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We compared the suitability of the linoleic-oleic acid ratio (L:O) of serum cholesteryl esters and erythrocyte membranes as indicators of dietary fatty acid composition. Forty-seven volunteers received a mixed natural diet with a polyunsaturated-saturated fatty acids ratio (P:S) of 0.2 for 3 wk and with P:S 2.0 for another 3 wk (HA group, 24 subjects) or vice versa (HY group, 23 subjects). Duplicate portion analysis revealed that dietary fat type was the only variable. The change in L:O in cholesteryl esters relative to the low P:S diet was 91.3 +/- 25.9% (means +/- SD) in the HA group and 85.1 +/- 18.8% in the HY group. The changes in erythrocyte membranes were 33.0 +/- 7.9% in the HA group and 22.8 +/- 4.9% in the HY group. Thus the effect on erythrocyte fatty acids was smaller but also less variable and the precision of the two measures was similar. Therefore the L:O of either blood component can be used as a marker of a subject's adherence to experimental diets differing in type of fat.

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Alkaloid-containing plants are an intrinsic part of the regular Western diet. The present paper summarizes the occurrence of alkaloids in the food chain, their mode of action and possible adverse effects including a safety assessment. Pyrrolizidine alkaloids are a reason for concern because of their bioactivation to reactive alkylating intermediates. Several quinolizidine alkaloids, β-carboline alkaloids, ergot alkaloids and steroid alkaloids are active without bioactivation and mostly act as neurotoxins. Regulatory agencies are aware of the risks and have taken or are considering appropriate regulatory actions for most alkaloids. These vary from setting limits for the presence of a compound in feed, foods and beverages, trying to define safe upper limits, advising on a strategy aiming at restrictions in use, informing the public to be cautious or taking specific plant varieties from the market. For some alkaloids known to be present in the modern food chain, e.g., piperine, nicotine, theobromine, theophylline and tropane alkaloids risks coming from the human food chain are considered to be low if not negligible. Remarkably, for many alkaloids that are known constituents of the modern food chain and of possible concern, tolerable daily intake values have so far not been defined.