Sugar vs fat? Know your poison

Is the veneer finally beginning to fade on the low-fat hypothesis? Is the pendulum finally swinging away from fat as the harbinger of all things evil, to a new culprit, sugar?

Despite living in the 'low-fat' era, many of us have been implicating sugar (and refined and processed starchy foods generally), not fat, as the dietary driving force behind many of our twenty first century health woes. Of course, the 'low-fat' paradigm remains a virtually impregnable stronghold, propped up by official government agencies and their perpetuation of (so-called) healthy eating advice and an omnipotent food industry flogging us 'low-fat' products at every turn (all in the name of good health, you understand). But is the veneer finally beginning to fade on the low-fat hypothesis? Is the pendulum finally swinging away from fat as the harbinger of all things evil, to a new culprit, sugar?

A new meta-analysis published last week in the BMJ, examining prospective cohort studies and randomised controlled trials, found that both types of studies showed an adverse effect of sugar on body weight in adults [1]. This only really marks the tip of the iceberg of the deleterious effects of sugar on health. As spelled out in an accompanying editorial, consumption of sugar, and carbs in general, raises postprandial blood sugar levels and adversely affects aspects of the metabolic syndrome, increasing insulin and triglycerides, whilst reducing levels of protective HDL cholesterol [2].

This will come as nothing new to readers of our award-winning book The Health Delusion in which we not only reveal that strong evidence implicating saturated fat in heart disease just doesn't exist, but worse still, replacing it with high GI carbs dramatically increases the risk. For example, in a cohort study of 53,644 men and women over 12 years, replacing 5% of calories from saturated fat with high GI carbs was associated with a dramatic 33% increase in heart attack occurrence [3]. Stop and think about that and you see just how dumb 'low fat' foods, typically laced with terrifying amounts of added sugars to make them palatable, really are.

The eminent Willett and Ludwig, in their editorial, sum up the scale of the problem by drawing parallels between the harm caused by sugar to that of tobacco and alcohol when they conclude "Healthcare providers could play an important role by routinely asking about consumption of sugar sweetened drinks as well as tobacco and alcohol use, by setting a good example, and by assuming leadership in public efforts to limit sugar as a source of harm" [2]. It's hard not to be seduced by parallels with the tobacco industry. Intake of added sugars accounts for 15% of our total energy (that's the equivalent to eating nothing but sugar one day each week), and powerful economic interests are vested in keeping the sugar flowing via the production and sale of sugar-laced foods and beverages. That the sugar lobby continues to be vociferous in their denials that sugar is bad for health, has more than faint echoes of a tobacco industry that once tried every trick in the book to perpetuate the lie that smoking didn't kill.

As Willet and Ludwig point out, there is no such thing as a desirable limit for sugar intake, with a linear association between sugar intake and adverse effects. And why stop at added sugars anyway, when our diets are awash with more covert sources of sugar? Modern diets are heavily permeated by highly processed and refined grain products (all the white and beige fodder), the high GI of which sends our blood sugar and insulin levels soaring (more so than pure sucrose in fact). We're also consuming fructose-laden fruit juices in greater volumes than ever before. Fructose might be a 'natural' sugar but it does things that other sugars don't due to the way it is metabolised, readily getting converted to fat in the liver and promoting insulin resistance and the nasty cluster of symptoms that is the metabolic syndrome.

That Penguin Books is reissuing John Yudkin's prophetic classic Pure, White and Deadly some 40 years after its first publication shows that we have come full circle. It is our lust for sugar, in all its forms, not fat, that is the true scourge of our modern diet. In the words of Yudkin himself "If only a small fraction of what we already know about the effects of sugar were to be revealed in relation to any other material used as a food additive, that material would promptly be banned" [4]. Which just about says it all.

[1] Te Morenga L, Mallard S, Mann J (2012) Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ 345:e7492

[2] Willett WC, Ludwig DS (2013) Science souring on sugar BMJ 346:e8077

[3] Jakobsen MU et al (2010) Intake of carbohydrates compared with intake of saturated fatty acids and risk of myocardial infarction: importance of the glycemic index. Am J Clin Nutr 91(6):1764-8

[4] Watts G (2013) Sugar and the heart: old ideas revisited. BMJ 346:e7800.