Trial and error over time has seen foods that have a obvious toxic effects be excluded from the human diet. Today acute poisoning from any food uncontaminated by bacteria is rare, the contamination is from bacteria in foods that when handled, stored and cooked properly are not toxic. This means that the far more important risk to our health is contamination of food by toxic biological substances such as bacteria and fungi. Bacterial contamination of food has been a major problem throughout human history. Acute illness from food contamination is characterized by symptoms which may include diarrhea, cramps, fever and vomiting. The risk of death from food contamination is much higher for the elderly, people who have a weak immunity system and the very young. Long term affects may also be present due the infections caused by the contaminated food that can weaken the immunity system, thereby make the body more prone to contracting other disease and illnesses.
Although the refrigeration of food has greatly improved the situation, outbreaks of bacterial poisoning are still occurring today. This is happening principally as a result of inadequate cooking of food, improper cleaning of equipment, cross contamination of cooked and raw food and preparation of food too far in advance. Illness is caused by bacteria multiplying in the intestines and by toxic proteins that the bacteria liberate there. The popularity of defrosting and cooking meat in microwave ovens often results in incomplete cooking and incomplete destruction of bacteria. Microwave ovens can have an uneven heat distribution which results in both over cooking and under cooking.
A common food contaminant is ecoli, which is especially found in hamburger mince. It causes server diarrhoea, which can be fatal. Bacterial contamination on the outside of the meat which will be cooked is normally harmless, since the heat will destroy the bacteria. However when the meat is transformed from its original structure (such as mince), some of the bacteria is transferred to inside the hamburger pattie and if the cooking is inadequate the bacteria can survive and cause food poisoning. In recent years there has been a rapid increase in food poisoning in most countries. The demise of home cooking and the popularity of fast food outlets and restaurants have contributed to this increase in food poisoning. In the US there are about 30 million cases a year, leading to about 10,000 deaths and an annual cost of $6 Billion dollars to the economy.