With MacroFactor radically expanding its micronutrient analytics, we thought this would be an opportune time to discuss micronutrients: what they are, what micronutrient targets represent, and considerations for tracking micronutrient intake.
This is part one of a five-part series:
1) Understanding Micronutrient and Essential Nutrient Categories
2) Understanding Nutrient Targets
3) Considerations for Micronutrient Tracking: Precision and Difficulty
4) Which Micronutrients Are Worth Monitoring?
5) Micronutrients are Important, But They Aren’t Everything
Our Knowledge Base also has an archive of additional information about each nutrient you can track in MacroFactor, including what the nutrient actually does, the likelihood of insufficient or excessive intake, and good food sources for each nutrient.
With that out of the way, let’s dive in!
What are Micronutrients?
Micronutrients are elements, chemicals, or substances that are needed for healthy growth and development. But, as the “micro-” prefix implies, micronutrients are substances you don’t need to consume in large quantities. Whereas you’d generally consume dozens or hundreds of grams of each macronutrient (carbohydrates, fats, and proteins) each day, intake requirements for micronutrients are generally measured in milligrams or micrograms.
Most micronutrients are classified as either vitamins or minerals. Vitamins are organic molecules that either can’t be synthesized by the body (like Vitamin C), or can’t be synthesized in sufficient quantities for optimal health (like niacin). Minerals are inorganic elements the body needs from external sources, like calcium, iron, and magnesium.
Vitamins can be further subdivided into water-soluble and lipid-soluble vitamins. Water-soluble vitamins can typically be easily absorbed and readily excreted. Fat-soluble vitamins, on the other hand, are typically absorbed better when consumed along with some dietary fat, and they can typically be stored in the body’s tissues. So, if you consumed a lot of a water-soluble vitamin today, like vitamin C, your vitamin C levels won’t stay elevated for weeks into the future. However, a large dose of a fat-soluble vitamin (like vitamin D) might have effects for weeks (or even months) after consumption.
There are nine water-soluble vitamins:
- Thiamin (vitamin B1)
- Riboflavin (vitamin B2)
- Niacin/Nicotinic Acid (vitamin B3)
- Pantothenic Acid (vitamin B5)
- Vitamin B6 (pyridoxal, pyridoxine, and pyridoxamine)
- Biotin (vitamin B7)
- Folate/Folic Acid (vitamin B9)
- Vitamin B12 (various cobalamins)
- Vitamin C (ascorbic acid).
All water-soluble vitamins primarily function as important coenzymes, cofactors, or biological precursors to coenzymes or cofactors (substances that make it significantly easier for specific chemical reactions to occur). For example, vitamin C facilitates important chemical reactions involved in building collagen proteins.
There are four fat-soluble vitamins:
- Vitamin A (various retin- compounds, along with provitamin carotenoids)
- Vitamin D (various calciferols)
- Vitamin E (various tocopherols and tocotrienols)
- Vitamin K (various phylloquinones and menaquinones).
Unlike the water-soluble vitamins (which are all cofactors or coenzymes), it’s impossible to broadly classify the function of the fat-soluble vitamins. For example, Vitamin K is broadly similar to the water-soluble vitamins – it primarily functions as a cofactor, and it doesn’t readily accumulate in your body. Vitamin D, on the other hand, is a steroid hormone that can influence gene expression in any cell type with nuclear Vitamin D receptors. Vitamin E primarily functions as an antioxidant, while also regulating an enzyme that influences smooth muscle development.
Minerals are a bit trickier to classify than vitamins. Minerals are inorganic elements, rather than organic compounds. We generally consider “minerals” to be elements that are essential for normal health and development, excluding the four major elements found in most organic compounds: carbon, hydrogen, oxygen, and nitrogen.
Of the remaining elements, we know that some are essential for good health (for example, calcium and magnesium), but there’s scientific debate about others (for example, the USDA considered chromium to be an essential element, whereas the EFSA does not). Furthermore, the body seems to be adept at handling even more elements (for example, lithium and boron) in a way that suggests that they may have important biological functions, despite no critical function being identified yet.
So, we know there are at least 15 elements that are essential for human health
Of those 15, only 14 are generally considered to be “minerals.” Cobalt is incorporated into vitamin B12 (which is an essential vitamin), but there are no known (human) functions of elemental cobalt.
As previously mentioned, there’s not yet a scientific consensus about whether chromium is an essential element – it would be considered a mineral by health authorities in the US, but not in Europe.
Furthermore, there are circumstantial reasons to believe that lithium, boron, fluorine, silicon, vanadium, nickel, bromine, and strontium may be essential elements (in which case, they’d be classified as “minerals”). Basically, your body has tidy ways of handling and excreting these elements, which is generally the case for elements that serve important biological functions, but not for elements that don’t serve important biological functions.
However, specific critical purposes for these elements have not been identified in humans, so it’s possible that these elements were critical for one of our distant ancestors, and that the biological pathways associated with handling these elements have simply been preserved to the present day, despite these elements no longer playing important roles in human health and development. It’s also possible that the body can efficiently handle these elements because they’re chemically similar to other elements the body regularly works with – for example, lithium is in the same column of the periodic table as sodium and potassium, and strontium is in the same column as magnesium and calcium.
So, we don’t actually have a tidy list of elements that should be classified as minerals. There are 14 sure bets, with another 9 “maybes.”
