FWD 2 American Botanical Council - HerbalEGram - March 2016

HerbalEGram: Volume 13, Issue 3, March 2016

Food as Medicine: Broccoli
(Brassica oleracea, Brassicaceae)


Editor’s Note: Each month, HerbalEGram highlights a conventional food and briefly explores its history, traditional uses, nutritional profile, and modern medicinal research. We also feature a nutritious recipe for an easy-to-prepare dish with each article to encourage readers to experience the extensive benefits of these whole foods. With this series, we hope our readers will gain a new appreciation for the foods they see at the supermarket and frequently include in their diets.


The basic materials for this series were compiled by dietetic interns from Texas State University (TSU) in San Marcos and the University of Texas at Austin (UT) through the American Botanical Council’s (ABC’s) Dietetic Internship Program, led by ABC Education Coordinator Jenny Perez. We would like to acknowledge Jenny Perez, ABC Special Projects Director Gayle Engels, and ABC Chief Science Officer Stefan Gafner, PhD, for their contributions to this project.



By Hannah Baumana and Stephanie Darbyb

a HerbalGram Assistant Editor
b ABC Dietetics Intern (TSU, 2015)



History and Traditional Use

Range and Habitat

Broccoli is a cultivar of wild cabbage. Wild cabbage originated along the northern and western coasts of the Mediterranean Sea, where it became a domesticated food crop thousands of years ago. Over time, the wild cabbage was eventually bred by growers into distinctly different varieties or cultivars of B. oleracea, including broccoli, Brussels sprouts, cauliflower, collard greens, and kale.1 Because B. oleracea hybridizes so easily, taxonomy for members of this species varies depending on the source. Other scientific names for broccoli include B. oleracea var. italica and B. oleracea, broccoli group.

Broccoli is a fast-growing annual food crop that grows two to three feet tall and yields broccoli crowns, or florets, within 60-150 days (growing time primarily depends on variety and climate conditions).1 The broccoli vegetable is usually eaten at the crown stage, which is actually the immature flower (inflorescence) stage. When the plants remain in the field past the crown stage and allowed to flower, they produce broccoli seeds. Broccoli sprouts are produced when broccoli seeds are grown with light and water for approximately 3 or 4 days.

Broccoli is characterized by its thick stalk and a crown of densely-packed flower heads arranged in a tree-like fashion, both of which are edible.1,2 The branching nature of this vegetable allows for numerous sprouts that form the crown. Though green broccoli is the most common cultivar, purple broccoli and Romanesco broccoli, which has greenish-yellow heads that grow in a conical shape, also are available on the market. If allowed to flower, broccoli produces small yellow or white blossoms.


Phytochemicals and Constituents

Broccoli is a very nutrient-dense, low-calorie vegetable. One cup of broccoli florets contains the same amount of protein as one cup of rice, with one-third fewer calories.3 Broccoli is also high in vitamins C, K, and A, folic acid, and soluble fiber. As a therapeutic food, broccoli consumption is recommended for treating xerophthalmia, or abnormal dryness and inflammation of the conjunctiva and cornea of the eye due to vitamin A deficiency, infantile scurvy resulting from vitamin C deficiency, and anemia resulting from folate deficiency.4 In a clinical study of 14 volunteers who consumed 200 g of broccoli once a day for seven days, blood tests showed an increase in serum concentrations of the carotenoid lutein and vitamin E.


Important secondary metabolites found in broccoli include selenocysteine, glucosinolates, and phenolic compounds. Selenocysteine is a form of selenium, which plays a role in anticancer function by increasing glucosinolate production.5 Glucosinolates found in broccoli are sulfur-containing compounds, most highly concentrated in the stalks, that greatly enhance detoxification processes in the body. Glucosinolates in turn are converted into isothiocyanates, which have antibacterial and antifungal properties.6 Phenolic compounds, including phenolic acids and flavonoids, are also found in significant quantities in broccoli, particularly in the seeds and sprouts, providing protection against free radicals and oxidative stress, and reducing inflammation.5

A specific type of glucosinolate called glucoraphanin can further be converted into sulforaphane, its more bioactive isothiocyanate form. It is a chemopreventive agent that activates antioxidant enzymes and decreases inflammation.7 One study determined that glucoraphanin content varied by as much as 10-fold among different varieties of broccoli found in supermarkets and also that the broccoli seeds and sprouts contained much higher concentrations of glucoraphanin (as much as 50-fold greater.)8 Broccoli sprouts contain the highest levels of glucoraphanin, which has the valuable ability to aid the human body in metabolizing environmental pollutants and carcinogens, eliminating them through the urine.9

