Lesson 9: Micronutrients

Table of Contents


At this point I have discussed considerations regarding energy intake (measured in calories) and the various macronutrients that contain calories. However, there are still several other aspects of foods and drinks that impact our overall health. In this lesson I will discuss one of these aspects, micronutrients.

Micronutrients are essentially the non-macronutrient components of food we consume. This includes all vitamins and minerals, but also includes many other compounds that are present in foods called phytonutrients (ie, polyphenols and flavonoid compounds found in fruits and vegetables). There are far too many individual micronutrients to discuss all of them in detail. Therefore, I will address micronutrients as a whole and a few select micronutrients thought to be of larger public health concern.

Note: Phytonutrients are present in all foods (and many beverages) and are one of the reasons why certain food items can exert health impacts beyond just the sum of their measurable individual components.

Tip: This is wheicon for cronometerre cronometer.com can prove very useful. Simply plug a typical day of eating into that website and it will tell you if you are eating too little or too much of a large variety of micronutrients. While it is not perfect (ie, it does not include iodine and the food database is not complete), it will provide a general idea of how a person is doing.

Note: When discussing desirable quantities of nutrients, the typical terms used are the dietary reference intakes (DRI) as follows:

Estimated average requirement (EAR): The average daily nutrient intake level estimated to meet the requirement of half the healthy individuals in a particular life stage and gender group.

Recommended daily allowance or recommended dietary allowance (RDA): The average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group. This is two standard deviations above the EAR.

Adequate intake (AI): The recommended average daily intake level based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate – used when an RDA cannot be determined.

Tolerable upper limit (TUL): The highest average daily nutrient intake level that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As intake increases above the TUL, the potential risk of adverse effects may increase.

To be clear, more scientific evidence is required to establish EAR and RDA levels than to establish an AI level. When there is not sufficient scientific evidence, an AI is set based on how much of a nutrient the generally healthy population typically consumes. Also, while many people think it is important to reach the RDA daily, in actuality many people would be fine consuming less than this. Thus, while aiming for the RDA is generally advisable, it is also generally not overly important to ensure you hit it every single day.

The graph below gives a visual representation of EAR, RDA, and TUL. AI, being an estimate, cannot be appropriately placed in any specific location on this graph. The “Safe Intake Range” can vary in size between different nutrients; some will have a narrower window of safe intake while some will have a wider window.

This figure was modified from (Biesalski, 2018).

General vitamins and minerals

Pretty much all foods have some variety of micronutrients, but there are certain foods that have considerably more than others. This is a primary reason why fruits and vegetables are considered to be so healthy. They have a lot of nutritious aspects despite (most of them) having relatively few calories. Eating a variety of different fruits and vegetables, including different colors and types, will ensure you consume a plethora of different micronutrients. As different food groups can have different types of micronutrients, this is one of the main reasons eating a variety of different food groups as opposed to following a restrictive diet can support a healthy lifestyle, as advised in the 2020-2025 Dietary Guidelines for Americans (DGA). Beverages also can have many micronutrients so their intake should not be ignored in this regard.(Ferruzzi, 2020)

Impact of food preparation

One consideration when eating a variety of different foods is how they should be prepared, and specifically if this leads to better yields of desired nutrients or increased yields of undesirable nutrients. For the purpose of obtaining micronutrients it is generally better to consume food that has been cooked in some manner as this degrades the food matrix to a degree, thus allowing the nutrients to be more easily absorbed.(Thakur, 2020) Further aspects of food preparation are discussed in Lesson 10.

Utility of a multivitamin/multimineral supplement?

A question that frequently comes up is “Should I take a multivitamin?”. This has not been settled in the literature. Essentially, there is no evidence of harm from taking a generic multivitamin/multimineral supplement (MVMS) that has nutrients at relatively low doses (well below the TUL), and taking one daily can help many people meet the EAR of a variety of different nutrients.(Biesalski, 2017; Blumberg, 2018) However, there is potential harm in taking some of the mega dose supplements, specifically vitamin A, vitamin E, and beta-carotene.(Schwingshackl, 2017; O’Connor, 2022) Additionally, the majority of the literature suggests taking a daily MVMS does not improve health outcomes in any as of yet measured manner.(Schwingshackle, 2017; Kim, 2018) A 2020 review article found that randomized trials generally show no benefit to vitamin, mineral, or fish oil supplements on the risk of major non-communicable diseases (ie, cardiovascular disease, cancer, type 2 diabetes) in people without clinical nutritional deficiencies.(Zhang, 2020) A 2022 systematic review and meta-analysis (“SR/MA”) found that multivitamins may slightly decrease the risk of developing cancer, but the odd’s ratio was only barely significant at 0.93 with a 95% confidence interval spanning 0.87-0.99; otherwise no benefit was seen for prevention of cardiovascular disease (“CVD”) or all-cause mortality (“ACM”).(O’Connor, 2022)

Overall, I feel a MVMS may be beneficial in people with restrictive or low calorie diets, but they should not be used as a substitute for a variety of healthy nutritious foods.

