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Potential risks to health caused by eating contaminated foods
Endocrine disrupters (EDs) are substances which can interfere with the endocrine system causeing adverse health effects.
The endocrine system consists of glands, hormones and receptors; it helps to control and regulate energy levels, reproduction, immunity, growth and development. Endocrine glands secrete hormones which circulate around the body and bind with specific receptors in target cells regulate tissue functions and processes. For example, the gonads produce sex hormones (e.g. testosterone, progesterone) which target the brain, gonads and sex organs and influence sexual development, maintenance of reproductive function and behavior. EDs can act by disrupting normal bodily balance and functionality; they can also initiate bodily functions or processes at abnormal times. EDs may, therefore, play a role in the increased incidence of declining sperm counts, congenital malformations in children, certain cancers (breast, ovary, testicular and prostate), retarded sexual development and retarded neurobehavioral development.
The who main classes of EDs are natural hormones and man made chemicals. Natural hormones
Natural hormones include estrogens (responsible for the development of female secondary sexual characteristics and regulation of the menstrual cycle) and androgens (which stimulate or control the development and maintenance of masculine characteristics). Other naturally occurring hormones include: phytoestrogens (found in some plants); and mycoestrogens (produced by some fungi, e.g. certain Fusarium species produce zearalenone).
Natural hormones are present at very low levels in animal food products such as meat, dairy products and eggs. Levels can rise if hormones (natural or synthetic) are used for veterinary purposes, for growth promotion, or enhanced milk production. In 1988 the EU banned the use of all hormonally active substances as growth promoters in food producing animals and although the ban has been challenged, it remains in place. Phytoestrogens
Phytoestrogens are thought to benefit health by helping to prevent cardiovascular disease, osteoporosis and some cancers: they have also been implicated as EDs. Phytoestrogens are present in a wide range of plants (including fruits, vegetables and products derived from them); soya beans and their related products have been most widely investigated.
Implicated phytoestrogens include: daidzein, genistein, daidzin, genistin, formononetin, biochanin A, coumestrol, 4-methoxycoumestrol, enterolactone, enterodiol, apigenin, luteolin, quercetin and resveratrol.
Resveratrol (found in wines, red grapes and juice, Blueberries, bilberries, cranberries and peanuts) has become popular as a nutritional supplement. In addition to its antioxidant properties conferring the health benefits described above, it has also been liked to the ‘French Paradox’ (the French diet is relatively high in saturated fat, but deaths from coronary heart disease are low). However, despite these positive features, resveratrol demonstrates oestrogenic activity and associated health concerns are currently being a ddressed. Other phytochemicals
‘Phytochemicals’ is a general term for describing physiologically active substances produced by plants. Some have been implicated as EDs because they demonstrate androgenic activity, e.g. hesperetin and maringenin (citrus fruits), coumaric acid, ferulic acid, syringic acid and taxifolin (tea and red wine), chlorogenic acid (coffee), and chlorophylline (all green plants).
Glucosinolates are present in a range of plants. Some of their metabolites (thiochyanates) contriute to the pungent flavors associated with mustard, watercress, horseradish and wasabi; these chemicals have been associated with thyroid enlargement. Man made chemicals
Man made chemicals implicated as EDs include synthetic hormones (including those identical to natural hormones) and substances synthesized for agricultural and/or industrial purposes. Those which have entered the food chain include;
Bisphenol A (oestrogenic activity) – use is strictly controlled for the manufacture of food containers (plastics, can linings/coatings and water pipes). Entry into the food chain is via migration from contact materials.
Phthalates (a variety of effects) – once used to manufacture cling films and other food contact plastics but now use is limited to printing inks and adhesives used in food packaging. Phthalates take a long time to degrade in the environment. Consequently, and despite reduced use, major human exposure is still thought to occur via the food chain. Phthalates concentrate in foods such as butter and cheeses.
Dioxins (PCDDs), furans PCDFs and polychlorinated biphenyls (PCBs) ( a variety of effect thought to result if absorbed at high levels for long periods of time) – entry into the food chain is via the environment. PCBs were specifically manufactured for a variety of industrial applications until use was discontinued about 20 years ago. PCDDs and PCDFs arise as unwanted by-products from a variety of industrial processes. Industrial release continues to be governed by pollution prevention and control regulations resulting in reductions in environmental levels; this is considered to be the best way managing the situation. However, these chemicals persist for long periods and there is virtually no scope for eliminating them from the food chain once they have entered it. Current opinion is that any risks posed are out weighed by the benefits arising from a balanced diet which contains only trace levels of these chemicals which fall below the regulatory limits in force. Major food sources are those high in animal fat (milk, meat, fish and eggs).
Pesticides ( a variety of effects) – entry into the food chain is via the environment. Pesticides posing the greatest cause for concern include: camphechlor (progesterone, testosterone and adrenal disrupter, and altered reproductive function); chlordecone (thyroid carcinoma, benign tumours, and oestrogen and androgen receptor binding affinites); DDT (oestrogenic disrupter); hexachlorobenzene (thyroid and gonadal disrupter); lindane (oestrogenic disrupter); mirex (variety of effects including blocking of ovulation); acetochlor and alachlor *thyroid disrupters); atrazine (variety of effects including testosterone disruption, inhibitioin of hormone metabolism and delay of postnatal development); linuron (androgenic activity); maneb (variety of effects including thyroid inhibition); thiram (variety of effects including thyroid disruption); zineb (variety of effects including thyroid dysfunction); and vinclozolin (anti androgenic activity). Other purported EDs
Some metals (e.g. chromium, copper, iron, lead, tin, zinc, arsenic, mercury and cadmium), some food additives/preservatives, e.g. butyrate hydroxyanisole (BHA), vitamin B (folic acid), and beta-carotene have also been implicated as EDs. It has been suggested that EDs may develop in foods during cooding. For example, the carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5b] pyridine (PhIP) which can form in meat during high temperature cooking (grilling, frying and barbequing) is estrogenic. Consequently, it may be advisable to use smaller, leaner pieces of meat for faster, lower temperature cooking. Conclusions
Consumer concerns relating to the potential health risks posed by chemicals implicated as EDs appearing in the food chain are understandable; they are validated by scientific opinion and the efforts being made to address the problem at the governmental and regulatory level. However, it is important to remember that no clear relationship has been established between exposure to EDs and adverse health effects. In addition, those effects which have been described may not necessarily be the result of endocrine disruptive activity. There is a vast amount of information available on the topic and some is conflicting. It is clear that a great deal more research is needed before any definite conclusions can be reached. In the meantime, it may be prudent to try to select those food likely to have had least exposure to potential EDs. Care with cooking, particularly at high temperatures, could also be worthwhile.
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