Micronutrients are nutrients that are required in relatively miniscule amounts. Unlike macronutrients, micronutrients provide no energy (calories). Yet without each of the micronutrients, we would be completely incapable of functioning or even using the energy the macros provide. In short, we’d be dead.
The micros can be divided into two categories: vitamins and minerals.
Each of the vitamins and minerals plays an array of life-sustaining roles throughout our bodies. These roles were typically discovered by studying animals with specific known deficiencies or by studying people with a specific set of symptoms and determining that these symptoms were all relieved by replenishing a certain chemical. For example, vitamin C was discovered when British sailors in the 18th century who were deprived of fresh fruits and vegetables during long ocean voyages developed the condition called “scurvy,” and were cured by being given citrus fruits like limes, hence the nickname, limeys. Beri beri—thiamine (Vitamin B1) deficiency—and pellagra—niacin (vitamin B3) deficiency—were similarly discovered when groups of people whose circumstances severely limited their access to certain foods resulted in bizarre symptoms. In the U.S. today, most residents get enough of most of the vitamins and minerals they need from food or at least have relatively easy access to foods that supply those nutrients—with the possible exception of vitamin D, vitamin B12, calcium, and iron for certain people due to age or dietary choice. And at least one of the minerals, sodium, is frequently overconsumed. I will discuss these exceptions in the tables below.
What I will not discuss is how much of each vitamin and mineral we need, the serving sizes of foods we would need to eat to get those amounts, and whether we (meaning you) should consider taking a supplement of certain vitamins or minerals. Why? For several reasons. First, as I said, with rare exceptions, eating a healthy, balanced diet that maintains our weight provides the vitamins and minerals in the correct amounts we need: I mention those exceptions in the tables below. Second, as humans, we tend to think that if a little is good, a lot must be better, but for the micronutrients, this has so far not been proven true, and excessive amounts of some can be dangerous. Nevertheless, the mainstream media and some nutrition and fitness gurus like to preach the saving power of mega-amounts of their various pet micronutrients (an interesting coincidence that these “pet micronutrients” just happen to be the same ones those nutrition and fitness gurus tend to be selling…hmm?) . As a result, we have become overly focused on individual micronutrients, when in fact these nutrients must all balance each other and work together.
Vitamins
Humans require some 13 vitamins, of varying complexity: vitamins A, C, D , E, K, B1 (thiamin), B2 (riboflavin), B3 (niacin), pantothenic acid (sometimes called B5), B6 (pyridoxine), Biotin (occasionally called B7), folate (occasionally referred to as B9), and B12 (cobalamin). Vitamins are small but fairly complex organic molecules (meaning that they are derived from living things, although some are now synthesized in labs).
Vitamins can be divided into two categories—fat-soluble and water-soluble—based on whether they dissolve only in fats or in watery media like blood, which governs how they are absorbed, transported throughout the body, stored, and excreted.
A couple of critical things are worth remembering about the difference between water- and fat-soluble vitamins.
Our bodies don’t store the water-soluble vitamins. Any excess amounts of the water-soluble vitamins you take (in excess of the body’s needs) are quickly excreted in urine. This is why you might have heard that taking mega-amounts of vitamin C and the Bs just gives you very expensive pee and also why you need to ensure you ingest foods rich in the water-soluble vitamins regularly—because your body can’t store them, it keeps getting rid of the excess!
Fat soluble vitamins can be stored in body fat; this is why people who consume very large amounts of carrots, which are rich in the plant form of vitamin A, Beta carotene, may notice that the palms of their hands might turn orange, due to the unattractive accumulation of the beta-carotene in the little palmar fat pads. But while overconsuming beta-carotene is probably not dangerous, consuming excessive amounts of vitamin A from animal sources, called retinoic acid, is not only unsafe, it can even be lethal! Retinoic acid is an extremely powerful chemical. Miniscule amounts of retinoic acid are used as a prescription medication (for example to treat severe acne) but it is so toxic to fetal development that women of child-bearing age who take retinoic acid to treat their acne must sign a waiver that they are using a 100-percent effective form of contraception. And as arctic explorers discovered in the 1800s, as little as an ounce of polar bear liver can cause death, and walrus and seal liver have also caused human fatalities. Although the reason why arctic mammals accumulate such large amounts of retinoic acid in their livers isn’t known for sure, one theory is that they absorb and store the retinoic acid from the large amounts of marine algae they eat and that this storage protects them in some way.
