We all know vegetables are good for us, but they aren’t created equal. While they’re all a source of fibre – something the majority of us should be eating more of – as well as vitamins, minerals and antioxidants, these compounds are less concentrated in some varieties.
That said, all vegetables are nutritious, says Rhiannon Lambert, a nutritionist, the founder of the top Harley Street clinic Rhitrition and the author of The Science of Plant-Based Nutrition, her recently published comprehensive vegetable bible.
It’s why plants have been central to human diets throughout history. Despite preconceptions of cavemen dining on bounties of meat, “it’s pretty obvious that the majority of what everybody was eating was vegetable matter” such as sea kale, samphire and nettles, says Dr Annie Gray, a food historian and the author of The Bookshop, the Draper, the Candlestick Maker: A History of the High Street.
This was still the case into the 19th century. The Victorians ate whatever vegetables were in season and available at their local market, or could be grown in their garden, including the now lesser-seen marrow, skirret and Japanese artichokes, she explains.
Nowadays, these little-known vegetables have declined in popularity and given way to the more exotic aubergine and bok choy (though potatoes, carrots, onions and peas remain the nation’s firm favourites, polls show).
While the vegetables we eat have changed through the generations, one thing that has remained the same is their important role in our health. They enhance our immune system and maintain our bones, muscles and organs. “Five a day” is the mantra that has been drilled into us for the last two decades but the consensus is the more, the merrier. Recently, scientists have called for people to aim for 30 different varieties of plant per week (though, admittedly, this includes nuts, seeds and whole grains, as well as vegetables and fruit).
Despite their vital role being clear, the number we’re buying has reached a 50-year low and meat eating has become much more common, which is only encouraged by recent high-protein and carnivore diet trends. Simultaneously, Britain has seen the return of Victorian-era diseases such as scurvy (a severe vitamin C deficiency) and rickets (caused by a lack of vitamin D and calcium), as well as rocketing hospitalisation due to malnutrition and iron deficiencies.
So, if we’re eating fewer vegetables, it’s important to make sure we’re maximising our nutritional bang for buck. While “including as many different types of vegetables in your diet is the goal”, some varieties do come up trumps, Lambert explains. Red, orange and yellow vegetables are high in vitamins A and C, while dark greens contain iron and folate but those with a high water content – cucumber, marrow and cabbage – offer fewer nutrients.
Here’s her pick of the most nutritious veg.
A nutritional powerhouse loaded with vitamins, minerals, antioxidants and phytonutrients, broccoli is rich in vitamins C and K, which support immune function and bone health. It also contains sulforaphane, a potent antioxidant known for its anti-inflammatory properties which has been shown to reduce the ability of cancerous cells to multiply.
Additionally, broccoli is rich in fibre, folate and potassium, promoting heart health and aiding in digestion. The combination of these nutrients and antioxidants makes broccoli an excellent vegetable to include in your diet. Other cruciferous vegetables – cauliflower, Brussels sprouts and cabbage – are also excellent for us, though there are slight differences in their nutritional composition.
The healthiest way to eat broccoli
To retain the nutrients in broccoli, steam it or eat it raw in salads or as snacks. Avoid boiling for long periods and overcooking in general. This can lead to a significant loss of water-soluble vitamins (vitamin C and folate) and antioxidants.
Often considered a “superfood” due to its dense nutrient profile and high antioxidant content, kale is an excellent source of vitamins A, C and K, as well as fibre, calcium and iron. It contains powerful antioxidants such as quercetin and kaempferol, which act to reduce oxidative stress and inflammation. The high levels of lutein and zeaxanthin in kale support eye health. Its impressive array of phytonutrients contributes to overall health, making it a top choice for a nutrient-dense diet.
The healthiest way to eat kale
Similar to broccoli, to retain the nutrients in kale, lightly steam it or consume it raw in salads or smoothies. Avoid boiling for extended periods or overcooking, as these methods can reduce its vitamin content and overall nutrient density.
Vibrant and nutrient-dense, bell peppers are available in various colours, each offering unique health benefits. They are exceptionally high in vitamin C, vital for immune function, skin health and wound healing. Bell peppers also provide vitamins A and E, potassium and fibre. Their rich antioxidant profile, including beta-carotene, lutein and zeaxanthin, supports eye health and protects against oxidative damage, which can contribute to ageing and health problems such as heart disease. The phytonutrients in bell peppers make them a versatile and delicious addition to any diet.
