Is soy good for us?

I was recently asked to write a piece about soy products for a publication and thought that I would share my views on soy with my followers on this blog.

The consumption of soy products has grown in popularity in Western societies in recent decades on the notion that soy is a healthy food. After all soy is eaten in numerous countries in Asia without ill effect. And I too jumped on the soy bandwagon in my 20s consuming soy milk instead of cows milk (and scouting out every other soy product under the sun). I still see a lot of clients in my nutritional practice who come to me initially consuming soy milk.

Here’s the thing: traditional Asian societies only ever ate soy beans (which are technically a legume) that were very long fermented (i.e. for numerous days or weeks) eg miso, natto, tempeh, soy sauce or tamari (which is wheat-free soy sauce). This is because soy beans contain extremely high levels of  phytates which wreak havoc on the body including creating nutritional deficiencies, gut permeability (leaky gut) and inhibiting certain digestive enzymes. Traditional societies discovered that only through a process of very long fermentation can the toxic levels of phytates in soy beans be reduced making soy beans more digestible. Small infrequent consumption of these traditionally long fermented soy bean products is ok for the average person who is not suffering from any digestive issues. However, eating large amounts of unfermented soybeans on a regular basis is not a good idea (eg soy milk, soy cheese, soy yogurt, tofu, edamame, soy flour).

Beyond the issue of phytates, soy has additional problems. Soy beans also contain phytoestrogens which adversely affect hormones and can lead to reproductive issues such as infertility.  A study at the Harvard School of Public Health found that consuming just 1 cup per day of soy milk decreased  sperm count, especially in men who were overweight or obese. Other studies found that phytoestrogens in soy may adversely effect male reproductive hormones and sperm capacitation (an important process sperm must go through after being ejeculated into the female reproductive tract). Soy phytoestrogens also have potentially harmful effects on women. A large review of 47 studies found that soy phytoestrogens reduced levels of LH and FSH, 2 hormones essential to fertility and reproductive health, and increased menstrual cycle length (source: Chris Kresser). I don’t think it is coincidental that I see many vegetarian yoga practitioners who eat large amounts of tofu in their diet and are unable to fall pregnant.  Studies show that fermenting soy decreases but does not completely eliminate phytoestrogens.

The research on soy is not however clear-cut. Some studies (like the ones mentioned above) show harm, while others show no harm. On this basis I take a highly precautionary approach. Given that soy is not essential to health, is not nutrient-dense, contains extremely high levels of phytates and that soy phytoestrogens may cause reproductive and endocrine problems, I would recommend avoiding unfermented soy entirely and only consume long-fermented soy products in small infrequent amounts. The table below sets out a quick summary.

The Perfect Human Diet- DVD review

I recently watched a documentary film (rented from iTunes) called ‘The Perfect Human Diet’ (not to be confused with the book called ‘The Perfect Health Diet’ by Paul Jaminet, although the subject matter is very similar). The film was released as a DVD on 1 January 2013.

The film looks at evolutionary and scientific factors to determine what we are biologically designed to eat. The upshot: we are genetically programmed to eat a diet of the type eaten by our paleolithic (hunger gatherer) ancestors 2+ million years ago- essentially a diet rich in animals (muscle meat, organ meat and fat) and plants (including nuts and berries).

On the whole I give this DVD a big thumbs up. It’s is a terrific introduction for anyone new to ancestral (primal, paleo) diets who would prefer to watch a DVD instead of reading a text or scouring websites. It’s also great for anyone who is familiar with a paleo diet but would like confirmation of it from an evolutionary and scientific basis. And of course paleo-anthropology geeks like me would relish it.

Here are some of the salient points that emerged from the DVD:

• Journalist CJ Hunt (the narrator) suffered from a near death experience (heart attack) at 24 while running. At the time he was eating according to the USA food pyramid guidelines (ie a conventional diet) and felt constantly hungry. He then embarked on a quest over the next 10 years to find, in his words, “the perfect human diet”. To this end he experimented with a range of nutritional philosophies such as vegetarianism, blood type diet, vegan diets etc (does this journey sound familiar to you?? Been there. Done that. Bought the T-shirt….). He then came across the paleo diet and started doing his own research. What transpires is a marriage of science and evolution in determining what we are biologically designed to eat.

• Modern diseases and illnesses are a result of a departure from what our genes are biologically designed for (including a departure from an ancestral diet). “We are so far off base from what we are genetically designed to eat”.

• The film features many international paleo heavyweights including Loren Cordain (author of The Paelo Diet), Robb Wolf (author of The Paleo Solution), Gary Taubes (author of Good Calories, Bad calories), Michael Eades (author of Protein Power),  and the work of Price Pottenger Nutritional Foundation (which supports the work of nutritional pioneer Weston A Price).

• The paleo diet is not a fad or a trendy movement. Or, if it is, it is a 2.6 million year diet- in fact the oldest human diet.

