In a Nutshell
Recent studies have made us re-think what we know about saturated fats, vegetable oils, and trans fats. It has made us rethink whether fats and oils from all sources have the same health affect, and has lead us to question how their preparation may change the landscape of our nutrition.
We have all heard that saturated and trans fats increase our risk to heart disease (CVD), and that unsaturated fats found in oils such as canola, soybean, corn, and peanut reduce the risk. If you do a quick google search you will find a pile of conflicting articles (many however do not actually cite a peer-reviewed study, like this article does). So here’s what we know…
1. Most studies findings suggest and agree that trans fats have an association of increased risk of CVD among other disease. So the logical question is…. What are trans fats and where do they come from? Trans fats are vegetable oils that were put through the process of hydrogenation to become solid. You would be wise to avoid these in foods. (Souza et al., 2015)
2. Another common question is do we create trans fats when we cook with high heat/fry with vegetable oil? The answer is yes. While studies do not all agree on the level and amount of trans fats created the general consensus is that high heat frying and even stir frying can create some (albeit low amounts in most cases) trans fats. The hotter and longer the heat i.e. frying oils in restaurant deep fryers which are used repeatedly the more likely there will be an increase in trans fats in your food. (Shabbir et al., 2014) (Przybylski & Aladedunye, 2012)
3. If you're going to perform high heat cooking as previously stated with vegetable oils, some of the best ones are canola, peanut, or avocado oil versus oils such as olive oil. Olive oil does not have a high smoke point… meaning at lower temperatures, sometimes as low at 220 degrees (in some cases) olive oil begins to smoke. When an oil smokes it begins to oxidize creating free radicals. Free radicals are highly reactive and damage other cells it comes in contact with. Simply put, when a vegetable oil is smoking, it means the oil is not only losing its nutritional value, it is also creating harmful chemicals, that we then eat.
If you're going to fry using the same oil/fat multiple times (especially in a restaurant), you may in fact be better off using a saturated fat such as lard, which will not increase trans fat in food, and is a much more stable frying agent.
4. Not all vegetable oils are created equal. While the value of consuming these oils whether you’re cooking with them, using them in salads or in some other food preparation is that we get a healthy dose of Omega 3’s and Omega 6’s (essential fatty acids our body does not make on its own), how they are prepared may be of concern to you, as it is to me. Olive and avocado oils for example tend to be cold pressed. However, the canola oils, safflower, peanut butter, soybean, and corn oils for example are almost always chemically extracted with a gas called hexane gas. Hexane gas is poisonous to human beings, and while it is removed from the oil after processing, studies indicate that there often remains a .02% content of it in oils we consume. The FDA claims this is not harmful to humans in such low quantities…. Which may be true, but of course, time will tell.
In most cases the food processing of oil looks like this... They take the seed, soak it in hexane gas to extract the oil (which is done because they can extract more, and more cheaply than expeller pressing it). Once the oil is extracted they have to boil the oil to evaporate out the gas. Once the oil boils it often smells rancid so then they chemically treat it to deodorize it. It's then bottled and put on the grocery shelf.
So when you buy vegetable oil, read the label. If the label does not say it is expeller pressed, you can assume it is chemically extracted. (expeller pressed is as it sounds a press that squeezed out the oil, as is cold pressing) As always if you can get it organic and/or GMO free that’s a good idea as well. (Since there is a good bit we do not know about GMO’s yet, and there’s a good bit we don’t know about pesticides yet).
5. Saturated fats, similar to vegetable oils are not all the same. Saturated fats are natural, and come from animal sources (mainly). However, the sources appears to have some bearing on the health benefit or detriment of the saturated fat. For example in one study saturated fat consumed from beef appeared to show an increased risk of CVD. (Faghihnia, Mangravite, Chiu, Bergeron, & Krauss, 2012) In another study, saturated fat from milk appeared to show no risk of increased risk of CVD, but possibly decreased risk of CVD. (Lovegrove & Givens, 2016) So more studies are needed to explore how various saturated fat sources may have different impacts on our health. That being said and based on previous data, national recommendation say your diet should consist of less than 10% saturated fat. (Souza et al., 2015) So if you eat 1500 calories that means you should have less than 150 calories or 16 grams of saturated fat to remain at the low risk level. (assuming 1500 calories is an appropriate number of calories based on your weight, and activity level)
6. So let's conclude that saturated fats are ok in moderation, this means cooking with them may be once again trending. Saturated fats, such as lard can withstand high heats and they are not in danger of becoming nor transferring trans fats into our foods. This makes saturated fats excellent for use in fryers where the frying agent (i.e. fat) is used repeatedly like at a restaurant.
At home you might you might consider a balanced approach by using olive oil if you’re cooking at a low heat (i.e. the oil isn’t smoking). Then when cooking at high heats you may want to switch over and use lard. Another approach and possibly a better approach is you could switch over to avocado oil only, or use an expeller pressed canola, peanut oil. Anyone of these approaches can help you obtain the Omega’s you need, and prevent consuming the toxin you don’t, while keeping your cholesterol in check.
Souza, R.J., Mente, A., Marloeanu, A., Cozma, A. I., Ha, V., Kishibe, T.,... Anand, S.S. (2015). Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. Bmj, 351. doi:10.1136/bmj.h3978
Shabbir, M., Dilber, Raza, A., Suleria, H., Saeed, M., & Sultan, S. (2014). Influence of Thermal Processing on the Formation of Trans Fats in Various Edible Oils. Journal of Food Processing and Preservation, 39(6), 1475-1484. doi:10.1111/jfpp.12367
Przybylski, O., & Aladedunye, F.A., (2012). Formation of trans fats during food preparation. Can J Diet Pract Res, Summer (73), 2nd ser, 98-101. Doi: 10:3148/73.2.2012.98
Faghihnia, N., Mangravite, L.M., Chiu, S., Bergeron, N., & Krauss, R.M. (2012). Effects of dietary saturated fat on LDL subclasses and apolipoprotein CIII in men. European Journal of Clinical Nutrition, 66(11), 1229-1233. doi:10.1038/ejcn.2012.118
Lovegrove, J.A., & Givens, D. L. (2016). Dairy food products: good or bad for cardiometabolic disease? Nutr Res Rev., 29(2), 249-267. doi:10.1017/S0954422416000160
Siri-Tarino, P.W., Chiu, S., Bergeron, N., & Krauss, R. M. (2015). Saturated Fats Versus Polyunsaturated Fats Versus Carbohydrates for Cardiovascular Disease Prevention and Treatment. Annual Review of Nutrition. 35(1), 517-543. doi:10.1146/annurev-nutr-071714-034449