The healthiest way to eat bell peppers
To retain the nutrients in bell peppers, eat them raw in salads or as snacks, or lightly sauté or roast them at moderate temperatures, such as in a tray bake, below 200C, which will provide a delicious flavour. Prolonged high-temperature cooking above 200C, or boiling, can lead to a loss of water-soluble vitamins (particularly their high vitamin C content), as well as damaging the delicate phytonutrients.
An excellent source of vitamins, minerals and antioxidants, sweet potatoes are a top choice for nutrient density. They are particularly rich in beta-carotene, which the body converts into vitamin A, which can help to support various vital functions such as vision, immune function and skin health.
Sweet potatoes also provide dietary fibre, promoting healthy digestion and stable blood sugar levels. On top of all that, they are a great source of vitamin C, manganese and potassium, all contributing to overall health. The antioxidants in sweet potatoes help combat inflammation and oxidative stress, further enhancing their nutritional value.
The healthiest way to eat sweet potatoes
To retain the nutrients in sweet potatoes, bake, roast or steam them with the skin on. The skin of sweet potatoes is often what contains the majority of fibre, so keep this on for additional fibre intake. Avoid frying or boiling them for long periods, as these methods can diminish their nutrient content.
Red cabbage offers an impressive number of vitamins, minerals and antioxidants. It’s particularly high in vitamin C, which helps to protect cells, maintains skin health, vessels, bones and cartilage, and aids in wound healing. Red cabbage is also a great source of vitamin K, important for blood clotting and bone health, and vitamin A, which supports vision and skin health.
The deep purple colour of red cabbage is due to its high content of anthocyanins, powerful antioxidants that help reduce inflammation and may protect against chronic diseases, nutrients that you won’t find in green or white cabbage. In fact, red cabbage contains significantly more vitamin A, vitamin C and antioxidants than its green or white counterparts. Red cabbage also contains fibre, which aids in digestion and promotes a healthy gut microbiome.
The healthiest way to eat red cabbage
To preserve the nutrients, it’s best to eat it raw in salads or lightly sauté it. Fermenting red cabbage, as in sauerkraut, is another excellent way to enhance its nutritional value, particularly by adding probiotics, making it great for your gut health. Avoid boiling for long periods, as this can lead to a significant loss of its vibrant colour and water-soluble nutrients such as vitamin C.
Carrots are well known for their high beta-carotene content, which the body converts into vitamin A, supporting vision, immune function and skin health. They also provide a good amount of fibre, which promotes healthy digestion and stable blood sugar levels. Carrots contain antioxidants such as lutein and zeaxanthin, which are beneficial for eye health. The phytonutrients in carrots contribute to their vibrant colour and nutritional benefits, making them a versatile and nutritious vegetable.
The healthiest way to eat carrots
While carrots are a great snack raw, cooking them may actually “improve” their nutritional profile. This is because cooking helps to break down the cell walls, making the beta-carotene more easily absorbed and converted into vitamin A by the body. Steaming or lightly boiling carrots is optimal to preserve their nutrient content while enhancing their bioavailability. Avoid boiling for long periods and overcooking them.
Beetroot is a vibrant root vegetable known for its high nutrient and antioxidant content. Rich in folate, manganese and potassium, beetroot supports heart health and overall well-being. It contains betalains, powerful phytonutrients with antioxidant and anti-inflammatory properties. Beetroot is also high in nitrates, which can improve blood flow and lower blood pressure. Its deep colour is a testament to its rich phytonutrient profile, making beetroot a valuable addition to a healthy diet.
The healthiest way to eat beetroot
To retain the nutrients in beetroot, cook it by steaming or roasting at moderate temperatures, or consume it raw in salads or juices. Pickling introduces gut-friendly bacteria, though it leads to a small amount of nutrients being lost. Avoid boiling and prolonged high-temperature cooking, as these methods can lead to nutrient loss, especially of water-soluble vitamins, such as vitamin C, and minerals.
Onions are often forgotten about when speaking of vegetables, but they are a highly nutritious and versatile ingredient, used in a wide range of dishes. They are an excellent source of vitamins C and B6, folate and potassium. Onions are rich in antioxidants, particularly quercetin, which holds antioxidant and anti-inflammatory properties that may help to lower high blood pressure and therefore reduce the risk of heart disease. Additionally, onions are rich in prebiotics, which promote the growth of beneficial gut bacteria and support digestive health.
Both white and red varieties are great. Red onions contain greater levels of anthocyanins than white onions, a phytochemical which has been linked to reducing the risk of chronic diseases. Meanwhile, white onions contain quercetin, which holds antioxidant and anti-inflammatory properties that may help to lower high blood pressure. The combination of vitamins, minerals, antioxidants and prebiotics in onions supports immune function, heart health and overall well-being. Whether eaten raw, sautéd, roasted or caramelised, onions are a flavourful and health-boosting addition to any diet.
