What makes a good cooking oil?

This article was written by one of The Food Medic team; registered dietitian – Maeve Hanan

It can be confusing to figure out which oils are the best to use when cooking, as there are a few things to consider. So this article will break this down and list 5 of the best oils to cook with. 

A good cooking oil is ‘heat stable’ which means that it doesn’t break down or oxidise as quickly when exposed to heat. The smoke point is the temperature where the fat begins to break down, so a higher smoke point means that an oil is more heat stable (1). 

We also need to consider the health impact of oils. The 2 main types of fats found in oils are saturated and unsaturated fats. All oils contain a combination of both of these fats in different combinations. Those that contain more unsaturated fat rather than saturated fat are better for our heart health (2). Oils can also contain antioxidants, like vitamin E and polyphenols, that are both good for our health and help with increasing the smoke point of the oil. As well as this, we need to look at the evidence for how different oils impact our health.

How the oil has been produced and processed also makes a difference. For example, cold-pressed oils  tend to have a higher antioxidant content but a lower smoke point than refined oils that have undergone more processing. 

‘Best’ is of course subjective and no oil needs to be 100% avoided – unless you have been advised otherwise by a health professional. So individual taste preference and price are also important considerations, and you can be flexible with this and choose different oils for different dishes and purposes. For example, although coconut oil is very high in saturated fat (hence why it doesn’t appear on this list) you might like how it tastes in Thai curries, whereas one of the oils listed below could be used for everyday cooking.  

Olive oil

This delicious oil is very nutritious as it’s high in unsaturated fat, polyphenols, vitamin E and vitamin K. We also have strong evidence that consuming olive oil is good for our health, particularly as the fats and polyphenols in olive oil promote heart health (3, 4).

Refined olive oil has a high smoke point, whereas extra virgin olive oil (EVOO) has a medium to high smoke point. Although all types of olive oil are good for us, EVOO contains more polyphenols than refined olive oil, and frying with EVOO has been linked with a lower risk of heart disease (5).

Rapeseed or ‘vegetable’ oil

Rapeseed oil (A.K.A. ‘canola oil’ in the US and Canada) has a medium to high smoke point and is high in unsaturated fat –  including the plant-based form of omega-3 alpha linoleic acid (ALA). This oil is also high in vitamin E and vitamin K.

There is also evidence that rapeseed oil is good for heart health and insulin sensitivity (6). 

A cheaper way of buying rapeseed oil in the UK and Ireland is to go for ‘vegetable oil’ as if you look at the label this tends to contain 100% rapeseed oil. 

Sunflower oil

Sunflower oil is used by many as their cooking oil of choice. Its high smoke point makes it suitable for cooking at high temperatures. 

Sunflower oil is sometimes seen as unhealthy or overly processed. As mentioned above, edible oils are processed to different degrees and we get pros and cons from this. The way sunflower oil is refined does reduce its antioxidant content, but it is still high in  unsaturated fat and vitamin E (7).

This reputation may be because a modified version of sunflower oil can be used in food processing and industrial settings, and when this becomes ‘partially hydrolysed’ it produces trans fat which isn’t good for our heart. Luckily this doesn’t occur in home kitchens as hydrogen needs to be present for this to occur, and the food industry has also massively reduced the amount of trans fat in the UK food supply (7). 

Some people are concerned that the high omega-6 content of sunflower oil leads to inflammation. Although omega-6 is involved in inflammatory pathways, consuming omega-6 is linked with reducing inflammation and lowering cholesterol (8. 9). The overall consensus is that omega-6 (and hence sunflower oil) doesn’t lead to inflammation, but many people benefit from adding more omega-3 to their diet due to its health and anti-inflammatory effects. 

Avocado oil

If you don’t mind the price tag, avocado oil is a very heat-stable oil to use for high-temperature cooking. 

This oil is also high in vitamin E and unsaturated fat, including omega-3 (in the form of ALA). This combination of nutrients support a healthy heart. 

