia, but rather in the form of a processed, concentrated, soy-derived food additive called soy protein isolate (SPI), whose isoflavone content may or may not be comparable to that in traditional soy foods.

On the other hand, there is a quieter, but nonetheless disturbing, body of research out there that is linking higher intakes of soy with a variety of unwelcome health outcomes, including thyroid disorders in susceptible people, increased rates of food allergies (especially peanut), intolerances and asthma, and the potential for sexual development problems in children fed soy formula.  If the body of evidence continues to grow and proves these associations more definitively, there are probably a few different biological mechanisms at work here.

• Soy may influence the sexual development of children (especially children fed soy formula as infants) and the hormonal balance of women through the effect of naturally-occurring compounds called “phytoestrogens.” Phytoestrogens are plant estrogens similar enough in structure to the hormone estrogen produced in humans that they can actually bind to our estrogen receptors; soy isoflavones are one of several phytoestrogens present in soy.  Phytoestrogens appear to have potentially beneficial and potentially detrimental effects, which complicates the matter of evaluating soy’s healthfulness.  One one hand, researchers believe that phytoestrogens may compete with more biologically potent human estrogen for receptor sites in our body’s various tissues, and in so doing, it may DECREASE the risk of estrogen-linked cancers like breast cancer in adult women.  But in infants who are still developing, introducing high levels of soy phytoestrogens through soy formula can build up in their tiny bodies quite quickly and possibly influence their sexual development adversely.  Virtually all data on this possible association comes from animal studies– not human studies–so the evidence is not iron-clad that soy formula will increase the risk of problematic sexual development in human children.  However, animal studies suggest that possible side effects could be low testosterone leading to infertility in males and early-onset puberty in females.

• An effect of soy on the thyroid could be mediated by compounds in soy called goitrogens, naturally-occurring compounds that suppress the thyroid’s function by blocking its ability to take up iodine.  In soy, the isoflavone called genistein (which may be one of the same compounds responsible for soy’s beneficial effect on protecting against breast cancer), is goitrogenic.  To be sure, soy is not the only food in which similar goitrogenic compounds naturally occur: cruciferous vegetables (including broccoli, cabbage, turnips and brussels sprouts), millet, and strawberries also contain various types of goitrogens.  So what makes soy different than these other foods?  For starters, the goitrogens in most of these other foods are generally deactivated by the cooking (or fermentation) process.  What’s more is that we tend not to eat these foods in such quantities that the goitrogens in them–neutralized or not–will have any sort of adverse effect on us.  Unlike these other foods, however, the goitrogenic isoflavones in soy are not neutralized by typical cooking and fermentation processes.   In the case of, say, infants, whose sole source of nutrition is soy formula… or adults who are knowingly or unknowingly eating multiple foods everyday “fortified” with soy protein, the levels of goitrogens may become problematic and wreak a bit of havoc on the thyroid… particularly in people with underlying thyroid problems or who are genetically susceptible.  Low-levels of thyroid hormone (hypothyroidism) can cause attention-deficit disorders, memory problems, depression, loss of energy, thinning hair and weight gain.

• The third may be attributable to the fact that, since the launch of genetically modified (GMO) soy in 1996, >90% of soy grown in the world is now GMO, meaning that genes from different species of plants/animals are artificially injected into the soy plant to create novel proteins that our bodies have not before encountered in nature.  Some researchers suspect that in susceptible people–like young children who have immature digestive systems or people with weak/inflammed digestive systems (‘leaky guts’)– these unfamiliar proteins can trigger immune responses to both themselves and to similar proteins which result in food allergies and intolerances, which are notably on the rise for some inexplicable reason.

One would have hoped that the FDA might have forced GMO soy developers (like Monsanto) to show evidence that their products did not, in fact, result in such outcomes before allowing them to unleash their products en masse into our food supply in the mid 1990s–as was done in many European countries.  But one would be disappointed to learn that this did not, in fact, come to pass.  And so, 13+ years after we’ve all been slipped GMO soy protein in everything from our infant formulas and granola bars to our breakfast cereals and fast-food burgers, evidence is just now trickling in that confirms some of these suspicions on the safety of processed soy in general–and GMO soy in particular.

So what’s an eater to do?

My vegetarian and vegan friends rely heavily on soy as a high-quality, complete source of vegetarian protein.  And health authorities keep telling those of us who eat meat to eat less of it… so wouldn’t soy be a lower-fat, healthy substitute?  It’s confusing to be sure.  I’ll be the first to admit that science has yet to offer a definitive answer on soy, but since this column is called “What I’m Eating Now,” I’ll give you my informed opinion, based on the state of the science and expert opinion today as I have come to understand it, on what I recommend with regards to soy. (And I should mention as a caveat that I don’t eat soy protein at all, since I have a digestive intolerance to it.  It’s worth mentioning that soy can be a difficult-to-digest protein for many, which is why the Asian cultures needed to ‘tame’ it through fermentation in many of their traditional foods.)

RED LIGHT SOY FOODS: Foods that just about everyone should avoid.