Tip: For individuals who are dieting to lose weight and thus consuming relatively few calories, it will be harder to obtain all of the desired micronutrients. It makes more sense in this setting to include a MVMS.

Specific micronutrients of concern

The 2020-2025 DGA mentions several nutrients of public health concern for being deficient in typical diets; these include calcium, potassium, dietary fiber, and vitamin D. In certain life stages other nutrients are also of concern:

  • infants primarily fed breast milk – iron, zinc, choline, also B12 if the breast milk comes from someone who does not consume animal products
  • toddlers – iron
  • adolescent males – phosphorus, choline, magnesium
  • adolescent females – phosphorus, choline, magnesium, iron, folate, B6, B12
  • pregnant women – iron, folate, iodine, choline
  • elderly – B12
  • B12 is additionally of concern for individuals who do not consume animal products

The DGA additionally mentions that sodium is typically overconsumed. As fiber was discussed in Lesson 7 I will not discuss that here. I will briefly discuss sodium, potassium, calcium, vitamin D, and iron as these are the nutrients deemed important enough to include on the new formulation of nutrition labels and also deemed important enough for the DGA to include lists of foods that are good sources of these nutrients.


Sodium is commonly used in table salt; while nutrition labels are useful to determine how much sodium is in any specific item you must be careful to also consider how much salt you use to season food.

Recommended intake

In 2019 guidelines for sodium intake were updated to state that an AI level is 1,500 mg daily for people ≥14 years old while for health benefits consuming <2,300 mg daily is beneficial.(National, 2019) The AI was not set lower due to a lack of studies looking at lower daily intake. The American Heart Association, however, actually recommends that an ideal sodium intake is <1,500 mg per day. There has been a lot of controversy in the literature over the years regarding an “optimal” sodium intake level for health, so much so that in 2016 an analysis was done of the literature base showing that the conflicting sides typically cited studies with similar views.(Trinquart, 2016)

Sodium controversy

While most researchers seem to agree that when salt intake is too high it can elevate blood pressure and lead to worse health outcomes, the controversy exists regarding what threshold of salt intake may be too low. Some data suggest better outcomes with salt intake at 3,000-5,000 mg per day(O’Donnell, 2015), and some data suggests that when salt intake is too low it leads to activation of the renin-angiotensin-aldosterone system (“RAAS”) which can worsen health outcomes.(Graudal, 2017) However, other literature suggests any meaningful RAAS changes are transient.(He, 2013)

Additionally, the vast majority of the sodium literature uses measurements that are known to be inaccurate. Different results can be seen when studies consider sodium measurements via dietary intake vs. urinary output(Milajerdi, 2019), measurements at baseline only vs repeat measurements(Olde, 2017), and measurements with trials of different lengths, populations of different ages, and different baseline blood pressure measurements.(Huang, 2020) Even spot urine measurements compared to 24 hour urine measurements can make a large difference.(Yin, 2021) From a pair of very interesting studies published in 2013 and 2015 we actually know that sodium can follow weekly and monthly cycles in the body and 24-hour urinary measurements need to be collected for 7 consecutive days to be able to accurately determine sodium intake, which has rarely happened in the literature to this point. (Rakova, 2013; Lerchi, 2015) Even if the above were not issues, some people have blood pressure that is much more sensitive to changes in sodium intake than others, meaning individual people are affected to variable degrees by similar sodium intake.(Farquhar, 2015)

Looking at more recent analyses and reviews:

