Research Review

Messina M, Redmond G. Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: a review of the relevant literature. Thyroid. (2006) 16:249-58.

Soy foods are a traditional staple of Asian diets but because of their purported health benefits they have become popular in recent years among non-Asians, especially postmenopausal women. There are many bioactive soybean components that may contribute to the hypothesized health benefits of soy but most attention has focused on the isoflavones, which have both hormonal and nonhormonal properties. However, despite the possible benefits concerns have been expressed that soy may be contraindicated for some subsets of the population. One concern is that soy may adversely affect thyroid function and interfere with the absorption of synthetic thyroid hormone. Thus, the purpose of this review is to evaluate the relevant literature and provide the clinician guidance for advising their patients about the effects of soy on thyroid function. In total, 14 trials (thyroid function was not the primary health outcome in any trial) were identified in which the effects of soy foods or isoflavones on at least one measure of thyroid function was assessed in presumably healthy subjects; eight involved women only, four involved men, and two both men and women. With only one exception, either no effects or only very modest changes were noted in these trials. Thus, collectively the findings provide little evidence that in euthyroid, iodine-replete individuals, soy foods, or isoflavones adversely affect thyroid function. In contrast, some evidence suggests that soy foods, by inhibiting absorption, may increase the dose of thyroid hormone required by hypothyroid patients. However, hypothyroid adults need not avoid soy foods. In addition, there remains a theoretical concern based on in vitro and animal data that in individuals with compromised thyroid function and/or whose iodine intake is marginal soy foods may increase risk of developing clinical hypothyroidism. Therefore, it is important for soy food consumers to make sure their intake of iodine is adequate.

My comments: After last week's newsletter, I received an email regarding the third Q&A where I made some comments about thyroid and metabolism and weight loss. The person who emailed me had mentioned having consumed a lot of soy protein products and running into problems with hypothyroid; she also mentioned having some clients with similar issues.

Since I've been researching various proteins for the book I'm finishing up (on protein, duh), and due to the controversy over soy protein, I started digging a little bit deeper into this issue and felt it was an issue worth addressing in the newsletter.

To give readers a brief background on the topic, the thyroid gland releases two primary hormones T4 and T3 in a ratio of roughly 80:20 and does so in response to the hormone TSH (thyroid stimulating hormone). Most T3 is actually made in other tissues (especially the liver) from the metabolism of T4. T3, along with the catecholamine (adrenaline/noradrenaline or epinephrine/norepinephrine depending on which side of the pond you're on) are two of the primary regulators of human metabolic rate. I should mention that iodine intake plays a crucial role in thyroid metabolism with inadequate intake of iodine causing thyroid problems.

Soy proteins are known to contain hormonal mimics called phytoestrogens. This include genistien, daidzein and others. A great deal of controversy exists over the impact of these types of compounds in the human diet; while phytoestrogens may have some beneficial effects (especially in post-menopausal women for whom low estrogen can predispose towards heart disease and bone loss) other research shows negative impacts. The effect of phytoestrogens in men is far less studied and understood. There is likely to be a sex and population specific response to these compounds.

Without getting into the myriad arguments involved over soy proteins, I want to focus on the thyroid issue since that's the main topic of the above review paper.

Early work, in animals, had supported the idea that soy proteins could actually increase thyroid (mainly T4) output but the above work suggests a very different effect in humans (other animal research also shows a negative impact of soy protein, primarily the isoflavones/phytoestrogens present in soy).

The above review is a current examination of the topic and concludes that, for individuals with normal thyroid functioning, soy has little impact. However, in individuals with pre-existing low-thyroid (hypothyroid) symptoms, soy proteins can exert a negative impact. Research has shown that soy protein intake may increase the dose of thyroid medication needed and another review (Doerge DR, 2002). has shown, using mainly animal work, that the phytoestrogens in soy can impair the enzyme (thyroid peroxidase) responsible for proper thyroid hormone production. That same review found that while soy protein itself could not induce a hypothyroid state, a high phytoestrogen intake coupled with a low iodine intake could.

I bring up this last point because the main provider of iodine in the modern diet is iodized salt and even there, diet surveys have shown a downward trend in overall iodine intake (due to a reliance on processed food and less iodinization of salt). I could see a high intake of soy products (which are being used to fortify some foods such as cereals and protein bars, in addition to the use of soy protein powders) coupled with a misguided attempt to minimize salt intake (often seen in athletes/bodybuilders who are obsessed with some notion of eating 'clean') potentially causing problems with overall thyroid metabolism.

