Nutrient Density Part 1:  Spending Calories Wisely

There are plenty of tools available to the general public that allow you to take better control of your eating habits to help you (depending on your goals) maintain, lose or gain weight. Calories calculators, macro-tracking apps, training routine apps etc. are commonly available and are gaining in popularity as their effectiveness is proven repeatedly by the success of ordinary people in the real world.

However, macronutrients and calories, while hugely important, only make up part of the picture that is total health. The next level of importance encompasses micronutrients such as vitamins, minerals and phytonutrients, which are often under-appreciated by many in the world of bodybuilding (although this trend is definitely changing) and over-esteemed in some “alternative health” circles.

You can (and should) only eat a certain amount of food everyday. This can be considered your “Calorie Budget” and with this budget you consume (buy) foods that provide you with the macro and micronutrients that you need to build a healthy body. Basically you spend your calories buying nutrients and just like a financial budget, you need to learn how to spend wisely: to get the most nutritious bang for your buck... so to speak.

To understand that, we first need to understand what nutrient density means. In its simplest form, the nutrient density of a diet is defined as the crude nutrient intake (in g, mg or μg) per total energy intake (in kcal) {1}. This can be similarly applied to individual foods where more nutrient-dense foods are those that contribute more beneficial nutrients for a given amount of calories to the overall diet {2}.

More nutrients + Less Calories = Higher Nutrient Density

To get a better understanding of how this works, below I’ve included a simple table showing the nutrient content of 100 kcal portions of some common foods. It’s really important to look at food samples with the same caloric value so that we can accurately compare the nutrient content of one food with others. As we mentioned earlier, calories are our nutritional currency so to be good nutrient shoppers we need to look at which foods give us more nutrients for the same caloric price.

The table below is made using values taken from the “USDA Food Database” which is a very useful tool for learning the macro and micronutrient content of a whole host of common foods. I highly recommend checking it out if you’re curious. Additionally I’ve included, in one of the columns, the DRIs (Dietary Reference Intakes) for adult men {3,4} to give a clearer idea of the quantity of each vitamin and mineral needed to (at least) prevent a deficiency.

That’s a lot of numbers, right? Let’s break it down a little.

Each colored column represents the nutrient content a 100 kcal portion of a different food with the name of that food given at the top of each column (along with the portion size in grams). The column on the far left indicates the specific nutrient (macronutrient, vitamin or mineral) and you can follow the row across to each food column to find the corresponding value.

I’ve purposefully put table sugar (red) on one extreme of the table and spinach (green) on the other to show the differences between the two. If you look at the red column, you’ll see that table sugar is virtually devoid of all nutrients (apart from trace quantities of iron and riboflavin). This is to be expected, as table sugar is a highly refined product, it is literally a purified form of one single chemical: sucrose (the chemical name for sugar). On the other end of the scale is spinach, which contains significant amounts of virtually every nutrient listed (Popeye was clearly on to something).

In the middle, we have other foods that, while far superior to sugar, are not at the superstar levels of spinach. Take some time to look over the different nutrient values for each food and take into account the serving size in grams; we’ll come back to that later.

The problem with nutrient density is standardizing a system for measuring it so we can compare other foods. For example some different methods use single nutrient scoring for each food, while others score based on multiple nutrients with a multiple nutrient approach giving a better picture of the food as a whole. Some include beneficial macronutrients like protein and fiber, while others simply focus on vitamins and minerals. Some rate foods according to portion size, others per 100 kcal serving, which in my opinion gives a better means of comparison. Some give more importance to nutrients needed in larger quantities and some even deduct points for the presence of “undesirable” nutrients such as saturated fat or sugar {2,5-8}. As you can see, there are a huge amount of variables to take into account and it’s no surprise that an international standard still hasn’t been adopted.

To further complicate matters there are other factors (besides vitamins and minerals) found in food that potentially offer significant health benefits but, until recently, have rarely been taken into account when comparing the nutritive properties of food. These are generally plant-derived substances such as lycopene (found in tomatoes) or zeaxanthin (egg yolk, orange peppers) which are powerful antioxidants or compounds that have known anti-cancer effects such as glucosinolates (broccoli, cabbage) amongst others. The ORAC score (Oxygen Radical Absorbance Capacity), a measure of the anti-oxidant capacity of food is also often neglected. That said, one system was devised to take into account these other important factors, which is the ANDI (Aggregate Nutrient Density Index) score. However, while this is a step in the right direction, validation of the ANDI score doesn’t seem to exist in the scientific literature, which is a red flag in my book. It also fails to take the protein content of foods into account, which is a major oversight in my opinion. You can find lists of ANDI sores online and it’s worthwhile checking them out to get a better idea of the nutrient density of different foods.

