Nutrient density in my food
In this post I’ve focused on the role of so-called micronutrients in the human body. I’m not going to address the effect of nutrients on our gut microbiota (see my post on the distinction between host and microbiome in the human holobiont).
“There are great variations in the types of nutrients in real food and thousands-fold variations in the amounts in different foods.”
I’m fascinated by what I’ve discovered. There are great variations in the types of nutrients in real food and thousands-fold variations in the amounts in different foods. Quite often the nutrients in certain types of food simply pass through us after we’ve eaten them because of the ways they are bound up in our food. Even when our bodies do take up nutrients, sometimes we can’t use them properly because other nutrients needed for them to work properly aren’t there at the same time.
What are nutrients?
In a nutshell, nutrients are the chemical substances in our food that we need to live and function healthily. There are two types of nutrients. Those that we use in large quantities as fuel for our bodies are called macronutrients. Those that we require in lesser amounts as non-fuel but are equally essential to support our bodily functions are called micronutrients.
Macronutrients consist of proteins, fats, and carbohydrates which I describe in human metabolism. Micronutrients consist of things like vitamins (e.g., vitamin B complex, vitamin C, vitamin D3, vitamin K2), metals (e.g., calcium, iron, magnesium, sodium, zinc), amino acids (e.g., glycine and lysine), other minerals (e.g., phosphorous, sulfur), essential fats (e.g., omega-3 and omega-6) and phytochemicals (e.g., berberine, quercetin, resveratrol).
Micronutrient density
The density of a micronutrient is a measure of how much of it is present in a particular type of food expressed as a proportion of (for example) the calories in or the weight of that food. This can be seen in examples provided below in Figure 1, in which priority micronutrients are expressed as per calorie and per gram. Specifically in Figure 1 (RHS) we can see that to get enough of six priority micronutrients, we would need to consume 7g of liver, or alternatively, more than 4,000g of refined grains [1]. In other words, the authors of that paper show that liver is a denser source of those micronutrients than refined grains.
I’m interested in understanding which types of real food contain lots of certain micronutrients in order to decide how to reduce the supplements I take.
Importance of micronutrients
It is documented that we require approximately 40 essential micronutrients for most metabolic and developmental processes in our body [2]. Of those, six priority micronutrients (iron, zinc, folate, vitamin A, calcium, and vitamin B12) have been identified as causing problems when people do not get enough [1].
People around the world appear to be suffering from a shortage of micronutrients, even in wealthy European and North American countries. These deficiencies can be manifest in obvious ways in the short-term [1], identified, and reversed with adequate supplementation. More insidiously, micronutrient deficiencies can take years to take effect and may only become obvious later in life once chronic diseases are diagnosed [2, 4, 5].
“…bioavailability is a concept that we should be familiar with to identify those natural foods that contain the micronutrients we need and that are available to us versus those foods that contain the same micronutrients but that we cannot absorb from our intestines.”
Micronutrient bioavailability
I touched upon the concept of bioavailability in “Human Metabolism” and stated “Things in our food are considered bioavailable if we can absorb them from our intestine. In other words, they are biologically available to our bodies”.
I pay attention to two types of micronutrient bioavailability, namely the bioavailability for uptake from our food and the bioavailability for use within our bodies once absorbed (taken up).
The first type of bioavailability is important because “the amount of bioavailable nutrients in a food is almost always lower than the amount of nutrients the food contains” [3]. Therefore, bioavailability is a concept that we should be familiar with to identify those natural foods that contain the micronutrients we need and that are available to us versus those foods that contain the same micronutrients but that we cannot absorb from our intestines.
Once absorbed a micronutrient may or may not be available for us to use in our bodies depending on its need for other substances to be present. This is called synergy.
