Placebo-controlled tests of chemical food additives: are they valid?

Placebo-controlled studies of effects of monosodium L-glutamate (MSG) and mixed synthetic food dyes in humans which have led to claims that these additives are safe in general use may be questioned on 3 methodological grounds: both active substance and placebo may be inadequately specified in published reports and potent common food allergens are used as placebos.