Dispelling nutrition myths, ranting, and occasionally, raving

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Bacteria: the next weight loss craze?


Recent research has indicated that a change in gut microbial flora following gastric surgery may contribute to weight loss in patients. This conclusion was reached following a study on mice. A group of mice underwent gastric-bypass surgery, their gut microbial flora was monitored, and then some of that bacteria was transferred into mice that had not undergone surgery.

There were also two other groups of mice that underwent “sham” surgeries (their intestines were snipped apart and then reconnected). One of these groups continued to be fed a high calorie diet post-surgery while the other was put on a restricted diet.

There are a few things about this study that intrigue me. I think it’s important to note that the mice place on the restricted diet lost the same amount of weight as the mice that underwent the true bypass surgery. To me, this indicates that the level of obesity in these mice may not have been the same as the level required for weight loss surgery in humans.

I also find it curious that the mice that received the gut flora apparently had no pre-existing gut flora of their own. I’m not sure if this is an error in reporting but you would be extremely hard-pressed to find a human without pre-existing gut-flora (perhaps if they’d been on a very high dose course of antibiotics). We also know that gastric bypass surgery can result in nutrient deficiencies and it’s possible that the presence of the bacteria found in these post-surgical mice might also increase the risk of malnourishment.

Finally, and most importantly, even if weight loss in mice can be attributed to the presence of certain bacteria in the gut, mice are not the same as humans. Do mice have the same gastro-intestinal flora as humans? Do they react to surgery in the same way as we do? Do they have the same relationship to food as we do? I would hazard to guess that the answer to all of these questions is no.

While this research is very interesting, and may in the long-term provide us with further insight into obesity and weight management, at this point I would be extremely cautious when interpreting the results.


Of mice and omegas

Apparently the anti-omega-3 supplement trend is continuing. The latest piece of research comes from BC and shows that, in combination, omega-6 and omega-3 polyunsaturated fatty acids may be increasing inflammation in the body. The study concluded that omega-3 supplementation could be increasing gastrointestinal distress in the elderly. According to a news article quoting the lead author, “levels of omega 6 are so high in our bodies that any more unsaturated fatty acid — even omega 3, despite its health benefits — will actually contribute to the negative effects omega 6 PUFA have on the heart and gut”.

I don’t dispute the likelihood that many of us are now consuming too much omega-6. However, this study is not affecting my decision to take omega-3 supplements. As a dietitian, I know that it’s better to get my nutrients from food and I should be eating more fish. Because I don’t eat as much fish as I should, I take an omega-3 supplement.

Why isn’t this study influencing my decision to pop an omega-3 supplement every second day? Well, the study was done on mice and recent evidence shows that mice studies may not be the best models for humans. In addition, the mice were fed a high fat diet (40% of total calories) with fat coming from canola oil and corn oil, with some mice being given fish oil as well. From where I sit, this is not much of an approximation of my fat consumption and I’m sure that applies to many of you as well. I get fat from olive oil, butter, dairy products (especially yoghurt and cheese), nuts and nut butters, coconut oil, eggs, etc. Very little of my fat intake comes from canola or corn oil. In addition, 40% is quite a high intake of calories from fat – the Acceptable Macronutrient Distribution (AMDR) for fat is 20-35% of total calories.

If you are consuming all (or most) of your fat from canola and corn oil and you’re eating a high-fat diet (and if you’re a mouse) then perhaps this study should give you pause before you decide to start taking an omega-3 supplement. However, I think that you should be more concerned about the excessive consumption of a limited variety of fats than you should be about adding omega-3 PUFAs to the mix.