The question of whether there is a place for oils in a whole food plant based diet is a contentious one and whereas some will say yes, others will say no and I fall into the latter camp.
First of all it is important to differentiate between saturated fats and unsaturated fats as, although they all contain the same amounts of energy (9kcals per gram) they exert different effects on our bodies.
There are four main saturated fats: Lauric acid, stearic acid, palmitic acid and myristic acid and it is the latter two that are known to have adverse effects on our cardiovascular (CV) health. These particular saturated fats are found in palm oil and coconut oil. In fact, in terms of saturated fat, coconut oil comes out top, with approximately 82g per 100g! Olive oil contains around 13g and sunflower oil 10g. As a general rule, the more solid the oil at room temperature, the more saturated fat it contains and coconut oil demonstrates this perfectly. The version that you can buy in liquid form has undergone a process called fractionation which basically means that it is more processed. We know that it is vital to reduce the saturated fat content of our diets for our health as it is linked to increased risk of a number of diseases such as coronary heart disease and stroke, as well as obesity and related cancers.
Unsaturated fats can be split into two groups: monounsaturated (avocado and olive oils) and polyunsaturated (rapeseed, corn and sunflower oils). They are considered more beneficial to CV health, however there are studies that have shown olive oil and soybean oil worsen endothelial function in the same way as saturated fat from burger and chips.
Endothelial cells line the inside of every blood vessel in the body and those in our arteries excrete nitric oxide. This allows the muscles in the arterial walls to relax and the artery to expand, allowing more blood flow. When the endothelial cells are damaged, they are unable to perform this function and it results in functional narrowing of the artery. Studies have shown that one single high fat meal can impair endothelial function for up to six hours, so imagine what a full day of eating this way will do!
Now, you need some fat in your diet; without it you would not be able to absorb the fat soluble vitamins A, D, E and K; it is a source of essential fatty acids (you need these from your diet as your body cannot make them itself) and interestingly some studies have shown that it helps you to absorb my favourite spice, tumeric.
But should oils contribute to our overall fat intake? In my opinion, no they should not.
The reason I feel this way is that vegetable oils are basically liquid fats that have been taken from the whole plant food, such as sunflower seeds, avocadoes and olives. As a result of the whole food being left behind, the extracted oil contains concentrated amounts of fat but little to none of the fibre, vitamins and minerals and beneficial compounds of the original source. It is easy to overconsume and can contribute significantly to your overall daily energy intake. For example, 1tbsp of avocado oil contains about 125kcal and 14g of fat, whereas eating the avocado as a whole fruit will give you 80kcal and 8g of fat (per ⅓ of a medium pear). In addition, you will be consuming a host of vitamins and minerals, fibre and protein and other beneficial compounds contained therein. In addition, some studies have shown that when certain oils are heated, they undergo a complex process called oxidation which results in harmful products being produced from the oil and these can negatively impact our health.
On the other side of the argument, it has been shown that the powerful antioxidant and polyphenol, Oleocanthal, found in olives, is present in cold pressed, extra virgin olive oil. This compound has been shown to increase good cholesterol (HDL) while decreasing bad cholesterol (LDL), lower blood pressure, improve endothelial function and reduce CRP (a marker of inflammation). The more processed olive oils do not contain this compound so if you choose to include oil in your diet, this is probably the best option, however I would avoid heating it.
Personally, as an advocate of a whole food plant based diet, I believe it is most beneficial to health to eat foods in their whole form and avoid foods which have undergone processing and for me, oils are included in this category. By choosing to consume whole food sources of fats, such as nuts and seeds, avocadoes and olives, I know that I am also providing my body with the associated range of healthful properties contained in these whole foods.