Nutrient density - what is it?
Nutrient-dense is a term often used to describe the kind of foods we are encouraged to eat more of. What does it mean? How can you tell if a food is nutrient dense? What about energy density?
Nutrient density and energy density are two hugely important, but fairly straightforward concepts.
A food that is nutrient-dense is high in nutrients (vitamins, minerals, high-fibre carbohydrates, lean protein, and/or healthy fats) but relatively low in energy (kilojoules) per gram. There are a few exceptions - for example, nutrient-dense foods high in "healthy fats" such as nuts, seeds, avocado and oily fish are also high in energy. But as far as the big picture goes, nutrient-dense foods give you a lot of nutritional "bang for your buck". The more nutrient-dense foods we eat, the more likely we are to meet our nutritional requirements - that is, to obtain all the vitamins, minerals, trace elements and other beneficial compounds we need.
Energy density is a measurement of the amount of energy (kilojoules) per gram of a food. Energy-dense foods provide a lot of energy for a relatively small weight of food, often in the form of added fats and sugars. The more energy-dense foods we eat, the more likely we are to consume more energy than we require, and any excess energy will be stored in our body for later. Regular consumption of energy-dense foods can also lead to fewer opportunities to consume the more nutrient-dense foods we need, and result in nutritional deficiencies.
It's when we look at the relation between nutrient density and energy density that things get really interesting. Aside from the few exceptions discussed above, nutrient-dense foods are generally low in energy density. This is often due to having a high water content (some fruits and vegetables, reduced fat milk and yoghurt), a high fibre content (wholegrains, legumes), or both (many fruits and vegetables).
So, how can you tell if a food is nutrient-dense?
As a general rule, whole foods that have undergone no or minimal processing are likely to be both nutrient-dense and lower in energy. Fruits, vegetables, wholegrains, many dairy products, lean meats, fish, poultry, legumes, nuts and seeds (and dishes made with these ingredients).
How about energy-dense foods?
These are usually foods that have undergone more processing, and are often high in fat and sugar, and low in fibre and/or water. Cakes, biscuits, pastries, many desserts, takeaways, fried foods, chips, sweets, sugar-sweetened drinks, alcoholic beverages, mayonnaise, butter are some examples.
Here is a great illustration of energy density and nutrient density at work:
Both of these desserts contain the same amount of energy (kilojoules), but kilojoules per gram (energy density) is very different.
On the left, mixed berries, low fat plain yoghurt and a sprinkle of toasted cereal, for a total weight of 300 grams. On the right, strawberries and cream, and a total weight of 140 grams.
As for nutrient density, as the dessert on the left contains a greater variety and amount of berries, therefore more nutrients; and the low fat yoghurt and cereal provide additional protein, calcium, vitamins, minerals, and fibre.
So how does this translate to everyday eating?
The Ministry of Health "Healthy Eating Active Living" pamphlet, and the Heart Foundation "Healthy Heart" visual guide are both excellent resources to point you towards nutrient-dense foods that are also low in energy density.
British Nutrition Foundation. (2016). What is energy density? [Website]. Retrieved November 20, 2018, from https://www.nutrition.org.uk/healthyliving/fuller/what-is-energy-density.html?limitstart=0
Heart Foundation. (n.d.). Healthy heart visual guide. [PDF]. Retrieved November 20, 2018, from https://www.heartfoundation.org.nz/shop/nutrition/docs/healthy-heart-visual-food-guide-a4-2016.pdf
Ministry of Health. (2015). Healthy eating active living. [PDF]. Retrieved November 20, 2018, from https://www.healthed.govt.nz/system/files/resource-files/HE1518_Healthy%20Eating%2C%20Active%20Living.pdf