10 March 2014

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Health Report 28 min 3 speakers 8 chapters transcribed 3 days ago

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Transcript generated automatically by AI and may contain errors.

What is the main question about bugs inside us and their link to obesity and diabetes?

Dr. Norman Swan 0:00

Hello and welcome to the Health Report with me, Norman Swan. Today, could the bugs inside you and me be making us fat and giving us diabetes? And if that's true, you might want to go out and find some thin people to do something unspeakable with their poo. More wasted money in health care that could be spent more wisely. And speaking of fat, a story on diet and nutrition that ran prominently last week. Which could have left you confused or misled, so I thought I'd give you a chance to hear about it in detail. It was a large study in mice, basically looking at whether living longer is about what you eat or how much you eat. One of the study's leaders was Professor Steve Simpson, who's director of the Charles Perkins Centre at the University of Sydney.

Steve Simpson 0:43

It was the most complicated study and indeed the most ambitious study ever to look at macronutrition in any animal, particularly any mammal. What we set out to do was to look at the interactive and individual effects of protein, carbohydrates and fats in the diet of mice and that requires a very large number of dietary treatments. Rather than the typical study which would look at a control diet with standard mouse food and compare it to a high fat diet What we did was design twenty five diets that spans ten different ratios of protein to fat to carbohydrate at one of three total energy densities and allowed our mice to feed ad libiton throughout their lives.

Dr. Norman Swan 1:29

Ad libiton. So that means

Steve Simpson 1:31

they could eat as much as they liked, their foods never ran out and they could eat when and as much as they wished, but they were confined to a single dietary composition throughout.

How did the researchers design the massive mouse macronutrient study?

Dr. Norman Swan 1:41

And the proposition that you were testing was whether or not the gross composition of the diet, so forgetting about vitamin C or antioxidants or some mineral compound or other, that at a big level grossly protein, carbohydrate, fat, do they make a difference to how long you live?

Steve Simpson 1:58

Absolutely. These are the main energy yielding or caloric nutrients. We wanted to look at the contribution of the balance of macronutrients in the diet. And we had plenty of reason from earlier work on a range of other animal systems, including humans. all the way down to slime moulds and flies, we'd shown that the balance of macronutrients was critically important when it came to the health and longevity of organisms of all types. And what we did was to say well let's parse the interacting contributions of macronutrients, not just

Dr. Norman Swan 2:37

So a holistic study. And you're also looking at the proposition as to whether or not calorie restriction extends life in its own right.

Steve Simpson 2:45

Yes, exactly. It's clearly there's huge amounts of evidence across a whole range of organisms that if you modestly restrict calorie intake Many organisms live longer. But when you look in detail at that literature, nobody has properly parsed the source of those calories.

Do calories alone determine lifespan or do protein‑carb‑fat ratios matter more?

Steve Simpson 3:02

So that leaves begging a really big question. Is it calories per se that matter?

Dr. Norman Swan 3:07

Or what happens to your diet when you cut your calories?

Steve Simpson 3:10

Well, yes, and the form in which the calories come in your diet. So is a calorie a calorie? So if you eat fewer calories or eat more calories, are you going to live longer or less long as a result of the calories themselves or Is it really much more important from where those calories come? In other words, whether they're in the form of protein, carbohydrate or fat? And whether or not the combination of those things matter, the ratio of different nutrients one to the other and whether that has more of an impact on your health and longevity than just pure counting calories. And overwhelmingly the data from this study indicate that it isn't calories that matter, it's the form in which they come and in particular the proportions of protein to carbohydrate calories in the diet.

Dr. Norman Swan 3:57

So let's go to the findings.

Steve Simpson 3:59

What we found was several things. Firstly, the calories don't explain how long mice lived. Now this is clearly a study on mice, not on humans, and so the findings we need to take with a little bit of caution.