That only makes sense in cases where you have no additional data suggesting that some foods are healthier than others.

Also, if a few foods exist which exhibit chronic toxicity at low doses, but you don't know which foods those are, wouldn't it be safer to limit the total number of different foods you consume, as to limit the chance of consuming a particularly bad one by chance? While atypical, there could be cases where the toxicity curve is relatively flat, and lower doses don't really protect you. For example, an endocrine toxin that simulates a hormonal signal even at a low dose.