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We eat food because we enjoy it, but also because our bodies need the nutrients within foods to survive and

thrive. Nutri on is the scien fi c study of food and nutrients and their eff ects on body structure, func on and health.

It is a complex science to study because we do not consume nutrients alone; we consume them in the combina ons

provided through the foods we eat. This food provides us with nutrients that fall into six categories: water, carbohy-

drates, lipids, proteins, vitamins and minerals. Each nutrient category has an important role in the body and this textbook

dedicates a chapter to each. We will also explore how our diges ve tract separates these nutrients from each other

into forms that can be absorbed, transported and used in the body. Further, we will explore some key nutri on-related

concepts such as energy metabolism, energy balance and nutri on for physical ac vity. This examina on will be done

primarily with a Western science lens. However, most chapters will also off er an Indigenous lens to complement our

understanding of food and nutri on. This chapter provides the fundamental concepts that will guide our more in-depth

explora on of nutri on in the rest of the textbook.

By the end of this chapter, you will be able to:

• Defi ne the terms nutri on, diet, nutrient, essen al nutrient and phytochemical.

• Diff eren ate between processed and whole foods.

• Describe the use of food addi ves as well as organic and gene cally modifi ed foods.

• Explain the scien fi c study of nutri on, including its strengths and limita ons.

• Cri cally evaluate nutri on sources.

We are all on a diet, as this term refers to the total food that a person regularly eats. Since there is a diversity of

diets, there is also diversity in the types of food and nutrients we consume. Nutrients are substances obtained from food

that are used for the maintenance, growth and survival of an organism. Some of these nutrients are essen al, meaning

that the body cannot make them itself and that they must be obtained from the diet. For example, essen al amino acids,

essen al fa y acids, vitamins, minerals and water are all essen al nutrients. Other nutrients have important roles in the

body and can help us thrive, but they are not absolutely required from the diet for growth and survival.

Recall that there are six categories of nutrients: water, carbohydrates, lipids, proteins, vitamins and minerals.

Some of these categories comprise several diff erent types of nutrients. For example, sugars, starches and fi bre are all

carbohydrates, while fa y acids, sterols and phospholipids are all lipids. Nutrients are grouped into categories based

on their structural or func onal similari es. Figure 1.1 shows, for instance, how all carbohydrates have a similar basic

structure.Figure 1.1: The similar molecular structure of diff erent types of carbohydrates.

Carbohydrates, lipids, protein and vitamins are organic nutrients, meaning that they are made of carbon chains.

Conversely, water and minerals are inorganic because they do not contain carbon.

Nutrients can further be divided into macronutrients and micronutrients. Macronutrients are found in higher

propor ons in the body and are required in larger quan es from the diet. Micronutrients are found in much smaller

quan es in the body and are required in smaller amounts from the diet. The amount of a nutrient required does not

necessarily dictate how important it is. Defi ciency of both macronutrients and micronutrients can have nega ve effon health.

 ects

While an understanding of nutrients is key, remember that nutrients are not food. Food contains nutrients, but

the health eff ects of a food or diet cannot always be predicted by knowing its nutrient content. This is an example of

nutri onism – a term that describes why reducing the eff ects of foods to the sum of their parts can be problema c. For

example, whether a food has carbohydrates in it alone does not tell us whether it is healthy or not. Understanding nu-

tri on also requires an understanding of how nutrients and other substances in food interact with each other, as well as

how the eff ects of nutrients diff er between people.

Food and drink can also provide us with substances that are not classifi ed as nutrients. Phytochemicals, alcohol,

caff eine and toxins are naturally found in some of the foods and beverages we consume. They are some mes referred to

as non-nutrients because they are not required for the growth and survival of the organism but are nonetheless found in

food. With respect to our health, these non-nutrients may have posi ve eff ects (phytochemicals), nega ve eff ects (alco-

hol, toxins), or both (caff eine). Phytochemicals and toxins are explored below, while the psychoac ve drugs caff eine and

alcohol are explored in Chapter 4.Phytochemicals, or plant chemicals, are non-nutrients found in plants that may have posi ve health eff ects. For

instance, they are believed to be partly responsible for the reduced risk of cardiovascular disease and cancer in those

who consume higher amounts of fruits and vegetables (Alissa & Ferns, 2017; Riboli & Norat, 2003). In addi on to fruits

and vegetables, phytochemicals are found in whole grains, beans, legumes, nuts and spices. Plants make phytochemicals

to promote their growth and reproduc on (Molyneux et al., 2007). The more environmental stressors that a plant has,

the more phytochemicals it tends to produce (Chalker-Sco , 1999). The main categories of phytochemicals are fl avonoids

and carotenoids. They are responsible for the bright colours found in fruits and vegetables (Figure 1.2).

Flavonoids tend to promote a bright blue, red or dark colour pigmenta on in plants. They are abundant in

parsley, blueberries, black tea, citrus fruits, wine and cocoa. They have an -infl ammatory, an -tumour and an oxidant

eff ects (Panche et al., 2016).

Carotenoids contribute to the yellow, orange and red colours

Figure 1.2: Phytochemicals help give fruits

and vegetables their vibrant colours.

found in plants such as pumpkins, sweet potatoes, carrots and squash.

Like fl avonoids, they have an oxidant eff ects. They can also be used to

synthesize vitamin A in the body and are accordingly associated with eye

health. They have further been shown to have posi ve eff ects on the

cardiovascular system as well as on cogni ve func on (Eggersdorfer &

Wyss, 2018).

To date, tens of thousands of known phytochemicals have been

iden fi ed. Since research is s ll ongoing and the eff ects of phytochemical

supplementa on remain unclear, there are no health claims that have

been approved by Health Canada for individual fl avonoids. However, a

diet that favours a wide range of plants of varying colours can provide a

variety of phytochemicals.

Toxins are naturally occurring substances found in plants and animals that can have harmful eff ects on the

body. Organisms make toxins as part of their metabolism or as a defence against predators. Many foods contain toxins;

they are mostly unavoidable. This is typically not a cause for concern, however, because adverse eff ects from toxins are

rela vely low (Dolan et al., 2010). As Paracelsus, the 16th century father of toxicology famously said, “It is the dose that

makes the poison.” Indeed, almost anything, including water, can be toxic if it is consumed in excessive amounts.

It is important that toxins are consumed in low enough amounts that they do not become a poison. That is why

organiza ons including Health Canada and the US Food and Drug Administra on limit the amount of toxins allowable in

food. The World Health Organiza on (WHO) further recommends several strategies we can use to limit the risk from food

toxins. These include discarding old, mouldy, bruised, damaged or discoloured food or food that does not smell fresh or

has an unusual taste (World Health Organiza on, 2018b). Since mushrooms and other wild plants can produce potent

toxins, they further recommended only consuming those that are non-poisonous, such as those sold at the grocery store.