  • A 2020 SR/MA of cohort studies found a linear increased risk of CVD for any level of sodium intake greater than 1 gram dialy; the risk increase was 6% for every additional 1 gram of sodium intake.(Wang, 2020)
  • In 2020 a comprehensive review of the literature evaluating the merit of dietary recommendations to consume low amounts of sodium overall found no compelling evidence that meeting the current sodium intake recommendations will yield beneficial outcomes, there is evidence to suggest this may increase harm, and there is lots of evidence to suggest that it is not realistic for most people and populations to meet these guidelines, which implies we will never be able to perform adequate randomized controlled trials to evaluate them.(O’Donnell, 2020)
  • In contrast, in 2021 a review took the stance that optimal sodium intake may be as low as 0.5-1 grams daily based on estimates of sodium intake throughout human evolutionary history; additionally, data indicate that the RAAS system does not activate very significantly to conserve sodium above this point.(Yin, 2021)
  • A 2021 SR/MA of 85 trials of at least 4 weeks duration with 24-hour urinary sodium measurements found a mostly linear dose-response relationship of sodium intake changes and blood pressure responses.(Filippini, 2021) More specifically:
    • Every ~2.3 gram decrease in urinary sodium excretion associated with a decrease in systolic blood pressure (“SBP”) of 5.56 mmHg and a decrease in diastolic blood pressure (“DBP”) of 2.33 mmHg.
      • In individuals without hypertension the decrease in SBP was 2.30 mmHg, there was no statistically significant decrease in DBP (-0.80 mmHg with a 95% confidence interval of (-1.89, 0.29)).
      • In individuals with hypertension the decrease in SBP was 6.50 mmHg and in DBP was 3.00 mmHg.
    • There was little evidence of a blood pressure effect in individuals without hypertension whose sodium intake was <2 grams daily.
  • A 2021 ecological analysis examining 24-hour urinary sodium excretion and healthy life expectancy as well as mortality across many different countries found(Messerli, 2021):
    • Life expectancy increased with increasing sodium intake up to 4-5 grams daily, then flattened out and subsequently decreased.
    • ACM was negatively correlated with sodium intake.
    • These correlations persisted after correcting for country gross domestic product (“GDP”) and body mass index (“BMI”) measurements.
    • In a sensitivity analysis looking at the 46 countries with the highest gross national income per capita, sodium intake adjusted for GDP & BMI still correlated positively with life expectancy at birth (r2 = 0.53) and negatively with ACM (r2 = 0.50).
  • A series of reviews by mostly the same authors highlights the clear benefit of avoiding excessively high sodium intake(He, 2020) and discusses the various methodological concerns that may explain why low sodium intake (<2-3 grams daily) may seem to increase the risk of poor health outcomes when in reality it may not (and may even be beneficial).(Cook, 2020; He, 2021)
  • A 2022 SR/MA found increasing levels of sodium intake beyond 2 grams daily associated with increased risk of hypertension when evaluating studies that utilized 24-hour urinary sodium excretion measurements.(Filippini, 2022) Studies that used less rigorous methodology did not see an increase risk until consuming at least 3 grams of sodium daily.
  • A 2022 review article addresses several of the controversies in the literature and challenges the conclusions of two of the publications listed above (O’Donnell 2020, Messerli 2021), noting methodological and other flaws that make their conclusions potentially erroneous.(Cappuccio, 2022)
Sodium conclusion

With all of this controversy in mind, I suggest people with elevated blood pressure decrease sodium intake to <2300 mg daily, if possible, whereas people with normal blood pressure can likely consume up to 5000 mg daily without significant increased risk of other issues, assuming this does not cause a significant increase in their blood pressure. Going towards this higher threshold may be particularly beneficial for individuals who suffer from light-headedness, dizziness, or near-fainting on a regular basis. Salt-sensitive individuals who do have a significant increase in blood pressure may benefit from keeping their sodium intake below the lower threshold.

There is ample debate about the utility of aiming for a sodium intake considerably lower than 2300mg daily; the AHA does recommend <1500mg daily for people at higher risk, but as indicated above there is lots of controversy surrounding this recommendation. For individuals with high blood pressure, I think it is worth trying to decrease sodium intake to <1500 mg daily; consider taking your blood pressure several times prior to doing this and then ~4-6 weeks after doing this (to give time for everything to stabilize) and see if there has been a significant decrease. If so there is a higher chance the lower threshold is beneficial.

Note: One additional consideration is sodium lost in sweat. For people who sweat a large amount (ie, individuals who do manual labor in heat or athletes who practice for an extended duration in hot temperatures), a substantial amount of sodium can be lost in sweat.(Bates, 2008; Baker, 2017) Sodium intake will need to be increased to help replace whatever is lost in the sweat, and this can help improve performance. A universal replacement strategy is hard to derive due to significant variability in sodium loss rates. Barring a method to measure the actual sodium loss, simply trying different quantities of replacement and seeing what allows you to feel best (without elevating your blood pressure) should be a suitable strategy.

