Tuesday, 8 October 2013

Comparing Common Cooking Fats

I have often been frustrated by the crude characterisations that abound in relation to different types of fats, since I learnt in my biomedical degree studying nutrition, that most fats are a mixture of several kinds of lipid molecules, often evenly split across 3 kinds, or at least with a significant percentage of a lipid that is not commonly thought of in relation to that particular dietary fat. We tend, for example, to talk about olive all as being monounsaturated, but ignore its 21% content that is polyunsaturated linoleic acid.

Recently while looking up some fats on the web, I was struck by this table below which appears on the
Wikipedia page on Suet. I cannot find who made the table, but I hope they do not mind me reproducing it here, appropriately credited.

Sadly, it does not list coconut oil, so I have added that data here:
Saturated fat = 91g/100g; Monounsaturated fat = 6g/100g; Polyunsaturated fat = 3g/100g; Smoke point = 350 °F (177 °C).

I find this kind of comparative data useful also because it shows quite clearly something that many
nutritional biochemists and evidence-based nutritional bloggers have been trying to get people to understand for years now: That industrial seed/plant oils are not healthier just because they have minimal saturated fat in them. On the contrary, what they have instead of saturated fat is polyunsaturated fat, usually of the Omega 6 variety which is pro-inflammatory and which has been found in large long-term meta-analyses to correlate with an increases in dislipidemia and in cardiovascular disease deaths. All polyunsaturated fats also oxidise VERY easily (often in the pan, if not already in the bottle), producing oxidative stress in our cells when we ingest them.

So, even if you are not convinced that saturated fat is great to eat large amounts,
you would have to be crazy to swap it for an Omega 6-rich oil, as so many do in choosing margarine over butter and sunflower oil over lard.

In fact, counter-intuitively, the higher the saturated fat in these relatively bad oils is, the less they are probably bad. This is because the saturates prevent, to some degree, the oxidation of the polyunsaturates. Hence, if I had to eat any of these seed oils, I would choose the rice bran over the canola. Frankly though, I see no reason to touch any of them with a 10-foot barge-pole.....Anything with upwards of 30% Omega 6 is just asking for trouble if it appears regularly in your diet.

Smoke point is also worth a look for thinking about how you use a particular fat - note for instance that butter has a low smoke point, which means frying stuff with it at anything higher than the lowest of low flames for longer than a minute will produce known carcinogens of the acrylamide variety. This is true of all high-temperature frying, but the lower the smoke point of a fat, the easier it will be to destroy its molecular structure and create something of unknown potential risk. Seed oils became popular in the first place because of their capacity for high-temperature frying, but given they are so toxic in the first place, this is really a bad idea.

If, like me, you love your butter and your olive oil, consider smothering them on after the food has cooked, rather than frying stuff with them.

And if you are determined to eat something crispy and fried as an occasional treat (like me!), use a high smoke point saturated fat to fry with, and accompany it with plenty of anti-carcinogens, including raw garlic (for the allocin), cruciferous and other sulphurous veggies (for the indoles and hepato-protective phytochemicals), and turmeric (for the curcumin), knocked down with a small glass of Bordeaux or Shiraz (for the resveratrol) or a cup of green tea (for the polyphenols).

Comparative properties of common cooking fats (per 100g)
Total fatSaturated fatMonounsaturated fatPolyunsaturated fatSmoke point
Sunflower oil100g11g20g (84g in high oleic variety[3])69g (4g in high oleic variety[3])225 °C (437 °F)[4]
Soybean oil100g16g23g58g257 °C (495 °F)[4]
Canola oil100g7g63g28g205 °C (401 °F)[3][5]
Olive oil100g14g73g11g190 °C (374 °F)[4]
Corn oil100g15g30g55g230 °C (446 °F)[4]
Peanut oil100g17g46g32g225 °C (437 °F)[4]
Rice bran oil100g25g38g37g213 °C (415 °F)
Vegetable shortening (hydrogenated)71g23g (34%)8g (11%)37g (52%)165 °C (329 °F)[4]
Lard100g39g45g11g190 °C (374 °F)[4]
Suet94g52g (55%)32g (34%)3g (3%)200°C (400°F)
Butter81g51g (63%)21g (26%)3g (4%)150 °C (302 °F)[4]

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