Introduction to Human Nutrition

340 Introduction to Human Nutrition

the form of depression or, less often, a schizophrenia-
like disorder. Neurological signs such as unsteadiness,
diffi culty walking, and involuntary movements
develop as the illness progresses and, by the time of
death, patients become completely immobile and
mute.

The link between BSE and vCJD

A geographical association exists whereby the major-
ity of BSE cases occurred in the UK and the majority
of vCJD cases were also reported there. The emer-
gence of BSE preceded vCJD, indicating a temporal
association. Studies of stored human brain tissue
internationally have not identifi ed the histopatho-
logical changes characteristic of vCJD before the
current BSE epidemic. Incubation period and patho-
logical lesion studies in mice and molecular typing
studies demonstrate that vCJD is similar to BSE but
different from other TSEs. It is now widely accepted
that vCJD was transmitted to humans through the
consumption of contaminated food.
Estimates of future prevalence of vCJD vary widely
as too little is known about the disease, especially

regarding the incubation period between exposure to

the infective agent and the emergence of symptoms.

14.7 Chemicals affecting food safety

Chemicals may be present in food owing to their

natural occurrence in soil (e.g., cadmium, lead) or

from fungal contamination (e.g., afl atoxins, ochra-

toxin), from algal contamination [e.g., amnesic shell-

fi sh poisoning (ASP), diarrhetic shellfi sh poisoning

(DSP), azaspiracid shellfi sh poisoning (AZP), para-

lytic shellfi sh poisoning (PSP)], from industrial or

other pollution [e.g., lead, mercury, polychlorinated

biphenyls (PCBs), dioxins], from agricultural and vet-

erinary practices (e.g., pesticides, fertilizers, veteri-

nary drugs) or from food processing and packaging

techniques [e.g. acrylamide, polycyclic aromatic

hydrocarbons (PAHs), 3-monochloropropane-1,2-

diol (3-MCPD), bisphenol A diglycidyl ether

(BADGE)] (Box 14.1).

Toxicological assessment of these substances is

largely carried out on an international basis by expert

groups such as the Joint Expert Committee on

Box 14.1 Principal groups of chemicals affecting food safety

Microbial toxins

Plant toxins

Process contaminants

Environmental contaminants

Food contact materials

Naturally occurring

contaminants

Principal chemicals

affecting food safety

Food additives

Additives Contaminants Residues

Food flavorings

Pesticide residues

Veterinary drug residues

Processing aids