BfR
|
Annual Report 2014
46
Bioavailability of hydrogen cyanide from
cyanogenic glycosides
Bitter apricot kernels, linseed and manioc contain rela-
tively high concentrations of cyanogenic glycosides.
These natural plant ingredients contain chemically bound
hydrogen cyanide which is released by chewing through
the ß-glucosidase enzyme of these plants. Ingestion of
a sufficiently high dose of hydrogen cyanide can lead to
acute poisoning (see box). The BfR therefore dealt with
the question of whether the consumption of bitter apricot
kernels, linseed and manioc could be associated with
risks to health.
A human study with twelve subjects was conducted for
this purpose. The subjects received either bitter apricot
kernels (approx. 2 g), linseed (31 g), manioc (approx.
100 g) or persipan (100 g, produced partly from bit-
ter apricot kernels) each morning. All foods used in the
study contained the same dose of 6.8 mg hydrogen
cyanide. The hydrogen cyanide concentrations in the
subjects' blood, which were measured at regular intervals,
showed significant differences. While the hydrogen cya-
nide values only rose slightly after consuming persipan,
they were approximately ten times higher in the cases of
manioc and bitter apricot kernels, placing them within a
range that would be expected after a dose of 6.8 mg of
isolated hydrogen cyanide. The hydrogen cyanide values
measured after the consumption of linseed lay between
the two extremes described above.
The effect of the ß-glucosidase enzyme on the toxicity of
foods containing hydrogen cyanide was made clear for
the first time by the BfR study. Only high enzyme activity
leads to the fast release of hydrogen cyanide and thus to
toxicity that is comparable with isolated hydrogen cyanide.
This can be observed in bitter apricot kernels (or bitter al-
monds) and in manioc, and the relevant literature confirms
this finding: cases of death have been reported after the
consumption of these foods in large amounts. In contrast,
the natural enzyme activity in linseed is much lower. In
persipan, intensive heating during production largely de-
stroys the plant enzyme. In this case, only intestinal bac-
teria could contribute to the release of hydrogen cyanide.
>>
Hydrogen cyanide is released when chewing bitter apricot
kernels, linseed and manioc, but legal regulations and
consumption recommendations reduce the risk of
impaired health.
Linseeds are a very popular addition to muesli and
baked goods, but they contain chemically bound
hydrogen cyanide.
