Author Archives: Bill Shrapnel

Should we worry about trans fats?

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Trans fats are bad news for heart health but what should we do about them? Should we give them top billing in the new Dietary Guidelines, demand trans fats be declared in nutrition information panels on food labels, or regulate them in some other way? Hang on … haven’t we already dealt with trans fats?

All fats in our diet are made of substances called fatty acids. Although there are hundreds of them, fatty acids can be grouped into three broad classes – saturated, monounsaturated and polyunsaturated. By far the majority of mono- and polyunsaturated fatty acids have a characteristic ‘bent’ shape, which the scientists call cis. However, a small proportion of unsaturated fatty acids are ‘straight’ and this trans shape gives them different physical properties, more like saturated fats. Fats with a high proportion of trans fats (or saturated fats) tend to be solid, not liquid like oils rich in cis fatty acids.

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Fruits and vegetables don’t prevent cancer

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Evidence that fruits and vegetables prevent cancer has fallen away over the last decade but our national nutrition authorities continue to perpetuate the myth. Why don’t they just review the science and give us the facts?

In 1981 the eminent epidemiologists Richard Doll and Richard Peto wrote a famous paper in which they argued that many cases of cancer were due to environmental factors and were therefore potentially preventable. It was suggested that poor diet was second only to smoking as a cause of cancer and could account for 35% of cases. Based on the evidence available at the time, Doll and Peto suggested that increased intakes of fruits and vegetables may prevent cancer. A generation of nutritionists and dietitians embraced the idea with a passion and started communicating the good news.

Better evidence now available

The early evidence suggesting protective effects of fruits and vegetables against cancer came primarily from case-control studies, with all their well-documented bias. Over the last two decades much better evidence in relation to fruits, vegetables and cancer has become available as large prospective studies and in some cases pooled analyses of these studies have been conducted. Most of the results are negative.

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Nutrition authorities ignoring vitamin D deficiency

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On 12 June a symposium titled ‘Should Australia and New Zealand allow more vitamin D into the food supply?’ was conducted in Melbourne under the auspices of the International Life Sciences Institute (ILSI). Excellent speakers outlined the current vitamin D status of Australians, the consequences of vitamin D deficiency, current dietary recommendations and intakes, and options for public health action. But are our national nutrition authorities listening?

Vitamin D recommendations

Dietary vitamin D recommendations are relatively new in Australia. After long assuming that a sunny country provided its people with adequate vitamin D, our health authorities introduced Nutrient Reference Values in 2006 in response to increasing evidence that a significant number of Australians and New Zealanders may have less than optimal (vitamin) D status. Adequate Intakes of vitamin D were considered to be 5 μg/day for children and young adults, 10 μg/day for adults aged 51-70 years and 15 μg/day for adults over 70 years of age. These recommendations mirrored those in the United States at the time.

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The sodium debate: heat or light?

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Lowering sodium intake has been a constant in dietary guidelines for decades and is widely recommended as part of healthy eating advice. The conventional view is that eating too much sodium increases blood pressure and thereby increases the risk for cardiovascular disease. Yet the benefits of sodium reduction are being hotly debated with experts around the globe trading arguments in journals, on-line debates and the mainstream media. What’s driving this debate? 

In November 2011, O’Donnell and colleagues published a study on the relationship between urinary sodium and the risk for cardiovascular disease. Urinary sodium is a good way to estimate how much sodium people are eating as, generally speaking, ‘sodium in equals sodium out’. As higher sodium intake is known to be linked with higher blood pressure, the expectation might have been that the higher the sodium excretion, the higher the risk for cardiovascular disease. However, the relationship turned out to be J-shaped. In other words, high intakes of sodium were indeed associated with higher risk for cardiovascular disease, but so were low intakes of sodium. How can that be? Does eating too little sodium cause harm?

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Do calorie-rich foods make you fat?

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High fat, calorie-rich foods have long been thought to be fattening and policymakers continue to recommend their restriction in order to prevent obesity. However, scientific support for this advice has fallen away. The latest research suggests that identifying foods that promote future weight gain is much more challenging than previously thought, with carbohydrate quality playing a central role.

Traditional dietary advice for preventing obesity has revolved around eating less calorie-rich food. In the 1980s and 1990s the best way of achieving this was thought to be by limiting total fat intake and this became the core strategy for the prevention of obesity. It made good sense as gram-for-gram fat contains more calories that protein or carbohydrate – lower fat foods are lower calorie foods. By the turn of the century, dietary advice for obesity prevention evolved to limiting intake of ‘energy dense’ (calorie dense) foods. This was a small change in emphasis as the key drivers of energy density are fat and water content.

