Is MSG making people fat?

[jgm]

I'm starting this topic because I know several eGulleters have excellent knowledge of how scientific studies are run, and how to interpret the results.

A news story out this week cites a study done on 750 Chinese men and women between the ages of 40 and 59:

They divided the eaters into three groups depending on how much MSG they used. Those who used the most were nearly three times more likely to be overweight even when the groups were controlled for physical activity and total calorie intake.

Here's a link to the UNC report:

Link

I read the story in the Chicago Tribune, which allows comments after its stories. And there were some very interesting comments. One person recommended people go to www.migraineweb.com, which has a list of ingredients it claims "always contain MSG":

Hydrolyzed Protein:  (plant, vegetable, any kind)

Sodium or Calcium Caseinate

Autolyzed Yeast, Yeast Extract

Yeast Food,  Yeast Nutrient

Textured Protein

Glutamic Acid

and other processed foods that "often contain MSG or create MSG during processing":

Bouillon or Stock

Broth (chicken, beef, any kind)

Carrageenan

Whey protein, whey protein concentrate, whey protein isolate.

Soy sauce, soy protein isolate, soy protein concentrate.

Malt Extract or Flavoring, Malted Barley

Maltodextrin

anything Protein fortified

Another reader speculated that MSG is a neurotoxin that affects a person's setpoint that determines their weight, or perhaps that weight gain could be the body's way of diluting MSG's effects.

I'm interested in what others think of this information, both that in the UNC article and in the other info I've listed. I'm interested in hearing some "educated" opinions. Or comments.

[Jason Campbell]

Well my 'educated' response, without reading the original paper, is that a study group of so few subjects, combined with only one ethnic group- plus the restrictive age range- suggests it probably doesn't prove much. Does the paper examine any economic reasons for MSG usage (I ask as I haven't been able to access it)?

[Chris Hennes]

Well my 'educated' response, without reading the original paper, is that a study group of so few subjects, combined with only one ethnic group- plus the restrictive age range- suggests it probably doesn't prove much.  Does the paper examine any economic reasons for MSG usage (I ask as I haven't been able to access it)?

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The selected group was chosen because their food intake was relatively easy to measure: they were rural Chinese villagers who prepared the vast majority of their own meals at home. It does not examine the reasons for MSG usage, simply pointing out that it is used frequently in Chinese cooking (the average use was 0.33 grams per person per day). The correlation found was quite strong: naturally the study "proves" nothing, but adds another piece of data to indications that MSG has adverse and poorly understood health risks.

Edited August 15, 2008 by Chris Hennes (log)

[slkinsey]

The UNS article says:

“We found that prevalence of overweight was significantly higher in MSG users than in non-users,” He said. “We saw this risk even when we controlled for physical activity, total calorie intake and other possible explanations for the difference in body mass. The positive associations between MSG intake and overweight were consistent with data from animal studies.”

What this doesn't answer, of course, is whether there is something about the overweight people that made them prefer higher levels of MSG. We already know that two people with the same physical activity and total calorie intake can differ widely in weight. So somehing is making the overweight person overweight. So here's the question: Is it the extra MSG that makes that person overweight, or is it the "something" that makes that person prefer extra MSG?

[Chris Hennes]

What this doesn't answer, of course, is whether there is something about the overweight people that made them prefer higher levels of MSG.  We already know that two people with the same physical activity and total calorie intake can differ widely in weight.  So somehing is making the overweight person overweight.  So here's the question:  Is it the extra MSG that makes that person overweight, or is it the "something" that makes that person prefer extra MSG?

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Right -- a very interesting study would be to take two groups of people who don't eat much MSG and add it to one of the groups' diets and see if that group gains weight, on average. I haven't seen any large-scale studies of this nature, however.

EDITED TO ADD: Or course, the flaw with this study would be that since MSG makes food taste better, that group would be naturally inclined to eat more of it . Maybe instead of adding to the food they could take MSG supplements.

