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Role of Plant-Based Superfoods in Reducing Inflammation

Plant chemicals (or phytochemicals), which have an effect on human health, are known as ‘plant bioactive compounds’. They are commonly found in the so-called ‘superfoods’ or ‘functional foods’. Plant bioactive compounds are found in various plant-based food sources like fruits, vegetables, legumes (including lentils, peans, and beans), whole grains, nuts, seeds, herbs, and spices. In this article, we explain their role in reducing inflammation with the help of the available scientific literature.

Vegetables are a source of plant bioactive compounds.

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What are plant-based superfoods?

How are plant-bioactive compounds classified, and which plant based superfoods contain specific classes of these compounds?

What is the scientific evidence (from human studies) to prove that plant bioactive compounds or certain plant-based superfoods are effective in reducing inflammation?

What are plant-based superfoods?

Plants contain certain chemicals (known as phytochemicals). Consumption of these can have many beneficial effects on the human body. These plant chemicals, which have a beneficial effect on human health, are known as ‘plant bioactive compounds’. Foods, which contain these plant bioactive compounds, are commonly called ‘superfoods’ or ‘functional foods’. These plant-based superfoods include fruits, vegetables, legumes (including lentils and beans), whole grains, nuts, seeds, herbs, and tea. These plant bioactive compounds, when extracted and used in a medicinal form such as a pill or liquid, are called ‘nutraceuticals’. 

Plant bioactive compounds are found in plant based foods (superfoods) like fruits, vegetables, legumes (lentils, beans, and peas), whole grains, nuts, seeds, herbs, and tea.
Plant bioactive compounds are found in plant based foods (superfoods) like fruits, vegetables, legumes (lentils, beans, and peas), whole grains, nuts, seeds, herbs, and tea.

Hundreds of plant bioactive compounds are known to date. Many have a variety of health benefits like reducing the risk of cancer and cardiovascular diseases. However, here we will discuss only those, on which human studies have been carried out to show that they are effective in reducing body inflammation. They reduce inflammation, mainly by acting as anti-oxidants and reducing the damage caused by free radicals like Reactive Oxygen Species (ROSs).

Before we go into the scientific studies, let us first get an overview of all the classes of plant bioactive compounds and the different plant-based superfoods that contain specific classes of these compounds.

How are plant bioactive compounds classified, and which plant-based superfoods contain specific classes of these compounds?

All plant bioactive compounds are first divided into groups like:

  1. Carotenoids: e.g. β carotene in carrots
  2. Alkaloids: e.g. piperine in black pepper
  3. Organosulphur compounds: e.g. allicin in garlic
  4. Polyphenols, and others.

Polyphenols are further classified like:

  1. Lignans: e.g. SDG in flaxseeds
  2. Stilbenes: e.g. resveratrol in grapes
  3. Flavonoids, and others.

There are 6 groups of flavonoids. These are anthocyanins, flavanols, flavanones, flavones, flavonols, and isoflavones.

Anthocyanins are found in red and purple fruits and vegetables. The color imparted to these fruits and vegetables is due to the anthocyanins. Examples of these fruits and vegetables include berries like strawberries, raspberries, blueberries, and black berries; cherries, grapes, and red cabbage.

Food sources of anthocyanins and anthocyanidins include berries, grapes, and red cabbage.
Anthocyanins are present in food sources like berries, grapes, and red cabbage.

Flavanols are found in red wine, cocoa and chocolate from cacao beans, and black and green tea.

Food sources of flavanols include red wine, cocoa (chocolate) from cocao beans, and black and green tea.
Flavanols are found in red wine, cocoa and chocolate, and tea.

Flavanones are found in citrus fruits like lemon, lime, and orange, and their juices. The content of flavanones is many times higher in the peels or skin of these fruits.

Food sources of flavanones include citrus fruits like lemon, lime, and orange, and their juices
Flavanones are found in citrus fruits.

Flavones are found in celery, parsley, and oregano.

Food sources of flavones include celery, parsley and oregano.
Flavones are found in celery, parsley, and oregano.

Flavonols are found in onions, ginger (gingerol), leafy greens like spinach, broccoli, and asparagus.

Food sources of flavonols include onions, ginger, leafy greens, broccoli, and asparagus.
Flavonols are found in onions, ginger, spinach, broccoli, and asparagus.

Isoflavones are found in turmeric (in the form of curcumin), soy and soy products (like soy milk, tofu, tempeh, and edamame), and other legumes.

Food sources of isoflavones include turmeric, soy and soy products (like soy milk, tofu, tempe, and edamame), and other legumes.
Isoflavones are found in turmeric, soy and soy products, and legumes.

What is the scientific evidence (from human studies) to prove that plant bioactive compounds or certain plant-based superfoods are effective in reducing inflammation?

Lycopene

Lycopene is a carotenoid and is related to other carotenoids like β-carotene. It imparts red color to fruits and vegetables.

Lycopene is found in high amounts in tomatoes but is also found in watermelons, pink grapefruits, pink apricots, and pink guavas (5). Two studies [Riso and colleagues, 2006 and Kim and colleagues, 2011] showed that lycopene can reduce inflammation.