Lowering the fat content or energy density of the diet as a means of preventing obesity makes so much sense to nutritionists and dietitians that it is seldom challenged but the unfortunate reality is that these recommendations can no longer be supported scientifically.

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Now sugar is ‘addictive’

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The current ‘debate’ about sugar and health descended into farce last Sunday night with the broadcast of a 60 Minutes program in which it was suggested that sugar ‘is as addictive as the hardest drugs’.

The argument behind this claim rests on the supposedly similar responses in the brain to sugar and cocaine. The brain contains a reward centre that is designed encourage survival behaviours, such as eating and sex. If these things were not pleasurable humans would not eat or reproduce and the species would disappear. Foods, sugar, fat and especially the combination of sugar and fat trigger this reward centre, and so does cocaine. So, with a huge leap of faith and imagination, sugar equals cocaine.

An American neuropsychologist on the program claimed that … sugar kills way more people than any psychoactive drug – an absurd claim that simply cannot be supported scientifically. I have never seen any credible scientific study that attempted to associate sugar intake with increased risk of death. Scientists have gone to great lengths to investigate the role of dietary factors in preventable disease but sugar intake simply does not feature in their calculations. In susceptible people, the risk for tooth decay may increase with the consumption of carbohydrates i.e. added sugars, natural sugars in fruits and even breast milk, and starch. But that’s it – that’s the health risk posed by sugar. Eating sugar does not kill people.

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Turning a blind eye to GI

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New research has strengthened the case that the glycaemic index of carbohydrate-rich foods affects the risk for cardiovascular disease and is a useful tool in weight management. But Australian health authorities are in denial, refusing to even look at the data.

Four decades ago nutritionists were taught that complex carbohydrate (starch) was desirable as it was slowly digested and absorbed, which led to a gradual rise in blood glucose and this was considered to be a good thing. In contrast, simple sugars were thought to be rapidly broken down and absorbed, giving a high blood glucose response. Although logical enough, it wasn’t true.

When the blood glucose-raising effects of various foods were actually measured it was found that some starchy foods, such as potato and rice, produced very rapid increases in blood glucose to high levels – higher than that of table sugar. Use of the terms simple sugars and complex carbohydrate is now discouraged by the World Health Organization.

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Wholegrains: the whole story?

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Nutritionists have embraced the concept of wholegrains with a passion claiming they are protective foods. But the evidence is inconsistent, which may be due to the methodology of the studies that have been undertaken so far. As the dietary fibres found in some grain foods are beneficial for bowel function and lowering blood cholesterol there is a case for basing cereal recommendations on fibre. Other aspects of the nutritional quality of cereal goods, such as nutrient density and glycaemic index are also relevant. Just recommending wholegrains is not enough.

When it comes to recommendations about grain foods the draft Australian Dietary Guidelines keep it simple: eat mostly wholegrain. The rationale is simple too: wholegrains are nutrient-rich and protective against a range of modern diseases such as cardiovascular disease, type 2 diabetes and obesity.

But is it true? How evidence-based is this advice?

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Is sugar ‘toxic’?

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Professor Robert Lustig argues that sugar, or fructose in particular, is ‘toxic’ and increases the risk for obesity and the metabolic syndrome. He paints a simple picture – glucose is good, fructose is bad – based on the differing metabolism of these sugars. He claims that fructose is similar to alcohol and should be taxed accordingly. Professor Lustig certainly has our attention but do his claims stack up?

In last week’s blog I looked at the reviews on sugar and health conducted by the European Food Safety Authority and the US Institute of Medicine. They both found that sugar is fairly benign with respect to chronic disease but can lower the nutrient density of the diet when intake is high, though this depends on which sugar-rich foods and drinks are consumed.

Professor Robert Lustig from the University of California has a very different view.

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Sugar and health: the expert view

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In a few short years sugar has replaced fat as the main dietary villain and the lay media is full of horror stories about the role that sugar plays in chronic disease. Scientific reviews of the role of sugar, health and disease by leading nutrition agencies tell a different story, finding sugar is fairly benign with respect to chronic disease. However, dietary quality may be affected at very high intakes of sugar.

Who are the experts?

During the last seven years there have been two comprehensive assessments of the role that sugar plays in health, one in Europe and one in the United States. One review was conducted by the European Food Safety Authority (EFSA) and published in 2010. In relation to nutrition, EFSA provides the most up-to-date and comprehensive scientific advice to support EU policy makers in their decision making process in the field of nutrition. EFSA’s advice on nutrient intakes provides an important evidence base to underpin nutritional policies, the setting of diet-related public health targets and the development of consumer information and educational programmes on healthy diets.

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