• There’s been a steady decline in human health since the agricultural revolution (which started 10,000) with the introduction of grains into the human diet for the very first time. Much emphasis was given to the fact that wholegrains are just as bad as, if not worse than, refined grains because they block the absorption of minerals.

• Early dietary advice from medical and scientific community (about 100 years ago) was a low carb/sugar/starch diet. However that nutritional philosophy was turned on its head with the low fat movement starting 50 odd years ago. When fats are reduced, carbohydrates inevitable increase. With this change in macronutrient emphasis, human health really started deteriorating.

•  There was great myth busting around the notion that dietary fat doesn’t make you fat and in fact high carbohydrate loads are responsible for fat gain.

• The conventional food pyramid is essentially a “feedlot pyramid” as farmers follow it to fatten up cattle.

• Nutrient-dense animal foods doubled early human brain size.

• Good discussion on protein releasing slow steady state energy throughout the day in contrast to carbohydrates which cause energy spikes and crashes.

• A tour of a supermarket showed that most of what is sold is not consistent with what our genes are designed to eat. Boxed cereal in particular is no better than eating straight sugar and you would only do so if there was nothing else to eat and you were on your death bed and imminently needed glucose to the brain. Man, and to think I grew up on the stuff thinking that all that granola and puffed wheat was good for me.

Here are what I thought were the 2 main shortcomings of the film or what I thought needed further clarification:

1. While it was great to see the film really emphasising the dangers of sugar and refined grains, there was interestingly no mention at all of what I call public enemy number 3: industrial seed oils (eg canola, cottonseed, vegetable oil, margarine etc). Maybe it’s case of “slowly slowly catchy monkey” i.e. let’s get the public comfortable with the dangers of sugar and refined grains first before we explode their brains with another ubiquitous component of modern diets- processed oils. It would, however, have been prudent in my view to have had at least passing mention to this third category of dietary toxins.

2. The film takes what I call a very strict paleo view of the human diet ie no milk post weaning, lean meat, no grains even if properly prepared. Taking  each of these in turn:

• on the issue of milk, the strict paleo view is that hunter gatherers did not drink milk post weaning and ergo humans are not designed to drink milk. I have thought long and hard over the past few years about the relevance of milk in the modern human diet and after much research I concur with the views of Chris Kresser on this subject: just because our paleolithic ancestors didn’t consume a certain type of food doesn’t mean that we shouldn’t consume it if 4 conditions are met: (a) it’s nutrient dense (b) it’s non toxic (c) you have the relevant enzymes to digest it and (d) you enjoy consuming it (the last condition is my contribution!). In relation to milk, like all food, everything come down to its source and processing as not all milk sold on the market is the same. For more information on this issue I suggest you speak to me in person or click here and here.

• there was mention a few times to the importance of eating “lean” meat. I find the reference to lean meats (which often pops up in the paleo text books) confusing and contradicts the references to the importance of eating fat and in particular the brain and other organ meats of animals which are naturally high in saturated fat. Hearing references to lean meats might confuse the public into thinking that we should be eating a low fat diet. Perhaps the reference to lean meat might have something to do with the fact that the wild animals hunted down by our hunter gatherer ancestors were leaner than the farmed cattle we consume today. Or perhaps lean meat refers to muscle meat as opposed to fat and organ meats and bones which should also be consumed. My view is that if you eat the whole of the animal – like our ancestors did-  then you can’t go wrong. If anyone can explain to me why paleo heavyweights refer to lean meats I’d love to hear it.

• Grains, even whole grains, are touted as being strictly out on a paleo diet for they were cultivated as part of the agricultural revolution a mere 10,000 years ago when our hunter gatherer ancestors abandoned nomadic lifestyle to an agrarian one. The film explains that grains block the absorption of minerals leading to bone density loss (there was no mention in the film that “phytates” primarily found in the outer husk of grains are responsible for this damage to our osteo skeletal structure).  However, nuts get a tick on a paleo diet but there was no mention of the fact that nuts also contain phytates. Phytates are significantly reduced by proper preparation through long soaking and dehydrating (today called activating nuts), sprouting or fermenting. Dr Weston A Price in the earlier part of last century discovered that all traditional societies the world over prepared grains, legumes, seeds and nuts through one or more of these proper preparation techniques to reduce the phytate content. My view is that if nuts are going to be consumed, they too must be properly prepared otherwise I wouldn’t recommend their consumption. Secondly while I don’t personally consume grains (as I don’t think they are very nutrition dense for all the effort involved to properly prepare them) I do think that the occasional consumption of properly prepared grains (eg sourdough, sprouted, long soaked) is fine if you don’t have blood sugar issues or allergies and if you favour the gluten-free grains (eg rice, buckwheat). In this regard my nutritional philosophy is more aligned with the Weston A Price foundation than strict paleo.

One of my favourite quotes from the film:

Q: Is a paleo diet convenient? A: It’s hell of a lot more convenient than diabetes, cancer and cardio-vascular disease.

Click here to view the film’s website including trailer.

Now I’d like to hear from you. Have you seen The Perfect Human Diet? If so what was your view? Do you agree with my comments?