Phytonutrients and their health benefits

Phytonutrients and their health benefits

You may have heard people talk about eating blueberries, turmeric, cacao, or another proclaimed ‘superfood’ because it’s good for their health.  But what is in these foods that makes them so healthy?  And what are the health benefits?

Nutrients are substances that we get from our food that keep us alive and help to support the health and functioning of our bodies.  Plant foods, such as fruits and vegetables, are often rich in micronutrients (vitamins and minerals) and provide necessary macronutrients too.  Many are also rich sources of phytonutrients.

What are phytonutrients?

Just like macronutrients is an umbrella term that encompasses carbohydrates, fats and proteins, and micronutrients encompasses the vitamins and minerals, phytonutrients is an umbrella term that encompasses a group of compounds that originate in plants and have a beneficial effect on human health.  You may have heard terms like phytochemicals, polyphenols, or nutraceuticals used in a similar way to phytonutrients.  This blog by Monash Nutrition explains the difference between these terms.  This article will focus on phytonutrients.

Some examples of better-known phytonutrients include curcumin (found in turmeric), quercetin (found in particularly high levels in onions), and resveratrol (found in particularly high levels in grapes).  However, unlike the macro- and micronutrients, the number of compounds that fall under the umbrella of phytonutrients is in the hundreds to thousands.

Currently, the major dietary source of phytonutrients for many people is tea or coffee, due to the regular habitual consumption of these beverages.  But fruits, vegetables, nuts, legumes, cereals, whole grains, herbs, and spices are all good sources of phytonutrients and provide various combinations of phytonutrients in the diet.

Generally, individual types of phytonutrients are found in multiple different foods. For example, catechins are found in tea, cocoa and fruits. Individual foods also contain multiple different phytonutrients. For example, apples contain flavanols, cinnamic acids and quercetin.

Do we have an RDI for them?

While we know that including phytonutrients in the diet has beneficial effects for health, there is currently no recommended daily intake level.

One of the reasons for this is that there are so many individual compounds that fall under the umbrella of phytonutrients.  We also don’t know enough about how all of these individual compounds interact with the human body and carry out their effects to be able to set a target for recommended intake. 

However, food-based dietary guidelines around the world promote regular daily consumption of fruits, vegetables, cereals, wholegrains, nuts, and legumes.  So, while there aren’t specific recommended intake levels of phytonutrients, by following food-based dietary guidelines you would ensure a rich and varied phytonutrient intake.

Snapshot from the Eating and Activity Guidelines for New Zealand Adults showing the recommended intake of phytonutrient-rich foods such as fruits, vegetables, grains, legumes, (nuts) and seeds.

What impact do they have on nutrition and health?

Unlike vitamins and minerals, there are no specific disease conditions linked to an inadequate or deficient intake of phytonutrients.  However, epidemiological evidence shows an inverse relationship between dietary intake of phytonutrients/phytonutrient-rich foods and risk of several major chronic diseases.  This suggests that including more phytonutrients in the diet reduces the risk of certain diseases.

Cardiovascular diseases (diseases of the heart and blood vessels) are a major cause of death and disease globally.  Consumption of flavonols (present in fruits, vegetables, tea, and red wine) and flavanols (from tea and cocoa) in adequate quantities has been linked to beneficial outcomes for cardiovascular disease mortality and biomarkers.  Similarly, intake of coffee and its main phytonutrient, chlorogenic acid, was dose-dependently associated with a reduced risk of type 2 diabetes in a meta-analysis of 28 studies.  Therefore, drinking more coffee, up to about 5 cups a day, may lower the likelihood of developing type 2 diabetes. 

Researchers are also looking into ways that phytonutrients can help with controlling the increase in blood sugar levels after a meal and in reducing levels of oxidative stress in the body, along with other ways that phytonutrients can help to reduce the risk of chronic diseases.

While consumption of phytonutrients from plant-based foods can provide beneficial health effects, it is also important to consider the toxicity of these compounds.  If consumed in high-doses (such as in some dietary supplements) or for prolonged periods, certain phytonutrients can have negative effects such as increasing the risk of cancer.  It is always best to seek advice from a health professional before taking dietary supplements and, where possible, to get your nutrients and phytonutrients from eating whole foods.

Take home message

Phytonutrients are compounds found in plants that are good for our health.  While there is no recommended intake for phytonutrients, preventing their inclusion in sustainable nutrition models, including plenty of them in the diet is beneficial.  The best way to do this is to eat a variety of fresh fruits, vegetables, nuts, legumes, cereals, whole grains, herbs, and spices every day. This is consistent with existing dietary advice for inclusion of high amounts and diversity of healthy plant foods in sustainable healthy diets.

This Thought for Food was written by Margaret Murray, a researcher in human nutrition from Monash University, Australia.

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