Tip: Consider purchasing a potassium-enriched salt substitute to use instead of sodium if you believe your sodium intake is too high. This has recently been studied to good effect and generally shows much promise.(Henry, 2021; Yin, 2021) Just be cautious if you have known chronic kidney disease and need to be on a potassium-restricted diet.


Potassium is widely considered to be highly prevalent in bananas, but even higher amounts are found in beans and potatoes. While it is dangerous if your potassium level gets too high, it’s extremely difficult for this to occur from food intake (with a possible exception for individuals with significant kidney disease – if this applies to you, please consult your healthcare provider regarding dietary changes) and thus as long as you are not taking potassium supplements this is generally not a concern.

Recommended intake

In 2019 guidelines for potassium intake were updated and this represented a major change.(National, 2019) Previously from the 2005 DRI report the potassium AI was set at 4,700 mg per day in adults “based on blunting the severe salt sensitivity prevalent in African-American men and decreasing the risk of kidney stones, as demonstrated in a 3-year double-blind controlled study”. However, with the new guideline they wanted to present a value more applicable to the general public for health purposes and not simply to ameliorate potential health conditions. They used two nationally representative surveys: the Canadian Community Health Survey-Nutrition 2015 & the National Health & Nutrition Examination Survey 2009-2014 and considered adults with normal blood pressure without a self-reported history of CVD. They considered the highest median intake across the two surveys, mathematically rounded, to be the most appropriate basis for establishing the potassium AI values.

Thus, while the old recommendation was for everyone ≥14 years old to aim for 4,700 mg daily, the new recommendation is for adult males to aim for 3,400 mg daily and adult non-pregnant/non-lactating females to aim for 2,600 mg daily.

Potassium conclusion

While many people still consume less than the new recommended numbers (after all, the new targets were set from median intake values of generally healthy populations), the deficiency in dietary intake is not nearly as striking as it was with the prior targets. Eating a generally healthy diet with some sources of higher potassium foods should make it much more doable to meet potassium guidelines without significant difficulty.

Vitamin D

It’s too early to have definitive research regarding Vitamin D and COVID-19, but if anyone is concerned or thinks it may be beneficial, taking 2,000 international units (“IU”) daily should be a safe amount and can help prevent deficiency or insufficiency. The below research does not consider COVID-19; overall the jury is still out regarding a potential beneficial impact of supplementation.(de la Guía-Galipienso, 2021)

Recommended intake

Vitamin D has received much attention and research over the last 1-2 decades. Revised guidelines for vitamin D intake were published in 2011.(Institute, 2011) These considered many studies of vitamin D related to various health outcomes and only found a compelling impact on bone health; from this they determined their recommendations. These state “Practically all persons are sufficient at serum 25OHD levels of at least 50 nmol/L (20 ng/mL). Serum 25OHD concentrations above 75 nmol/L (30 ng/mL) are not consistently associated with increased benefit.” To accomplish achieving 50 nmol/L they recommend daily intakes of 400 IU for age 0-12 months, 600 IU for age 1-70 years, and 800 IU for those >70 years old, using a compilation of studies done at high latitudes and in Antarctica (where sunlight exposure would not contribute significantly to vitamin D levels).

Evidence for supplementation?

Since then, there have been several additional studies relating vitamin D supplementation to health outcomes. There does not seem to be any meaningful benefit for weight loss(Perna, 2019) or for athletic performance.(Ksiazek, 2019) There does seem to be a small benefit seen for decreasing cancer mortality but not cardiovascular mortality or ACM per one review(Zhang, 2019), while a more recent review did find a borderline significant 5% decreased risk of ACM with vitamin D supplementation.(Ruiz-García, 2023) A SR of observational studies highlighted some of the inconsistencies in the literature and proposed that there seems to be a threshold below which lower vitamin D is associated with increased mortality but above which no significant correlation is seen.(Heath, 2019) This threshold varied in different studies but was generally ≤75 nmol/L (30 ng/mL). Studies have generally not found a consistent benefit for fall prevention, fractures, or other nonskeletal health outcomes.(Pilz, 2019)

More recent reviews found similar conclusions. Much of the association of low vitamin D levels with various negative health statuses is likely due to reverse causality (ie, due to associated inflammation decreasing vitamin D levels) and there is very little evidence of any meaningful benefit of supplementation across the wide array of randomized controlled trials that have been performed.(Reijven, 2020) The implications of vitamin D supplementation for CVD were more recently reviewed with no net health benefits found.(de la Guía-Galipienso, 2021; Michos, 2021) An even more recent review evaluating randomized controlled trials and Mendelian randomization studies (I discussed the concept of Mendelian randomization studies in Lesson 8 if you are curious) similarly found no benefit to supplementation in individuals without deficiency for a variety of different health outcomes.(Bouillon, 2021)

Note: See below in the Calcium section for additional discussion on the risk of falls and fractures.