Food sources of lycopene include tomatoes, watermelons, pink grapefruits, pink apricots, and pink guavas
Lycopene is found in tomatoes, water melons, pink grapefruits, pink apricots, and pink guavas.

Astaxanthin

Astaxanthin also belongs to the group of carotenoids and is related to other carotenoids like β-carotene.

It is found in high amounts in marine animals like salmonid, shrimp, and crayfish. The characteristic orange-red color or salmonid flesh is due to astaxanthin. [Boussiba S and colleagues, 2000]. It is also available as supplement. These supplements are prepared from a variety of marine algae. One study [Park and colleagues, 2010] showed that astaxanthin can reduce inflammation.

Food sources of asthaxanthin include salmonids, shrimps, and crayfish
Astaxanthin is found in salmonids, shrimps, and crayfish.

Flavonoid-rich diet

Two studies [Chun and colleagues, 2008 and Landberg and colleagues, 2011] showed that a flavonoid-rich diet reduced inflammation. These studies had a mix of flavonoid-rich foods and did not study any particular flavonoid-rich food.

Anthocyanins

Two studies [Edirisinghe and colleagues, 2011 and Karlsen and colleagues, 2007] evaluated specifically whether the anthocyanin group of flavonoids (from berries and black currants) reduced inflammation. In both the studies, participants had lower inflammation marker levels, suggesting that anthocyanins were effective in reducing inflammation.

Tea

Two studies with black tea [Neyestani and colleagues, 2010 and Steptoe and colleagues, 2007] and two studies with green tea [Basu and colleagues, 2011 and Oyama and colleagues, 2010] showed that tea could reduce inflammation. This shows that black tea is also effective in reducing inflammation.

Cocoa and Chocolate

Three studies [Hamed and colleagues, 2008, Monagas and colleagues, 2009, and Stote and colleagues, 2012] showed that derivatives of cacao beans like cocoa and  chocolate could reduce inflammation.

Olives and Olive Oil

Apart from containing omega 3 fatty acids, olives and their derivatives like extra virgin olive oil are also rich in polyphenols. Two studies showed that olives or their derivatives reduced inflammation [Bitler and colleagues, 2007 and Bogani and colleagues, 2007]. This reduction in inflammation may be due to the combined effect of omega 3 fatty acids and polyphenols.

Plant bioactive compounds with anti-inflammatory and anti-oxidant properties are also available as supplements. Apart from reducing inflammation, there is scientific evidence that certain compounds like polyphenols may be helpful in losing weight.

Prebiotics and probiotics are healthy bacteria that can also help to reduce body inflammation. To read a detailed article on this topic, click here.

Other simple interventions to reduce body inflammation are calorie restriction, and reduced intake of saturated fats and high glycemic index carbohydrates. To read a detailed article on this topic, click here.

Summary

Plant chemicals (or phyto-chemicals), which have a beneficial effect on human health, are known as ‘plant bioactive compounds’. Individual compounds or group of these compounds are often marketed as ‘nutraceuticals’. Plant bioactive compounds are found in various plant based food sources. These food sources are commonly known as ‘superfoods’ or ‘functional foods’. They include fruits, vegetables, legumes (including lentils and beans), whole grains, nuts, seeds, and tea. Many have a variety of health benefits like reducing the risk of cancer and cardiovascular diseases. But, is there evidence (from human studies) to show that they reduce body inflammation? Human studies are available for flavonoids as a group, and for individual compounds like lycopene, asthaxanthin, and anthocyanins. Studies are also available for certain foods like tea, cocao and chocolate, and olives.

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References:

  1. https://www.researchgate.net/publication/221918619_DNA_Damage_Protection_and_Induction_of_Repair_by_Dietary_Phytochemicals_and_Cancer_Prevention_What_Do_We_Know/figures?lo=1
  2. Food sources of flavonoids. https://www.aicr.org/resources/blog/flavonoids-in-your-foods-where-to-get-them/
  3. Anne M. Minihane and colleagues. Low-grade inflammation, diet composition and health: current research evidence and its translation. 2015.
  4. Philip C. Calder and colleagues. Health relevance of the modification of low grade inflammation in ageing (inflammageing) and the role of nutrition. 2017. 
  5. Antioxidants in Food, Vitamins and Supplements

Attributions for images used in this article:

  1. Asparagus
  2. Beans
  3. Berries
  4. Brocolli
  5. Celery
  6. Chocolate
  7. Citrus fruits
  8. Crayfish
  9. Fruits
  10. Ginger
  11. Grapes
  12. Lentils
  13. Nuts
  14. Olives and Olive Oil
  15. Onion
  16. Oregano
  17. Parsley
  18. Pink apricots
  19. Pink grapefruit
  20. Pink guava
  21. Red cabbage
  22. Red wine
  23. Salmon meat
  24. Seeds
  25. Shrimps
  26. Soy and soy milk
  27. Spinach
  28. Tea
  29. Tomatoes
  30. Turmeric
  31. Vegetables
  32. Watermelons
  33. Wheat

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