ORANGES are not the only fruit that make it on to supermarket shelves in a way Mother Nature never intended. Dyed to meet our brighter colour expectations, oranges are among thousands of other foods that have been mixed, flavoured, treated, pumped with preservatives, waxed, sprayed with oil or generally tampered with in the name of better taste and longer shelf-life. Even 'fresh baked' bread can contain up to 16 chemicals used to keep it 'fresh', writes Ruth Winter in the latest edition of The Consumer's Dictionary of Food Additives. While fruits and vegetables are sprayed with fungicides, pesticides, herbicides and other anti-spoilants to ensure that they are unblemished, chickens are fed a chemical that will make the meat look more yellow - and more appetising. The result is some of the foods on shop shelves are so nutritionally challenged they are recognisable only by the picture on the box. Neither your mother nor a chicken would recognise some of the chicken soups on sale today, Winter says. Even if a product claims to have no preservatives, it may have enough sodium (usually in the form of common salt) to save it for future generations as well. According to the American National Cancer Institute, consumers are swallowing close to 150,000 substances that have been added to the food they eat, from the time it is grown to processing and packaging. For example, the 'flavouring' listed on a carton can mean any one of 2,000 natural or chemical substances that are used to replace the flavour lost during processing. Similarly, the meat on our plates could be laced with hormones that the farmer feeds his cattle, or sedatives given to pigs on their way to slaughter. Winter explains that the drug can appear in the pork we eat when there has not been sufficient time for the tranquilisers to wear off before the pig is killed. In 1978, 74.6 million kilograms of additives were added to processed meat alone in the United States. Today, that has risen to 165 million kg a year. No similar statistics are available for Hong Kong, according to the Department of Health. Of course, not all food additives are bad. But even if you can pronounce their names, how do you tell the harmless from the harmful? While the effects of monosodium glutamate (MSG) are more commonly known, what about those of nitrates? And nitrites? Under Hong Kong's Food and Drugs (Composition and Labelling) regulations, manufacturers are required to list ingredients of prepackaged food in descending order of weight and volume. 'If an additive constitutes one of the ingredients of a food, it shall be listed by its specific name or by the appropriate category or by both name and category,' the Health Department says. But what does that mean in real terms if 'flavouring' or 'spices' can be any one of 2,000 or more substances, and 'colouring' can be any one of 80 dyes? Most of these are safe, but some are toxic. Colouring can be especially confusing. Only a fraction of the 80 dyes that were used at the turn of the century are in use today, and even then there is little information about their effects. We took a random selection of local and imported items on supermarket shelves to check the situation in Hong Kong. The sample ranged from Narcissus-brand canned spiced pork cubes, Garden chocolate-flavoured chiffon cake and BBQ prawn crackers to Maggi chicken stock, Hi-C chrysanthemum tea and Healthy Choice honey-roasted and smoked chicken breast. Generally, additives were labelled under such broad categories as 'spice', 'natural colour', 'natural flavouring', 'colour and flavouring' and 'preservative'. The most detailed ingredients lists were those given for the Kraft cheese slices produced in Australia and the Dan Cake range from Denmark. A scan of the carton of Mr Juicy Gold fruit juice told us it contained such additives as natural flavouring, preservative and natural colour. But how do you find out exactly what these are? Well, you can't. It is not company policy to reveal these details, according to a spokesman for manufacturer United Soft Drinks, not that there's anything wrong with the addition of Vitamin C or citric acid - used in products ranging from eye lotion and hair colouring to treatments for dissolving urinary bladder stones. Other items gave much more detailed information: Maggi Chicken Stock lists salt and sugar as main ingredients, ahead of chicken, from which the flavour is supposed to be derived. Guanylate, which has caused mutations in experimental animals, appears on the list, too, along with monosodium glutamate, soy sauce, palm fat, yeast extract, caramel and yet more spices. The treatment of oranges seem pretty tame in comparison - merely enhancing the colour of the peel by applying citrus red No. 2, a harmless dye. Those worried about getting carcinogens with their curry sauce have some good news: according to the Cancer Institute, scientists believe it is unlikely that additives contribute significantly to the overall cancer risk in humans. Still, Winter argues that long-term effects of many chemicals have not been adequately assessed. She notes that some additives, judged to be safe 20 years ago, have since been recognised as harmful. In the 23 years she has been compiling her consumer's guide, Winter says, 35 widely used additives that had once been approved for food use were later judged to be unsafe, most of them because they were found to be carcinogenic. She also points to another evil - neurotoxins - which poison the nervous system and wreak havoc with normal functions like the ability to learn. In the meantime, research continues into additives such as MSG and the artificial sweetener aspartame, which will hopefully clear up uncertainty about their effects on our health - and our nerves.