Phytonutrients/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
Carbohydrates
Carbohydrates are a large group of organic compounds made by plants. Examples of carbohydrates are sugars, starch and cellulose and they provide our bodies with energy.
- Potatoes, yams and kumara contain carbohydrates, are called starchy vegetables and provide energy for our bodies.
- About a quarter of the plate should be made up of starchy foods, non-starchy vegetables should make up half the plate.
Vitamins and minerals
Vitamins and minerals are natural substances found in a wide range of foods and are essential to maintaining 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. Eat vegetables that contain iron, with vegetables containing Vitamin C to help the iron be absorbed into the body. Spinach, silverbeet, parsley, leeks, broccoli and mushrooms are good sources of iron.
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.
Fibre
Fibre keeps the digestive system healthy, helps keep healthy body weight and decreases the risk of heart disease and cancer. Fibre has also been found to lower cholesterol levels by reducing the reabsorption of cholesterol produced by the body to help with the digestion of fat (Ötles & Ozgoz, 2014).
- All vegetables contain some fibre; some more than others. Vegetables that are high in fibre are broad beans, peas, spinach, watercress, green beans, sweet corn, silverbeet, cabbage, butter beans, broccoli and Brussels sprouts.
- Carrots, parsnips, turnips, potatoes and kumara have a special type of fibre in their skins so scrub them instead of peeling them. Bake kumara and potatoes with the skin on.
- Prepare and cook vegetables the right way to preserve their valuable nutrients and fibre. Leave the peel on whenever possible.
- Vegetables that belong to the cabbage family (cabbage, cauliflower, turnips, swedes and Brussels sprouts) contain compounds that may be good at protecting against cancer.
References
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3649719/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3949128/
- https://link.springer.com/book/10.1007/978-0-387-30443-4
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4644575/
- https://www.ams.usda.gov/grades-standards/vegetables
- https://www.nal.usda.gov/fnic/fruit-and-vegetable-information
- https://plants.usda.gov/home/plantProfile?
- https://www.ers.usda.gov/topics/crops/vegetables-pulses/
- https://www.fas.usda.gov/commodities/fruits-and-vegetables
- https://www.ers.usda.gov/data-products/vegetables-and-pulses-data/vegetables-and-pulses-yearbook-tables/
- https://www.fda.gov/food/food-labeling-nutrition/nutrition-information-raw-vegetables
- https://www.fda.gov/food/food-labeling-nutrition/nutrition-information-raw-fruits-vegetables-and-fish
- https://www.fda.gov/media/70792/download
- https://www.who.int/elena/titles/fruit_vegetables_ncds/en/
- https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/fruit-vegetable
- https://www.sciencedirect.com/topics/food-science/fruit-vegetable
- https://www.sciencedaily.com/vegetables
- https://doi.org/10.1016/B978-0-12-823380-1.00013-7
- https://www.researchgate.net/publication/227160213_Vegetables_and_Vegetable_Products
- https://www.researchgate.net/journal/Journal-of-Vegetable-Crop-Production-1540-7357
- https://www.cancer.gov/about-cancer/causes-prevention/risk/diet/cruciferous-vegetables-fact-sheet
- https://www.cdc.gov/pcd/issues/2016/16_0259.htm
- https://onlinelibrary.wiley.com/doi/book/10.1002/9780470958346
- https://www.gbif.org/species/
- https://en.wikipedia.org/wiki/Vegetable
- https://en.wikipedia.org/wiki/List_of_root_vegetables
- https://en.wikipedia.org/wiki/Leaf_vegetable
- https://en.wikipedia.org/wiki/List_of_vegetables
- https://en.wikipedia.org/wiki/Lists_of_foods
- https://www.fao.org/fruits-vegetables-2021/en/
- https://www.itis.gov/servlet/SingleRpt/SingleRpt?
- https://www.fao.org/in-action/inpho/crop-compendium/fruits-vegetables/en/
- https://www.fao.org/family-farming/detail/en/c/1364793/
- https://books.google.com/books/about/Vegetables.html?id=Ce_wAAAAMAAJ
- https://books.google.com/books/about/Vegetables.html?id=6jrlyOPfr24C
- https://www.self.com/topic/vegetables
- https://www.cabi.org/isc/datasheet/
- https://www.myplate.gov/eat-healthy/vegetables
- https://www.nature.com/articles/162910b0
- https://www.tandfonline.com/doi/abs/10.1080/13669870802380825
- https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD008552.pub2/abstract
- https://www.forbes.com/sites/daphneewingchow/2021/02/28/five-reasons-why-sea-vegetables-could-be-the-future-of-produce/
- https://pfaf.org/USER/Plant.aspx?
- https://plants.ces.ncsu.edu/plants/
- https://plants.ces.ncsu.edu/plants/
- http://www.theplantlist.org/
- https://www.nutritionvalue.org/
- https://www.vegetables.co.nz/health/vegetable-nutrition/
