Vegetable nutrition

Fresh vegetables are naturally low in fat, salt and sugar, making them an excellent food choice. Visit the recipe section of this website to discover delicious ways with vegetables.

Vegetables provide energy, vitamins, minerals and fibre and there is growing evidence of additional health benefits from a range of phytonutrients.

Some vegetables contain higher levels of carbohydrate and are often called starchy vegetables. These are usually roots and tubers (see vegetable classifications) such as potatoes, yams, kumara, taro and sweet corn. The starchy vegetables are higher in energy (kilojoules) because of their carbohydrate content.

Other vegetables are classified as non-starchy. Non-starchy vegetables tend to have a higher water content, and are lower in energy but often richer in vitamins and minerals.

Aim to make half your dinner vegetables and choose a range of different coloured vegetables. About one-quarter of the plate should be starchy foods for energy.

These are naturally occurring plant compounds. There are thousands of these different phytonutrients in vegetables, usually in small amounts. Plants produce them for their own protection from insects or bacteria, as pigments for photosynthesis (energy production) and flavour. They are often responsible for the bright colours of fruits and vegetables, and research is showing that these compounds may help reduce the risk of disease and promote health. Examples of phytonutrients are lycopene in tomatoes, beta-carotene in carrots and glucosinolates in broccoli.

There is no single magic phytonutrient that can be isolated and turned into a daily tablet! The most protective effect comes from eating a wide variety of phytonutrients as they occur naturally in plant foods.

Phytonutrients may work in lots of different ways to protect against disease and promote health. Modes of action that are being investigated include anti-inflammatory activity, boosting the body’s antioxidant defences, modulating gut microflora, lowering cholesterol, fighting bacteria and supporting the body’s immunity.

Main phytonutrients in vegetables

Unlike nutrients (vitamins and minerals) no recommended dietary intake levels have been established for phytonutrients. Health claims are not permitted (with the exception of some carotenoids that can be converted to vitamin A) and further human trials are required to substantiate the potential benefits suggested below.

Phytonutrients	Research on Potential Health Benefits	Vegetable Sources
Carotenoids
• Pro-vitamin A carotenoids: alpha-carotene, beta-carotene and beta-cryptoxanthin	Vitamin A activity (our body converts these carotenoids to vitamin A). Research indicates the carotenes may help to slow the ageing process, reduce the risk of certain types of cancer, improve lung function, help keep skin healthy and reduce complications associated with diabetes but more research is needed.	In many vegetables but high in carrots, pumpkin and green leafy vegetables
• Lycopene	Some studies have shown that diets rich in lycopene may reduce the risk of prostate and some other cancers as well as heart disease.	Tomatoes, watermelon
• Xanthophylls: lutein, zeaxanthin	Lutein and zeaxanthin are found in the retina and lens of the eye and are thought to play a role in maintaining proper vision as we age and may reduce the risk of macular degeneration and cataracts.	Dark green leafy vegetables such as spinach, silverbeet, lettuce; sweet corn
Glucosinolates, isothiocyanates	Glucosinolates (or their breakdown products the isothiocyanates) may reduce the risk of certain types of cancer by boosting enzymes that detoxify carcinogens.	Brassica vegetables: broccoli, cauliflower, Brussels sprouts, cabbage, kale, radish, swede, turnip, watercress
Phenolic compounds – including Polyphenols *
• Flavonoids	Over the past decade, scientists have become increasingly interested in the potential for various dietary flavonoids to explain some of the health benefits associated with fruit- and vegetable-rich diets. Health benefits include reducing cancer, diabetes and heart disease risk, helping maintain healthy bones, brain and vision.	Beans, onions, leafy vegetables, tomatoes
• Phenolic acids	More study is required but phenolic acids may have benefits for heart health and immunity.	In most vegetables but especially potatoes
• Anthocyanins	Research indicates anthocyanins may have a wide variety of health benefits including protecting against the signs of ageing, reducing the risk of cancer and diabetes. They may be neuroprotective to help prevent neurological diseases and improve aspects of vision.	Red, blue/purple vegetables – eggplant, purple broccoli, red/purple kumara, radish, rhubarb
Allium sulphur compounds	A whole range of health benefits have been suggested for the Allium sulphur compounds. In vitro and animal studies indicate Allium compounds may reduce the risk of certain types of cancer, assist in preventing heart disease and have antimicrobial activity.	Garlic, leeks, onions, chives
Other compounds
Betalains	The betalains have received less attention than the more common natural red pigments, the anthocyanins. However, research indicates they have anti-inflammatory properties and may boost the body’s detoxification enzymes.	Beetroot, silverbeet, spinach (red and yellow varieties)
Falcarinol, falcarindiol	These compounds have attracted interest for their potential as anti-cancer compounds. However, at high levels these compounds can be toxic.	Carrots, celery, fennel, parsley, parsnips
Saponins	Saponins have been shown in some studies to have a number of protective effects in the human body, including reducing the risk of cancer, lowering cholesterol, and preventing heart disease.	Alfalfa sprouts, asparagus, beans, spinach
Phytosterols	Phytosterols may compete with cholesterol for absorption and lower cholesterol in the bloodstream. There is also some evidence phytosterols may help prevent cancer cell growth and may fight atherosclerosis by controlling the development of plaques.	Asparagus, beans, lettuce, peas, brassica family e.g. broccoli, swedes, cauliflower
Fructans	Research indicates fructans may have various health benefits especially for the digestive system and immunity. Because they improve mineral absorption they may have benefits for bone health. They also have effects on cholesterol metabolism and may have benefits for heart heath.	Onions, leeks, garlic, asparagus
Capsaicinoids	Capsaicinoids may have multiple potential beneficial effects including pain relief, cancer prevention and weight loss, plus to a lesser extent, benefits for the cardiovascular and gastrointestinal systems.	Capsicums, chillis

