Why Eating Out in Hong Kong Could be Damaging to Your Health Part 3 – Toxic Cooking Oils in Hong Kong

Why Eating Out in Hong Kong Could be Damaging to Your Health

Part 3 – Toxic Cooking Oils in Hong Kong

Date 31/12/19

Written by: Miles Price, Functional Medicine Practitioner & Clinical Nutritionist

In Hong Kong, you can get an idea of what cooking oils are used by seeing what is sold in the supermarkets and what is used by the F&B industry. On the supermarket shelves you’ll see a predominance of the toxic polyunsaturated cooking oils like canola, sunflower, soyabean, corn oils, with butter or coconut oil only being given a small space to entice shoppers.

More worryingly, a study from 2017 conducted by the Consumer Council Hong Kong, found that by testing 60 edible cooking oils, 46 of them contained a carcinogen, glycidol1. Glycidol is made during the manufacturing process of the cooking oil and is, according to the International Research Agency on Cancer, a class IIA carcinogen. There are no safe levels set for it by other countries. When looking at the variety of Cantonese dishes which require oils in their cooking, and the number of those dishes we have per day, or per week, there’s no defining what our exposure to this carcinogen is. This is surely one way we could be insidiously harming ourselves with restaurant dining.

Miles Price

Currently there is no industry survey of Hong Kong’s F&B outlets’ use of cooking oils (double check please!). But through my observations and speaking to individual outlets, it seems that soyabean, peanut, and canola oils are the predominant oils used in the trade.

The key questions that are important to gauge are:

  1. How long do the chefs cook with the oils?
  2. What temperatures are the oils heated to?
  3. How many times do they reuse any unused oil?

How you use the oils is a huge factor for how dangerous they will be to our health. There is a tipping point with these oils, at a certain temperature and beyond a certain time the polyunsaturated content is oxidized to create hydroperoxides. These highly damaging free radical oxides damage DNA, lipid membranes, neurons and other tissues throughout the body. Whether or not chefs are aware of cooking times or temperatures is another point to raise. One study has highlighted that by cooking for just 25 minutes, the increase in lipid peroxides jumps 11-fold2. I’m sure typical cooking times in restaurants over lunchtimes and dinners range from 2-4 hours at a time, so how does this reflect in the peroxide values produced?

A study in 2019 on the rancidity of used cooking oils coming from fast food restaurants showed that the majority of oils contained ‘hazardous secondary oxidative products’ and that the consumption of these oils was increasing3. Only time will tell how long this ticking-time bomb of oxidation takes to create the chronic conditions we see in society. We already see in Hong Kong an increasing number of heart disease, dementia, and diabetic patients and studies have demonstrated increased lipid peroxides in patients with Alzheimer’s disease, heart disease and cancer4,5,6.

Educating the F&B community will be key to helping them understand when a cooking oil has gone rancid and should be discarded. Furthermore, using relevant up-to-date local research data will guide the community to informed choices on which oils to source but more importantly, how long to cook with oils, and what temperatures to cook at. My belief is that going back to the traditional fats of yesteryear will be a long-term education process so in the meantime let’s lobby the government to steer the F&B community towards a more healthy approach to oil use.

Missed Part 1? Understand the history behind the ubiquitous use of toxic cooking oils here

Missed Part 2? Uncover the difference between fats and why there is so confusion regarding this major nutrient here



  1. https://www.scmp.com/news/hong-kong/education-community/article/2102921/46-samples-cooking-oil-sale-hong-kong-contained
  2. Determination of lipid oxidation products in vegetable oils and marine omega-3 supplements


  1. Evaluating the rancidity and quality of discarded oils in fast food restaurants


  1. Oxidative Stress and Lipid Peroxidation Products in Cancer Progression and Therapy


  1. Cardiovascular diseases: oxidative damage and antioxidant protection.


  1. Lipid peroxidation and Diabetes Mellitus





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