The soy controversy: More questions than answers

Ten days ago, we sent you a message on new research that was raising concerns about the safety of soy. Since then, many of you have written back to us to ask how you should alter your diet, or to point out apparent contradictions in the soy research. (For example, wouldn’t most Asians have dementia and breast cancer based on their soy consumption?)

Understandably, we’ve all been distracted lately. But since the President and other leaders have asked that we try to get back to “normal” as much as possible, we wanted to answer the most common questions you raised about soy.

Before we address the science, we should address one overriding concern. Several of you asked about the sources and reliability of the soy studies. If, for example, cattle ranchers finance a study that shows soy isn’t as safe as meat, can the results be trusted?

We agree that knowing the source of the study’s financial support is critical. In this case, however, there are powerful and well-funded industries on both sides of the debate. The dairy and agriculture industries may wish to discredit soy. But companies like Archer Daniels Midland and Monsanto, some of the largest suppliers of soy, have an interest in seeing this legume become commonplace on our dinner tables.

It’s also important to point out that HSI has absolutely no “soy agenda.” We will not benefit by having every member decide to abandon soy completely or to eat only soy in the future. Our sole concern is to alert you to possible risks that you may not be hearing about elsewhere, so you can make an informed decision about how and whether to include soy in your diet.

Now, to your questions

1) “If soy leads to dementia, breast cancer, and other conditions, why aren’t those diseases more prevalent throughout Asia, especially in Japan?”

According to information we’ve received from the Weston A. Price Foundation and Dr. Joseph Mercola, the average soy consumption in Japan and China is close to 10 milligrams per day, which is about two teaspoons. (Original source: Fukutake M, Takahashi M, Ishid K, Kawamura H, Sugimura T, Wakabayashi K; Food Chem Toxicol, 34:457-61.) This is substantially lower than the amount consumed by those Americans who use soy as a dairy or protein substitute.

Asians, you see, don’t use soy as a protein replacement. They use it to complement rich protein sources, such as fish. There’s some conjecture — although we were unable to locate a formal study — that this combination with other protein may mitigate some of soy’s potential risks.

Furthermore, while Americans and Europeans eat a great deal of processed soy (like tofu), Asians eat only carefully fermented soy (like Miso), using processes to remove the natural toxins and preserve soy’s benefits.

2) “I take soy lecithin to help lower cholesterol. Are the dangers associated with soy lecithin the same as the potential dangers of soy protein?”

I spoke with Sally Fallon of the Weston A. Price Foundation. She explained that the lecithin is basically the residual product left over after all the oil is squeezed from the soybean. Therefore, she explained, the concentration of pesticides in soy lecithin tends to be very high. I asked if that was the primary concern and if it could be addressed by using organic soy in lecithin production. She said yes, but warned that it’s difficult to find organic soy lecithin.

So concerns over soy lecithin arise from the possible presence of pesticides, rather from risks associated with soy protein. And it’s true that many studies have indeed shown that soy lecithin can help lower cholesterol levels.

We should note one additional concern, however. We found information on Dr. Mercola’s website indicating that soy lecithin supplements given during perinatal development could alter “synaptic characteristics in a manner consistent with disturbances in neural function.” (Original source: Bell JM, Whitmore WL, Cowdery T, Slotkin TA, “Perinatal dietary supplementation with a soy lecithin preparation: effects on development of central catecholaminergic neurotransmitter systems.” Brain Res Bull 1986 Aug; 17(2): 189-95)

3) “I gave up dairy and switched to soy milk. Does the information you provided relate to soy milk, as well? What other alternatives are there?”

An 8-ounce glass of soy milk contains approximately 20 mg of isoflavones, the phytoestrogen found in soy. One study showed that a dose of 30 mg of isoflavones per day affected thyroid function in Japanese women. Another study showed that American women, who consumed 45 mg per day, demonstrated hormonal disturbances after one month. (I’m having details of these studies mailed to me, so I can’t provide the citation here. However, I didn’t want to delay responding to your concerns any further.)

As far as alternative milk sources are concerned, there are several: rice, almond, oat, and multi-grain. Unfortunately, they’re not entirely free from concern either. Rice milk, for example, has a higher sugar content than soy milk. Some brands of almond milk contain corn syrup or brown rice syrup. Depending on your tolerance level for sugars, they may prove to be a better alternative. Still, you should read the ingredients carefully.

It’s difficult for us to make a wholesale recommendation on this, as there are both benefits and risks to eating soy. Dr. Jonathan Wright, M.D., advises his patients and readers that, until the safety debate is better resolved, they should restrict their soy consumption to no more than three servings per week.

While our goal at HSI is always to provide you with answers, we too feel there are many open questions left in the debate over soy. We’re continuing our research and will keep you updated on any relevant developments. In addition, we’re putting together a more detailed research report covering the benefits and dangers of soy.