Is Air Frying Healthier Than Deep Frying? Which Oil's Best for Each Method and How Do They Compare to Cooking?

Photos of the devices that were used in the study. No sign. differences were observed between the Tefal and Phillips devices, which makes it unlikely that you'd seen different results w/ your air frying device at home.

Methodology: Deep-frying was carried out in a domestic electric fryer (TRISTAR, FR-6929) with adjustable temperature up to 190 °C, 1.75 L capacity, and maximum load of 200 g per L. A portion of potatoes cubes (200 g) was fried in 1.5 L of vegetable oil, at 175 °C, during 6 min. The temperature was periodically controlled with a calibrated digital thermometer. Air-frying was tested in two different equipment’s: Actifry (Tefal, SERIE001) with a nominal power of 1400 W, and Airfryer (Philips, HD9220) with a nominal power of 1425 W. A portion of potatoes cubes (300 g) was involved in 3.6 g of vegetable oil, and fried during 20-25 min (Actifry) or 15-20 min (Airfryer; manual agitation at 10 and 15 min), adjusted to the equipment’s specifications.

What's the latest on frying and your health, anyway? In one of the most recent reviews of the health effects of fried foods, Luke Forney highlights that "[n]ot all fried oil[/food] is equal" - or, as I would like to say: not all fried food is evil ;-) As a SuppVersity reader you will be aware of the so-called "French Paradox", i.e. the observation that the French eat all the good foods, the Americans deem unhealthy (high-fat cheese, absolutely non-whole grain baguette, etc.) and wash it down with liters of red wine and still have a significantly better heart health and smaller waists than their low-fat munching Amerian friends.

The "Spanish Paradox" shows no significant increase in heart disease risk (not shown in this figure) and, if anything, a non-significant reduction in all-cause mortality with increasing amounts of fried foods in the diet (Guallar-Castillón 2012).

For fried foods, however, it's the "Spanish Paradox" (Guallar-Castillón 2012; Gadiraju 2015), as frying is much more important in the Spanish than it is in the French cuisine. On the other hand, the Spaniards eat fried foods no more than three times per week and, probably, more importantly, (a) make the right oil choice(s) by choosing refined olive oil (not extra-virgin) over higher omega-6 or less stable oils and (b) avoid using oils repeatedly (that's a common practice in every fast-food restaurant). Thus they prevent the formation of both harmful phytosterol oxidation products (from using extra-virgin vs. regular olive oil | Ryan 2009) and polycyclic aromatic hydrocarbons (from (re-)using oils or using oils with a low heat stability, e.g. soybean oil, walnut oil, etc.).

Addendum: The topic of reusing oils is important enough for an addendum based on a study that has been published one day after I published this article.

Figure*: Changes in key-markers of oxidation (total polar material, TPM, and acid value) in french fries and breaded chicken, (Sung 2017).

In their experimental analysis of the oxidative properties of a commercial standard frying oil mix of soybean oil and palm olein (6:4 ratio with 650 ppm added tocopherols) as it is used in many fast food restaurants, Song et al. (2017) show that the key-markers of oxidation increase by more than two- and tenfold within less than 20 and less than 10 frying cycles (both happens even in the best fast food restaurants) in potatoes = french fries (Figure*, left) and breaded chicken (Figure*, right), respectively.

With that being said, Forney's review also reminds us that it's not necessarily the often overestimated amount of oxidized fat in fried foods that's making fried food lovers fat and sick. Rather than that, it is their high calorie-density and thus their significant contribution to "weight gain and obesity, which then increase diabetes, hypertension, and hyperlipidemia, which in turn are the most important factors leading to cardiovascular disease such as heart attack and stroke" (Forney 2016) - so, never forget: calories count, it's just more complex than CICO.