There is no healthy seed oil. Every version sold as one carries the same fat, and the fat is the problem. Cold pressed rapeseed oil still oxidises inside you. Pressing it without heat leaves the smell and the vitamin E in, and leaves every polyunsaturated molecule exactly as fragile as the refinery version. It goes into your cell walls and breaks apart there at 37 degrees the same as the cheap stuff. Organic sunflower oil still oxidises inside you. The pesticide was never what hurt anyone. Two thirds of the bottle is a fat that falls apart in air, light and heat, and an organic sunflower makes exactly the same fat. High oleic sunflower oil is the industry admitting the ordinary kind was the problem. They bred the polyunsaturated fat down because it kept going rancid in the fryer, and the bottle they sell you is still a solvent-extracted, bleached, deodorised oil from a seed nobody ever ate for its fat. Flaxseed oil is the most fragile oil you can buy. It is the oil painters use because it hardens in air, it goes rancid in weeks even in the fridge, and the omega-3 it is sold for is the plant kind your body converts at about 1 in 100. The capsule is a bottle of paint base with a health claim. Grapeseed oil is the worst in the aisle, 70% polyunsaturated, and it is marketed as the clean one. It will do more damage per spoon than the sunflower oil it is sold as an upgrade from. Walnut, hemp and pumpkin seed oils are the same fat at a higher price. The health shop keeps them in the fridge and tells you to finish them fast because the shop knows what happens to them in a month, and your body is a warm cupboard you cannot open. Toasted sesame oil is the only one with a tradition, and the tradition was a teaspoon over a finished dish. Fry in it by the cup and you are doing what no Chinese grandmother did, with the same fragile fat as everything above. Every one of those bottles goes off on a shelf, breaks apart in a pan, and carries on breaking apart in the walls of your cells for the two years it lives there. A better label does not change a fat. Butter, dripping and tallow have never needed one, because there was nothing in them to go wrong.

The biggest gain in height ever recorded for any group of human beings belongs to South Korean women, and it is 20 centimetres in one century. In 1896 a Korean woman born that year would grow to about 142 centimetres. Four foot eight. In 1996 a Korean woman born that year would grow to about 162. Five foot four. 20 centimetres. 8 inches. No other population of women on earth has gained as much, and almost no population of men has either. In 1970 a South Korean ate about 5 kilos of meat a year and drank almost no milk. Rice, kimchi, a little fish. By 2020 she ate over 50 kilos of meat a year, and her children drank milk at school. Her cousin in the north, same blood, same grandmother, is still on the 1970 plate, and is still the 1970 height. The women gained more than the men did, which is the quiet part. A girl's growth is the first thing a poor country spends on last, and the first thing a rich one finally pays for. The tallest women on earth are Dutch, at 5 foot 7, in the country that drinks the most milk. The shortest are in Guatemala, at 4 foot 11, in a country that lives on maize. A century of the most careful measuring ever done, in 200 countries, and the result is a map of who got the cow.

The paint trade sorted every fat on earth into three bins two centuries ago, and the bin your cooking oil sits in is the one that goes hard on a canvas. Drying oils: linseed, walnut, poppy, safflower, sunflower. Spread them thin in air and they set solid. A painter wants exactly that. Semi-drying oils: soybean, corn, rapeseed, cottonseed. They go tacky and then they go hard, slower. Non-drying oils: olive, lard, tallow, butter. They stay what they were. Nobody has ever primed a canvas with dripping. The sorting is done by one thing: how many weak points the fat has for oxygen to attack. Oxygen gets in at the double bonds, the chain breaks, the fragments cross-link, and the liquid becomes a film. The smell of a freshly painted room is the aldehydes coming off the oil while it does it. Your cell membranes are built from the fat you eat, on a turnover of about two years. For fifty years the guidance has told you to build them from the drying bin and to fear the bin that does not change. An old painting cracks. The gallery calls it craquelure and spends a fortune slowing it down. Your seed oil is doing it on the inside, warm, with no curator.