Vegetables
For each one: how to use it, the best version, how to prepare it, what it does, and where it goes wrong.
Bean sproutsCheap, raw and mostly water. The only thing to think about is hygiene.Read on
How to use it
Raw over a salad, or stirred into a hot dish at the last moment. Blanch them if you are unsure where they came from.
The best version
Grown yourself from mung beans, or fresh from a chiller in a shop that sells through quickly. Crisp and white, not limp or browning at the tips.
How to prepare it
Rinse under running water. If you do not grow them yourself and you are in a risk group, cook them briefly: that costs you the crunch and takes out the risk.
What it does
The point of bean sprouts is not one compound but the price per kilo of something raw and fresh. No trial has tested them on their own, and that is here because it is true.
Watch out
Sprouts carry the highest contamination risk of any vegetable, because they grow warm and wet and are eaten raw. In a survey of 298 shop-bought samples, E. coli was found in 14.8 percent, a Listeria species in 12.3 percent and Listeria monocytogenes in 1.3 percent. Salmonella was not found.
If you are pregnant, older, or immunocompromised, do not eat them raw. This is the only vegetable on this page where that applies.
Broccoli sproutsThree days old and many times stronger than the grown vegetable. The only vegetable you grow on your own worktop.Read on
How to use it
Raw, a handful, through a salad or over a plate that is already finished. They belong with the meal, not in the pan.
The best version
Grown yourself from organic sprouting seed. Shop-bought sprouts sit in a chiller for days and the active compound drains away. A glass jar with a sprouting lid is the whole kit.
How to prepare it
Rinse them twice a day for three to four days. Do not heat them: the enzyme that turns the precursor into sulforaphane does not survive a hot pan, and what you are left with is a garnish.
What it does
Sulforaphane, given as a concentrated broccoli sprout extract, lowered fasting blood glucose and HbA1c in obese patients with dysregulated type 2 diabetes. The same compound suppressed glucose production in the liver, by a different route than metformin takes.
Where the mechanism sits has been worked out in cells. The indoles and isothiocyanates from cruciferous vegetables, sulforaphane from these sprouts among them, triggered the death of damaged cells in two human colon cell lines. They also raised the defence enzymes the cell makes itself, by up to seventeen times, and when the cells were then exposed to a carcinogen they were left with under twenty percent of the DNA breaks.
In obese mice, glucoraphanin, the precursor of sulforaphane in these sprouts, did three things: energy expenditure went up, white fat began to behave more like brown fat, and the inflammation and insulin resistance that come with obesity went down.
Watch out
Those two studies are about cells in a dish and about mice. A mechanism that works in a cell is not evidence that it does anything in a person, and keeping those apart is half the work on this site.
What was tested in people is a concentrated extract, not a handful of sprouts. What grows on your worktop delivers less, and nobody has worked out how much less. Eat them because they are a cheap and potent vegetable, not to manage your blood sugar.
Sprouts grow warm and wet, which is what bacteria want too. Rinse twice a day, use clean water, and throw them out if they turn slimy or smell sour.
CarrotThe vegetable where preparation makes the biggest difference. Raw, you get less than half of it.Read on
How to use it
With a meal that has fat in it, because the pigment only dissolves in fat. Cooked as a vegetable, or grated through a salad with a dressing.
The best version
Firm, smooth skinned, ideally still with the tops on if you want them fresh. Old winter carrots are sweeter and fine for soup.
How to prepare it
Boil them and mash them, with fat alongside. That is not a matter of taste: it is the difference between nearly all of it and less than half.
What it does
How much beta-carotene you actually absorb depends on what you did to the carrot. In volunteers with an ileostomy, where everything not absorbed could be measured, 65.1 percent of the beta-carotene was taken up from cooked, pureed carrot and 41.4 percent from raw, chopped carrot. Both meals had fat with them.
Watch out
Without fat alongside, most of it is lost however you cook it. A raw carrot as a snack is a fine snack and not a source of vitamin A.
CeleryOne of the vegetables highest in nitrate, and the base under nearly every soup that tastes of anything.Read on
How to use it
Raw as a stick, or as the base of a soup or stew with onion and carrot. The leaves are not waste and carry the most flavour.
The best version
Firm, smooth stalks that snap rather than bend, with the leaves still on. Celery and leaf celery are two different things: you eat the first and season with the second.
How to prepare it
Pull the strings off the outer stalks with a peeler. For soup, do not: those strings cook out and give up flavour.