A few additional things about vitamins are important to note.
- A number of the water-soluble vitamins play similar or coordinating roles—those seemingly repetitive descriptions in the table below are not misprints or oversights.
- Most vitamins are active in every cell, tissue, and organ in the body, but a deficiency may be noticed only in particular kinds of cells or tissues. Certain types of cells, for example the ones that form skin, hair, and the lining of the digestive tract, have very short lives: they turn over and need to be replaced very quickly. But if we are malnourished, that replacement can suffer. For that reason, those are the areas likely to show the quickest effects of a deficiency.
- Certain diseases or medical conditions (and even the drugs used to treat them!) can increase or decrease the need for specific vitamins—and vice versa. There can be a number of reasons for this, too many to cover here, but I will mention a couple of important examples. Note: if you have a disease or medical condition that was diagnosed by your primary care physician (PCP) and you’re taking any medications, even over-the counter medications or vitamin/mineral supplements, you should always let the PCP know about them all. You should also discuss any supplements you’re considering taking with the PCP. And even if you’re healthy, when the nurse or PA or med tech asks if you’re taking any medications, tell them about any supplements you’re taking as well!!! The examples below might help you understand just how dangerous it is for a person to attempt to control conditions they might have on their own without medical supervision:
- A disease or condition that impairs digestion and absorption of nutrients (like celiac disease, Crohn’s disease, ulcerative colitis, removal of part of the stomach or intestines, or even normal aging) can increase the need for certain vitamins. Two prime examples are the decrease in our ability to absorb vitamin B12 as we age; and a reduction in the ability of the small intestines to absorb folate, vitamin B12, all of the fat-soluble vitamins, and the minerals, iron and calcium, in patients suffering from celiac disease. If you have a disease or condition that your doctor has told you affects micronutrient absorption, you need to work with a nutritionist who specializes in working with people with your condition.
- Some medications can interfere with the absorption of particular vitamins from the digestive tract. If your doctor prescribes one of these drugs, s/he should discuss with you dietary changes that will enable you to consume more of those vitamins that you’ll need to take. Several medications are taken in a form that is not actually active in the body until they undergo a chemical modification; since these modifications are made by enzymes that require a certain vitamin, taking the drug increases your requirement for that vitamin. .
- The anti-seizure medication, phenytoin (Dilantin), has a very complex relationship with the vitamin folate (the form of folic acid in the body). Dilantin lowers the levels of folate in the blood. However, if a person who is taking Dilantin for seizures takes a folic acid supplement to replenish those low folate levels (as a woman would need to do if she could get, or is, pregnant, because of the demonstrated importance of folic acid for nervous system development), the supplement can inactivate the Dilantin she is taking, resulting in seizures (so women with seizures who want to get pregnant must work with their doctors to carefully manage medications and folate status). No one should attempt to perform this “balancing act” on their own – they need to rely on the advice of a professional.
- Alcohol use disorder also can result in deficiencies of some vitamins, partly because the enzymes that digest alcohol in the body require and use up those vitamins.
- Our bodies are constantly undergoing little internal wounds and bruises, whether we realize it or not. So, the ability to form blood clots when these wounds occur is a requirement for survival. But some people are at risk for developing excessive numbers of blood clots, which can lead to strokes and other dangerous conditions. These people are treated with a prescription medication that prevents clot formation, commonly called a blood thinner. Vitamin K is a required component in the normal blood clotting process. And because of that, it actually prevents one particular blood thinner, Coumadin, from working. Thus, people who take this drug must ensure they consume the same amounts of vitamin K-containing foods on most days: Too much vitamin K and they can start to form clots, too little and uncontrolled bleeding could result.
Again, if you are taking medications regularly, it’s imperative that you inform your health care providers so they can work with you to ensure you’re getting the right amounts of vitamins.