The healthiest way to eat onions
To retain the nutrients in onions, cook them by lightly sautéing over a medium heat or roasting at moderate temperatures, or consume them raw in salads. Avoid deep-frying and prolonged high-temperature cooking, as these methods can destroy beneficial compounds. Exposing onions to a low heat over a long period of time, such as when cooked into sauces, may reduce some antioxidants but only by a very small amount and does not dramatically change their nutritional value.
Rich in vitamins, minerals and antioxidants, cauliflower is particularly high in vitamin C, which supports immune health, maintains healthy skin and protects cells. The vegetable is also a good source of vitamin K, which plays a role in bone health and blood clotting, and folate (vitamin B9), which is important for DNA synthesis and cell growth, as well as being essential during pregnancy. Like broccoli, cauliflower also contains sulforaphane, a potent antioxidant that is known for its anti-inflammatory properties and has been shown to reduce the ability of cancerous cells to multiply. Its fibre content supports digestion and helps maintain a healthy gut.
The healthiest way to eat cauliflower
To retain the nutrients in cauliflower, steaming or roasting it at moderate temperatures is ideal. Avoid boiling for long periods, as this can lead to nutrient loss, particularly of water-soluble vitamins, and can result in a less desirable texture. Cauliflower can also be used as a low-carb substitute for grains, such as in cauliflower rice or pizza crust, which is particularly useful for people with diabetes, who require lower glycemic index (GI) foods.
Mushrooms are particularly high in B vitamins (such as riboflavin, niacin and pantothenic acid), which can support energy production and brain health, as well as selenium, potassium and copper. Selenium is a key mineral needed to support the immune system. Mushrooms are one of the few non-animal sources of vitamin D when exposed to sunlight; however, if mushrooms haven’t been exposed to UV light or direct sunlight, they are unlikely to contain high levels of vitamin D2. It’s also important to note that the type of vitamin D found in mushrooms (D2) is less bioavailable than D3, which is found in animal products or algae. However, mushrooms also contain immune-modulating nutrients such as beta-glucan, which can support the body’s ability to fight infections. Mushrooms also contain several prebiotic strains which can promote a healthy gut microbiome.
The healthiest way to eat mushrooms
Mushrooms can be sautéd, grilled, roasted or added to soups and stews. To increase their levels of vitamin D, leave them in direct sunlight for 15-20 minutes before cooking. Avoid overcooking to preserve their nutrient content.
A nutrient-dense vegetable, asparagus is particularly high in folate (vitamin B9), which is crucial for DNA synthesis and cell growth. It’s also a good source of vitamins A, C, E and K, which together can support immune function, skin health, cell health and bone health. Asparagus is rich in antioxidants such as glutathione, which can help to combat free radicals, molecules that can damage your body’s cells. Asparagus also contains fibre, which can help in digestion and promote a healthy gut microbiome.
The healthiest way to eat asparagus
To preserve the delicate nutrients in asparagus, it’s best to steam, grill, or roast it lightly. Avoid overcooking or boiling for extended periods, as this can lead to a loss of vitamins and a less appealing texture.
Peas are a highly nutritious legume, packed with vitamins, minerals and plant-based protein. They are an excellent source of vitamins A, C, and K, which support immune function and overall cellular health and contribute to the body’s ability to repair tissues. They also contain B vitamins, particularly thiamine and niacin, which aid in energy metabolism and support the health of nerves and muscles.
They are also a great source of minerals such as magnesium, potassium, and calcium. Additionally, peas contain phytonutrients such as carotenoids and flavonoids that help protect the body against oxidative stress and inflammation. The soluble fibre in peas helps regulate cholesterol levels, particularly LDL cholesterol, and supports digestive health by promoting the growth of beneficial gut bacteria. With their high fibre and significant plant-based protein content, peas contribute to a feeling of fullness and are a valuable plant-based source of iron, essential for red blood cell production and efficient oxygen transport throughout the body.
The healthiest way to eat peas
To retain bright colour and nutrients in peas, lightly steam or sauté them. Avoid boiling for long periods, as this can lead to a loss of water-soluble vitamins and a mushy texture.