Edited August 17, 2008 by Chris Hennes (log)

[Anna N]

Does anyone know the amount of ADDITIONAL MSG (since I understand it occurs naturally in many foods) that someone on a Western diet of fast/processed foods consumes in a day?

[Jason Campbell]

MSG intake suppresses weight gain, fat deposition, and plasma leptin levels in male Sprague-Dawley rats.

http://www.ncbi.nlm.nih.gov/pubmed/18559279

[nickrey]

First year statistics: a strong correlation does not equal causality.

Let's create our own headline:

Ice cream sales and shark attacks are strongly correlated: headline = Eating ice cream causes shark attacks.

We must ask is there a third factor that led the group to use more MSG that caused the group to be overweight? For example, is MSG used only by the wealthier people who can afford more food?

I'm with Chris, let's run an experiment: preferably with control groups, random allocation to treatments, and researchers who do not know who is in which group.

[slkinsey]

We must ask is there a third factor that led the group to use more MSG that caused the group to be overweight? For example, is MSG used only by the wealthier people who can afford more food?

Not having read the paper, which is gated, I note that the authors say in the article that "we controlled for physical activity, total calorie intake and other possible explanations for the difference in body mass." This would presumably account for most of the extrinsic factors such as socioeconomics.

[nickrey]

We must ask is there a third factor that led the group to use more MSG that caused the group to be overweight? For example, is MSG used only by the wealthier people who can afford more food?

Not having read the paper, which is gated, I note that the authors say in the article that "we controlled for physical activity, total calorie intake and other possible explanations for the difference in body mass." This would presumably account for most of the extrinsic factors such as socioeconomics.

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I too only got the abstract but it has the words:

With adjustment for potential confounders including physical activity and total energy intake, MSG intake was positively related to BMI

They appear to have partialled out the effect of physical activity and total energy intake. This is typically based on an assumption of a linear relationship, which may not be the case.

I'd simply caution that one non-replicated correlation study makes a hypothesis, not proof.

Unfortunately once the media gets a hold of something like this it often becomes folklore.

[Jason Campbell]

I think we can't have any 'educated' debate when we can't access the report. I tried through my Athens Account but this didn't work.

Without reading [and understanding] the paper then we have to fall back onto 'educated' common-sense. Always dangerous.

From a 'common-sense' angle, there has been generally accepted research (WHO) that suggests Japan's obesity crisis has a correlation with their adoption of Western foodways. This is relevant as MSG has a cultural tradition in Japan, less so in China. Something that springs to my mind is the possible relevance of cultural perception of obesity, not all cultures find obesity the 'turn-off' that we in the West do. I seem to remember some research done about 15 years ago on the fattening of pigs which found that by adding MSG to their [lower cost] feed the producer was able to induce the pigs to eat food that they would not normally prefer, hence fattening them up more cheaply. I will have to search for the e reference though.

If we extrapolated that, then the hypothesis might be that those in the lower economic strata use MSG to make unpalatable foods more unctuous. But we would have to examine not just the calorie intake but the foods consumed.

[culinary street urchin]

Too many unknowns and too many shady researchers abusing the public's paranoia about 'toxins'. MSG could be the next big thing - like aspartame!

Bottom line is body fat mass is a simple equation of caloric intake vs. calories burned on a day to day basis. It's physics. It takes very few 'extra' calories over a life time to gain alot of extra fat. A single can of beer every day can add up to many lbs of fat in just a few years.

I would want to know how they controlled for food intake, because over eaters tend to underestimate their calorie intake. In fact, it would take just a few self deluded 'faties' consuming extra MSG to skew the entire results.

Here's a thought, what if the weight gain was not fat, but increased muscle mass or bone density? When I started working out I actually gained a little weight, even though I was also burning fat. Maybe MSG speeds the repair of muscle tissue and increases bone density?

[Jason Campbell]

"the average use was 0.33 grams per person per day"

If this is the case then it can be explained by increased consumption of meat.