Recently oils and fats, particularly polyunsaturated fats (PUFA’s) are getting a bad reputation. Some health professionals are advocating for the complete removal of all high PUFA foods while others focus on only removing “inflammatory seed and vegetable oils.” People in the metabolic space claim that PUFA oils are very easily oxidized leading to widespread inflammation and advocate for the replacement of PUFA fats with saturated fats which are more heat-stable (read my article on PUFA’s here). In the plant-based community, there is a large “no oil” movement where even things like olive oil are not acceptable. My concern here is that we have quite a lot of data supporting the detrimental effects of saturated fats, mostly animal fats on overall health and hormone health and fertility while conversely showing how both PUFA’s and MUFA’s improve health markers. So the switch from PUFA’s to saturated fat is not an evidence-based approach for health and fertility. I am also concerned that low-fat diets are being promoted for women in the plant-based community. Women have a higher need for fats than men during the reproductive years. Fats are the building blocks to cholesterol and cholesterol is needed to make reproductive hormones. It is true that the body can make its own cholesterol and that low blood cholesterol levels are not needed to make hormones (we need cholesterol in the cells, not in the blood where they can cause heart disease) but without adequate intake of essential fatty acids like PUFA’s of MUFA’s (essential means they need to be ingested as the body can not make its own) hormone production and energy production can decrease. For vegan and plant-based women it can be difficult to eat enough fat without consuming oils in moderation. Read my article on the best and worst fats for fertility here:
So the question is if oils are a healthful part of a diet for women, which oils are best?
Although saturated fats found in butter, lard, coconut oil, shortening and palm oil are heat stable and not easily oxidised they have been shown to raise cholesterol levels in the blood which can contribute to heart disease, inflammation, estrogen excess and impairment of fertility. Saturated fats consistently perform worst for health markers compared to all other fats and oils. Monounsaturated fats like olive oil, avocado oil, good quality non GMO canola oil and macadamia oil are slower to oxidise and have a high smoke point, there are usually cold-pressed and retain a lot of nutrients. These are the best oils to cook with and also to use for salad dressings. Polyunsaturated oils like grapeseed oil, sunflower oil, mixed vegetable oils, corn oil, cottonseed oil, soybean oil are more easily oxidised and are often very cheaply produced using chemical extractions that use chemicals like hexane. They are then further bleached and deodorised. During this process, they lose a lot of their nutrition and so synthetic antioxidants are added back into the oil to help offset oxidation (this is seen most in oils used for deep frying). Furthermore, many seed and vegetable oils can be GMO (some not all) and have a very high omega 6 content which disrupts the balance of omega 6 to omega 3, especially when consumed in commercial deep-fried foods. The ratio of omega 6 to omega 3 is the main reason that scientists believe that seed and vegetable oils lead to inflammation.
Although there is much concern over high PUFA oils in the diet, it’s important to remember that the majority of negative health effects from seed and vegetable oils occur with commercial deep frying. Cooking at home is far less likely to create problems as it’s difficult to reach the heat required to oxidise oils. Commercial deep-frying oils are also reheated for days at a time which creates the majority of the poor health outcomes. Even though there are some negative health consequences, particularly with deep-fried foods, PUFA oils still outperform saturated fats like butter for overall health in the research.
Top tips for buying and using oil
- choose non-GMO,
- choose oils that are mechanically extracted: cold-pressed or expeller-pressed. Oils must specifically specify that they are cold-pressed or expeller-pressed on the bottle. If they do not say so, you can assume they use a chemical extraction process.
- Follow the advice on the label and store and cook with your oils accordingly. Some oils oxidise quicker than others with heat so should only be eaten cold and not used in cooking.
- Pay attention to shelf life and expiration date. Most oils have a shelf life of 6-24 months but this varies greatly depending on the type of oils used. Once oils have expired they oxidise and turn rancid
- choose oils that also contain omega 3 to keep the balance of omega 6 and omega 3 happy
- Watch out for the addition of unhealthy oils in processed foods and limit overly processed foods.
- the addition of high oleic sunflower oil in many organic health products is generally safe as high oleic sunflower oils are very high in monounsaturated fats and low in polyunsaturated fats, they are usually also expeller-pressed not chemically extracted.