Updated: May 27, 2022
Written by Dietitian Angie,
Medically Reviewed by Dr. Daniela Steyn
Does every food have a function? Yes, every food we eat performs a role in the body, but some foods have more benefits than others. Food contains macro and micronutrients that perform functions in the body. Macronutrients form the bulk of our diets and provide the body with energy, muscle and tissue repair and skin, brain and eye health and organ protection. Our bodies require micronutrients in smaller amounts and are broken down into three categories: vitamins, minerals and phytonutrients. These micronutrients do not provide the body with calories. Still, they have a supportive role in growth and development, immune protection, energy formation and many other critical roles in the body.
Functional foods may be anti-inflammatory or have cardio protective properties, be immune promoting, or crucial in shaping the gut microbiota. Others have antidiabetic, anti-arthritic, neuroprotective, antihypertensive, antimicrobial, antioxidant, anti-cancer, cholesterol-lowering, and hormone metabolic properties. In comparison, others are less beneficial and can even be pro-inflammatory. Bioactive compounds give foods these health-beneficial properties.
Functional foods, nutraceuticals, and bioactive compounds have been of interest for many decades. But they have also caused a lot of confusion for the consumer. I want to attempt to clarify these complex concepts.
When functional foods have been marketed, you may have heard the words "miracle" or "super" foods, but we urge you to be cautious of such claims as no food may be described as such.
Due to a lack of global consensus on meaning, The Bureau of Nutritional Sciences of the Food Directorate of Canada proposes the following definitions (Health Canada):
"A nutraceutical is a product isolated or purified from foods generally sold in medicinal forms not usually associated with food. A nutraceutical demonstrates a physiological benefit or protects against chronic disease."
"A functional food is similar in appearance to, or maybe, a conventional food, is consumed as part of a usual diet, and is demonstrated to have physiological benefits and or reduce the risk of chronic disease beyond basic nutritional functions."
Even though the law does not define functional foods and nutraceuticals, the Food and Drug Administration (all foods and drugs in Canada fall under the FDA) regulates these foods.
What is a bioactive compound?
Bioactive compounds are the parts of functional foods that provide and enhance beneficial health effects to the body when consumed. Simply put, bioactive compounds (also known as phytochemicals or phytonutrients - when specifically coming from plants), are the part of the functional food that makes it functional and gives health benefits to our bodies when we eat them. These compounds also include prebiotics, probiotics, synbiotics (combination of prebiotics and probiotics), and postbiotics (the by-product of a probiotic).
Without these bioactive compounds, the functional food would not have beneficial health effects because the chemical compound targets the mechanisms that prevents and treats disease. There are more than 25 000 phytonutrients found in plants. Fruit and vegetables are rich sources of phytonutrients as well as wholegrains, tea, nuts, seeds, herbs and spices. When this bioactive compound is put into a capsule, pill or powder and consumed as a supplement, it is called a nutraceutical.
Postbiotics are enzymes, peptides, polysaccharides or other such by-products that result after probiotic breakdown or lysis. Their signaling molecules may have cholesterol-lowering, blood pressure-lowering, anti-inflammatory, immunomodulatory, anti-obesogenic effects.
An everyday example that may help you to remember would be a delivery bicycle or motorcycle. A motorcycle/bicycle is for transport and recreation; if we put a delivery box on the back of the bicycle (bioactive compound); the bicycle has additional function to its usual transport or recreational function and may be called a delivery bike (functional food). Without the delivery box, it cannot be called a delivery bicycle, i.e. it loses its additional function. But the delivery box can be sold as a separate item (nutraceutical).
Here are some helpful tips to consider when determining whether a food is functional, which you can use when planning your meals:
Health benefits- the food item should aid in the reduction of diseases and enhance the function of its target.
The nature of the food- it should look like traditional food.
Level of function- it should have benefits over and above its basic nutritional function.
Consumption pattern – it should be part of a regular diet;
Some countries may view functional foods differently depending on what is commonly eaten.
Functional foods may also be modified, i.e. enhanced, enriched or fortified such as orange juice with added calcium, iodized salt or drinks with plant extracts.