So we have several different issues at stake here. It seems obvious that individuals with pre-existing thyroid problems (and note that women, the main target for soy foods, are more likely to have low thyroid levels) should limit their soy protein intakes. As well, someone who is steadfastly trying to avoid salt may want to limit their intake of soy protein to avoid any potential problems. If soy protein is consumed in large quantities, adequate iodine intake will be necessary.

So...recommendations. First and foremost realize that the issue is not with soy per se but rather with the phytoestrogens found in soy. Whether isolated soy proteins (such as powders or what is used to fortify some cereals and protein bars) even contain large amounts of the phytoestrogens is up to debate; isolated soy protein (powder or otherwise) is likely to be different from soy containing foods (such as soy beans, tofu, tempeh, etc).

Trying to avoid every last bit of soy intake (for example, a typical soy protein fortified cereal may contain a few grams at most of soy) seems misguided. Clearly, living on nothing but soy foods and soy fortified products is misguided as well. To me a happy medium seems the best; assuming no pre-existing thyroid problems, soy products are probably safe in some moderation. Just don't make them the sole source of your protein; there are plenty enough other high quality protein powders out there including whey, casein and milk powder.

Interview with Christian Finn

1. Hi Christian, thanks for joining us. Who are you and why should we care what you have to say?

CF: Although I don't know what the goals of your readers are, I'm guessing that most of them want more muscle, less fat, or some kind of combination of the two. I've spent the best part of the last decade trying to achieve the same thing. I've worked with a lot of different people, read a lot of research and experimented a lot on myself. Hopefully, some of the things I've learned will help your readers get better results in less time and with less effort.

2. Tell us about your own past athletic accomplishments or current goals.

CF: Well, the truth is that my athletic accomplishments amount to zero, other than running 100 meters in 13.2 seconds when I was about 16. I was never really any good at sports. I was always the last guy to be picked for the soccer team, for example. Nobody wanted me in their side, so I was just put in defense and told to stay out of the way. I've done a few different martial arts (a couple of styles of Karate, and some Judo). But, that's about it.

I go to the gym mainly because I like to look and feel as good as I can. It gives me the opportunity to try out new training routines, diets, and supplements to see if they actually work. It helps me work off the stress of running a business, improves my mood, and gives me a good excuse to stop working and get out of the house. I also like eating, and find it very difficult to stop at just one bowl of cereal or one cookie. It's a case of either not having them in the house or eating the whole pack. If I didn't go to the gym most days I'd probably be extremely fat

Right now, my goal is to lose some of the fat I've gained over the winter and get more defined before I go on holiday.

3. What's the best piece of training advice you've heard lately?

CF: From a guy on a forum somewhere:

lift weights

put them back down

repeat n times where n = 2-8

eat a lot

repeat few days later with more weight

My note: this is something I wrote (half-jokingly, which means it's half-serious) about how to apply some bit of research on how to lift for size gains.

4. What about the worst?

CF: I was in the gym the other day and saw this guy trying to do an overhead press while kneeling on a Swiss Ball. When I asked him why he was doing them on a Swiss Ball instead of on the floor, he said that doing them in an "unstable environment" made them "more functional for his core", and suggested that I do the same.

Because he was working so hard just to stay balanced, he was using a tiny weight, and wasn't really working his shoulders to any significant degree.

I'm sure that training in an unstable environment is useful for some people. I remember reading an article about a professional surfer who did a lot of work on unstable surfaces. And I can understand the thinking behind that. Training on an unstable surface should (in theory at least) help to prepare him for the unpredictability that he's going to experience on a surfboard on the ocean.

But I seriously question the value of programs that seem to place so much emphasis on the core, as if it's a new section of the body that's only just been discovered. I think people underestimate how much work their "core" does during other exercises. The other week, for example, I went back to doing single-arm dumbbell rows after a few months of doing rows with a barbell, and when I woke up the next day, my obliques felt really sore. I'd never realized before how much work they were doing just to keep my torso stable.

I'm not questioning the value of training the "core muscles," just some of the methods being promoted to do so.

5. Who in this field has influenced you and who do you listen to?

CF: Bryan Haycock: With Hypertrophy Specific Training (HST), Bryan did a good job of popularizing more frequent workouts, as opposed to the "train each muscle group once per week" philosophy that had become so popular in the 1990's. Although a lot of bodybuilders used to train this way before steroids became so popular, I think that HST brought the benefits of this type of training to a new audience.

Stuart McGill: I've read a lot of his research, and there's so much attention to detail in there.

I recently had the good fortune to go on a 2-day course that he presented and he had so much energy and enthusiasm for what he was doing. Sometimes I feel really jaded after reading through the latest bit of nonsense in the fitness magazines, or after I get the millionth question about the best way to 'loose' weight (for some reason, almost everyone seems to write 'loose' instead of lose). McGill's enthusiasm was contagious, and left me feeling a lot more refreshed and motivated.