Safflower oil

Safflower oil is another high smoke point oil that can be used for high temperature cooking like frying, searing, browning and deep-frying

This oil also provides a good amount of unsaturated fat (in the form of omega-3) and vitamin E, as well as a small amount of vitamin K

A limited amount of research has found that consuming safflower oil may be beneficial for cholesterol, inflammation and blood glucose levels (10, 11). 

Don’t forget that heat and light eventually causes all oils to break down and become rancid, so make sure to store these away from sunlight, don’t reuse cooking oil and reduce cooking times and temperatures where you can. Oil can become thick and cloudy when stored in the fridge, so a cupboard is usually the best storage option. 

References:

1. Choe, E., & Min, D. B. (2007). Chemistry of deep‐fat frying oils. Journal of food science, 72(5), R77-R86. [accessed July 2022 via: https://pubmed.ncbi.nlm.nih.gov/17995742/]
2. Schwingshackl, L., Zähringer, J., Beyerbach, J., Werner, S. W., Heseker, H., Koletzko, B., & Meerpohl, J. J. (2021). Total dietary fat intake, fat quality, and health outcomes: a scoping review of systematic reviews of prospective studies. Annals of Nutrition and Metabolism, 77(1), 4-15. [accessed July 2022 via: https://pubmed.ncbi.nlm.nih.gov/33789278/]
3. Gaforio, J. J., Visioli, F., Alarcón-de-la-Lastra, C., Castañer, O., Delgado-Rodríguez, M., Fitó, M., … & Tsatsakis, A. M. (2019). Virgin olive oil and health: Summary of the iii international conference on virgin olive oil and health consensus report, JAEN (Spain) 2018. Nutrients, 11(9), 2039. [accessed July 2022 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6770785/]
4. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). (2011). Scientific opinion on the substantiation of health claims related to polyphenols in olive and protection of LDL particles from oxidative damage (ID 1333, 1638, 1639, 1696, 2865), maintenance of normal blood HDL cholesterol concentrations (ID 1639), maintenance of normal blood pressure (ID 3781),“anti‐inflammatory properties”(ID 1882),“contributes to the upper respiratory tract health”(ID 3468),“can help to maintain a normal function of gastrointestinal tract”(3779), and “contributes to body defences …. EFSA journal, 9(4), 2033. [accessed July 2022 via: https://www.efsa.europa.eu/en/efsajournal/pub/2033]
5. Sayon-Orea, C., Carlos, S., & Martínez-Gonzalez, M. A. (2015). Does cooking with vegetable oils increase the risk of chronic diseases?: a systematic review. British Journal of Nutrition, 113(S2), S36-S48. [accessed July 2022 via: https://pubmed.ncbi.nlm.nih.gov/26148920/]
6. Lin, L., Allemekinders, H., Dansby, A., Campbell, L., Durance-Tod, S., Berger, A., & Jones, P. J. (2013). Evidence of health benefits of canola oil. Nutrition reviews, 71(6), 370-385. [accessed July 2022 via: https://pubmed.ncbi.nlm.nih.gov/23731447/]
7. BNF (2009) “Culinary oils and their health effects” [accessed July 2022 via: https://archive.nutrition.org.uk/bnf-publications/briefingpapers/culinary-oils-and-their-health-effects.html]
8. https://www.ahajournals.org/doi/10.1161/circulationaha.108.191627
9. https://pubmed.ncbi.nlm.nih.gov/29610056 
10. https://pubmed.ncbi.nlm.nih.gov/1905474/
11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3115398/ 
12. Dietetics Today “Characteristics of Various Oils” [accessed July 2022 via: https://www.todaysdietitian.com/newarchives/images/0215-2.pdf] 
13. Nutritics nutritional database [accessed July 2022 via: https://www.todaysdietitian.com/newarchives/images/0215-2.pdf] 

What makes a good cooking oil? was last modified: July 15th, 2022 by Maeve Hanan