Research conducted on glucoraphanin and sulforaphane shows promising results for subjects living in regions with heavy air pollution, such as China.10 The ability to remove toxins from the body has also opened up research into the possibility of using glucoraphanin as a treatment for the lung disorder chronic obstructive pulmonary disease (COPD), which can be caused by smoking or other environmental factors.11 Sulforaphane also has an antibiotic effect on microbes, notably Helicobacter pylori, which causes stomach ulcers, gastritis, and can lead to gastric cancers.9

Preparation methods affect the quantity and quality of glucosinolates, sulforaphane, polyphenols, and antioxidant activity in the broccoli plant.12 In general, boiling broccoli resulted in the largest losses of glucosinolates, as these compounds are water-soluble. Broccoli boiled for 10 minutes lost 40% of its glucosinolate content when compared to fresh broccoli.13 Microwaving, steaming, or blanching for 2-5 minutes at temperatures lower than 100° C allows for the greatest retention of glucosinolates, as well as the enzyme needed for hydrolysis of glucoraphanin to its most active form, sulforaphane. Cutting or chopping prior to cooking also maximized this effect.5 In some studies, steam-processed broccoli demonstrated a higher antioxidant capacity due to the increased bioavailability of phenols and flavonoids.5,12 Storage also plays a role: the processing necessary to produce commercial frozen broccoli may degrade the bioavailability of sulforaphane when compared to fresh broccoli.14

Proper selection and storage of broccoli is the key to maximizing nutrient value. Crowns should be dark green or purple depending on the variety, and stalks and stems should be firm to the touch. Broccoli sprouts should have green tops and white stalks. Any yellowing or wilting indicates the loss of nutrients.3 The crowns should be washed prior to use. Sprouts should be washed immediately prior to use and be consumed within a few days of purchase.


Historical and Commercial Uses

Broccoli was first cultivated in Italy and introduced to Britain, other European countries, and North America in the 18th century.3,15 The flower crown was traditionally used in its sprouted form, and was described as “Italian asparagus” when it was first introduced to the American colonies. Broccoli hybrids, such as broccolini and broccoflower, are becoming more common in supermarkets. These hybrids fall within the same species and varietal as broccoli, and with similar nutrient compositions of other plants in the genus Brassica.3

Broccoli has a history of medicinal use in its native Mediterranean area, predominantly in Greece. Ancient literature provides examples of broccoli-based treatments for gynecological disorders.16 Later, it became a panacea for many different conditions, including gastric upset, tetanus, skin infections, and, possibly, dropsy. (Now medically known as edema, dropsy is an abnormal accumulation of fluid, usually in the lower extremities, caused by cardiac insufficiency.)

In modern times, broccoli is available year-round at most supermarkets. While it is most common to consume broccoli in its whole form, health companies and agricultural producers are exploring the possibility of broccoli in other forms. In an effort to reduce waste, by-products of broccoli cultivation (e.g., stalks and leaves) are being studied for their nutritive value and content of bioactive compounds. Through extraction, these nutrients and bioactives add value to otherwise wasted products, and could be used in supplements or as food additives.17 Broccoli sprouts and broccoli seed extract are also popular additives to nutritional beverages due to their high glucoraphanin concentrations.18


Modern Research

Broccoli sprouts are high in bioactive compounds that have been shown to benefit patients with type 2 diabetes, various types of cancer, and cardiovascular diseases.

In patients with type 2 diabetes, a diet that contained high levels of broccoli sprouts could lower serum insulin levels and diminish insulin resistance.19 The high levels of sulforaphane were also shown to significantly decrease oxidative stress, presumably through the compound’s known ability to prevent the generation of oxidative radicals and by activating antioxidant enzymes. In a clinical study of 81 diabetic patients, consumption of fresh broccoli sprouts (10 g/day) for four weeks was associated with a significant reduction in serum insulin concentrations.20 However, further studies need to be done to determine the most effective dosage and duration of treatment.