I’ve found three examples that help me to understand the concepts [1,3]. Two of these (chemical form and presence of antinutrients in our food) refer to availability from food and one (synergy) refers to internal availability within our bodies once absorbed from our food:
The chemical form of the nutrient
There are two forms of iron in our food, namely haem and non-haem. Haem iron is found mostly in animal meats and is much more easily absorbed by our bodies than the non-haem iron found in plants
The presence of substances that make the micronutrient we are interested in less available to us – these may be referred to as antinutrients
Phytate is common in nuts, seeds, and grains. It binds to calcium, magnesium, iron, copper, and zinc which makes those micronutrients less available for absorption by us through our intestine
Oxalate is present in plants like rhubarb, tea, spinach, and parsley. Oxalate binds to calcium and may prevent its absorption
Nutrient synergy - the presence of compounds in real food that make the micronutrient we are interested in more internally available to us
I take a daily vitamin D3 supplement because I live in Scotland, a part of the world with especially short daylight in the winter. The supplement I take also contains magnesium and vitamin K2. The magnesium activates the vitamin D3 and the vitamin K2 combined with D3 aids in calcium absorption
“...when I eat real foods containing bioavailable micronutrients, I’m maximizing my chances of good health because of the potential for micronutrient synergy”
Micronutrient Synergy from natural foods
It is estimated that there are approximately 50,000 [6] to 70,000 [1] compounds in natural foodstuffs, most of those in plants. It is also known that animal-sourced foods contain many essential micronutrients and bioactive compounds that are not found in plant-sourced foods [7]. However, we do not how many of them are micronutrients, how many are in synergy with micronutrients, both, or neither.
It has been shown that micronutrient food synergy is associated with healthy metabolism and with chronic diseases when we get things wrong [7]. The way I look at things, when I eat real foods containing bioavailable micronutrients, I’m maximizing my chances of good health because of the potential for micronutrient synergy.
Micronutrient dense real foods
With a good understanding of bioavailability, what might be the best sources of real food for me to eliminate supplements as much as possible? To answer that question I’m relying on a paper written by scientists in America and Switzerland [1].
The authors looked at the bioavailability of six priority micronutrients (iron, zinc, folate, vitamin A, calcium, and vitamin B12) in a range of plant- and animal-sourced foods. They then chose sensitive sections of the human population and calculated how much of those foods would need to be consumed in order to provide an average 1/3 of a recommended daily intake of those micronutrients.
Figure 1: Calories and grams required to provide an average 1/3 of recommended intakes of “priority nutrients”. Taken from reference 1
Figure 1 shows the calories (LHS) and grams (RHS) of each food type required to provide an average 1/3 of the recommended consumption of the priority micronutrients to women of reproductive age. Note that the data in figure 1 are ranked according to intake of calories (LHS).
Women of reproductive age are considered to be an especially sensitive part of the population. The authors found that the results did not differ notably in rank order for other population groups.
Summarising the average data in Figure 1, the authors conclude that foods with very high micronutrient density include organs, small dried fish, dark green leafy vegetables, bivalves, crustaceans, goat, beef, eggs, milk, canned fish with bones, lamb/mutton, and cheese. Most of the categories described are self-explanatory except for dark green leafy vegetables. The authors took data from America, sub-Saharan Africa, south and southeast Asia, and Latin America on vegetables such as spinach, kale, lettuce, Swiss chard, pumpkin leaves, amaranth, cabbage, casava, broccoli, and watercress [1].
“…foods with very high micronutrient density include organs, small dried fish, dark green leafy vegetables, bivalves, crustaceans, goat, beef, eggs, milk, canned fish with bones, lamb/mutton, and cheese.”
Goat milk and pork contained high amounts of micronutrients. Foods of moderate micronutrient density include yogurt, fresh fish, pulses and teff. All other foods included in the analysis were found to be of low micronutrient density.
I wanted to understand how much (rather than the calorie content) of each food type might need to be consumed every day. To make life easy, I took the data for the top 10 foods and ranked them in order of grams of food needed per day (from the RHS of Figure 1; Figure 2).
