The sweet nectar that we relish in our morning coffee, the teaspoon we sprinkle over our cereal, the childish delight of candy floss. We all know that too much sugar is bad for us, but there is a growing wealth of evidence to suggest that rather than just being a guilty pleasure sugar is actually toxic to us.
Robert Lustig is the public face of the anti-sugar movement. His 90 minute lecture, ‘Sugar, the bitter truth’, has over a million hits on youtube. I wanted to summarise what he says.
When we talk about sugar in food terms we almost always mean sucrose. It is Sucrose and Fructose to which I refer whenever I mention sugar (rather than Glucose which is actually pretty vital for us)
Diets and the majority of nutrition related advice hold to the basic assumption that:What you eat = What you burn + What stays in your body
In other words, if you eat less and do more, you will burn more calories than you eat, losing weight.
Lustig challenges this assumption saying that not all calories are the same. There are different fat, sugars, proteins etc which all effect our body in different ways. The traditional assumption says that if you want to burn the calories from a chocolate biscuit you need to go for a 20 minute run!
He argues that the obesity epidemic currently faced by the western world is a result of reducing the fat content of our diets based on an incorrectly carried out data from over 40 years ago.
When we eat glucose insulin is triggered to help break it down and 80%- 90% of the calories will be absorbed by cells in your body or stored as useful glycogen. Various other mechanism are in place but the outcome is that less than 1% of the original calories undergo de novo lipogenesis (DNL) and are stored as harmful fats.
Fructose/Sucrose however doesn’t trigger insulin and as such, per calorie, 3 times as much needs to be phosphorilated by the liver compared to glucose. Also the mechanism that the liver used to break it down increases DNL meaning that compared to glucose which produces between 0-5%, up to 30% ends up as fat.
In addition to this, when we ingest glucose a pathway to our brain is triggered telling us we are no longer hungry.With the bad sugars though, the pathway is not triggered. In fact they lead to higher reward levels from the brain for eating the bad sugars!!!
These bad sugars are in fact broken down by our bodies in the exact same way as Ethanol (alcohol). We all know about developing a beer belly. The current health crisis is, in effect, soda belly.
So what can we do? He says that exercise doesn’t work by burning calories but it is still good for you. When you exercise;
- Insulin levels go down as it works more effectively in your muscles
- Stress levels reduce with automatically reduces appetite
- DNL occurs at a much lower rate (what we refer to as higher metabolism)
As well as exercise, Lustig argues for the importance of a high fibre diet. Stating that wherever you naturally find fructose in there is much more fibre in the same place for example with sugar cane. Fibre is good for you because it reduces rate of absorption of carbs in your gut, so you feel less hungry, although you do fart more. (As he put it we have a choice, fart or fat.)A high fibre meal also speeds up transit of “full-up” signal.
Coke and alcohol are the same. Fructose is ethanol without the buzz!
They are metabolised in the same way. You wouldn’t give your child a beer, why give them a coke.
Essentially, when you take in calories from sugar that isn’t glucose, you are really just drinking fat.
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