Herbs and spices
For each one: how to use it, the best version, how to prepare it, what it does, and where it goes wrong.
Black pepperIt is not here for the taste. Piperine opens the door for compounds your liver would otherwise break down before you use them.Read on
How to use it
On anything with turmeric in it, and wherever else you like it. A pinch is enough: this is a key, not a dose.
The best version
Whole corns in a mill. Pre-ground pepper loses its volatile oil and with it its smell, and what you have left is dust with heat in it.
How to prepare it
Grind it fresh, at the end. Cooking it from the start turns it bitter.
What it does
Piperine blocks the breakdown that happens in the liver and the gut wall. In healthy volunteers, curcumin was barely detectable in the blood after 2 grams of powder; with 20 milligrams of piperine alongside it, absorption rose by 2000 percent, with no adverse effects at that dose.
Watch out
What opens the door for curcumin opens it for medicines that leave by the same route. A pinch on your food is not the problem. A piperine supplement while you are on medication is a question for your doctor and not for a website.
Ceylon cinnamonThe cinnamon you can use daily, because the compound that burdens your liver is not in it.Read on
How to use it
Through oats, yoghurt, coffee, baking, and through savoury stews. Daily is fine, and that is exactly why this is the species.
The best version
True Ceylon, Cinnamomum zeylanicum, recognisable as a quill made of many thin layers, like a cigar. Cassia is one thick, hard bark that curls over. If the jar just says cinnamon, it is almost always cassia.
How to prepare it
Simmer a quill and take it out again, or use it ground over food. Ground cinnamon loses its smell quickly, so buy small jars.
What it does
The advantage of Ceylon is what is missing from it. Coumarin can damage the liver and is present in cassia, the cheap cinnamon in nearly every jar. Ceylon cinnamon does not contain it, which is why the European risk assessors proposed replacing cassia with it.
Watch out
The story about cinnamon and your blood sugar is about the other species. In this trial, people with impaired glucose tolerance took 6 grams of Ceylon cinnamon with a glucose load, and nothing happened to their glucose or their insulin. The drops you read about everywhere come from cassia, which is the cinnamon with the coumarin in it.
GarlicThe one kitchen herb with a blood pressure effect you can compare to medication. Cutting it and waiting is half the work.Read on
How to use it
Raw, or added late and briefly heated. In dressings, through guacamole, over roasted vegetables.
The best version
A fresh bulb with tight skin and hard cloves, not the chopped kind from a jar. A green shoot inside means it is old, and the shoot itself can come out.
How to prepare it
Chop or crush it and leave it for ten minutes before it goes near heat. The enzyme that makes the active sulphur compound is only released by the damage and needs a moment, and heat stops it dead.
What it does
In people with high blood pressure, garlic does what a pill does. Across 12 trials with 553 participants between them, systolic pressure fell by an average of 8.3 mmHg, and across 8 trials with 374 participants diastolic pressure fell by 5.5 mmHg.
Watch out
Those trials used garlic preparations, mostly aged garlic extract, and not a clove out of the pan. They were also run in people who were already too high: at a normal blood pressure there is nothing to lower.
GingerAgainst nausea it is the best studied thing in your kitchen. Beyond that, more is claimed than measured.Read on
How to use it
Fresh and grated through food, as tea, or pressed through a juice. For nausea, as tea or as a piece to chew.
The best version
Fresh root with smooth, tight skin. Dried powder is a different product with a different taste and less of the volatile oil.
How to prepare it
Young root does not need peeling, and scraping with a spoon beats peeling with a knife. Grate it fine, because in chunks it gives up almost nothing.
What it does
For nausea and vomiting in pregnancy, ginger has been set against other treatments across 33 randomised trials. Against placebo it came out at a relative risk of 1.68 for improvement, and nausea fell by 1.21 points on a ten-point scale.
Watch out
The reviewers call this evidence low quality themselves, and on vomiting alone ginger did no better than placebo. It helps the sick feeling, not the being sick.
TurmericDemonstrably works on pain, and on its own barely reaches your blood. That is why black pepper stands next to it.Read on
How to use it
Through hot food, in a curry, through soup, through rice. Always with black pepper and some fat.
The best version
Fresh root, or ground powder from a single origin. Turmeric is one of the spices that gets cut and dyed, so buy from a seller who says where it came from.
How to prepare it
Cook it in fat, with a pinch of black pepper. It stains everything it touches, your worktop and your fingers included.
What it does
Against knee osteoarthritis it has been tested and it works. Eleven randomised trials with 1258 people between them found less pain on both the visual scale and the WOMAC questionnaire, and against anti-inflammatory drugs turmeric came out ahead on pain. A higher dose did no better than a lower one.
Watch out
Curcumin on its own is barely absorbed. After 2 grams of powder, blood levels in healthy volunteers were undetectable or very low; with 20 milligrams of piperine, the compound in black pepper, absorption rose by 2000 percent. Turmeric without pepper is mostly colour.
The trials use curcuminoids in capsules, at doses a teaspoon of powder does not reach. Through your food it is a good habit rather than a treatment.