At the top of the hierarchy of lettuce varieties is romaine, due to its greater nutritional value. It is rich in essential vitamins including A, C, K and folate, as well as calcium, phosphorus, magnesium, and potassium. Its darker green leaves indicate a higher concentration of beneficial antioxidants and phytonutrients that can support eye health and help protect against degenerative eye conditions. Despite being lower in energy and fibre compared with some leafy greens, romaine lettuce still provides significant nutritional benefits. Its high water content also aids in hydration, and its mild flavour makes it a versatile ingredient in salads and sandwiches, enhancing the overall nutritional profile of meals.
The healthiest way to eat romaine lettuce
Romaine lettuce is best consumed raw to preserve its nutrient content. Avoid cooking lettuce, as heat can cause it to wilt and lose its nutrient content, especially its water-soluble vitamins and delicate antioxidants.
Green beans are a good source of vitamins and minerals, particularly vitamin C, vitamin K, folate and manganese. Manganese supports metabolism, bone health and wound healing. Green beans are also a source of fibre, which supports digestion and helps maintain a healthy gut microbiome. Green beans also contain polyphenols such as flavonoids, which have antioxidant and anti-inflammatory properties. While not as nutrient-dense as some other vegetables, they are still a healthy and versatile addition to meals, offering a balance of vitamins, minerals and phytonutrients.
The healthiest way to eat green beans
Green beans are best when lightly steamed or sautéd, preserving their texture and nutrients. Blanching them briefly in boiling water and then plunging them into ice water can also retain their colour and nutrients. Avoid overcooking.
They are a staple vegetable to many for a reason. Potatoes provide a good source of vitamins C, pyridoxine, niacin and folate, as well as potassium, manganese, magnesium and phosphorus. They are versatile and can be prepared in a variety of ways, making them a popular choice in many diets. They contain fibre, even more so when consumed with the skin on. However, their high GI means they can cause a rapid spike in blood glucose, making them less ideal for those managing blood sugar levels, such as people who have diabetes. Despite this, potatoes offer valuable nutrients and are a good source of energy because of their high carbohydrate content, at a relatively low cost, meaning they are a staple to many people’s diets.
The healthiest way to eat potatoes
To maximise the nutritional benefits of potatoes, bake, roast or steam them with the skin on. This helps preserve their fibre and nutrient content. Avoid deep-frying (such as chips), as this introduces unhealthy fats and significantly increases the calorie content and may take away from their nutritional value.
Sweet corn can be a great addition to your diet as it contains important nutrients such as vitamin C and folate, which are important for overall cellular health. It is also a great source of the antioxidants lutein and zeaxanthin, which are known to promote and protect eye health. While sweet corn generally contains more sugar than most other vegetables, it is also a great source of fibre. Regardless of its sugar content, the fibre present in sweet corn makes it a low GI food as fibre prevents the rapid blood sugar spikes that are seen in high-GI foods. Reasoning for its lower ranking simply comes down to the fact that it isn’t as nutrient-dense as other vegetables; however, sweet corn can still be a part of a very healthy, balanced diet.
The healthiest way to eat sweetcorn
To retain the nutrients in sweet corn, it’s best to steam or grill it. Avoid boiling sweet corn for long periods, as this can lead to a loss of water-soluble vitamins such as vitamin C. Light cooking methods help maintain its sweet flavour and nutrient profile. When looking to buy tinned sweet corn, try to opt for those lower in added sugar or salt.
Celery is often overlooked due to its high water content and is therefore thought of as a vegetable that doesn’t do much for you in terms of nutrition. Yet it is low in calories and provides vitamins C and K, potassium and folate. Celery contains antioxidants such as flavonoids and vitamin C, which help protect cells from damage. Its high water content aids in hydration, and the fibre it provides supports digestion. While not as nutrient-dense as some other vegetables, celery is rich in phytonutrients with antioxidant and anti-inflammatory properties, making it worthy of inclusion in a balanced diet.
The healthiest way to eat celery
Similar to the other vegetables, it is recommended to consume celery raw in salads or as a snack, or lightly steam it, and to avoid boiling or prolonged cooking, as these methods can cause a loss of water-soluble nutrients.
Cucumber is a refreshing vegetable with a very high (96 per cent) water content, making it hydrating but relatively low in nutrients. While it does provide some nutrients such as B vitamins, vitamins C and K, copper, phosphorus, potassium and magnesium, it lacks the nutrient density of many other vegetables.
Cucumbers contain some antioxidants, such as flavonoids, which may help reduce inflammation and protect against oxidative stress. The skin of cucumbers also contains fibre, which supports digestion and promotes a healthy gut microbiome, but overall they are not as nutrient-rich as other options such as leafy greens or cruciferous vegetables.