Finally, and maybe most importantly, let me get back to the mega-amounts of vitamins I mentioned earlier. The idea that consuming more vitamins (or minerals) than is provided by a healthy diet or by the average drug store or supermarket daily multivitamin/mineral could be beneficial is very controversial and supported by little to no good quality evidence. Daily multivitamin-mineral products should provide no more than 100% of the average recommended intake for average adults, children, or whomever is specified on the label. The table below focuses on the functions of the vitamins in their required amounts (i.e., the amounts shown to prevent actual deficiency diseases) demonstrated by strong evidence. True deficiency diseases manifest themselves quickly—your hair falls out, your gums bleed, you lose teeth, you develop fissures at the corners of your mouth, your mental status changes in a matter of days, you get diarrhea—depending on the specific vitamin deficiency – well, you get the idea. But these symptoms can be just as quickly reversed when diagnosed and properly treated—usually just by eating more healthy foods. Obviously, that is not the case for diseases like heart disease, diabetes, and cancer, which probably take decades to develop. Therefore, the kinds of research that would need to be done to demonstrate that taking mega-amounts of certain vitamins helps prevent certain “long-term” chronic diseases are extremely challenging and essentially impossible to conduct in humans. Why? Because we can’t even control humans’ food intake, exercise, and other habits for a day, let alone the decades it would take to determine if a person’s eating habits influenced their chance of developing a chronic disease like cancer or diabetes. Not only can we fully control rodents’ diets and lifestyles even from before birth, their lifespans are far shorter, so when they do develop diseases of aging, it’s in a matter of months, not decades. We also know and can control the genetic makeup of every one of our rodent subjects. These characteristics would all seem to make rodents the ideal research subjects for studying the effects of food on long-term chronic disease risk. But—and this is a huge but—lab animals differ from humans in significant ways: They differ in their nutrient requirements, how they digest food, how their bodies store and use nutrients and eliminate waste, and their susceptibility to what we consider chronic diseases of aging, not to mention their propensity and ability to make food and drink choices freely. For this reason, when you hear what the media promises is an “earth-shaking” nutrition research finding, the first thing you need to ask is what species were involved in the research… If the subjects were lab animals—rats, mice, guinea pigs, rabbits—the findings likely have very limited implications for our own health. And if the subjects were humans, the second question to ask is whether the study was done by a supplement manufacturer or another party with a financial interest in the outcome of the research! Is there any hope that we’ll ever understand the role of nutrition in chronic disease? We’re trying – please see my comments near the end of this entire Micronutrients section.
And for the reasons I’ve just discussed, the table below lists the main functions of the vitamins, their most plentiful and common food sources, and who should be concerned about the possibility of needing more—or less—of that vitamin.
| Vitamin | Function(s) | Food(s) | Should You Worry about Deficiency? |
| Fat-soluble vitamins | |||
| A | Critical for vision, antioxidant | Red meat, brightly colored vegetables | Best to get this vitamin through vegetables |
| D (one of the few vitamins in short supply in healthy diets) | Bone structure, immune function | Fatty fish (e.g. salmon & tuna), fortified dairy foods | Possibly; many people have insufficiency, but should not take more than the amount in a daily vitamin without consulting your PCP. |
| E | Antioxidant | Whole grains, seeds, nuts | No! Vitamin E supplements serve no purpose and may even be harmful. |
| K | Blood clotting | Green leafy vegetables | No. See the note above if you are taking a blood thinner. |
| Water-soluble vitamins | |||
| B1 (thiamin) | Energy metabolism | Whole grains, vegetables, animal products | No, unless you are on a zero-carb diet |
| B2 (riboflavin) | Energy metabolism | Whole grains, vegetables, animal products | No, unless you are on a zero-carb diet |
| B3 (niacin) | Energy metabolism | Whole grains, vegetables, animal products | No, unless you are on a zero-carb diet |
| Pantothenic acid | Energy metabolism and transport | Whole grains, vegetables, animal products | No |
| B6 (pyridoxine) | Neurochemical synthesis, blood cell maintenance, skin regeneration | Whole grains, vegetables, animal products | No, unless you have advanced kidney disease or alcohol use disorder |
| Biotin | Energy metabolism, hair and skin growth | Eggs, organ meats, fish, some vegetables | No, unless you consume raw egg whites regularly |
| Folate | Critical for nervous system development, development and function of rapidly dividing cells | Fruits, vegetables, beans, whole grains | No, unless you have a disease that affects digestion or take phenytoin. If you can become pregnant, you should take a multivitamin that provides 400 micrograms. |
| B12 (cobalamin) | Fat transport across membranes, blood cell function | Foods of animal origin; cereal, nut milk, or nutritional yeast that has been fortified with vitamin B12 | Yes, if you are an older adult or follow a strict vegetarian or vegan diet |
| C | Skin and membrane integrity, antioxidant | Fruits and vegetables | No, unless you eat NO fruits or vegetables |
Minerals
We need at least 16 minerals, which are simple elements like calcium, chlorine, chromium, copper, fluorine, iodine, iron, magnesium, manganese, molybdenum, nickel, phosphorus, potassium, selenium, sodium, sulfur, and zinc (carbon, nitrogen, hydrogen, and oxygen are also elements but they are needed in larger amounts).
