Chewing the fat
Fat finds itself in the spotlight once again. One minute we are being urged to avoid it and told that very low fat diets are the way to go; the next we are encouraged to gorge on it, Atkins style. The conflicting viewpoints on fat are like a ping-pong game, aren’t they?
That said however, throughout fat’s fluctuating popularity, there has been one constant: that saturated animal fats are bad news for the heart. But it now seems that even this conventional wisdom is a big fat lie?! Have a look at this link:
http://www.boston.com/lifestyle/food/articles/2010/02/24/the_ongoing_arguments_over_our_consumption_of_saturated_fats/
Well if that is the case, current fat recommendations will be turned upside down! With articles like this one bombarding us day in and out it’s no wonder there is confusion out there. What do you believe? What is “good or bad” fat? What exactly are we allowed to be eating? Is it butter or margarine? Full cream or semi-skimmed milk? Grizzly fat on steak allowed or not? Crispy chicken skin, to eat or not to eat? Read on to find out what you should really be doing.
Some background
Over the past 30 years health experts have been advocating the need to eat less animal fat. Yet despite this move away from saturated fat there seems to have been no effect on the lowering of the incidence of cardiovascular disease. In fact, in parallel years the levels of obesity and Type 11 diabetes have soared, especially in children. As a result, experts are now being forced to ask whether saturated fats deserve the bad rapport they have had and if efforts to lower dietary fat (particularly saturated fat) have caused a whole new set of chronic disease problems.
The study that has caused the stir was a meta-analysis of prospective epidemiologic studies (review of a population studies). The study stated, “there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of heart disease. However (and this is the important bit, that I will touch on later!) more data is needed to elucidate whether Cardiovascular disease (CVD) risks are likely to be influenced by the specific nutrients used to replace saturated fat.”
What science says:
Numerous trials and studies have been done in this area. The results have been interesting and are summarised below:
1) An American physiologist Ancel Keys was the first to come up with the diet-heart hypothesis in the 1950’s after some of his research showed that a high intake of animal fat not only raised cholesterol levels but was also strongly linked to heart attacks. In one of his studies (the Seven Countries study) he looked at 15 populations in seven countries and found that the amount of fat and the type of fat people ate affected the levels of CVD. From this research he drew further correlations which prompted health experts to recommend that saturated fat intake should be reduced (those found in butter, lard and fatty meat) in favour of monounsaturated fats (olive oil, sunflower oil and corn oil) and polyunsaturated oil (oily fish, linseeds, flaxseeds). Many who are skeptical about fat’s role in heart disease claim that gaping holes exist in this initial research that led to saturated fats being branded a killer! The Intuits’ for instance eat a lot of animal fat yet do not have high rates of heart disease, how does one explain that?
2) One of the biggest studies carried out that looked into heart health was the US Women’s Health Initiative (WHI) which consisted of almost 500,000 women, over 8 years. Initially this study looked at the effect of the reduction in the total dietary fat on heart disease. However, a recommendation after the study had started was to look at types of fat rather than just total fat. This was done in the Dietary Modification Trial. Findings from this trial showed that women who made the biggest reductions in their dietary levels of saturated fats also had the biggest reductions in their blood “LDL” cholesterol (or “bad” cholesterol). A low blood level of LDL cholesterol is associated with a lower risk of problems such as heart attacks. A major limitation of this trial was that it did not examine the impact of the currently recommended low saturated diet on heart disease. This is now the big question scientists are asking.
3) The INTERHEART study enrolled 12,461 patients who had suffered a heart attack, from 262 medical centres in 52 countries. Controls were 14,637 healthy people without heart disease. The study concluded that reducing the intake of saturated and trans fats, replacing them with poly- and monounsaturated alternatives, such as olive, rapeseed, nut and seed oils was the way to go for a healthy heart.
4) A meta analysis (review of studies) of 27 studies published by the British Medical Journal in 2001 concluded that although there was “still only limited and inconclusive evidence of the effects of saturated fat on cardiovascular disease, however they still did advise a permanent reduction of dietary saturated fat”.
What does this all mean?
a) Summary of the scientific evidence:
It is really difficult to prove causal links between diet and disease as there are so many confounding factors involved. There is good evidence that excessive amounts of saturated fat increase the risk of heart disease, but its only ONE of the factors. We shouldn’t be completely avoiding all forms of saturated fat. There are different forms of saturated fat and some have stronger associations with heart disease than others. The fat in red meat for example is a form called stearic acid and isn’t linked to heart disease whereas the types of saturated fat (lauric and myristic acid) found most commonly in “tropical” oils (i.e. palm kernel and coconut) and in dairy products have a much stronger association with heart disease.
Although cheese, whole milk, beef, poultry and pork all contain some saturated fat, these foods also contain a diverse mixture of other fats including monounsaturated fats and polyunsaturated fats. This varied mixture of fats may be one of the reasons why it is hard to prove a direct link between saturated fats and heart disease. It is therefore important to focus on saturated fat in the context of the whole diet.
The findings in the controversial study are definitely interesting but it is important not to take every finding you read at face value. Sometimes health messages get distorted and misinterpreted. The study did also state that “more data is needed to elucidate whether CVD risks are likely to be influenced by the specific nutrients used to replace saturated fat”, and on this basis still advised a reduction of dietary saturated fat. However, this little yet important bit was left out.
b) Explanation for the whole new set of chronic diseases that have arisen as a result of reducing saturated fat intake:
What has happened to consumers in an attempt to cut down on the consumption of butter, lard, suet and other saturated animal fats are two things:
- Firstly, they have switched to margarine and spreads made from trans-fats. Trans-fats have since been found to be more harmful than saturated fats on diabetes and heart disease.
- Secondly, consumers have started eating copious amounts of commercially made low fat foods that are higher in sugar and fructose corn syrup. Eating too many high sugar foods leads to high calorie intakes, increased levels of blood sugar and triglycerides which again in turn increase the risk of diabetes and heart disease.
The Ki Fit Team’s take home message:
Negotiating this fat maze is not easy. At the end of the day it all boils down to the “m” word. Moderation. We definitely don’t need to avoid animal fat completely and there is no reason why we can’t have moderate amounts of it in our diet. Too much of any type of fat day after day will result in obesity which is itself a risk factor for heart disease as fat is an energy dense molecule. The aim of the game should therefore be to ensure that your overall fat intake is within healthy limits.
Fat Fact : The current UK health recommendation is to get no more than 35% of your total calorie intake from fat. No more than 11% of that should be saturated fat derived from animals. Trans- fats should not provide more than 2% of a person’s dietary energy intake. The upper limit for fat intake for women is therefore a daily total of 70g of fat (20g of which can be saturated) and for men 95g (30g of which can be saturated).
Learning to decipher fat figures is a good skill to have. According to the Foods Standard Agency, a high-fat food contains 20g or more of total fat (5g of saturated fat per 100g). Look for instead for foods that are low-fat containing 3g of total fat (1.5g of saturated fat) or less. And a word of warning, just because a food is 90% fat free it does not mean you can eat yourself silly. Check the label as the food may not even necessarily be low fat. In some cases, low fat foods are high sugar-so therefore high in calories too.
References:
1) Thomas B, Bishop J. Manual of dietetic practice.4th ed. Blackwell Publishing Ltd.2007
2) Geisller C, Powers H. Human Nutrition. 11thedition. Elsevier Ltd. 2006
3) Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr .2010
4) Keys et al. The Diet and 15 year Death Rate in Seven Countries Study. AJ Epid. Vol 124. No 6: 903 – 915
5) Yusaf S et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. Lancet. 2004.
