Antioxidants protect tyres, fuel and frozen food; the supplements have not proven useful
The word antioxidant sells pills, but its biggest jobs are industrial: keeping rubber supple, fuel from gumming up engines and cooking oils from turning rancid. In the body, cells run their own antioxidant defences, yet supplements marketed on the idea have not been shown to improve human health.
Oxidation is a chemical reaction that can generate free radicals, and antioxidants are compounds that hold it back. The original meaning was narrower: a substance that stopped oxygen being used up. Around the turn of the twentieth century chemists studied them mainly for industry, to slow metal corrosion, aid rubber vulcanisation and stop fuel from polymerising into deposits inside combustion engines.
Biology came later. Early work focused on rancidity, the oxidation of unsaturated fats, measured by sealing fat in a jar with oxygen and tracking how fast the gas disappeared. The discovery that vitamins C and E act as antioxidants transformed the field. Researchers realised that a good antioxidant is usually something easily oxidised itself, and studies of vitamin E showed these molecules work as reducing agents, often mopping up reactive oxygen species before they harm cells. Living cells rely on molecules such as glutathione and enzymes like superoxide dismutase for this. Plants developed their own versions, including vitamin C and polyphenols, after moving onto land, and flowering plants evolved many antioxidant pigments, especially in the Jurassic, to cope with oxygen by-products of photosynthesis.
Food preservation leans on them heavily. Oxygen and sunlight are the main culprits, so food is kept dark and sealed, and cucumbers are even waxed. Fresh produce cannot simply be starved of oxygen, since it still respires and turns off-colour and foul-tasting, so its packaging holds about 8 percent oxygen. Unlike microbial spoilage, oxidation continues fairly quickly in the fridge or freezer, which is why additives such as tocopherols and the synthetic BHT matter. Fatty foods are rarely dried; they are smoked, salted or fermented instead, and olive oil gets some protection from its own natural antioxidants.
Plastics and rubber need the same help. Natural rubber and polybutadiene, with double bonds in their backbone, are especially vulnerable to oxygen and ozone, and sunlight accelerates the damage. Manufacturers add radical scavengers, antiozonants and light stabilisers so materials keep their strength and flexibility, and medicines may include antioxidants or sequestrants like EDTA to block metal-driven oxidation.
Source: Antioxidant
