By Linia Patel
Fat cooked well is delicious. Yet through conditioning we feel guilty reaching for the crackling on the roast pork. Decades of anti-saturated fat messaging have led many to believe that eating fat is bad for you. As a result, “low-fat” and “fat-free” products now dominate the supermarket aisles. However, in the last year or so there has been a flurry of news stories on the subject of saturated fat that have challenged conventional thinking.
One school of thought suggests that saturated fats are not associated with cardiovascular disease and butter should be put back on the breakfast table. But on the other hand, a group of manufacturers and retailers announced they are going to reduce the amount of saturated fat in some of the nation’s favourite biscuits. The reason? To help reduce the number of deaths from heart disease as part of government's responsibility deal to reduce saturated fat in foods. So, who is right? Are saturated fats bad for you or not? Should we be eating more or less?
saturated fat and heart disease
The theory that saturated fat in the diet raises blood cholesterol which in turn causes heart diseases is known as the diet-heart/lipid hypothesis. It owes its existence to an American biochemist, Ancel Keys. In 1953, Ancel published a scientific paper in which he showed an apparent relationship between the amount of fat in the diet and heart disease rates in six different countries. The conclusions from this observational study were simple: Less saturated fat which will lower blood cholesterol which will decrease your risk of cardiovascular disease. It is from this research we were advised to cut fat intake to 30% of total energy and saturated fat to 10%.
There were some problems with Key’s study, which have been challenged over the years. A particularly vocal cardiologist from Crydon University Hospital (Aseem Malhotra) sparked a debate in October 2013 with an Article in the British Medical Journal where he argued that saturated fats aren’t associated with cardiovascular disease. In his article, Dr Malhotra disputes the idea that there is a direct cause and effect between cholesterol levels and heart disease. “A simple association of two observations does not prove that they are causally linked. Causation can only be proved by randomized controlled trials (RCT’s)” he says. RCT’s to an extent are the gold standard in research. They are clinically controlled trails in which all variables except the one of special interest are held constant. They allow scientists to make clearer conclusions.
Another good way of validating scientific evidence is to look at the results from a meta-analysis. A meta-analysis is a way of pooling and studying the body of available evidence on a specific topic. In the BMJ article, Malhotra used the results from a meta-analysis that pooled 72 individual studies to gauge how different fats influence the risk of a heart attack or other cardiac event such as angina to further validate his argument. Within this meta-analysis when researchers compared participants with the highest and the lowest intake of saturated fats, they found no clear difference between the risk of heart disease or other cardiac events. Similarly, they found no significant difference between those consuming high or low amounts of the supposedly healthy unsaturated fats.
Despite what seems like strong evidence, other scientists still disagree with Malhotra and say that more research is needed before we can dismiss current guidelines. On the surface, meta-analyses sound convincing, however they too have their limitations. Firstly a meta-analysis is a sweeping summary of all the data (so get a lot of attention), however nutritional studies vary widely in the way they are set up. Often the strengths and weaknesses of individual studies get lost. For example a lot of nutrition studies rely on food recall and self-reporting. Can you remember what you ate yesterday? The day before? How about the week, month or year before? Unlikely. If participants do respond they are also likely to respond in a way that makes them look as good as possible, therefore giving data that isn’t representative of the reality. This makes it difficult to get clear conclusions from studies. Confounding factors like misreporting of dietary intakes or not accounting for sources of replacement energy also affect the validity of the results. How applicable the results are to a healthy population is also in question as some of the studies used involved people with a pre-existing health condition.
Is more saturated fat better?
The cholesterol story is complex. Most of us are now familiar with the idea of “good” (high density lipoprotein, or HDL) and “bad” (low density lipoprotein, or LDL) cholesterol. But it seems more complex than just that. Research shows that saturated fat is believed to raise levels of low density lipoprotein (LDL) which in turn raises cardiovascular risk. However only one type of LDL cholesterol seems to be associated with saturated fat intake. This type of cholesterol is called type A (large buoyant). The second type of cholesterol is called type B (small, dense), it is associated with carbohydrate intake and is linked to cardiovascular disease.
So while the evidence to date shows that saturated fat is not associated with heart disease risk, it also doesn’t “prove” that eating more saturated fat is better for you. Until the picture becomes clearer, dietitians are recommending that people stick to current guidelines. Why? Because we really need more data before confusing the public even more. Current guidelines generally encourage us to limit saturated fat to 11% total energy intake. They also recommend that we swap out saturated fats – found in foods like dairy -- for unsaturated fats like olive oil, rapeseed oil, sunflower oil, nuts and seeds. There is ongoing debate about which polyunsaturated fats are best.
The real crux of the matter is what you fill your “saturated fat” gap with. Fat is full of flavour, so when you take fat out, food doesn’t taste as good. The food industry has compensated with this loss of flavour by adding more sugar to our food. There is mounting scientific evidence that diets high in sugar are a risk factor for heart disease and metabolic syndrome. So dieticians argue that while they welcome changes to reduce saturated fat in everyday products they also want manufacturers to be mindful what they replace it with. Consumers too need to be label savvy.
The heart of the matter
All this is a good reminder that individual changes to one nutrient can have a knock-on effect on another. Concentrating on a single food source to protect health is never a good idea. Eating well is about balance and moderation. Granted, moderation is not sexy and moderation is also different for each individual. However, for us all when we are making adjustments to our diets we need to think about the overall balance of the food and nutrients that we are eating. We need to consider our whole diet, the variety of foods we have, how many portions of vegetables and fruit we eat, our intake of whole grains, legumes, quality protein, how much olive oil and oily fish or salt we consume. In essence, it’s about going back to the basics and eating real food. Real food that’s cooked from scratch. This change alone will address your intake of healthful versus harmful fats and will dramatically reduce the amount of refined sugar in your diet.
Linia Patel is a leading dietitian and sports nutritionist. She's passionate about empowering people to better manage their health and optimise their performance through learning the essence of healthy eating. Outside of work, Linia is a wannabe triathlete. Visit her website: www.liniapatel.com.
References
- Malohtra A. Saturated fat is not the major issue. 2013. BMJ:347:6340
- Clifton P. Saturated fat is not the major issue. 2013. BMJ: 347:6847
- Mann J. Saturated fat in not the major issue. 2013. BMJ: 347:6851
- Mozaffarian D, Micha R, Wallace S. 2010. Effects on coronary heart disease if increasing polyunsaturated fat in place of saturated fat; a systematic review and meta-analysis of randomized controlled trails.
- Estruch R, Salas Salvado J, Covas M, Corella D et al. 2013. Primary prevention of cardiovascular disease with a Mediterranean diet. N.Engl J Med:1279-90
- Livingstone B. Black A. 2011. Markers of the validity of Reported Energy intake. J Nutr 133.3
- Webb, F, Whitney W, Sizer F, Whitney E. 2011. Nutrition: concepts and controversies.