Another important factor that hasn’t been accounted for in many of these systems is the bioavailability of nutrients in different foods. Bioavailability is defined as the proportion of an ingested nutrient in food that is absorbed and utilized through normal metabolic pathways {9} (basically how much of a nutrient your body can absorb). It is generally accepted that the bioavailability of many minerals is significantly higher in animal-derived foods compared to plant-derived foods {10,11} due to the presence of substances such as fiber and phytates in plant foods which actually inhibit mineral absorption. What that means is that even if a plant food is high in a mineral (such as iron in spinach), not all of that mineral is necessarily absorbed during digestion.

Currently, one method for scoring nutrient density which seems to be gaining acceptance in the scientific community is the NRF9.3 index {8}. NRF means Nutrient Rich Foods and “9.3” refers to the nine favorable nutrients taken into accounts (protein, fiber, vitamins A, C & E, Calcium, Iron, Magnesium & Potassium) and three undesirable nutrients (saturated fat, added sugar and sodium).

To better understand this, in the NRF9.3 index, 100 kcal each of:

• spinach gets a score of 695
• tomatoes get a score of 249
• fat-free yogurt gets 75
• lean roast beef gets 33
• 100% wholegrain bread gets 20
• and cheesecake gets... -15 (Yes, that’s right, “NEGATIVE 15”, it is indeed a sad day for us all).

As you can see, this is quite a limited range of nutrients and the reduction of score due to the presence of certain “undesirable” substances may unnecessarily lower the score of otherwise nutrient dense foods. However, the NRF9.3 still offers a good, scientifically validated index for comparing the nutrient density of foods and therefore I will refer to it regularly in this guide.

Thankfully, despite the confusion over which system is best, all systems come to the same conclusion when it comes to the most nutrient dense foods; fresh vegetables, followed by fresh fruits… surprise, surprise!

Fresh vegetables and fruit, in general, provide a much greater amount of nutrients per calorie than any other food group. This is the reason that I encourage my clients to consume as much vegetables as possible without the necessity to track the calories. The calorie content of vegetables (in general) is so low and the nutrient content so high that it makes perfect nutritional sense to not restrict their consumption.

So, that’s it? Just eat more vegetables? Knowing the nutrient density of foods can serve much more important functions in the design of a healthful diet. We’ll discuss just exactly how to do that in Part 2 of this article.

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Bibliography

1. Willett WC. Nutritional epidemiology. New York, NY: Oxford University Press, 1998.
2. Drewnowski A. Concept of a nutritious food: Toward a nutrient density score. American Journal of Clinical Nutrition. 2005. p. 721–32.
3. Institute of Medicine, Food and Nutrition Board. DRI dietary reference intakes: applications in dietary assessment. A report of the Subcommittee on Interpretation and Uses of Dietary Reference Intakes and the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Washington, DC: National Academy Press; 2000
4. Ross a C, Taylor CL, Yaktine AL, Del HB. Dietary Reference Intakes for Calcium and Vitamin D. Nutrition 2011
5. Hansen RG, Wyse BW, Sorenson AW. Nutrition quality index of food. Westport, CT: AVI Publishing Co, 1979.
6. Lachance PA, Fisher MC. Educational and technological innovations required to enhance the selection of desirable nutrients. Clin Nutr 1986; 5:257– 67.
7. Drewnowski A, Fulgoni V III. Nutrient profiling of foods: creating a nutrient-rich food index. Nutr Rev 2008;66:23–39.
8. Fulgoni VL III, Keast DR, Drewnowski A. Development and validation of the Nutrient Rich Foods Index: a tool to measure nutrient density of foods. J Nutr 2009;139:1549–54.
9. Hurrell RF. Bioavailability - a time for reflection. Int J Vitam Nutr Res 2002;72:5–6.
10. Lynch S. Food iron absorption and its importance for the design of food fortification strategies. Nutr Rev 2002;60(7), S3.
11. Gibson RS, Bailey KB, Gibbs M, Ferguson E L. A review of phytate, iron, zinc, and calcium concentrations in plant-based complementary foods used in low-income countries and implications for bioavailability. Food Nutr Bull 2010, 31(2 suppl2), S134-S146.