Replacing dietary fat with sugar and refined carbohydrates is probably damaging to health

Heart disease is a topic I have written extensively about here in these blog posts.  In 2008 I wrote two posts entitled ‘Do you know how to look after your heart’ part 1 and part 2.  In part two I wrote extensively about refined carbohydrates and blood sugar levels and how these appear to be a greater risk for heart disease than dietary fat.  Eating a diet loaded with foods with a high glycaemic index or high glycaemic load has been increasingly linked with a raised risk for heart disease and other health problems.  High glycaemic index foods (foods that release sugar quickly into the body) include most refined carbohydrates like white bread, long-grain rice, sweets, biscuits, sugary foods and many other processed carbohydrates and processed foods. 

By contrast certain types of fat, especially the long chain omega 3 fatty acids (EPA and DHA) from marine sources have been linked to a reduced risk of heart disease.  Many studies have also found that there is not enough evidence to link heart disease to saturated fat or total fat intakes (e.g.1).  I feel quite strongly that the push to eat ultra low fat diets over the last 50 years has impacted negatively on our health (and mood) since it has often led to diets rich in carbohydrates, especially refined carbohydrates.  Look at a low fat yoghurt for instance, the natural fat is removed and, often, replaced with copious quantities of sugar.  Low fat products in general are often full of sugars.  Actually I think the low fat campaigns have been a BIG FAT LIE.

This month in the American Journal of Clinical Nutrition fat is mentioned in a number of studies (e.g. 2,3,4,5).  In a commentary (2) authors point out that “An independent association of saturated fat intake with CVD [cardiovascular disease] risk has not been consistently shown in prospective epidemiologic studies”, the authors also point out that if saturated fat is removed from the diet and then replaced with a higher carbohydrate intake, particularly a higher intake of refined carbohydrates, this is associated with an increased risk of heart disease – specifically a high carbohydrate diet is associated with increasing problems such as insulin resistance, increased triglycerides (blood fats associated with heart disease), increased levels of a particularly destructive type of cholesterol known as small dense LDL cholesterol.  The authors also note that high carbohydrate diets are also linked to a reduced level of HDL ‘good’ cholesterol (2).  They conclude that “there are few epidemiologic or clinical trial data to support a benefit of replacing saturated fat with carbohydrate” and “dietary efforts to improve the increasing burden of CVD risk associated with atherogenic dyslipidemia [blood fat disorder linked to health problems] should primarily emphasize the limitation of refined carbohydrate intakes and a reduction in excess adiposity [body fat]”.

A research paper (3) looking at data on saturated fat and cardiovascular disease (which includes coronary heart disease and stroke) evaluated 21 scientific studies which in total involved over 340,000 individuals followed for 5-23 years showed that “there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD [coronary heart disease] or CVD [cardiovascular disease]”.

Two other studies in the March issue of the American Journal of Clinical Nutrition (4,5) looked at the positive health benefits of the long chain omega 3 fatty acids, EPA and DHA, found in oily fish such as mackerel, trout, salmon and sardines.  In the first study (4) scientists show that supplementation with these fatty acids are beneficial in improving blood vessel function in individuals with type 2 diabetes.  In the second study (5) high intakes of EPA and DHA were associated with greatly reducing chronic disease risk. 

I am not advocating eating a diet that is packed with saturated fat, not in the slightest, personally I feel that the take home message from studies such as these is that a healthy diet, based around natural unprocessed and unrefined foods, is crucially important to prevent disease risk.  Any health-full diet will be rich in plant foods such as vegetables, fruits, beans and pulses, nuts and seeds and will include unprocessed meats and fish (especially oily fish), wholegrain unprocessed and unrefined carbohydrates.  Particularly I feel that omega 3 fats are important to health.  In a press release (6) the lead author of a study looking into heart disease and diet (7) said: “This isn’t just hype; we now have tremendous and compelling evidence from very large studies, some dating back 20 and 30 years, that demonstrate the protective benefits of omega-3 fish oil in multiple aspects of preventive cardiology“.  I also feel that refined carbohydrates are generally unnecessary and quite probably damaging to health when eaten regularly and consistently.

If you do not regularly, at least twice a week, eat oily fish then it would certainly be worth taking a fish oil supplement in order to provide your body with the essential omega 3 fatty acids.  For vegetarians and vegans a flaxseed oil supplement will provide the short chain omega 3 fatty acid, alpha linolenic acid.  Unfortunately the body is not very good at converting this into the long chain EPA and DHA forms that are crucial for health.  New vegetarian and vegan EPA and DHA supplements, made from algae, are becoming increasingly available and are worth looking in to.


(1)Mente A et al.  2009. A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease.  Arch Intern Med. 169(7):659-669.
(2) Patty W Siri-Tarino PW et al.  2010.  Saturated fat, carbohydrate, and cardiovascular disease.  American Journal of Clinical Nutrition.  91: 502-509
(3) Patty W Siri-Tarino PW et al.  2010.   Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease.   American Journal of Clinical Nutrition.  91: 535-546
(4)Stirban A et al.  2010.  Effects of n–3 fatty acids on macro- and microvascular function in subjects with type 2 diabetes mellitus.  American Journal of Clinical Nutrition.  91:808-813
(5)Makhoul Z et al.  2010.  Associations of very high intakes of eicosapentaenoic and docosahexaenoic acids with biomarkers of chronic disease risk among Yup’ik Eskimos.  American Journal of Clinical Nutrition.  91:777-785
(6)  American College of Cardiology (2009, August 3). Mounting Evidence Of Fish Oil’s Heart Health Benefits. ScienceDaily. Retrieved August 4, 2009, from¬ /releases/2009/08/090803173250.htm
(7)Lavie CJ et al.  2009.  Omega-3 Polyunsaturated Fatty Acids and Cardiovascular Diseases.  J Am Coll Cardiol, 2009; 54:585-594

Written by Ani Kowal