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Updated: Apr 24

Phytonutrients are important to study for the CNS exam. Phytonutrients, also called phytochemicals, are compounds produced by plants that provide health benefits to the human body. “Phyto” means plant, and all phytochemicals come from plants. 

These bioactive compounds are produced by plants for their protection against stress and predators. They also provide benefits to humans when we eat them. 

More than 10,000 phytochemicals have been identified. Phytonutrients are fascinating, but as a field, I think we’ve barely scratched the surface of what there is to know about them.  

We are going to take a look at a few that are the most well known and are most likely to be included on the CNS exam. 

And before I dive into what you want to memorize, there are a few things you shouldn’t bother with. 

  1. First - there’s no need to memorize the taxonomy of phytonutrients - it can be helpful to categorize phytonutrients by colors, but trying to memorize the full taxonomy is pointless, especially since there’s no true consensus on how to organize the phytonutrient family tree!

  2. Second - all the different types of polyphenols. I will highlight a few here that I think are worth understanding, but there are so so so many types of polyphenols that it would not be a good use of your time to parse out each type and try to memorize the specific foods. 

Here’s what I think you should know about phytonutrients: 

  • Red foods: lycopene

  • Especially cooked tomatoes, watermelon

  • Lycopene is a type of carotenoid, and in many cases, it becomes more bioavailable when it is heated. So cooked tomatoes will have more lycopene than raw tomatoes.  

  • Orange foods: beta-carotene 

  • Examples: carrots, sweet potatoes 

  • Beta-carotene is a precursor to Vitamin A, and does not have a TUL or risk of toxicity. There is a well known SNP, BCO1, that can influence the body’s ability to convert beta-carotene to active Vitamin A. 

  • Yellow Foods & Green Leafy Vegetables: Lutein & Zeaxanthin

  • Examples: corn, Yukon gold potatoes, kale, parsley

  • Lutein & Zeaxanthin are also types of carotenoids and are fat soluble. 

  • Blue/purple/black foods: anthocyanins and proanthocyanidins

  • Examples: blueberries, pomegranates, eggplant

  • Green tea: contains flavanols, especially known for EGCG

  • Green tea is especially rich in the catechin epigallocatechin-3-gallate, which we call EGCG, and you’ll find the highest concentration in matcha tea powder. 

  • Cruciferous vegetables: sulforaphane

  • Ex: broccoli, cabbage, kale, broccoli sprouts

  • Sulforaphane Facts: what CAN’T this phytochemical do? We could spend 20 minutes on this phytochemical alone, but the primary fact to know is that it is very effective at upregulating and supporting detoxification pathways 

  • Note: sulforaphane is an organosulfur compound. Indoles, such as I3C, which converts to DIM, is also an organosulfur compound, and is also found in cruciferous vegetables. Indoles have anti-estrogenic properties. 

  • Allium family: Sulfides and thiols (also organosulfur compounds) 

  • Examples: onions, garlic, leeks, shallots, scallions

  • Onion Peel & Apples: quercetin

  • Quercetin is best known for its ability to stabilize mast cells, making a great phytonutrient for folks with allergies and histamine intolerance. 

  • Whole Grains: Lignans

  • Ex: flaxseeds, the bran layer of barley, buckwheat, millet, oats, rye

  • Lignans function as phytoestrogens, and are sometimes used for menopausal and postmenopausal symptoms; they’re also being studied for anti-cancer effects

  • Phytoestrogens include isoflavonoids, flavonoids, stilbenoids, and lignans

Honorable Mention!

These two are well known, so hopefully you don’t have to study them, but it’s important to know the following two phytochemicals as well!

  • Curcumin - found in turmeric, further activated by piperine in black pepper

  • Resveratrol - found in grapes and wine

These are the most basic phytochemical facts I would recommend memorizing. We share this and a few additional recommendations and resources in our CNS Prep Course!

Thanks for being here and good luck studying and don't forget to study your phytonutrients for the CNS Exam.


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