1. Soy infant formula. The figures I’ve seen show that 20%-25% of babies are being fed soy formula in this country, despite the fact that the American Academy of Pediatrics recommends only TWO
   

   Soy infant formulas are not recommended for milk-allergic babies unless they can't tolerate hypoallergenic, hydrolyzed cow's milk formulas, either.

   indications for the use of soy formula for feeding infants.  1) For vegan infants who are not breastfed; 2) For infants who suffer from a very rare and serious condition called galactosemia, in which they cannot digest lactose (milk sugar) at all, and therefore cannot have any milk-derived formulas. Unfortunately, it’s common practice for pediatricians to tell moms who think or know their babies have a sensitivity to cow’s milk protein (casein) to automatically switch to soy formula.  In fact, it is recommended to first try a hydrolyzed cow’s milk formula, in which the long milk proteins are “pre-digested” into smaller fragments called peptides that should not trigger allergic responses.  There are partially hydrolyzed formulas that contain peptides (small chains of a few amino acids) and elemental formulas, in which the milk proteins are completely broken down into individual amino acids (for hypersensitive infants).  It is always recommended to try these formulas in a milk-allergic baby first before resorting to soy-based formulas; however, their significantly higher cost (and stronger smells) may be prohibitive for many.  Because formula is an infant’s sole source of nutrition, the effect of some of soy’s more problematic compounds can be magnified in such large quantities in such tiny bodies. Soy protein can be difficult for babies to digest owing to the presence of naturally-occurrirng compounds called protease-inhibitors, and the phytates in soy can inhibit the absorption of various minerals, including calcium, iron and zinc. (Note that fermenting soy eliminates these latter problems, which is why traditional Asian foods are able to avoid these problems).   The use of soy formula also appears to be linked to higher rates of peanut allergy and other food intolerances than the use of cow’s milk formulas, so I’d recommend to exhaust all other options before using soy infant formulas if you can… especially if your baby is at high risk for developing food allergies.

YELLOW LIGHT SOY FOODS: If these are daily staples in your diet, I’d cut back to a few times/week for the whole lot combined.  But probably no need to avoid them altogether.

1. Processed foods and drinks containing soy protein isolate (SPI) or soy protein concentrate (SPC), like frozen veggie burgers (Boca Burgers, Gardenburgers, Morningstar Farms Garden Veggie patties), vegetarian meat substitutes made with “TVP” (textured vegetable protein), protein-fortified breakfast cereals (yes…this includes the wildly popular Kashi GoLean…please don’t shoot the messenger!), high-protein shakes or soy protein powders, most meal replacement/”energy” bars (and even some Granola bars, sadly), and soymilk.  (This has been the hardest paragraph I’ve written to date, as I know that many people are fiercely loyal to some of these products for their taste, convenience and ‘healthy’ halo…and frankly, I’m scared of the fallout I’m likely to get.) The fact of the matter is that (1) few Americans (even vegetarians) are protein deficient, so all of this added soy protein in our diets is nutritionally extraneous, (2) unless it’s labeled organic, the soy protein in these foods comes from GMO soy that has NOT been safety-tested in humans and is starting to be associated with some negative (but not life-threatening) health outcomes, (3) it is a highly-processed ingredient subjected to a host of unsavory chemical solvents that may retain toxic residues that can add up when consumed in large quantities, and (4) these foods contain 2-6x more isoflavones than traditional soy foods, delivering a concentrated dose of phytoestrogens that may mess around with your hormonal balance in an as-yet-unknown and possibly unwelcome way.  Now I’m not suggesting that it’s necessary go cold-turkey by any means, but I am suggesting that if your daily routine involves a bowl of Kashi GoLean in Soymilk for breakfast, a high-protein energy bar as an afternoon snack, and a frozen veggieburger for dinner, it might be a good idea to inject some healthy variety into your diet.

Sunshine Burgers are a rare breed of veggieburger: soy AND gluten free.

Alternatively, there are plenty of great convenience products out there that don’t use any soy at all that you might consider trying as well: Larabars are soy and gluten-free; There are a variety of non-dairy, soy-free, calcium-fortified “milks” for your breakfast cereals, including Oat milk, Almond milk, and Rice Milk, Hemp milk (which is a fantastic source of omega-3′s); Sunshine Burgers are sunflower and bean-based frozen veggieburgers that are both soy and gluten free; Mix1 makes refrigerated soy-and-lactose-free shakes that are high in protein, vitamins and fiber.  If you’re a protein-powder person, try hemp protein powder or whey protein isolate as good soy-free, gluten-free, low-lactose alternatives to soy protein powder.

GREEN LIGHT SOY FOODS: Foods you can enjoy without worry.

1. Organic, fermented/traditionally-prepared Asian soy foods like tofu, natto, tempeh or miso. By choosing organic, you’re eliminating the big question mark hanging over
   

   When it comes to soy, do as your fictional Asian grandmother would do

   the use of GMO soybeans, and by choosing more whole, traditionally-prepared foods, you’re benefiting from the time-tested fermentation processes that help tame most of soy’s more problematic nutritional quirks.  As mentioned earlier, virtually all of the data that show a health benefit for soy foods in preventing breast cancer are based on studies of Asian women who ate these types of foods.  There’s no compelling data to suggest you should limit these foods in your diet that I have come across.

2. Organic edamame.  Edamame, or boiled young soybeans, contain a moderate amount of isoflavones and lower levels of anti-nutrients (the protease inhibitors and phytates discussed above) than mature soybeans do.  As a result, edamame make a fine snack whenever you get a hankering.  XXXXXXXXX
3. Soy oil (or vegetable oil containing soy oil) and soy lecithin: If you live in America today and eat anything that comes in a bag, box or wrapper, it’s virtually impossible to avoid these soy-derived ingredients.  Fortunately, you really shouldn’t have to worry about them.  Soybean oil, by definition, won’t contain any detectable protein, and soy lecithin is a phospholipid (also a type of fat) used as an emulsifier in foods (like chocolate, margarine or ice cream) to help keep fat and water from separating.  There shouldn’t be any actual soy protein in either of these ingredients; many (but unfortunately not all) people who are allergic to soy are even able to consume products that contain these ingredients.

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