*This is a diverse group of thousands of phytochemicals – other types include catechins, isoflavones and lignans. Vegetables are not major sources of these phytochemicals.

Source and acknowledgement: Plant and Food Research, Lincoln 2018

Vitamins and minerals are natural substances found in a wide range of foods and are essential to maintain a healthy body. Scientists have defined specific daily amounts necessary for good health.

Why they are important

Vitamin A stimulates new cell growth, keeps cells healthy and can help vision in dim light. Vitamin A is found in vegetables such as pumpkin, carrots, kumara, spinach and broccoli.

Vitamin B releases energy from food, and is good for the nervous system. Green vegetables contain Vitamin B.

Vitamin C is used in tissue repair, helps the immune system by fighting against infection and helps health in general. Vitamin C also helps iron in food to be absorbed. Capsicums and parsley are excellent sources of Vitamin C with significant amounts in broccoli, Brussels sprouts, cabbage, cauliflower, spinach, radishes, peas, beans, asparagus. Potatoes, turnips, tomatoes, kumara, spring onions, lettuce and leeks also contain Vitamin C.

Vitamin K helps blood clot. Turnips, broccoli, lettuce, cabbage, asparagus, watercress, peas and green beans have Vitamin K.

Calcium is necessary for healthy teeth, bones, hair and nails. Spinach, parsley, broccoli, celery, leeks, spring onions, cabbage and carrots contain calcium.

Potassium controls muscles and nerves and may be important in preventing high blood pressure. All vegetables contain potassium.

Iron is essential for red blood cells so that oxygen can be carried around the body. Vitamin C helps the absorption of non heme iron, and many vegetables are a good source of Vitamin C.

Avoid vitamin loss in vegetable preparation and cooking by:

Leaving the peel on as it contains vitamins as well as fibre.
Using a sharp knife. A blunt knife causes cell damage which leads to Vitamin C loss.
Cooking vegetables as soon as they are prepared. Don’t soak them in water as water-soluble vitamins (B and C) will be lost.
Using a small amount of water, or preferably, steam vegetables. Save the cooking water and use it in soups, stocks, gravies or enjoy as a drink.

Vegetable nutrition

Phytonutrients

Carbohydrates

Vitamins and minerals

Fibre