Toxicity in Food- Is natural always good?

The notion that 'natural' food may be harmful is not widely appreciated. The terms 'health', ‘organic', 'natural', 'unprocessed', 'no added chemicals' when applied to food suggest that the food is safe or more nutritious than its conventional counterpart but this is not necessarily true. All food is made up entirely of chemicals. In addition to well-known nutrients such as carbohydrate, fat, protein and water, food contains many other substances, often in very small amounts.

Any substance in food may have a degree of toxicity or 'poisonousness', whether it is natural, deliberately added, or a contaminant. There is nothing special about natural chemicals in food and no distinction should be made between natural and other substances when deciding if a food is likely to be hazardous. For example, a potato contains a number of poisonous substances such as nitrate, arsenic and solanine but in the amounts in which potatoes are normally eaten these natural substances are not hazardous. For this reason it is important not to consume large amounts of a small number of foods, as in some faddist diets, but to consume a wide variety of foods. This not only minimizes the amount of a particular potentially hazardous substance but also ensures that a range of essential nutrients are consumed.

Figure 29 lists a number of substances that occur naturally in food and have either caused illness or are suspected of being hazardous to health. Usually these effects have occurred only when excessive amounts of a food containing these substances have been eaten. In fact, for most of us there is little hazard from these foods. The concentration of these poisonous substances is so low in the food we eat that we would have to consume huge amounts over a long time for the toxic effect to show up. Nevertheless, it is import ant to realize that there are many potentially hazardous substances in our diet without any obvious effects on our health, and that this applies equally to 'natural' and processed foods. Natural foods can be harmful if they are contaminated with excessive amounts of environmental contaminants, or aflatoxin or other mycotoxins produced by some moulds.

Herbal teas

Herbal teas have become popular with an increasing number of people. Herbal and 'bush' teas contain a large number of different components, many of which have not yet been assessed for safety. Some teas can lead to disturbing effects. Tea made from the South Pacific kava plant has been associated with impaired breathing, vision and hearing, and other symptoms. Comfrey and tea made from the roots of sassafras contain substances that have caused cancer in laboratory animals. In addition, some teas can interfere with the therapeutic value of some drugs that are taken at the same time. The heavy consumption of these teas is not to be recommended. Tea, coffee and cola-type drinks contain caffeine (about 30, 40, and 10 milligrams per 100 millilitres respectively). Although individuals react differently to caffeine, the heavy consumption of these drinks can cause, in addition to stimulation, nervousness, increased urination, upset stomach and irritability (Chart 49).