Cruciferous Vegetables: Phytonutrient Powerhouse

October 30, 2019 • 3 min read
Summary

What are cruciferous vegetables?

Plant foods of the Brassica family like kale and Brussels sprouts provide health benefits like supporting the immune system and reducing risk of heart disease. These well-recognized vegetable superstars, informally referred to as cruciferous vegetables, include a diverse range of commonly eaten vegetables, seeds, and roots. While broccoli may be the most popular cousin of the Brassica family, there are countless other cruciferous options to choose from and exciting reasons to seek them out.

For those who eat with longevity in mind, the members of the Brassica botanical family maintain a front and center presence on many plates.

Health Benefits of Cruciferous Vegetables

These plant foods are highly prized for their nutritional value and even more so for their phytonutrient content. Cruciferous vegetables are high in vitamin C, fiber, folate and other B vitamins, vitamin K, potassium, calcium, and magnesium. They are also rich sources of important phytonutrients including carotenoids, polyphenols, and glucosinolates, which include indole-3-carbinol (I3C) (derived from the breakdown of glucobrassicin found in cruciferous vegetables) and sulforaphane (an isothiocyanate derived from glucoraphanin, a glucosinolate). 

The combination of vitamins, minerals, and health-promoting phytonutrients give cruciferous vegetables (or brassicas) their many health benefits, more of which have yet to be discovered. While research on these plant foods continues, one thing is clear: diets rich in cruciferous vegetables have been associated with decreased risk for chronic disease, as well as other important health benefits.

List of Cruciferous Vegetables 

Members of the Brassica family include:

  • Broccoli
  • Cauliflower
  • Kale
  • Watercress
  • Cabbage
  • Brussels sprouts
  • Bok choy
  • Arugula
  • Collard greens
  • Mustard greens and seeds
  • Turnips
  • Rutabaga
  • Wasabi

Cruciferous Vegetables and Thyroid Concerns

Addressing Hyperthyroidism

While cruciferous vegetables and their phytonutrients have been associated with a multitude of health benefits, there has been a long-standing suspicion that excessive amounts may be contraindicated in cases of hypothyroidism. Goitrin and thiocyanate are both anti-nutrients found in cruciferous vegetables that may reduce iodine absorption in the thyroid, which can potentially result in decreased synthesis of thyroid hormone. However, these compounds are deactivated by light cooking, which is great news for those concerned with the potential “goitrogenic” effect of crucifers. Practitioners may opt to advise those with hypothyroidism to eat mostly cooked crucifers. 

With their wealth of health benefits and wide variety of choices, regularly including brassica vegetables in the diet is a daily habit that is likely to pay off. As more research emerges about the mechanisms for these health benefits, brassicas will continue to be highly prized for their nutritional value, and even more so for their unique phytonutrient content.

Supporting the Immune System

Phytonutrients in brassicas have been found to inhibit inflammation, possibly by regulating epigenetic mechanisms related to the inflammatory cascade. Certain brassica phytonutrients have been shown to down-regulate the expression of NF-κβ to suppress pro-inflammatory molecules like cyclooxygenase 2 (COX-2), inducible nitric oxide synthase (iNOS), and prostaglandins. One phytonutrient in particular, 3,3’-diindolmethane (DIM), a compound derived from I3C, has been found to significantly reduce prostaglandin E2 (PGE2), nitric oxide, and other pro-inflammatory cytokines in animal studies. In other words, these phytonutrients may be interrupting the pro-inflammatory cascade that is a feature of chronic inflammation. These underlying mechanisms are only partially understood, but more studies are underway. 

Supporting Detoxification

Brassicas contain unique phytonutrients called glucosinolates, which are sulfur-containing molecules that exist almost exclusively in cruciferous plant foods. These compounds are converted to bioactive molecules within the body that support glutathione synthesis and up-regulate phase II detoxification enzymes in the body. DIM, indole-3-carbonol, and sulforaphane are examples of compounds derived from glucosinolates found in cruciferous vegetables, and they help to modulate detoxification in the body. Regular consumption of cruciferous vegetables may help to protect people with gene variants, or single nucleotide polymorphisms (SNPs), that affect key detoxification pathways.

Cruciferous Vegetables & Estrogen

DIM and indole-3-carbonol also support the detoxification and elimination of estrogen metabolites, which may be helpful for hormonal balance and protective against estrogen sensitive cancers.

Cruciferous Vegetables and Cancer: Reducing Risk with Antioxidant Activity

Research has long linked a diet rich in cruciferous vegetables with a reduced risk for certain cancers, namely breast, colorectal, lung, and prostate cancers. While their anti-inflammatory benefits certainly play a role in decreasing the risk for these cancers, the ability of these vegetables to support healthy detoxification pathways, via DIM and indole-3-carbonol, may also play a protective role against cancer. Glucosinolates may offer protection against certain cancers by modulating the activity of enzymes that detoxify carcinogens and metabolize sex hormones. 

One example is nuclear factor-2 (Nrf2), a transcription factor that plays a role in regulating inflammation and cancer prevention by up-regulating the genes that encode for antioxidant and detoxification enzymes like superoxide dismutase (SOD) and glutathione transferase (GST). Brassica phytonutrients, especially sulforaphane, support phase II detoxification and increase antioxidant capacity by working through the Nrf2 signaling pathway, which essentially instructs the body to increase its own production of antioxidant and detoxification enzymes. 

Cruciferous Vegetables Support Cardiovascular Health

Observational studies around the world have connected diets high in cruciferous vegetables with decreases in heart disease risk and mortality. The same pathways that support the immune system, and quell inflammation and oxidative stress in the body, such as Nrf2, have also been shown to reduce inflammation in the cardiovascular system. The anti-inflammatory effects of sulforaphane may help to explain the inverse relationships between cruciferous vegetable intake and heart disease risk and mortality. In addition to decreasing oxidative stress and inflammation, diets high in these vegetables may reduce low-density lipoprotein (LDL) cholesterol and protect against LDL oxidation in humans., Pre-clinical studies have found that brassicas may promote optimal platelet function, may have an anti-thrombotic effect, and may prevent atherosclerosis. 

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