The healthiest way to eat cucumber
Cucumbers are best consumed raw to maximise their hydration and nutrient content. They are perfect for salads, sandwiches, or as a refreshing snack. For added fibre and nutrients, leave the skin on.
Iceberg lettuce is ranked at the bottom due to its low nutrient density compared with other lettuce and leaf varieties. It provides very small amounts of essential vitamins and minerals, such as vitamins A, C, and K, and is lower in fibre and antioxidants than its darker-leafed counterparts. The light green, almost white colour of iceberg lettuce indicates a lower concentration of phytonutrients and beneficial compounds. While it contributes to hydration due to its high water content (approximately 96 per cent), its nutritional benefits are limited compared with more nutrient-dense greens such as romaine or cos lettuce.
The healthiest way to eat lettuce
Like romaine, iceberg lettuce isn’t often cooked or exposed to heat. It is best used raw in the likes of salads, sandwiches and other fresh dishes to provide a crisp texture. Avoid cooking lettuce, as heat can cause it to wilt and lose its nutrient content, especially its water-soluble vitamins and delicate antioxidants.
Vegetables and vitamins
Though we need them only in tiny doses, vitamins are key for keeping our bodies working properly. They bolster our immune system, strengthen our bones and keep our skin healthy. Our bodies can’t make them, so we need to get them from our diet.
“Vegetables are major sources of the essential vitamins, particularly vitamins A, C, K, folate and E,” explains Dr Maria Traka, the head of food and nutrition at the Quadram Institute. For example, vitamin A helps us see things in dim light, while vitamin K helps blood clot together so wounds can heal.
Unfortunately, popping a multivitamin isn’t necessarily a quick fix if you’re not eating enough vegetables. “Obtaining nutrients from whole foods maximises nutrient absorption and minimises the risk of over-intake,” which can be toxic, she explains. Over long periods, very high doses of vitamin A can weaken our bones, too much vitamin D can damage the kidneys and heart, and excessive amounts of iron can be fatal.
“Additionally, vegetables contain other beneficial components such as polyphenols, carotenoids and phytochemicals,” which aren’t present in supplements, Dr Traka notes. “Studies suggest these reduce the risk of many diseases, including cancer, cardiovascular disease, degenerative eye diseases and osteoporosis.”
Vegetables and fibre
Fibre is a carbohydrate that is found in plants. “It acts to push other materials through the intestines so promotes regular bowel movements, improves gut motility and can relieve constipation,” Dr Traka explains.
It helps fill us up, which can help prevent overeating and weight gain, improves our blood sugar control, so can protect against Type 2 diabetes, and feeds our gut microbiome, so is beneficial for our gut health, she notes. Fibre has also been shown to protect against inflammation, cardiovascular disease and bowel cancer, Dr Traka adds.
Per 100g, peas (6g), sweet potato (4g), Brussels sprouts (3.9g) and broccoli (2.6g) are among the most fibre-rich vegetables.
Vegetables and carbs
Hearty, high-carbohydrate vegetables are often demonised for being higher in calories than leafy greens and salad vegetables. However, potatoes, sweet potatoes, carrots, parsnips and sweet corn are still nutritious. They are starchy foods that are full of fibre and vitamins.
“They offer unique benefits that lower-carb vegetables may not provide,” explains Dr Traka. “They provide a quick and sustained source of energy. The fibre content in these vegetables promotes satiety, aids in weight management and helps regulate digestion and blood sugar levels.”
Cooking veg
Fresh vegetables are, of course, packed with nutrients, but frozen can be just as nutritious or, in some cases, superior.
For example, studies suggest frozen kale contains more antioxidants, while frozen broccoli has more B vitamins. This is because vegetables are frozen at their peak, which locks in their high nutritional value. However, frozen vegetables can lose some vitamins during cooking, as they release more water during cooking.
The picture is mixed in relation to tinned. “Some water-soluble vitamins such as B vitamins and vitamin C can be lost in the canning process or leach into the surrounding liquid,” Dr Traka explains. “Additionally, check the label and choose tinned vegetables that haven’t got added salt or sugar.”
When it comes to cooking, root vegetables drizzled with honey and roasted in the oven for an hour are obviously delicious. Unfortunately, minimal cooking is generally better, as it prevents nutrients from being lost, explains Dr Traka.
“Lightly steamed is better than boiled, as boiling vegetables in a lot of water causes B vitamins and vitamin C to escape into the water,” she says. When frying or roasting, avoid dousing vegetables in oil or butter as it adds unnecessary calories, she says.
The Science of Plant-Based Nutrition was published by DK on 27 June
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