Vitamin D conclusion

Thus, overall, with all of the research that has been done there has not been much at all to consistently show a benefit of vitamin D supplementation or otherwise raising your vitamin D level when it is already in the 50-75 nmol/L range (20-30 ng/mL). At the same time the TUL is set at 4,000 IU daily for ages 9 years old and older(Institute, 2011); though there is evidence that this TUL may be too high.(Rizzoli, 2021). Thus people who do not consume much vitamin D in their diet can either increase their intake of vitamin D-rich foods or safely supplement up to 1,000-2,000 IU daily to help ensure adequate blood levels are achieved.


Calcium is generally associated with dairy, but decent amounts can also be obtained in several other products such as some types of green/leafy vegetables, beans, and food/drink items that are calcium-fortified.


Note: Just because vegetables have a lot of calcium does not mean that much of the calcium is bioavailable. Specifically, vegetables with high amounts of oxalates (ie, spinach) will only contribute a small amount of calcium, while vegetables with low amounts (ie, kale) can contribute significantly more.(Melina, 2016)

Unfortunately, there is still much work to do to determine the bioavailability of all nutrients in all foods.(Melse-Boonstra, 2020) The DRIs consider this to some degree but eventually we will hopefully get to a point where we can list the actual bioavailable quantities of nutrients on nutrition labels as opposed to the total amount even if significant portions of the nutrients cannot be absorbed.

Recommended Intake

Along with vitamin D, guidelines for calcium intake were also revised in 2011.(Institute, 2011) This was done generally with data regarding calcium balance, with the goal of increasing bone mass in childhood & adolescence and then maintaining bone mass in adulthood. The RDA is set at 700 mg daily age 1-3 years old, 1,000 mg daily age 4-8, 1,300 mg daily age 9-18, 1,000 mg daily age 19-70 in males and age 19-50 in females, 1,200 mg daily age 51-70 in females (due to increased need associated with menopause), and 1,200 mg daily if >70 years old. The TUL is based on a relatively sparse literature base primarily focused on the risk of kidney stones and is set at 2,500 mg daily age 1-8, 3,000 mg daily age 9-18, 2,500 mg daily age 19-50, and 2,000 mg daily age ≥51. Of note, it is rather difficult to achieve these TULs with food intake alone.

Evidence for a reduction of fracture risk

Since the time of those guidelines more research has been done. A 2018 SR did not find any significant benefit of supplementation with vitamin D alone or with calcium in community-dwelling adults, noting that analyses that do find benefit typically include elderly individuals living in institutions and/or people with known osteoporosis.(Kahwati, 2018) A 2019 SR/MA concluded that while in observational studies higher vitamin D levels are associated with decreased risk of fracture, vitamin D supplementation alone does not seem to decrease this risk.(Yao, 2019) However, the studies that examined this used intermittent or relatively low doses of vitamin D (no more than 800 IU daily). On the other hand, supplementation of vitamin D with calcium was associated with a decreased risk of all fractures (relative risk 0.94) as well as hip fractures (relative risk 0.84) with greater effect seen in people >80 years old.

Evidence for harm

There have also been concerns of increased calcium intake potentially having a negative impact on cardiovascular health. In 2016 a SR/MA concluded that calcium intake below the TUL is not associated with increased cardiovascular risk in generally healthy adults and the data indicating concern came mostly from individuals with impaired kidney function.(Chung, 2016) A 2017 review found that increased dietary calcium intake may be protective while supplementation may be harmful.(Tankeu, 2017) A separate 2017 review summarized a lot of the controversy in the literature regarding this topic and generally concluded there seems to be no significant risk from increased dietary calcium but calcium supplements do impart some risk.(Reid, 2017)

Moving into more recent literature, a 2018 review(Li, 2018) on overall health aspects of calcium supplementation indicated a potential negative effect on cardiovascular risk, while a 2019 review took a more favorable view of calcium fortification in countries where low calcium intake is the norm.(Cormick, 2019) Authors of a more recent review(Wallace, 2020) concluded the majority of the negative association with CVD is due to methodological confounding, while a separate recent editorial(Morelli, 2020) suggested there are still unresolved concerns. A 2020 SR/MA of cohort studies and randomized controlled trials evaluating dietary & supplemental calcium intake and the risk of CVD found that increased dietary calcium does not increase the risk of CVD while calcium supplements do seem to increase the risk of coronary heart disease, especially myocardial infarction.(Yang, 2020)

