The consumption of ‘heart healthy’ vegetable and seed oil has increased drastically over the past few decades. People have shunned natural fat sources such as butter and lard in favour of these oils that are produced in something that looks more like a meth lab than your grandmas kitchen. So why is everyone telling us that these oils are good for us if they aren’t? The main reason- they are cheap as dirt to produce.
Why are they so bad?
The biggest problem with industrial seed oils is that they are way to high in omega-6 fatty acids. Overconsumption of these processed omega-6s creates an inappropriate inflammatory response in the body, which has been linked to obesity, arthritis and cardiovascular disease (1).
Humans evolved on a diet with a ratio of Omega-6 fatty acid to omega-3 fatty acids of approximately 1.
At this ratio omega-6 fatty acids are health promoting in the diet. However nowadays with the increase in industrial oils and processed food in the diet, it is estimated that we are consuming a ratio of around 16 to 1 (2).
Another problem with these oils is that they are easily oxidised. Polyunsaturated fats (such as your omega-6s) contain two or more double bonds. This means that oxygen can easily react with the fatty acids, in turn damaging them. Oxidised oils can then form harmful free radicals in the body which has been linked to a whole variety of diseases (3). Highly oxidative oils can also promote weight gain and insulin resistance (4). It is also interesting to note that whilst many people report that saturated fat increases your risk of heart disease, the attention is now turning to trans fats and seed and vegetable oils. Many studies have suggested that an increased intake of seed oils increasing your risk of cardiovascular disease (5, 6).
So what should you be avoiding?
Vegetable and seed oils that you should avoid due to a high level of Omega-6 polyunsaturated fatty acids include:
- Canola oil
- Rice bran oil
- Soybean oil
- Peanut oil
- Safflower oil
- Sunflower oil
- All margarines with no exception! Even the ‘heart healthy olive oil’ spreads are usually just a blend of mostly canola oil with a bit of olive oil mixed in so that they can claim it is good for you.
It is crucially important to read the labels of all the products that you buy as many things you think wouldn’t contain these harmful oils in fact do.
For high heat cooking saturated fats are best. This is because they are stable and very heat resistant. These include butter, coconut oil and ghee.
Extra virgin olive oil is also good for cooking at lower temperatures and is also good for salad dressings along with macadamia, avocado or flaxseed oils.
In saying that, this information is not meant to create paranoia. In small amounts or consumed infrequently, it’s quite likely that the effects will be minimal. As with everything, the dose makes the poison!
The takeaway message? Real food (plants and animals) that we have been consuming for thousands of generations is always the safer choice.
1. Hibbeln JR, Nieminen LR, Blasbalg TL, Riggs JA, Lands WE. Healthy intakes of n−3 and n−6 fatty acids: estimations considering worldwide diversity. The American Journal of Clinical Nutrition. 2006;83(6):S1483-93S.
2. Simopoulos AP. Evolutionary aspects of diet, the omega-6/omega-3 ratio and genetic variation: nutritional implications for chronic diseases. Biomedicine & Pharmacotherapy. 2006;60(9):502-7.
3. Freeman BA, Crapo JD. Biology of disease: free radicals and tissue injury. Lab Invest. 1982;47(5):412-26.
4. Storlien LH, Jenkins AB, Chisholm DJ, Pascoe WS, Khouri S, Kraegen EW. Influence of Dietary Fat Composition on Development of Insulin Resistance in Rats: Relationship to Muscle Triglyceride and ω-3 Fatty Acids in Muscle Phospholipid. Diabetes. 1991;40(2):280-9.
5. Lands WE. Dietary fat and health: the evidence and the politics of prevention: careful use of dietary fats can improve life and prevent disease. Ann N Y Acad Sci. 2005;1055:179-92.
6. Rose GA, Thomson WB, Williams RT. Corn Oil in Treatment of Ischaemic Heart Disease. British Medical Journal. 1965;1(5449):1531-3.