Lyle McDonald: I won't say too much here! Other than that your ability to analyze research and give it a real-world application (or explain why it doesn't have one) is as good as I've seen anywhere.

6. If you had to give trainees a single important piece of training advice in terms of making gains, what would it be?

CF: I'd say that persistence and self-discipline are two of the most important qualities to cultivate for anyone serious about making gains. Once you have a decent training and nutrition program, the key to long-term success is to stick with it, and not get distracted by every new "wonder" program that you read about. Most people who try chasing every rabbit that crosses their path end up suffering from paralysis by analysis. They get confused by all the different ideas and theories, and end up doing nothing. I think it's a lot more important to work hard and be consistent, than to waste your time and energy second-guessing whether the program you're using is "right" or "wrong."

7. What about nutritional advice? Is there any single place where you see trainees making a mistake in their overall nutrition?

CF: I think a lot of people try to overcomplicate things and lose sight of the basics. I get e-mails from people struggling to lose weight, for example, and they'll go into great detail about things like meal timing, meal frequency, how many supplements they're using or what nutrients they're combining in each meal. But when I ask them how calories they're eating each day, they have no idea. In many cases, making a change to their total calorie intake (eat more to gain weight, or eat less to lose weight) is enough to get things moving again.

8. In your own training past, what would you say was your worst mistake? Put differently, if you could go back and time and train more effectively, knowing what you know now, what would you do differently?

CF: I got confused by all the different approaches to training and nutrition, and never really applied myself properly. I was using the excuse that I needed more information to delay actually putting real effort into whatever I was doing at the time.

In my late teens and early 20's, the only sources of information here in the UK (other than books) were Muscle & Fitness and Flex. In a typical issue of Flex, you might have Mike Mentzer writing about how training to failure was the only way to grow, that you should be getting stronger at every workout, and that you could reach your genetic potential in one year or less if you were training properly.

But in the same issue, Stuart McRobert would recommend NOT training to failure, as it would lead to burn out. Then there'd be articles "written" by the top bodybuilders at the time, like Lee Haney, Gary Strydom or Berry de Mey, recommending a high volume of the training. At the time, I didn't realize that many of these articles were ghost written. Nor was I aware that almost all the professional bodybuilders in the magazines were using drugs to get into that kind of shape.

I had no real idea which author to believe, so I ended up wasting a lot of time trying training programs that were just not that effective.

At one time, I remember being so taken with Mentzer's advice that I followed the program he was recommending with an almost religious zeal. I was writing down everything I ate, recording my workouts, and taking extra rest days if I wasn't getting stronger in each training session.

I think I ended up working each muscle group directly once every 2 weeks or something silly like that. I even bought the Ayn Rand books Mentzer recommended, just to get into the mindset of the whole high-intensity "thing."

Obviously, it didn't work very well.

Then I decided to start using some supplements, so I tried Joe Weider's FRAC. My girlfriend at the time was really worried that I would "end up looking like the muscle men in the magazines" if I used it and kept telling me to stop.

Like most supplements around at the time, it had no effect on anything.

So, if I could do one thing differently, it would have been to focus all my time and energy on just eating and training right, rather than thinking that the answer to getting better results lay in discovering just one more technique, secret or magic supplement.

9. Describe the sort of training you do now

CF: This depends on what I'm trying to achieve. For example, if I'm trying to gain muscle I'll train with weights 3-4 times a week for around 45-60 minutes each time. Each muscle group is worked directly at least twice a week. I'll also do some moderate-intensity aerobic work 1-2 times per week. Nothing major, just some brisk uphill walking or cycling.

If my goal is to lose fat, I'll still train with weights 3 times each week, but I'll cut back on the volume of work I do for each muscle group. My goal here is more to preserve the muscle I have, and if I do too much while on lowered calories then I get burned out quite quickly. I'll also replace the moderate intensity aerobic work with some high-intensity interval training, and cut back on the frequency of my lower body workouts. So I might work the upper body twice a week and the lower body only once.

10. You run a website called Factsaboutfitness.com where you present an enormous amount of informational articles on proper training and eating, along with dispelling any number of old myths. What prompted you to start that website?

There were a few reasons I started the site. For one thing, I was frustrated by the lack of reliable information about nutrition and exercise. At the time, I was lecturing around the country for a company responsible for training personal trainers. I felt that much of the information I was teaching was outdated or just wrong. I was training people to pass an exam, rather than teaching them how to become better trainers and instructors, and I felt like I was wasting my time.

The worst thing was that nobody seemed to care. I told the person who was in charge of the course content that I felt some of it was need in serious revision. He agreed but did nothing about it, at least not while I was there anyway.