Studies have shown that the detoxifying qualities of broccoli can reduce excess estrogen buildup that can lead to breast cancer, fibroids, and endometriosis.21 There is also a significant correlation between consuming Brassica vegetables and reduction in the incidence of bladder cancer.22 Studies have also shown that high levels of sulforaphane can block cancer initiation and slow progression by modifying tumor suppressor genes.23 Lastly, indole-3-carbinol, the breakdown product of another glucosinolate in broccoli, glucobrassicin, has been shown to reduce the growth rate of cancer cells, increase the ability of the liver to detoxify toxic compounds, and decrease growth of the human papillomavirus (HPV), which is linked to the development of cervical cancer.3

Broccoli constituents exhibit significant potential for protection against the harmful effects of environmental toxins and carcinogens, including airborne pollutants. Studies in China have shown that glucoraphanin- and sulforaphane-rich broccoli sprout extracts can increase detoxification of benzene and acrolein metabolites, which resulted from human exposure to airborne pollutants.24 In vitro studies have shown that isothiocyanate compounds, particularly sulforaphane, both inhibit Phase I enzymes and induce Phase II detoxification systems, increasing the body’s defense mechanisms against cancer-causing compounds.25,26

Other mechanisms by which broccoli constituents exert their anti-cancer effects include: (a) inhibiting the proliferation of cancer cells by inducing cell cycle arrest; (b) inducing apoptosis (programmed cell death); and (c) reducing inflammation and angiogenesis (the formation of new blood vessels, which can feed tumor growth).

Broccoli’s cardioprotective benefits can be obtained by consuming the sprouts, as well as the mature florets. In one clinical study, 63 patients with type 2 diabetes consumed either dried broccoli sprout powder (5 or 10 g/day) or placebo for four weeks. Compared to placebo, broccoli sprout powder significantly reduced LDL cholesterol levels and increased total antioxidant capacity.27 In another study in hamsters, fresh broccoli sprouts had significant effects on cholesterol homeostasis.28


Health Considerations

There are a few considerations for consumers regarding broccoli consumption. Since broccoli contains high amounts of vitamin K, which aids in blood clot formation, patients taking blood-thinning agents, such as warfarin (known by the brand name Coumadin, among others), should check with their doctor to discuss the appropriate dosage based on their current vitamin K consumption. This goes for other vegetables in the genus Brassica that are also high in vitamin K.29 Broccoli can also cause bloating and gas as a result of its sulfur-containing compounds.

Another potential adverse effect linked to the consumption of broccoli is the risk of hypothyroidism. Broccoli contains goitrogenic compounds, or compounds with the ability to enlarge the thyroid gland and interfere with thyroid function.3 However, studies confirm that cooking inactivates and diminishes the effects of these goitrogens. In addition, due to their stage in the plant lifecycle, broccoli sprouts contain virtually no goitrogenic compounds, so those who are taking thyroid medications can still enjoy the long list of benefits from this whole food.30

Nutrient Profile31

Macronutrient Profile: (Per 1 cup raw broccoli, chopped)

31 calories

2.57 g protein

6 g carbohydrate

0.34 g fat

Secondary Metabolites: (Per 1 cup raw broccoli, chopped)

Excellent source of:

Vitamin C: 81.2 mg (135.3% DV)
Vitamin K: 92.5 mcg (115.6% DV)

Very good source of:

Folate: 57 mcg (14.3% DV)
Vitamin A: 567 IU (11.34% DV)

Good source of:

Dietary Fiber: 2.4 g (9.6% DV)
Manganese: 0.18 mg (9% DV)
Potassium: 288 mg (8.2% DV)
Vitamin B6: 0.16 mg (8% DV)
Riboflavin: 0.11 mg (6.5% DV)
Phosphorus: 60 mg (6% DV)

Also provides:

Magnesium: 19 mg (4.8% DV)
Thiamin: 0.07 mg (4.7% DV)
Calcium: 43 mg (4.3% DV)
Iron: 0.66 mg (3.7% DV)
Vitamin E: 0.71 mg (3.5% DV)
Niacin: 0.58 mg (2.9% DV)

DV = Daily Value as established by the US Food and Drug Administration, based on a 2,000 calorie diet.

Recipe: Sesame-Ginger Steamed Broccoli

Ingredients:

  • 1 lb. broccoli, cut into florets
  • 2 tablespoons mirin or sake
  • 1 tablespoon tamari or soy sauce
  • 1 tablespoon fresh ginger, minced
  • 1 teaspoon toasted sesame oil
  • Salt, to taste
  • 1 teaspoon sesame seeds


Directions:

  1. Place broccoli, mirin or sake, tamari or soy sauce, ginger, oil, and 1/4 cup water in a large (2- to 3-quart) sauté pan.
  2. Cover and bring to a simmer over medium heat.
  3. Steam 4 minutes, or until broccoli is bright green and crisp-tender. Drain off steaming liquid, then sprinkle broccoli with salt and sesame seeds before serving.


References

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