Many of the important notes I provided for vitamins also apply to minerals, including consulting your doctor regarding a specific disease or medical condition. Like water-soluble vitamins, many minerals are not stored in appreciably large amounts and need to be consumed regularly. And even those that appear to be abundant in our bodies, such as bone calcium, are easily lost when intake is deficient. As with vitamins, some conditions, such as alcohol use disorder, and medications can result in deficiencies in several minerals.
| Mineral | Function(s) | Food(s) | Should You Worry About Deficiency? |
| calcium | Bone structure; nerve and other cell, tissue, and organ function | Dairy foods, fortified orange juice and soy products | Yes, especially if you consume no dairy products or fortified “plant milk” |
| chlorine | All cell function, especially heart and nerve function | Everything | No |
| chromium | Unclear: may help the body utilize carbohydrates | Everything | No. Chromium supplements advertised to help regulate blood sugar may exceed safe levels! |
| copper | Required component of several enzymes | Many foods | No |
| fluorine | Component of bones and teeth | Black tea, other beverages, dried fruits | Yes, if your municipal water supply is not fluoridated or you consume and use no tap water |
| iodine | Central component of thyroid hormone | Iodized salt, shellfish, any salt-containing food | Probably not, unless you consume NO processed food, but best to switch to iodized salt for home use |
| iron | Central component of the red blood cell protein, hemoglobin, thus necessary for making red blood cells; | Animal foods and fish provide heme iron (iron from hemoglobin); spinach and other dark leafy greens, legumes like lentils, tofu, and iron-fortified cereal provide non-heme iron | Possibly: iron from plant sources (non-heme iron) is not as well absorbed by the body as is heme iron. Eating a food that provides vitamin C at the same meal (like adding lemon juice to a vegetarian chili) improves non-heme iron absorption. Avoid iron supplements unless prescribed by your health care provider as being absolutely necessary to reverse anemia: they are very hard on digestive function. |
| magnesium | Required for the function of hundreds of enzymes | Most foods, including leafy greens, nuts, beans, animal products | Possibly, due to poor diet, use of some medications, alcohol use disorder, and other conditions |
| manganese | Required for the function of many enzymes | Leafy greens, legumes, nuts, seeds | No |
| molybdenum | Required for the function of several enzymes | Legumes, whole grains, leafy greens | No |
| nickel | Unclear | Plant foods | Requirement is unclear, and some individuals with eczema may be sensitive to ingested or topical nickel |
| phosphorus | Required structural element in DNA, RNA, bones, teeth, and cell membranes | Most animal and plant foods, including dairy products, seafood, legumes, whole grains, nuts, seeds, vegetables, fruits | No |
| potassium | Vital for heart function, nervous system function, and function of all cells | Fruits and vegetables, whole grains | Yes, insufficient potassium intake is common among those who don’t consume enough plant foods; supplements are not overly well tolerated |
| selenium | Required for the function of a number of enzymes and structural proteins; antioxidant | Nuts, seafood, whole grains, organ meats | No, but selenium contents of plant foods depend on soil selenium, so some populations may be at higher risk |
| sodium | Required for maintenance of fluid balance, homeostasis, electrical activity in all cells | Processed foods, especially bread, cheese, processed meats, canned vegetables and soups, prepared meals, snacks, pickles, condiments | NO!!!! Most US residents over-consume sodium, not by adding salt to foods cooked and eaten at home, but from processed foods and those prepared elsewhere |
| sulfur | Critical component of some proteins and structural molecules | Animal foods, seafood, legumes, whole grains, cruciferous vegetables | No |
| zinc | Required for the function of some 100 enzymes, including a role in immune function | Seafood, animal products, legumes, nuts, seeds | No, except for those with alcohol use disorder, those with diseases that affect digestion, and possibly older adults; use of zinc supplements or lozenges to improve immune function, including preventing or treating respiratory infections rests on unclear evidence. |
If a Little is Good, Would More Be Better? When Should I Take More than the Recommended Daily Amounts of Vitamins or Minerals?