What it does
Celery is among the vegetables highest in nitrate, and nitrate becomes nitric oxide in your body, which relaxes your blood vessels. That mechanism was measured with beetroot juice: seven trials, 218 people with high blood pressure, systolic pressure down by 4.95 mmHg.
Watch out
Celery juice as a cure is a sales story rather than research. What was measured is the nitrate, in a different vegetable, in a different drink.
Celery is one of the fourteen allergens that have to be declared by law, and reactions to it can be serious. If it is in a soup, it belongs on the label.
CourgetteAlmost nothing but water and fibre. That is not a criticism: it is exactly why it fills a plate without filling up your day.Read on
How to use it
Grilled, roasted, through a soup, or raw in thin ribbons through a salad. It takes on the taste of whatever you put with it.
The best version
Small and firm, with a glossy skin. A big courgette holds more water, more seed and less taste.
How to prepare it
Leave the skin on, because the skin is where the colour is. If you want it grilled rather than stewed, salt it first and pat the water off.
What it does
Courgette has not been studied in people as a food on its own. It is here for what it does at the table: a large plate with little energy in it, which leaves less room for what you would rather eat less of.
Watch out
Taste a raw piece before you use it. If a courgette is badly bitter, throw it out: that is cucurbitacin, rare in cultivated plants and less rare in ones grown from saved seed.
CucumberWater you chew. Hydration is part of this page, and this is the cheapest form of it.Read on
How to use it
Raw, with anything. In water with mint, through a salad, as a slice against a plate that is too hot.
The best version
Firm end to end, with no soft spot. The small varieties taste of more than the long smooth ones.
How to prepare it
Leave the skin on, because that is where most of what is in it sits. Kept out of the fridge it stays firm longer than it does in the cold.
What it does
Cucumber has not been studied in people as a food on its own. It is here because drinking enough is easier when it tastes of something, and because it fills a plate without adding anything.
Watch out
The cucumber has nothing to hide and nothing to promise. Everything sold about detoxing and bloating is marketing rather than research.
Green beansThe legume you eat as a vegetable. Fibre and volume, and one of the few vegetables that barely suffers from being frozen.Read on
How to use it
With a hot meal, or cold through a salad with a dressing. Straight from the freezer is fine.
The best version
Snapping fresh: a good bean breaks with a crack. Limp beans bend instead, and taste of nothing.
How to prepare it
Boil them briefly and drop them into cold water, so they stay green and keep their bite. Cooked through they go grey and soft.
What it does
Green beans have not been studied in people as a food on their own. They are here because they bring fibre and volume to the place on the plate where a starchy side usually sits.
Watch out
Do not eat them raw. Raw green beans contain a lectin that irritates the stomach and gut, and cooking destroys it.
RocketOne of the leafy greens richest in nitrate, and nitrate is what opens your blood vessels.Read on
How to use it
Raw, over the plate after cooking. Through a salad, over pasta, over a pizza as it leaves the oven.
The best version
Wild rocket with narrow, deeply cut leaves tastes of more than the broad cultivated kind. Dark green and dry, not wet in the bag.
How to prepare it
Do not heat it. Wash and spin it dry, because water on the leaf dilutes your dressing and makes the whole thing limp.
What it does
Nitrate from vegetables is converted by bacteria on your tongue and becomes nitric oxide in your body, which relaxes your blood vessels. That is the mechanism by which beetroot juice, across seven trials in 218 people with high blood pressure, brought systolic pressure down by 4.95 mmHg.
Watch out
Those trials used beetroot juice and not rocket. The mechanism has been measured, this leaf has not, and that is a difference worth knowing before you expect anything from it.
RomaineThe lettuce with a firm heart and more taste than a butterhead. A bowl of leaves you build a meal around.Read on
How to use it
Raw as the base of a salad, or the hearts halved over the grill. The stiff rib holds a dressing where soft lettuce collapses.
The best version
A head with a closed heart and firm, snapping ribs. Loose leaves in a bag have already been washed, and that costs shelf life and taste.
How to prepare it
Wash leaf by leaf and spin dry. Cutting with a knife browns the edges faster than tearing by hand.
What it does
Leafy greens supply nitrate, and nitrate becomes nitric oxide in your body, which relaxes your blood vessels. That mechanism was measured with beetroot juice: seven trials, 218 people with high blood pressure, systolic pressure down by 4.95 mmHg.
Watch out
Romaine itself has not been tested that way. What you certainly get is volume and fibre; the rest is the mechanism and not this lettuce.