Here in the UK we look to the Government’s Food Standards Agency (FSA) to guide us regarding what we should be eating, and we also trust them when it comes to ensuring the food industry doesn’t offer us too much shite to eat. Or that’s the theory, anyway. In reality, I reckon the FSA does a pretty poor job on both these counts.
Just look here and here and here for examples.
Anyway, this week I learn that the FSA’s latest thrust to is to persuade us (again) of the perils of saturated fat. You can see what the FSA statement on this here.
Apparently, the FSA is aiming to ensure that saturated fat does not contribute more than 11 per cent of the calories we consume. This, we are told could prevent up to 3,500 deaths a year.
According to Rosemary Hignett, Head of Nutrition at the FSA: ‘Reducing our intakes of saturated fat is a major challenge but would have clear important health benefits.’ But is this really true? Does the science support saturated fat’s killer image, and does eating less of it really save lives?
Probably the most oft-quoted ‘fact’ about saturated fat is that it increases our risk of heart disease. This nutritional nugget is based on two main lines of ‘evidence’:
1. higher saturated fat intakes are associated with an increased risk of heart disease
2. eating saturated fat raised blood levels of cholesterol (and this, we are told, enhances or risk of heart disease)
Let’s examine these in turn.
Over the last 50-odd years, there have been more than two-dozen studies that have analysed the relationship between saturated fat and risk of heart disease [1-26]. All but four of these studies [9,11,19,25] found no association between saturated fat intake and heart disease. And in one study, higher intakes of saturated fat in the diet were found to be associated with reduced narrowing of the arteries supplying blood to the head (the carotid arteries) over time [27].
The largest analysis to date of the relationship between lifestyle factors and risk of heart attack was published in the Lancet medical journal in 2004 [28]. This study analysed a range of risk factors and heart attack risk in some 12,000 heart attack victims and 14,000 healthy individuals from 52 countries around the World. The researchers involved in this study identified several factors, including smoking, high blood pressure, diabetes, a low intake of fruits and vegetables, and low levels of physical activity that appeared to account for 90 and 94 per cent of heart attacks in men and women respectively. Curiously, this review makes no mention of animal fat, or even dietary fat in general, as being an important risk factor for heart attack.
Taken as a whole, the scientific evidence simply does not support the notion that saturated fat is bad for the heart.
From a scientific standpoint, these studies ” referred to as epidemiological studies ” can only at best find associations between things. A better way to test the concept that eating saturated fat causes heart disease is to get people to eat less saturated fat to see if this reduces their heart disease risk over time.
Ideally, studies of this nature should be double-blind, which means that neither the individuals in the study nor the researchers will know whether they are receiving the true intervention or not. These sorts of studies, known as ‘double-blind’ studies, are generally regarded as the gold standard of intervention studies. To date, only two such studies have been performed with regard to heart disease risk or death [37, 44], and neither showed any benefit.
There are some 20 other studies [29-36,38-43,45-50], of which just six [40,42,50,52,58,60] found benefit. So, of a total of 22 studies, 16 found no benefit from cutting back on saturated fat with heart disease risk.
This doesn’t seem like particularly convincing evidence of the supposed benefits of eating less saturated fat. And the evidence looks even less convincing when you consider that the studies that did find benefit are often what is known a ‘multiple intervention’ studies ” which in this case means that in addition to reducing saturated fat, the participants in these studies were subjected to at least one other modification. For example, in one study [29] individuals were given nutritional supplements. In two of the studies [47,49], individuals were asked to emphasise heart-healthy omega-3 fats as well as fruit and vegetables in the diet. The obvious question that multiple intervention studies raise is whether lowered saturated fat in the diet, or the other interventions, or a combination of these things, that proved effective. Because of these limitations, multiple intervention studies cannot be used to judge the effects of reducing saturated fat in the diet.
One way researchers can get a good idea of the overall effect of some treatment or approach is to perform what is known as a ‘meta-analysis’. Here, results from a number of similar studies are grouped together. The largest meta-analysis to examine the effect of modifying fat in the diet was conducted by UK-based researchers and was published in the British Medical Journal [51]. This particular review amassed the data of 27 individual studies. Neither deaths due to cardiovascular disease (such as heart attack and stroke) nor overall risk of death was found to be reduced by makes changes to intake of dietary fat. The results of this review support the notion that eating less saturated fat has little, if any, benefits for our heart and general health.
Never mind this overwhelming lack of evidence for the ‘benefits’ of eating less saturated fat, though, because this won’t stop some doctors and scientists from playing the cholesterol card (see notion 2 above): saturated fat raises cholesterol which we know is bad for the heart. So, eating less saturated fat will reduce cholesterol levels which has to be good for the heart, right?
As with saturated fat, if we really want to make a judgment of the true impact cholesterol has on health, we need intervention studies ” studies in which cholesterol levels are lowered and the effect of this assessed. In 2005 a meta-analysis of 17 studies in which subjects made dietary changes explicitly to reduce blood cholesterol levels was published in the Archives of Internal Medicine [52]. Overall, these studies brought about a 10 per cent lowering of cholesterol levels. Despite this, the amassed results showed no reduced risk of death, neither in healthy individuals, nor even in high-risk individuals who had a history of heart attack or stroke. Basically, taking dietary steps to reduce cholesterol levels (say by reducing saturated fat intake) has not been proven to save lives.
Some, no doubt, will clutch at straws and tell us that eating less saturated fat will reduce risk of other killers conditions such as cancer. Such individuals may be unaware of the results of the Women’s Health Initiative Study, in which outcomes for women put on a ‘healthy’ diet were compared with those on an ‘eat what you like’ diet over 7 ½ years. In this study, the ‘healthy’ eating women consumed 23 per cent less saturated fat than their ‘eat what you like’ counterparts (that’s actually a much bigger reduction in saturated fat intake than the FSA is heading us towards). And at the end of the analyses they found that the ‘healthy’ eating women did not enjoy a reduced risk in any one or more than 20 types of cancer [53-55].
Put this all together and it appears, to me at least, that the idea that cutting back on saturated fat will saves lives is not supported by the science. But then again, it wouldn’t be the first time that we’ve been given official dietary recommendations for which there is no good evidence.
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