Polyphenols and Mental Health

Dr. David Wiss

September 29, 2021

Mental Health

Polyphenols are naturally occurring organic compounds characterized by the presence of multiple units of phenol. A phenol compound is a stable six-carbon benzene ring that can donate an electron to scavenge free radicals, preventing oxidation (hence the term “antioxidant”).

Polyphenolic compounds can have complex and diverse chemical structures, including more specific categories such as tannins and flavonoids. These nutraceuticals offer a wide range of health benefits by reducing inflammatory processes, thereby improving mood and mental health symptoms. This science has become a piece of the emerging “nutrition for mental health” puzzle. It has recently been shown that the transformation of polyphenols in the intestines is in part facilitated by microbiota metabolism [1]. Polyphenols act as fuel for the beneficial bacteria inside of guts. There is a synergistic interaction between the polyphenols and fibers that are abundant in plant foods [2].

The most common polyphenols are tannins, which are found in virtually all families of plants. Dark chocolate, tea, and berries are some of the best-known sources. Herbs and spices (e.g., rosemary, sage, thyme, cumin, cinnamon) can also contain very high amounts of these anti-inflammatory molecules. Flavonoids have also received attention for their antioxidant properties. They are found in foods such as onions, scallions, grapes, and many others. Catechins are part of the flavonoid family and are abundant in green tea, which has several known health benefits (discussed below).

The amount and type of polyphenolic compounds in foods depend on their origin, ripeness, and how they were farmed, transported, stored, and prepared. The antioxidant potential of foods can quickly become compromised. While many aspects of food handling may be outside the average consumer’s control, practices such as buying organic products are beneficial. Research indicates that organic agriculture (particularly fruits) produces slightly higher polyphenol content and antioxidant capacity [3]. Juicing may also be one way to improve the intake of polyphenols, but might be best alongside a high-fiber meal that also has dietary fat. 

Polyphenolic compounds are partly responsible for the hues in plants. Therefore, to consume a wide range of beneficial antioxidants, consuming foods from all different color categories is wise. Think of these colors as Mother Nature’s way of saying, “pick me!

While supplements are indicated in some cases, the ideal situation would be to consume polyphenols in their natural state (i.e., with the food) [4]. Given what we now know about the role of gut microbiota in human health, the case for emphasizing real food is gaining traction. A diet comprised of ultra-processed and packaged foods is generally low in polyphenols, which may explain why individuals with low-quality diets generally have worse mental health, and why the transition to a whole-food plant-forward diet can improve mood. Instead of focusing on cutting out convenience foods, focus on adding anti-inflammatory foods! 

Polyphenols have been proposed as adjunctive treatments in psychiatric and neurodegenerative disorders, and trials are underway [5]. Animal studies have shown that phenolic extracts from parsley produce potent anxiolytic and antidepressant-like effects [6]. Findings contribute to the growing interest in the discipline of “phytomedicine” which appears more popular outside of the US. More funding is needed to advance this field forward, but recent strides are being made with respect to depression

Epigallocatechin gallate (EGCG) is an abundant catechin polyphenol in green tea and has been studied for its neuroprotective effects [7]. The green tea amino acid L-theanine has also been shown to reduce stress and anxiety in people exposed to stressful conditions [8]. Multiple compounds in plant foods work synergistically to confer benefits. For this reason, isolating nutraceuticals and consuming them in the supplemental form will never outperform real food but will be the only way to isolate effects through controlled trials. From clinical experience, we have observed that individuals with lower polyphenolic intakes display higher tendencies for stress eating (comfort food). 

 

How to Eat Anti-Inflammatory

Eating a wide range of fruits, vegetables, whole grains, beans, nuts, seeds, herbs, spices, and teas from a wide range of colors (and organic when possible) is the best way to maximize polyphenolic intake from the diet (known as “foods for mood”). These compounds work at the cellular level and are also involved in microbial processes that lead to the production of metabolites that interact with brain health, as well as reduce inflammation. Consumption of polyphenols in a food matrix that involves dietary fiber might prove to be the next frontier in the “nutrition for mental health” revolution. Wise Mind Nutrition can personalize a program for you to boost your mood and walk you through the steps to include more of these foods daily [9]: 

Fruits

  • Apples

  • Apricots

  • Blackberries

  • Blueberries

  • Cherries

  • Grapes

  • Nectarines

  • Peaches

  • Pomegranate

  • Plums

  • Raspberries

  • Strawberries

Vegetables

  • Artichokes

  • Asparagus

  • Broccoli

  • Carrots

  • Red Lettuce

  • Red Onion

  • Spinach

Grains

  • Oats

  • Rye

Beans

  • Black Beans

  • White Beans

Nuts and Seeds

  • Almonds

  • Cacao

  • Flax Seeds

  • Pecans

  • Walnuts

Fats

  • Olives

  • Olive Oil

Herbs, Spices, and Teas

  • Basil

  • Cinnamon

  • Cloves

  • Cumin

  • Ginger

  • Green Tea

  • Oregano

  • Parsley

  • Peppermint

  • Rosemary

  • Sage

  • Thyme


References

1. Marín L, Miguélez EM, Villar CJ, Lombó F. Bioavailability of Dietary Polyphenols and Gut Microbiota Metabolism: Antimicrobial Properties. Biomed Res Int. 2015;2015:1–18.

2. Loo YT, Howell K, Chan M, Zhang P, Ng K. Modulation of the human gut microbiota by phenolics and phenolic fiber‐rich foods. Compr Rev Food Sci F. 2020;19(4):1268–98.

3. Faller ALK, Fialho E. Polyphenol content and antioxidant capacity in organic and conventional plant foods. J Food Compos Anal. 2010;23(6):561–8.

4. Williamson G. The role of polyphenols in modern nutrition. Nutrition Bulletin. 2017;42(3):226–35.

5. Morris G, Gamage E, Travica N, Berk M, Jacka F, O’Neil A, et al. Polyphenols as adjunctive treatments in psychiatric and neurodegenerative disorders: efficacy, mechanisms of action, and factors influencing inter-individual response. Free Radical Bio Med. 2021;

6. Es-safi I, Mechchate H, Amaghnouje A, Kamaly OMA, Jawhari FZ, Imtara H, et al. The Potential of Parsley Polyphenols and Their Antioxidant Capacity to Help in the Treatment of Depression and Anxiety: An In Vivo Subacute Study. Molecules. 2021;26(7):2009. 7. Khalatbary AR, Khademi E. The green tea polyphenolic catechin epigallocatechin gallate and neuroprotection. Nutr Neurosci. 2018;23(4):1–14.

8. Williams JL, Everett JM, D’Cunha NM, Sergi D, Georgousopoulou EN, Keegan RJ, et al. The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review. Plant Foods Hum Nutrition Dordrecht Neth. 2019;1–12.

9. Pérez-Jiménez J, Neveu V, Vos F, Scalbert A. Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database. Eur J Clin Nutr. 2010;64(S3):S112–20.