Many studies have revealed that increased consumption of plant foods decreases diseases of the heart, Type 2 diabetes and cancers and this is because of the bioactive compounds they possess.
Flavonoids, Carotenoids, Glucosinolates and Isothiocyanates
Bioactive compounds are usually not found in food as a single element but rather as a few phytochemicals, working together to improve health. Eating fruits and vegetables of various colors every day increases your intake of phytonutrients, with darker colors containing a higher amount of phytonutrients.
Flavonoids are the most common polyphenols (or phenolic compounds). There are over 8000 polyphenols; others include curcuminoids, isoflavones, carotenoids and tocopherols, terpenoids (of which carotenoid is a member), triterpenes, phytosterols, peptides, poly unsaturated fatty acids, capsaicinoids, glucosinolates, alkaloids.
Carotenoids are fat-soluble, which means if they are cooked in a little healthy fat, their properties become more available to the body and better absorption occurs.
Bioflavonoids are water-soluble, therefore overcooking or using cooking methods such as boiling will lose those beneficial compounds.
Glucosinolates found in cruciferous vegetables, also known as brassica, give them their Sulphur aroma. They are known for their cancer-fighting properties. Cooking them for too long reduces these compounds; therefore, cooking for short periods or eating raw is a good choice. Steaming for approximately 90 seconds to retain their bright color is a good way to retain their health properties.
Isothiocyanates improve estrogen metabolism and breakdown in the body.
Lycopene is a red phytonutrient that is fat soluble and found in tomatoes and tomato based products, as well as guava and watermelon and pink grapefruit. When tomato is cooked with a little fat it increases absorption rate in the body. This phytonutrient has been shown to decrease the risk of prostate cancer in men.
We can benefit from these numerous health properties of plant-based foods if we aim for nine servings per day, which has been shown to prevent chronic disease11.
Some helpful, practical tips will encourage you to increase your fruit and vegetable choices on the phytonutrient spectrum:
The darker the fruit, vegetable or whole grain color, the higher the phytonutrient content.
Aim to include two of each color every day
Aim for nine servings or three at each mealtime. For example, include greens, mushrooms, and onions with an omelet. Add a salad and seeds at lunch and a vegetable stir-fry at dinner.
One serving is the equivalent of ½ cup of cooked or 1 cup of raw vegetable or a medium-sized piece of fruit (approximately the size of a tennis ball).
When cooked, the antioxidant levels increase in the following foods: spinach, carrots, broccoli, cabbage, red cabbage, green and red peppers, potatoes, tomatoes, mushrooms and asparagus.
Peeling and soaking fruit and vegetables in water leads to a decrease in antioxidant and nutrient content.
Introduce a new color and one more serving than you currently have each week until you reach your goal of nine daily servings.
Prepare a fruit and vegetable smoothie to incorporate these foods into your diet.
Make a vegetable stir-fry with a variety of vegetables.
Add cilantro, basil, chives or other herbs to salads and sandwiches.
Frozen fruit and vegetables are good to keep in your freezer; in particular, frozen berries retain their phytonutrients. Cruciferous vegetables like broccoli are not suitable to freeze; instead, use fresh.
Keeping fruit and vegetables visible in a bowl on a countertop can help to increase your intake.
Add ginger and spices to tea and cooking to benefit from their many health properties.
The table below shows some examples of bioactive compounds, their role functions in the body and examples of foods that contain them.
Homayouni et al.(2020). Postbiotics as novel health-promoting ingredients in functional foods.
Kris-Etherton et al.(2002). Bioactive compounds in foods: their role in the prevention of cardiovascular disease and cancer. AM J Med 113 Suppl 9B:71S-88S.
Martirosyan et al.(2018) Bioactive Compounds: The Key to Functional Foods. Bioactive Compounds in Health and Disease 8(7):36-39
Peng et al. (2020). Effectiveness of probiotics, prebiotics, and prebiotic-like components in common functional foods.
Pillai et al. (2021) Bioactive Compounds in Health and Disease 4(3): 24-39.
Tupas et al. (2020). Functional Foods and Health Benefits.
The Institute of Functional Medicine. www.ifm.org