I know I’m beginning to sound like a broken record, but this “mega” vitamin and mineral issue has become bigbusiness, making the proponents rich while providing the consumer little, or in most cases, no benefits and possible harm. Perhaps because of the miraculous and dramatic impact of reversing the ravages of thiamine or niacin deficiency with a simple vitamin, some people have latched onto the notion that any group of symptoms that has remained resistant to medical treatment must be the result of an undiscovered vitamin or mineral deficiency. At the same time, it seems that every other week, we’re being told that some vitamin or mineral has been associated with lower risks for cancer, better immune function (fewer colds, less chance of getting COVID-19), or stronger hair and nails, even when scientific evidence from real experiments is completely lacking! Unfortunately, ideas like this—that is, taking amounts of vitamins and minerals in excess of the recommended dietary allowances—make lots of money for the media, dietary supplement companies, and unscrupulous researchers, some of whom, shockingly , even have legitimate medical degrees or PhDs. Shame on them! And as I described for vitamins, the evidence for any beneficial effects of mega-quantities of minerals is weak at best.
With the exceptions I describe in the tables above, most healthy people get all the vitamins and minerals they need by eating a variety of foods. To get credible information about supplements, read my blogs and other reputable sources such as the US Office of Dietary Supplements fact sheets (https://ods.od.nih.gov/factsheets/list-all/). If you’re reading something and wondering whether to trust it or not, feel free to drop me a line. However, I strongly recommend you do this analysis yourself first by asking yourself the following questions:
- Is the writer/expert receiving any funding from food or dietary supplement companies or profiting from their advice in any other way? For example, have they written or contributed to a popular-press book or magazine article that espouses taking certain supplements? In the not too distant past, I would have made an exception for any scientific researchers whose work appears only in peer-reviewed medical journals, because review by one’s scientific peers is designed to identify and weed out biased, poorly designed, or outright fraudulent research, and because in the past, it was exceedingly rare for legitimate researchers to become shills, making profits from products or services that were based on their findings. But today, that’s far more common, and even some scrupulous researchers find themselves getting caught up in having their premature research findings being aired on the 6:00 news. In my professional experience, the profit motive appears to cloud even some experts’ judgement and can be a dangerous conflict of interest, which is why I don’t, and will never, endorse a product or accept funding from these sources.
- Is the person who is recommending you take a supplement encouraging you to buy the supplement he or she sells or to order it from a specific source (other than, say, Amazon)? Sometimes this financial benefit is cleverly masked and very difficult to uncover, but it’s important for understanding the motive behind such recommendations.
- Is the provider also recommending that you have them draw blood, take a saliva sample, or provide a hair sample for lab tests that your insurance does not want to cover? This is a dead giveaway that the provider is going to try to upsell you on unneeded supplements.
So I posed the question above whether we have any hopes of ever understanding how the foods we eat influence our long-term health. Believe it or not, this is considered the central challenge of the legitimate mainstream nutrition research community. Because it’s impossible to do controlled life-long trials on humans, medical nutrition researchers are deeply engaged in trying to identify prodromes or precursors, early warning signals or canaries in the coalmine, if you will, that reliably predict later disease. In research, we sometimes call them intermediary outcomes. Two notable examples of likely precursors to cardiovascular diseases are high blood pressure (hypertension) and elevated levels of low-density lipoprotein (LDL) cholesterol. They’re not perfect predictors—not everyone who has untreated hypertension or high cholesterol goes on to develop heart disease and not everyone who develops or dies from heart disease starts out with hypertension or high cholesterol—but right now they’re the best predictors we’ve got and we’re on the hunt for comparable canaries for Type 2 diabetes and the many types of adult onset cancer.
Where do Phytonutrients and Things Fit In?
If you’re a student of nutrition or you like to read about nutrition in the popular media, you might be wondering where things like phytonutrients—chemicals in plants (like lycopene and resveratrol) that might or might not be nutrients—fit into the micronutrient scheme. These substances are and have been the subject of extensive research for several decades, but their roles and necessity remain elusive. So stay tuned.