Cruciferous vegetables include broccoli, cauliflower, cabbage, bok choy, brussels sprouts, radishes, turnip, swede, mustard greens, watercress, rocket, kale and collard greens. These vegetables provide protein, carbohydrates, fibre and omega 3 fatty acids. Good sources of B-vitamins, Vitamin C, vitamin K, tocopherols (vitamin E), beta-carotene (Vitamin A precursors) and minerals: iron, calcium, selenium, magnesium, manganese, copper, phosphorus, potassium, and zinc. These vegetables are excellent sources of antioxidant enzymes, sulphur-rich and phytochemical compounds with many documented health benefits.
Bioactive molecules in cruciferous vegetables
Most health benefits associated with consumption of cruciferous vegetables are related to the active phytochemicals and sulfur molecules present in these vegetables. Flavonoids, anthocyanins and carotenoids are bioactive coloured compounds. Carotenoids are a class of yellow, orange and red fat-soluble pigments which the body converts to vitamin A. Anthocyanins are the largest class of blue and purple water soluble pigment compounds in nature. They give deep-red, blue and purple colours to fruits, vegetables, flowers, grains, seeds. Flavonoids form yellow pigment compounds. These phytochemicals exert anti-inflammatory and antioxidant activities, protecting the body and the DNA of our cells from free radical damage and slowing down aging. Free radicals are unstable and highly reactive molecules formed as a result of normal biological and metabolic processes, fighting infections, toxins and pollutants we are exposed to (from air, food, water, personal care and household products), chronic stress to number a few. A varied diet rich in vegetables, leafy greens, whole grains, nuts, seeds and fruits provide an abundance of phytochemicals which help:
- neutralize free radicals,
- reduce inflammation,
- activate detoxifying enzymes,
- maintain integrity of blood vessels and tissues,
- reduce LDL cholesterol and risk of plaques forming in the arteries help to protect against cardiovascular disease and dementia,
- inhibit cancer cell proliferation and promote cancerous cell death (apoptosis).
Cruciferous vegetables contain high amounts of sulphur-rich compounds which are natural pesticides against fungal infections and insects. These molecules are activated by protective mechanisms of the plant when the tissues of the vegetables are disrupted by biting, chewing, cutting, and have been associated with many benefits to human health including chemoprevention, prevention against cancer. Two of these phytonutrients are glucosinolates and S-methylcysteine sulfoxide.
Sulphur-containing amino acids (cysteine and methionine) compounds in cruciferous vegetables which have demonstrated antibacterial and antifungal effects.
Over 120 different glucosinolates have been identified. These sulphur-containing molecules give cruciferous vegetables their pungent and bitter taste and aroma. Glucosinolates are converted to bioactive molecules called isothiocyanates, known to have antifungal and antibacterial activities. Sulforaphane and indole-3-carbinol are two isocyanates which have been extensively studied for their ability to boost liver detoxification of harmful substances and excess hormones.
Sulphorafane stimulates activity of detoxifying Phase 2 liver enzymes to neutralize free radicals and eliminate toxins and harmful metabolites which can cause damage to cells and cause gene mutations, helping to slow down aging and protect against cancers.
Indole-3-carbinol has shown the ability to suppress the growth of oestrogen-dependant tumors in oestrogen-sensitive cells such as breast and ovarian cancers, inhibit breast tumor cell growth and prevent metastasis (spreading of cancerous cells to other sites in the body).
Glucosinolates in cruciferous vegetables may block iodine uptake by the thyroid gland and interfere with thyroid hormone production. High doses of some glucosinolates can cause goiter in humans in the presence of iodine deficiency. Glucosinolates have amazing cancer-preventive benefits and there is no need to be concerned about eating small serves of raw cruciferous vegetables, such as in a cole slaw salad or cabbage juice as part of a varied diet with adequate iodine intake. Cooking significantly reduces glucosinolates.
Those with hypothyroidism and iodine deficiency can enjoy small serves of cooked cruciferous vegetables but should avoid them raw. Maintaining optimal intake of iodine and selenium are key factors in supporting normal thyroid function, especially for those with hypothyroidism.
George Mateljan Foundation 2017, ‘What are the benefits of the sulfur compounds found in cruciferous vegetables?’ < http://www.whfoods.com/genpage.php?tname=george&dbid=45 >
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