Thursday, February 6, 2014

Why does fat get a bad name ?

Dr Carrie Ruxton, registered dietitian and member of the Meat Advisory Panel

Since the 1970s, dietary fats have been a major target of Government nutrition policy, with advice to lower fat intake making a regular appearance in dietary initiatives. Yet current science seems to indicate that not all fats are equal, suggesting that our rather negative view of dietary fats needs to be updated.

Fats can be grouped into two different ‘families’ called saturated and unsaturated fats. Within these, there are several categories of fatty acids, as shown below:
  • Saturated fats: mainly from animal foods, such as dairy products, chocolate and meat products (pies and pasties), but also from some plant foods, such as coconut
  • Omega-3 polyunsaturated fats: mainly from oily fish, eggs, red meat, nuts, seeds and marine oil supplements
  • Omega-6 polyunsaturated fats: mainly from vegetable oils, such as sunflower oil and rapeseed oil, poultry, eggs, avocado and nuts
  • Omega-9 polyunsaturated fats: mainly from olive oil, rapeseed oil and nut oils.
Traditionally, saturated fats were viewed as ‘bad’ while unsaturated fats were viewed as ‘good’. This was informed by people -based studies which suggested associations between high intakes of saturated fat and an increased risk of heart disease. However, this opinion has been challenged in recent years due to evidence that certain saturated fatty acids, such as myristic and palmitic acids, have a negative impact on blood cholesterol levels while others, such as stearic acid present in red meat, does not appear to affect cholesterol1 . This suggests that saturated fats behave differently in the body.

There is also debate from some nutrition commentators on whether saturated fat should be targeted at all in dietary recommendations due to the weak association between saturated fat consumption and mortality from cardiovascular disease. However, this view has not been accepted by Government experts and more evidence is needed.

In the meantime, it is wise to continue choosing lower fat, nutrient-rich foods which provide a variety of types of fatty acids in the diet. Lean red meat is a good choice as it is now lower in fat and calories thanks to changes in farming practices over the past few decades. In fact many people don’t realise that red meat, on average, contains more unsaturated than saturated fats. It also contains a range of fatty acids, including those from the beneficial omega-3 and omega-6 groups.

[1] Hunter JE, Zhang J, Kris-Etherton PM. Cardiovascular disease risk of dietary stearic acid compared with trans, other saturated, and unsaturated fatty acids: a systematic review. Am J Clin Nutr. 2010;91:46–63.

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