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nutritional diseases

Tuesday 13 April 2004

Food is essential for life, yet it contains numerous natural constituents and additives that may threaten human health. This mixture of natural compounds and chemical additives is the most complex and variable environmental exposure that humans experience.

A wide range of chemicals are natural constituents of foods, including carcinogens such as safrole in nutmeg and parsley and estragole in basil and fennel. Coffee contains more than 200 compounds, including tannins that may be carcinogenic. Natural pesticides are also found in plants, for example, 5- and 8-methoxypsoralen in celery, parsnips, and parsley.

Some scientists contend that natural plant pesticides and carcinogens are a greater threat to humans than are agricultural pesticide residues or industrial toxicants. Food may be contaminated by natural toxicants or microorganisms, for example, the liver carcinogen aflatoxin B1 or the deadly botulinum toxin.

Contamination with pathogenic viruses and bacteria continues to threaten public health. Hepatitis A virus, Salmonella enteritidis, Escherichia coli, Listeria monocytogenes, Campylobacter, and Cryptosporidium are common examples of food-borne infections. Additional toxicants can be generated in foods during preservation or preparation.

Broiling meat produces oxidized fats, pyrolysis products of amino acids, and carcinogenic polycyclic aromatic hydrocarbons. Foods preserved by smoking or by nitrate and nitrite additives may contain precursors of N-nitrosamines. These chemicals are potent carcinogens in many animal species, producing cancers of the mouth, esophagus, larynx, liver, and kidney.

Additional chemicals are added to foods either directly (chemical sweeteners, preservatives, food colors) or indirectly. Indirect additives include residues of drugs or hormones fed to animals, agricultural pesticides, industrial contaminants, and residues from food packaging. Low levels of metals such as mercury and lead, PCBs, and chlorinated hydrocarbons are present in our food supply.

Other metals, such as arsenic and cadmium, may be natural contaminants of water and soil in some geographic locations. The Food and Drug Administration monitors the levels of pesticides, metals, and industrial contaminants in food samples in the United States.

The level of some contaminants, such as dieldrin, approaches the acceptable daily intake that has been established as a safe threshold dose. Despite the considerable concern about additives and contaminants, regulation of their content in food is complicated by the detection limit of potential carcinogens, reliance on toxicologic assays using high doses of chemicals in rodents, and uncertainties in extrapolation of risk for humans under lifetime exposures at low doses.

Pathology

- nutritional deficiencies

- vitamins deficiency

  • biotin deficiency
  • foloic acid deficiency
  • scurvy
  • pernicious anaemia
  • riboflavin deficiency

- fluorin deficiency

- atherosclerosis
- obesity
- cachexia
- marasmus
- kwashiorkor
- pellagra

- hypercatabolic disease

- iodin deficiency (cretinism)

See also

- nutritional imbalance