Blood orange

Blood orange is an orange with anthocyanins, the same pigments that colour berries and red cabbage - a difference of colour and antioxidant, not of mechanism. It is a liberator like any citrus, and its short winter season means it is usually eaten fresh, which is the one thing in its favour. Citrus is on the elimination lists as a liberator, but the current review attributes its symptoms to its other amines — putrescine above all — competing for the enzyme that clears histamine.

Citrus is one of the groups the RPAH tables put highest on this axis, and a blood orange is citrus. The peel is where most of the salicylate is, which matters for zest and marmalade more than for the segments.

A blood orange is a sweet orange - a cultivar of Citrus sinensis, not another fruit - so it carries what an orange carries. What is genuinely particular to it is the anthocyanin that colours the flesh, and anthocyanins do not remove oxalate.

Blood orange carries its sugar mostly as free glucose and fructose rather than as sucrose, so there is little for sucrase to split. Sweetness and sucrose content are not the same measurement, and this fruit is the proof.

Citrus is the fruit family the low-FODMAP protocols leave IN, and a blood orange is a sweet orange: one medium fruit is a comfortable serving. The sugars are balanced - roughly as much glucose as fructose - which is what keeps an orange out of trouble where a pear or an apple falls into it. Juice is the exception on every citrus, because three oranges go into a glass and the fibre does not.

Oranges carry a small amount of fructan, enough to register and not enough to matter at one fruit. Where it starts to count is the pith and the peel - marmalade and candied peel concentrate the part of the fruit nobody eats on its own. A blood orange is no different, and its deep colour comes from anthocyanins in the flesh rather than from anything on this axis.

Blood orange: what matters on this axis is not how much fructose a fruit holds but whether it holds more fructose than glucose, because glucose carries fructose across the gut wall with it. An orange is close to even, which is why it sits low here while fruits with the same sugar content sit high. The blood orange is an orange in this respect as in every other.

Blood orange: fruit sits low on the nickel axis as a rule, and citrus with it: the metal comes up from the soil and concentrates in seeds, nuts and whole grains rather than in a fleshy fruit. Canned is the version to watch on this axis and not only here - acidic contents in a tin pull metal from the can, which is why tinned citrus is a different answer from a fresh one. Flyvholm's review is where that list comes from — cocoa, soya, oatmeal, nuts and legumes are the high-nickel foods, and no fruit is among them. It publishes no figure for any single food, so the tin is a general caution here rather than a measured one.