Flour and nickel: 20 foods rated

Buckwheat flour keeps the whole seed, hull fragments and all, which is what gives it both its colour and its nickel. The lighter the flour, the less of both.

• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431, nickel content of food and estimates of dietary intake

Chickpea flour is a ground legume, so it carries the legume nickel at flour density - a pancake or a fritter batter made from it is several chickpea portions.

• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431, nickel content of food and estimates of dietary intake

Coconut flour is dried, defatted coconut ground fine, so the nickel of the flesh arrives concentrated - and it is used in large proportions in gluten-free baking. The flesh's nickel is the measured part - the flour concentrates it by drying.

• Ruick G, Die Nahrung 32 (1988), nickel in 933 market samples - coconut among them

Lupin flour is a legume flour, high in nickel like the rest of the family, and it carries a separate allergen warning in the EU - two reasons to read for it rather than assume.

• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431, nickel content of food and estimates of dietary intake

Oat flour is milled from the whole grain, bran included, so it carries the oat's full nickel load in a form that blends invisibly into baking.

• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431, nickel content of food and estimates of dietary intake

Soya flour concentrates into a flour a legume named among the very high-nickel foods, and it is used in small quantities across industrial baking, where it does not announce itself.

• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431, nickel content of food and estimates of dietary intake

Almond flour is nothing but ground almonds, so it carries the nut's nickel - and it is used by the cupful in gluten-free baking, where wheat flour would have been. The quantity is the thing to watch, not the ingredient.

• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431, nickel content of food and estimates of dietary intake

Flax flour is the whole seed milled, hull included, and the hull is where a seed keeps its nickel. It is used in small quantities, which is what holds the level here.

• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431, nickel content of food and estimates of dietary intake

Cassava flour is a starchy root ground fine, and low in nickel, and the processing that removes the root's cyanogenic compounds - soaking, pressing, drying - takes soluble minerals out with them.

• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431, nickel content of food and estimates of dietary intake

Rice flour is milled from white rice, which has already had its bran removed - and the bran is where a grain keeps its nickel. Refining is what makes this low.

• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431, nickel content of food and estimates of dietary intake

Rye flour is milled from a low-nickel grain, and a dark rye flour keeps more of the bran the metal sits in than a light one does. Two national surveys put bread and cereals among the groups that deliver most of the dietary nickel — near the top because they are eaten in quantity rather than because they are concentrated, and neither publishes a figure for a single grain.

• Smart G.A. & Sherlock J.C., Food Addit Contam 4 (1987) 61-71, nickel in foods and the diet
• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431

Spelt is a wheat, and its flour behaves like wheat flour here: the milling takes out the bran and germ where the metal sits. Two national surveys put bread and cereals among the groups that deliver most of the dietary nickel — near the top because they are eaten in quantity rather than because they are concentrated, and neither publishes a figure for a single grain.

• Smart G.A. & Sherlock J.C., Food Addit Contam 4 (1987) 61-71, nickel in foods and the diet
• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431

Wheat flour is low in nickel because milling removes the bran and germ, which is where the trace metals sit; wholemeal flour keeps them and carries more. Two national surveys put bread and cereals among the groups that deliver most of the dietary nickel — near the top because they are eaten in quantity rather than because they are concentrated, and neither publishes a figure for a single grain.

• Smart G.A. & Sherlock J.C., Food Addit Contam 4 (1987) 61-71, nickel in foods and the diet
• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431

Whole wheat flour keeps the bran, which is where the nickel is - so it carries more than white flour does. Wheat is simply a low-nickel grain to begin with, which is why keeping the bran still leaves it here.

• Flyvholm M-A et al., Z Lebensm Unters Forsch 179 (1984) 427-431, nickel content of food and estimates of dietary intake