Figure 2: Weight (g) of food type required to provide an average 1/3 of recommended intakes of “priority micronutrients”. Data from reference 1
Figure 2 shows that liver is the richest source and 7g provides 1/3 of the recommended daily intake. Dark green leafy vegetables are ranked 10th and 239g would need to be eaten.
Overall (average) density is a useful starting place to consider where to get the most essential micronutrients but it doesn’t help us understand if any of these foods might be lacking in certain individual micronutrients. Look at Figure 3 to see the ranking of the top five (I’m trying to keep things manageable) foods based on availability of individual micronutrients.
Figure 3: Overall (average) and individual micronutrient densities for top-five foods. Data from reference 1
Figure 3 shows that bivalves are the only food type to contain at least a moderate amount of all six micronutrients. Other food types in the top five were low in at least one micronutrient, and dark green leafy vegetables were low in two. Therefore, if I rely on organ meats, I might need to be careful about calcium. If I rely on dark green leafy vegetables, I might need to be careful about zinc and Vitamin B12.
Finally, the authors highlight that certain foods (other vegetables, roots, tubers, plantains, nuts, and refined grain products) are low in all of the priority micronutrients.
How I try to get enough micronutrients?
Identify real foods that are a high density source of bioavailable nutrients
Grow vegetables using practices likely to boost micronutrient content
Source other food locally that is grown regeneratively
Prepare foods in a way that preserves their micronutrients
Avoid harm - food from feed lots, fish farms, and mono-crops
Avoid harm – products that are processed
Summary
The bioavailability of micronutrients from real food depends on the food type and their presence in a complex natural food matrix. My research has led me to conclude that no single food type contains all of the micronutrients I need but I am most likely to benefit from an assortment of the most nutrient dense plant- and animal-based food sources.
I still supplement my diet every day with a handful of vitamins, amino acids, metals, and phytochemicals but I have gradually fine-tuned my intake as I’ve understood more about real food. I’ll continue to experiment and learn what’s good for me at this stage in my life.
As always, what works for me may not work for you, and vice versa. Understanding what works for me has taken time, but it is worth it.
References
Beal T, Ortenzi F. Priority Micronutrient Density in Foods. Front Nutr. 2022 Mar 7;9:806566. doi: 10.3389/fnut.2022.806566. Erratum in: Front Nutr. 2022 Apr 25;9:908592. PMID: 35321287; PMCID: PMC8936507
Ames BN. Low micronutrient intake may accelerate the degenerative diseases of aging through allocation of scarce micronutrients by triage. Proc Natl Acad Sci U S A. 2006 Nov 21;103(47):17589-94. doi: 10.1073/pnas.0608757103. Epub 2006 Nov 13. PMID: 17101959; PMCID: PMC1693790
Kresser, C. Nutrient Deficiency: Why most of us are nutrient deficient and what to do about it. https://chriskresser.com/nutrient-deficiency/
Ames BN. Prolonging healthy aging: Longevity vitamins and proteins. Proc Natl Acad Sci U S A. 2018 Oct 23;115(43):10836-10844. doi: 10.1073/pnas.1809045115. Epub 2018 Oct 15. PMID: 30322941; PMCID: PMC6205492.
Beal T, Gardner CD, Herrero M, Iannotti LL, Merbold L, Nordhagen S, Mottet A. Friend or Foe? The Role of Animal-Source Foods in Healthy and Environmentally Sustainable Diets. J Nutr. 2023 Feb;153(2):409-425. doi: 10.1016/j.tjnut.2022.10.016. Epub 2023 Jan 19. PMID: 36894234
Barabási, AL., Menichetti, G. & Loscalzo, J. The unmapped chemical complexity of our diet. Nat Food 1, 33–37 (2020). https://doi.org/10.1038/s43016-019-0005-1
Jacobs DR Jr, Tapsell LC. Food, not nutrients, is the fundamental unit in nutrition. Nutr Rev. 2007 Oct;65(10):439-50. doi: 10.1111/j.1753-4887.2007.tb00269.x. PMID: 17972438