With superfood status, the humble broccoli (Brassica oleracea var. italica) is one of the most commonly consumed cruciferous vegetables.1 Originating from the Calabria region of Italy, its name derives from the Latin word ‘brachium’ meaning branch or arm to describe its distinctive branching florets.2
Glucosinolates are nitrogen sulphur-containing compounds found almost exclusively in broccoli and other Brassica vegetables. These compounds are responsible for the astringent taste and sulphurous aroma of broccoli1 which make it a challenge for kids to pile their plates high. Many studies have reported the benefits of isothiocyanates (the bioactive metabolites of glucosinolates) in supporting many aspects of health.
To Broccoli or Broccolini? That is the Question
If you’ve ever stopped to wonder whether broccoli or broccolini is best added to your shopping basket, you’re not alone. Broccoli is a good source of minerals (potassium, phosphorus, calcium and sodium), as well as protein and fibre. It is particularly rich in the glucosinolates, glucoraphanin and glucobrassicin.1 Recent research shows broccolini, a hybrid of broccoli and Chinese broccoli (kai lan), is also high in glucobrassicin,1 and is a good source of potassium, manganese and phosphorus.3 Broccoli contains almost twice as much vitamin C as broccolini, slightly higher folate, and marginally higher amounts of potassium and iron.2
Daily consumption of broccoli and other Brassica vegetables is an ideal way to increase intake of antioxidant phytonutrients. Those wanting to harness the exceptional health benefits of broccoli may also consider broccoli seed and broccoli sprouts supplements which deliver a concentrated source of therapeutic compounds, particularly glucoraphanin and sulforaphane.
Broccoli’s Bioactive Phytochemicals
As with herbs, different plant parts exhibit varying phytonutrient profiles. Glucoraphanin occurs in all parts of the broccoli plant, however broccoli seeds contain the highest amounts by weight.4,5 In the presence of the enzyme myrosinase, glucoraphanin is converted to sulforaphane - the primary bioactive phytochemical found in broccoli (see Figure 1 below, A).5 Myrosinase is present in the broccoli sprout, and is also produced by human intestinal microbiota.5
Another glucosinolate known as glucobrassicin (found in broccoli seed) is converted to Indole-3-Carbinol (I3C) by myrosinase. In the acidic conditions of the stomach, I3C is further converted to the highly bioactive compound 3,3’-Diindolylmethane (DIM) (see Figure 1, B).5
Figure 1: Metabolism of glucoraphanin and glucobrassicin to biologically active metabolites.5
Supporting Hormonal Health
Sulforaphane, I3C and DIM are all bioavailable and active in the human body and have numerous beneficial effects on oestrogen metabolism and in oestrogen sensitive conditions.5 Sulforaphane may support the conversion of oestradiol and oestrone preferentially to the antioestrogenic and antiproliferative 2-OH-oestrogens. It also inhibits aromatase activity in vitro, which may reduce the production of oestrogen from androgens.6 The urinary 2:16 OHE1 ratio increased by 29.5% when 16 healthy volunteers included broccoliin their diet (500 g/day) for 12 days, compared to controls.7
Sulforaphane’s Broad Spectrum Against Disease
Broccoli has been identified as a potent activator of cellular defence mechanisms. Sulforaphane significantly activates the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway to modulate phase II detoxification/metabolism enzymes, including NQO1 and GST.8 It thus has potential to modulate the expression of genes associated with redox balance, inflammation, detoxification and antimicrobial capacity.4 Sulforaphane also possesses neuroprotective effects9 and has been shown to modulate diversity of the gastrointestinal microbiota10 and protect the gastric mucosa against oxidative injury.11
Through multiple mechanisms, sulforaphane targets a wide range of diseases including neurodegenerative disorders, cancer, autoimmune disorders, cardiovascular diseases, inflammation, and metabolic disease (see Figure 2).12
Figure 2. Sources of sulforaphane and its broad spectrum against disease.12
[GLS: glucosinolates, SFN: sulforaphane)
Chemoprotective Effects
Dietary intake of broccoli is known to reduce the risk of cancer, and glucoraphanin and sulforaphane have confirmed chemoprotective properties.13In in vitro studies, I3C suppressed the proliferation of hormone dependant cancer cells, including breast, prostate, cervical and endometrial cancer cells, via its ability to induce apoptosis, inhibit DNA-carcinogen adduct formation, suppress free-radical production,stimulate 2-hydroxylation of oestradiol, and inhibit invasion and angiogenesis.14
A meta-analysis (n=18,673) found that high consumption of cruciferous vegetables such as broccoli is significantly associated with a 15% reduced breast cancer risk, particularly in post-menopausal women.15 A case control study of 965 men found that higher intake of Brassica vegetables, particularly broccoli (equivalent to 1 cup of cooked cruciferous vegetables/day) was associated with a significantly lower risk of prostate cancer compared to those lower intake (OR 0.58, indicating a 42% reduction in risk).16
Sulforaphane has exhibited potent chemosensitising capabilities across diverse cancer types, supporting its potential use as an adjunct to cancer therapy. When combined with conventional chemotherapeutic agents, sulforaphane synergistically inhibits cancer cell proliferation, invasion, migration, and metastasis while potentiating drug-induced apoptosis.12
The Benefits of Broccoli
A significant body of evidence has demonstrated the benefits of broccoli in reducing the risk of various cancers13 and supporting many diverse aspects of health. Rich in bioactive compounds, broccoli may be considered both food and medicine. While supplements containing broccoli seeds and sprouts provide therapeutic doses of bioactive compounds, patients should be encouraged to make this healthy vegetable a part of their everyday and enjoy its many benefits.