Much like fat-soluble vitamins, minerals serve a variety of different purposes. For example, calcium is necessary for bone health, and is also critical for allowing muscles to contract. Sodium and potassium are necessary for maintaining a bioelectrical potential across the membranes of nerve and skeletal muscle cells. Chlorine is critical for digestion, as a necessary component of stomach acid. Iron is an important component of hemoglobin and myoglobin, which your body uses to transport oxygen. Many other minerals function as cofactors for various chemical reactions.
Other essential nutrients
While vitamins and minerals get most of the attention, there are several other nutrients that play vital roles in health and development.
Essential fatty acids are types of fat that are necessary for optimal health and normal physical functioning, but that the body can’t manufacture. In that way, they’re functionally similar to vitamins. These essential fatty acids are classified as omega-3 (EPA, DHA, and ALA) and omega-6 (linoleic acid) fatty acids. They have a wide array of functions in the body, but are primarily implicated in regulating and influencing pro- and anti-inflammatory processes.
Essential amino acids are amino acids (building blocks of proteins) that the body can’t produce on its own, meaning they need to be consumed from food sources. Of the 20 amino acids used to build proteins in the body, 9 are considered essential:
Furthermore, six other amino acids are considered conditionally essential – the body can usually synthesize these amino acids in sufficient quantities, but there are situations where it may not be able to (for example, due to advanced age or certain liver conditions). The conditionally essential amino acids are:
Insufficient intake of essential amino acids will prevent your body from being able to build or repair certain proteins. For example, rice protein is very low in lysine, so lysine deficiencies are reasonably common in parts of the world that rely almost exclusively on rice to meet people’s energy needs. Lysine is necessary for collagen synthesis, so a lysine deficiency can lead to connective tissue disorders. Lysine is also used to create proteins that are necessary for fatty acid metabolism, so a lysine deficiency can lead to liver damage.
Essential fatty acids and amino acids must be consumed via diet because the body isn’t capable of synthesizing them. However, there are a few other molecules that the body can synthesize, but which it may not synthesize in sufficient quantities for optimal health.
Choline: the “other” essential nutrient
Choline exists in a state of limbo. It’s basically a vitamin, though medical and scientific organizations haven’t classified it as such. Your body can produce choline in the liver, but it doesn’t produce enough for optimal health (much like niacin). So, despite not fitting neatly into any of the other “essential nutrient” categories (vitamins, minerals, essential fatty acids, essential amino acids), choline is still considered an essential nutrient.
Choline is required to produce two different phospholipids that help preserve the structural integrity of cell membranes. Choline is also the core component of acetylcholine – one of the most abundant neurotransmitters.
Other nutrients that may be “conditionally essential”
Essential nutrients (like vitamins, minerals, essential amino acids, and essential fatty acids) are nutrients the body either can’t produce on its own, or nutrients that the body can’t produce in adequate quantities for optimal health. However, that’s a hazy boundary. As seen previously, some amino acids are “conditionally essential,” meaning that the body can generally produce those amino acids in sufficient quantities for optimal health, but that it can’t always produce those amino acids in sufficient quantities for optimal health.
With that in mind, there are other nutrients that may be conditionally essential – your body can produce these nutrients, but may not always produce them in sufficient quantities for optimal health.
Choline used to fall under this umbrella, until it was re-classified as an essential nutrient in 1998.
Creatine and carnitine are two nutrients that fall under this umbrella today. Both serve important purposes in the body (creatine helps maintain cells’ energy supply, and carnitine helps with fatty acid metabolism), both can be produced by the body, but the body may not always produce sufficient quantities of both of these nutrients for optimal health.
For example, low creatine intake is associated with an elevated risk of depression. Furthermore, early data suggest that creatine supplementation may help alleviate depressive symptoms (which would further suggest that the association between creatine intake and depression is indicative of a causal link, rather than being a mere association). However, most people with low creatine intake don’t exhibit depressive symptoms, thus suggesting that creatine may be a conditionally essential nutrient. For even more arguments in favor of creatine being considered a conditionally essential nutrient, you may enjoy a 2022 review from Ostojic and Forbes.
Carnitine is already firmly “conditionally essential,” but only in very specific situations. For example, some kidney diseases increase carnitine excretion, so people with those specific kidney diseases need to take supplemental carnitine. However, an argument could be made that carnitine is also conditionally essential for individuals with conditions (like metabolic syndrome and type 2 diabetes) that cause mitochondrial dysfunction. Multiple meta-analyses have found that carnitine supplementation can help improve insulin resistance and blood glucose regulation in individuals with obesity, type 2 diabetes, and insulin resistance. So, it’s possible that these individuals don’t produce enough carnitine for optimal health, and carnitine may eventually be classified as conditionally essential within those populations.
To be clear, this isn’t an exhaustive list, and I’m also not claiming that creatine and carnitine have been misclassified by the scientific bodies that designate nutrients to be essential or conditionally essential. I’m merely noting that micronutrient research is still an active concern, and the list of nutrients considered to be essential or conditionally essential can change over time. As mentioned previously, the US and Europe currently disagree about how to classify chromium. Furthermore, choline was only added to the list of essential nutrients in 1998. So, it’s entirely possible that other nutrients will be added to these lists over time.
The next article in this series will discuss nutrient targets: where they come from, what they mean, and how to think about them.