Nuts/Seeds and oxalates: 34 foods rated

Almonds carry much of their oxalate in the skin, so soaking and blanching them — which slips the skin off — takes part of it away. That is the one preparation step that changes the answer for an almond eaten whole.

Brazil nuts are oxalate-bearing like the other tree nuts, and they are the ones eaten in the smallest number - two or three at a time, because of the selenium. That accidental restraint is what keeps the actual dose modest for most people.

• Noonan SC & Savage GP, Asia Pac J Clin Nutr 8 (1999)
• USDA FoodData Central

Cashews are high in oxalate and unusually easy to eat in quantity - they are soft, mild and sold by the bag. The cashew creams and cheeses made from soaked, blended nuts are the form to watch: a cup of nuts becomes a sauce nobody portions.

• Noonan SC & Savage GP, Asia Pac J Clin Nutr 8 (1999)
• USDA FoodData Central

Ground hazelnuts are usually ground WITH the skin, since removing it first costs a step - so the flour keeps the skin, where the oxalate is, which the whole blanched nut does not. It is also used by the hundred grams in baking, where whole nuts would be counted.

• Noonan SC & Savage GP, Asia Pac J Clin Nutr 8 (1999)
• USDA FoodData Central

Hazelnuts are high in oxalate, and the published totals for them disagree between tables more than for most nuts. The skin is often said to hold most of it — that is documented for the almond, and no measurement compares a blanched hazelnut with a whole one. Rubbing the skins off after roasting follows the reasoning rather than a figure.

• Noonan SC & Savage GP, Asia Pac J Clin Nutr 8 (1999)
• USDA FoodData Central

Lentils are high, and they are the pulse that does not get soaked - they cook in twenty minutes straight from dry, which skips the step that would have removed part of the oxalate. Cooking them in plenty of water and draining is the substitute; a dal keeps its liquid and keeps the oxalate. Quinteros measured that on the pulses themselves and found every cooking method lowers the soluble fraction, with microwave and industrial processing more effective than ordinary domestic cooking.

• Quinteros A et al., Int J Food Sci Nutr 54 (2003), effect of cooking on pulse oxalate
• Gad S et al., Food Chemistry 8 (1982)

Peanuts are a legume rather than a nut, and they sit high here anyway - the botany does not rescue them. What does help is calcium: oxalate and calcium bind to each other in the gut and leave together, so peanuts with a dairy or fortified food alongside are absorbed less than peanuts alone.

• Jaeger Ph et al., Nephron Physiol 98 (2004)
• Holmes R et al., Kidney Int 59 (2001)

Pecans are high in oxalate and arrive almost entirely inside sweet baking - pie, praline, candied halves - where the portion is decided by the slice rather than by the nut. The sugar around them changes nothing about the oxalate.

• Noonan SC & Savage GP, Asia Pac J Clin Nutr 8 (1999)
• USDA FoodData Central

Pine nuts are used a spoonful at a time rather than a handful - they are the most expensive nut per gram, and that price is the portion control. They arrive mostly inside pesto, where the cheese alongside brings calcium that binds part of the oxalate they carry.

• Jaeger Ph et al., Nephron Physiol 98 (2004)
• Holmes R et al., Kidney Int 59 (2001)

The soya bean is high in oxalate, and its products separate sharply: tofu is pressed and the whey carries oxalate away with it, while soy flour keeps everything. It is the same split as on the FODMAP axis, for the same reason - what leaves in the water is what leaves.

• Noonan S.C. & Savage G.P., Asia Pac J Clin Nutr 8 (1999) 64–74, soaking and cooking reduce oxalate by leaching

Broad bean: pulses carry a moderate oxalate load, and cooking lowers it - boiling and draining takes soluble oxalate away with the water. That is measurable, and it is the reason a soaked and boiled bean differs from a raw one. Quinteros measured soluble oxalate in beans, chickpeas and lentils and found that every cooking method reduces it — the loss going into the water rather than disappearing.

• Quinteros A et al., Int J Food Sci Nutr 54:5 (2003) 373-377, soluble oxalate in beans, chickpeas and lentils

Chia seeds are moderate rather than high, and they are eaten by the tablespoon - but they are eaten daily by the people who eat them at all, and this axis is cumulative. Soaking them, which is how they are used, leaves some soluble oxalate in the gel rather than removing it.

• Noonan SC & Savage GP, Asia Pac J Clin Nutr 8 (1999)
• USDA FoodData Central

Chickpeas are moderate, and the soaking they need anyway takes soluble oxalate into the water - the same water people are already told to throw away for other reasons. Canned chickpeas have had that done for them, and rinsing the can takes a little more. Quinteros measured that on the pulses themselves and found every cooking method lowers the soluble fraction, with microwave and industrial processing more effective than ordinary domestic cooking.

• Quinteros A et al., Int J Food Sci Nutr 54 (2003), effect of cooking on pulse oxalate
• Gad S et al., Food Chemistry 8 (1982)

Red lentils are hulled and split, and that shows on the FODMAP and oligosaccharide axes, where they sit a level below the whole lentil. Hulling does not take the oxalate away, though: the seed coat carries part of it and the cotyledon carries the rest. Boiling in water you then throw away is the lever that works, and red lentils cook fast enough that people often keep the water.

• Noonan SC & Savage GP, Asia Pac J Clin Nutr 8 (1999)

Hemp seeds carry less oxalate than most nuts and seeds, but the group as a whole is not a low-oxalate food — almonds and cashews are well above them. They are eaten by the spoonful over a bowl rather than by the handful, and that habit is worth as much here as the level.

• Noonan S.C. & Savage G.P., Asia Pac J Clin Nutr 8:1 (1999) 64-74, oxalate content of foods and its effect on humans

Pistachios carry less oxalate than most nuts, but the group as a whole is not a low-oxalate food — almonds and cashews are well above them. Shelling them one at a time slows the portion down, which is the only brake this axis gets from a nut eaten as a snack.

• Noonan S.C. & Savage G.P., Asia Pac J Clin Nutr 8:1 (1999) 64-74, oxalate content of foods and its effect on humans

Walnuts carry less oxalate than most nuts, but the group as a whole is not a low-oxalate food — almonds and cashews are well above them. They arrive mostly as halves inside baking, where the portion is decided by the slice rather than by the nut.

• Noonan S.C. & Savage G.P., Asia Pac J Clin Nutr 8:1 (1999) 64-74, oxalate content of foods and its effect on humans