References
1. Langston F, Redha A, Nash G et al. Qualitative analysis of broccoli (Brassica oleracea var. italica) glucosinolates: investigating the use of mid-infared spectroscope combined with the chemometrics. J Food Comp Anal. 2023;123:105532. doi: 10.1016/j.jfca.2023.105532
3. Llorent-Martínez EJ, Ortega-Vidal J, Ruiz-Riaguas A, Ortega-Barrales P, Fernández-de Córdova ML. Comparative study of the phytochemical and mineral composition of fresh and cooked broccolini. Food Res Int. 2020 Mar;129:108798. doi: 10.1016/j.foodres.2019.108798. Epub 2019 Nov 21. PMID: 32036908.
4. Houghton CA. Sulforaphane: its "coming of age" as a clinically relevant nutraceutical in the prevention and treatment of chronic disease. Oxid Med Cell Longev. 2019 Oct 14;2019:2716870. doi: 10.1155/2019/2716870.
5. Watson GW et al. Phytochemicals from cruciferous vegetables, epigenetics, and prostate cancer prevention. AAPS J. 2013 Oct;15:951-61.
6. Licznerska B, Szaefer H, Matuszak I, Murias M, Baer-Dubowska W. Modulating potential of L-sulforaphane in the expression of cytochrome p450 to identify potential targets for breast cancer chemoprevention and therapy using breast cell lines. Phytother Res. 2015 Jan;29(1):93-9. doi: 10.1002/ptr.5232.
7. Kall MA, Vang O, Clausen J. Effects of dietary broccoli on human in vivo drug metabolizing enzymes: evaluation of caffeine, oestrone and chlorzoxazone metabolism. Carcinogenesis. 1996 Apr;17(4):793-9. doi: 10.1093/carcin/17.4.793.
8. Cao S, Wang L, Zhang Z, Chen F, Wu Q, Li L. Sulforaphane-induced metabolomic responses with epigenetic changes in estrogen receptor positive breast cancer cells. FEBS Open Bio. 2018 Nov 14;8(12):2022-34. doi: 10.1002/2211-5463.12543.
9. Bowen-Forbes C, Armstrong E, Moses A, Rahlman R, Koosha H, Yager J. Broccoli, kale, and radish sprouts: key phytochemical constituents and DPPH free radical scavenging activity. Molecules. 2023 Jun;28(11):4266.
10. Kaczmarek JL, Charron CS, Novotny JA, Jeffery EH, Seifried H, Ross SA, et al. Broccoli consumption impacts the human gastrointestinal microbiota. FASEB J. 2018 Oct;31(S1):965.18-965.18. doi: 10.1096/fasebj.31.1_supplement.965.18
11. Yanaka A. Role of sulforaphane in protection of gastrointestinal tract against H. pylori and NSAID-induced oxidative stress. Curr Pharm Des. 2017;23(27):4066-4075. DOI: 10.2174/1381612823666170207103943
12. Sailo BL, Liu L, Chauhan S, Girisa S, Hegde M, Liang L, Alqahtani MS, Abbas M, Sethi G, Kunnumakkara AB. Harnessing sulforaphane potential as a chemosensitizing agent: a comprehensive review. Cancers (Basel). 2024 Jan 5;16(2):244. doi: 10.3390/cancers16020244.
13. Yagishita Y, Fahey JW, Dinkova-Kostova AT, Kensler TW. Broccoli or sulforaphane: is it the source or dose that matters? Molecules. 2019 Oct 6;24(19):3593. doi: 10.3390/molecules24193593.
14. Aggarwal BB, Ichikawa H. Molecular targets and anticancer potential of indole-3-carbinol and its derivatives. Cell Cycle. 2005 Sep;4(9):1201-15. doi: 10.4161/cc.4.9.1993.
15. Liu X, Lv K. Cruciferous vegetables intake is inversely associated with risk of breast cancer: a meta-analysis. Breast. 2013 Jun;22(3):309-13. doi: 10.1016/j.breast.2012.07.013.
16. Joseph MA, Moysich KB, Freudenheim JL, Shields PG, Bowman ED, Zhang Y, et al. Cruciferous vegetables, genetic polymorphisms in glutathione S-transferases M1 and T1, and prostate cancer risk. Nutr Cancer. 2004;50(2):206-13. doi: 10.1207/s15327914nc5002_11.
