Kale, once known as 'peasants' cabbage,' was a cheap, hardy, and fast-growing dietary staple among farmers and low-income rural communities in the Middle Ages. During the Second World War, it became one of the vegetables promoted in the Dig for Victory campaign, which encouraged people to grow their own food in gardens and allotments.
Today, while the plant itself is relatively unchanged, kale has undergone a dramatic reputational makeover. Now beloved by wellness influencers and health-conscious diners, scarcely a trendy cafe or juice bar menu is complete without a kale salad or green smoothie. Celebrity devotees include Beyonce, who wore a 'KALE' sweatshirt in her 7/11 music video, and Michelle Obama, whose White House kitchen garden helped turn the leafy green into a symbol of healthy eating.
But is it really as nutritious as it is often made out to be, or are devotees simply forcing down bowls of worthy, joyless greens in the mistaken belief it is a miracle food? The truth is, according to nutritionist and author Jenna Hope, kale does deserve a place at modern tables, and she says almost everybody could benefit from including it in their diet.
What's So Special About Kale?
Gwyneth Paltrow once described kale as 'one of the best things you can put into your system.' While its status as a 'superfood' can sometimes be overstated, kale stands out for its nutrient density. A single serving of four heaped tablespoons of cooked kale provides around 25 calories, 2g of fibre, and meets 17 per cent of your daily calcium needs.
Ms Hope, author of How To Stay Healthy and founder of Jenna Hope Nutrition, says: 'Kale is a great source of key nutrients such as Vitamin C, which is important for immune function, and Vitamin K, which supports wound recovery.' Kale is a rich source of iron and folate, two nutrients essential for building healthy red blood cells, preventing anaemia, and supporting foetal development during pregnancy. It also offers some of the highest concentrations of lutein and zeaxanthin found in any leafy green, two plant compounds which support eye health. Lutein and zeaxanthin act as a natural pair of sunglasses for the eyes, filtering out harmful blue light and helping to protect against age-related macular degeneration (AMD).
What is more, kale is a very versatile ingredient for cooking as its robust, earthy leaves can withstand heat without turning to mush. 'People often aren't too sure what to do with kale,' adds Ms Hope. 'Using it as an alternative to spinach is a great place to start, and adding kale to smoothies, soups, salads, and stews is also an easy win. You can also blitz it into a homemade pesto or vegetable sauce for a delicious pasta dish too.' In smoothies, kale's earthy flavour is easily masked by sweet fruits like bananas, berries, or mangoes, making it a common feature in health juices.
Which Variety of Kale Is the Healthiest?
While all kale is highly nutritious, red kale — often labelled as Red Russian or colourful curly kale — is generally considered the healthiest overall. Its vibrant pigment comes from anthocyanins, powerful antioxidants that provide extra health benefits over standard green varieties. Research suggests that a diet rich in anthocyanins may help reduce inflammation, lower the risk of cardiovascular disease, and support cognitive function.
Ms Hope says that curly kale, the most common variety found in supermarkets, is an excellent source of vitamins K, C, and fibre, but typically has slightly fewer antioxidants than purple varieties. Baby kale has a more tender texture and is often gentler on the digestive tract, while cavolo nero often ranks highest in lutein, which is vital for eye health. Unlike other leafy greens, kale thrives in cold weather. During the war, it was a reliable source of fresh food throughout the winter when no other vegetables could grow.
Can You Eat Kale Raw?
Kale can safely be eaten raw — as long as you watch your portion sizes. Raw kale is very fibrous and is rich in a complex sugar called raffinose, which ferments in the lower intestine. When people eat too much or have digestive issues, it can cause severe gas, bloating, and discomfort. Ms Hope notes that for people with sensitive stomachs, cooking it may be the better option, as it softens the fibres, making it significantly gentler on your digestive lining. For the average person, a healthy portion of raw kale is about 40g to 80g per day. Massaging raw kale leaves with extra virgin oil or an acid like lemon juice breaks down the rigid cell walls, which softens the texture and makes it easier to chew and digest.
Does Kale Damage Your Thyroid?
For the vast majority of people, kale does not damage the thyroid when consumed in normal amounts. Kale is a cruciferous vegetable, like broccoli and Brussels sprouts. These plants contain thiocyanates and other goitrogenic substances which, in very large quantities, can 'compete' with iodine for uptake by the thyroid gland. However, experts agree that the nutritional benefits far outweigh the risks for most individuals. Steaming, sauteing, or boiling kale breaks down the enzyme (myrosinase) responsible for releasing goitrogenic compounds.
Can Kale Protect You Against Diseases?
Eating kale as part of a healthy, balanced diet has been linked to lowering the risk of heart disease and diabetes, as well as colon, breast, lung, and prostate cancers. As a cruciferous vegetable, kale contains specialised compounds like glucosinolates, which break down into cancer-fighting substances, such as sulforaphane, during digestion. Sulforaphane has been shown in studies to inhibit inflammatory pathways and slow the spread of tumour cells. The combination of dietary fibre and antioxidants helps regulate blood sugar levels and combat inflammation associated with type 2 diabetes. On top of this, regular consumption of leafy greens helps in lowering cholesterol and supporting overall cardiovascular function.
Which Foods Should You Pair Kale With?
To maximise kale's health benefits, experts recommend eating it with small amounts of healthy fat, like olive oil or avocado, as this helps your body absorb the fat-soluble vitamins and antioxidants. Dietary fats mix with digestive juices to form tiny particles called micelles, which transport nutrients across the intestinal walls and into the bloodstream, significantly boosting absorption. Ms Hope also recommends pairing kale with a squeeze of lemon juice to support iron absorption, particularly for people at risk of deficiency. When consumed together, the vitamin C (ascorbic acid) in lemon juice converts the plant-based iron in kale into a form that is much easier for your body to absorb. This can significantly boost how much of the plant-based iron the body uses. As well as foods that help the absorption of vital nutrients, it is important to be aware of the foods and drinks that can reduce the amount of nutrients the body absorbs. Food and drink rich in calcium, tannins (found in coffee and tea), and phytates (found in plant seeds, grains, nuts, and legumes) can hinder iron absorption. This means leaving at least an hour after drinking tea or coffee before or after eating a kale-heavy meal.