Most of the information in books and magazines seemed subject to commercial pressure from advertisers. There didn't seem to be anywhere to go for reliable, unbiased advice.

At first, I was just writing for my own enjoyment and satisfaction. I'd recently finished a master's degree, and really enjoyed just reading research papers and journals. But it just seemed a waste of time to keep it all to myself, so I started writing short summaries about what happened in the studies, and posted them on the site.

Then I started an e-mail newsletter so I could let people know when there was new material on the site. That was back in the day when e-mail spam filters weren't so prevalent, and the newsletter started driving a lot of traffic to the site.

When I asked people what else they wanted on the site, the answer was basically, "more information." So, I started a paid membership site, which helped to cover the costs of running the site. And it just grew from there.

Questions and Answers

Q: Should I take a post-workout carbohydrate/protein shake when I'm dieting?

A: This is one of those questions that I have gone around and around in my head about for a number of years. The basic issue goes something like this. We know that post-workout carbs go preferentially to muscle, but eating carbs post-workout raises insulin which might impair fat loss/the use of fat for fuel. However, at least one study (in endurance athletes) has shown that the body continues using fat for fuel following glycogen depletion and, at the end of the day, any post-workout calorie/fat burn tends to be somewhat small.

As well, I am of the opinion that promoting optimal recovery (which means carbs and protein at some time point around training) is more important than any small benefit that might be gained by not eating. Overtraining is enough of a risk when you're dieting without eliminating nutrients for recovery. If you need to reduce total carbohydrate intake to get a sufficient deficit, I'd rather see them taken out of other meals, not the one's around workout.

Q: I am about 12% bodyfat and have been dieting now for 6 weeks straight (only one week of which was truly dedicated to UD2 and the others were a modified Atkins special) and would like to continue until Aug when I take my vacation and 12 days off from my diet. so, if I dieted until Aug that would mean that I would be dieting for 13 weeks straight... so, is it necessary to throw a break in the middle of the 13 weeks or will I be ok if I just take my break on my vacation?

A: I don't think so. In my opinion most people diet for too long without a break. Between metabolic slowdown, hunger and general miserableness, they would be better off splitting up their dieting periods. This is even more true when you're lean and your body is fighting back that much harder.

In your specific case, I would suggest dividing your total 13 weeks of dieting into

6 weeks dieting

1 week break (run your 3 day UD2 carb-load into a 7 day break for 10 total days)

6 more weeks dieting

The 10 days off will help to reset some of the metabolic factors (leptin, insulin, etc) that slow fat loss and, if you avoid excessive dietary fat, you may actually lean out further during the break. Then you can do your final push of dieting down before your vacation.

Full diet breaks, along with how long I think people should diet before taking a break are discussed in both The Rapid Fat Loss Handbook as well as A Guide to Flexible Dieting (how often to take free meals and do refeeds are covered in this book as well.

Q: When I warmup, I usually pyramid up with a sets of 15, 12, 10 and 8 and then move into my working sets. Thing is, I'm usually already tired by the time I get to my main sets. Is there a better way to warmup?

A: Yes. A lot of folks, still influenced by the old muscle mags use the kind of high rep pyramid to warmup for their heavier sets, wasting energy and tiring themselves out in the process. I prefer, in general, a low repetition warmup with the goal of doing the minimal amount of work possible that will properly warm the individual up for their work sets.

Please note that there is some variability in how long it takes people to warmup. Some folks warmup relatively quickly while others take many more sets to really get 'clicking' (this seems to be more prevalent for women for some reason).

A generic warmup might be

50-60% of work weight for 5-8 repetitions

70-80% of work weigh for 3-4 reps

80-90% of work weight for 2-3 reps

90-95% of work weight for 1 rep

100% of work weight for 1 rep (optional)

rest three minutes and then begin with your first heavy set.

The first set is just to pump some blood through the joints and get you loosened up. As the warmup weights go up, the reps come down to avoid unnecessary fatigue. Taking a final repetition at the day's work weight is beneficial for some. If you often find that your second heavy set at a day's weight feels lighter, you should try that final single at 100% of your day's work weight.

So a typical warmup for say, a 225 lb squat might be something like

135X5-8 (nice and easy, getting stretched out)

165X3-4

185X2-3

215X1

225X1 (optional)

rest 3 minutes and then go into your work sets.

Finally, please not that the repetition counts above are just guidelines. Many people find that, during a warm-up set, there is a specific rep where the set starts to feel easier. That's a good repetition to stop on. So if on your first set, the 6th rep suddenly feels super easy compared to the 5th, go ahead and stop after number 6.

The above should let you get warmed up sufficiently without tiring you out unnecessarily.