These general thoughts are echoed in the most recent literature:

  • A 2021 MA of randomized controlled trials evaluating calcium supplementation of at least 500 mg daily found that supplementation led to a 15% increased risk of CVD and a 16% increased risk of coronary heart disease; most of this increased risk came from one relatively large study and if that study was eliminated there would only be a marginally increased risk of CVD with no increased risk of coronary heart disease.(Myung, 2021) Additionally, in this meta-analysis 92.8% of the included individual subjects were post-menopausal women; there is relatively little literature overall that includes men.
  • A 2021 review found calcium supplements possibly increase the risk of CVD as well as kidney stones and colon polyps, while dietary calcium intake does not seem to increase these risks.(Michos, 2021)
  • A separate 2021 review evaluating the literature took the viewpoint that the overall evidence does not support a significant increase in cardiovascular risk with calcium supplementation but there is an increased risk of kidney stones and gastrointestinal side effects.(Curtis, 2021)
  • A 2023 MA found no statistically significant increased risk of CVD from calcium supplements with or without vitamin D, though the authors acknowledge more research is needed for people with a high basleine risk of CVD.(Huo, 2023)
Calcium conclusion

Overall, it appears most beneficial to try to reach the RDA of calcium through dietary means (click here for a list of calcium-rich foods), to avoid supplementing beyond the RDA, and a case can be made for using lower dose calcium supplements (ideally <500 mg per dose, which practically would also help optimize absorption(Michos, 2021)) to make up a dietary deficiency especially in individuals at a higher risk of fractures.

Note: It is difficult to directly study the health risks of calcium supplementation because it is unethical and illogical to conduct randomized controlled trials where harm is measured as the primary outcome variable. Stated another way, nobody will conduct a study just to see if we can induce harm by giving people supplements. Thus, these harm outcomes will always have to be linked with other outcome variables of interest. This can be done, but as seen above the resulting data can be controversial (and has been controversial regarding calcium supplementation). We’ll have to await additional long-term trials to generate more comprehensive data.


Iron absorption can be variable between food items as well as between people. Iron is considered a nutrient of concern for adolescent females as well as pregnant women, but deficiency is somewhat common in all women who are menstruating as well as in athletes.(Sim, 2019)

Considerations in children

In young children it has been established that iron deficiency, even without the presence of anemia, can negatively impact neurodevelopmental outcomes.(Georgieff, 2019) However, we need more data on this, and it is not clear to what degree iron supplementation would actually help with developmental outcomes.(McMillen, 2022) In the US we typically screen children for iron deficiency anemia by checking a hemoglobin at the 1 year well visit, but possibly 2-3x as many children have low iron without anemia than low iron with anemia. Additionally, negative neurological outcomes can develop from deficiency while younger than age 1. For that reason, it may be better to screen high risk children earlier. Iron supplementation should likely begin between age 4-6 months in breastfed babies born at term (as they have iron stores from pregnancy that do not run out until this point) and younger than this in premature infants.

Considerations in women of child-bearing age

During pregnancy a woman’s blood volume increases significantly and thus a physiologic anemia tends to develop. Additionally, women need to consume more iron during pregnancy to help provide enough for the growing child.(Georgieff, 2019) With this in mind, it is recommended for pregnant women to consume 27 mg of iron daily. Adult women otherwise until age 50 are recommended 18 mg daily, considerably higher than the 8 mg recommended daily for men to help account for blood loss during menstruation. It can be difficult to determine your iron status without getting blood work; if low iron is determined then supplementing per a physician’s recommendations is generally advised. Given variability between individuals regarding absorption of dietary and supplemental iron, often repeat blood work needs to be done to determine if the supplementation scheme is effective.

Other considerations

There are also health concerns related to too much iron. This can occur due to medical conditions such as hemochromatosis but also if people take iron supplements unnecessarily. This can also extend to infants.(McMillen, 2022) On the other hand, it has been shown in people who follow vegetarian and vegan diets that they normally have lower ferritin levels (ferritin is a storage form of iron in the body) relative to people who consume meat, at least in part due to non-heme iron being less bioavailable than heme-iron (the type found in meat).(Haider, 2018) Whether this contributes to some of the health benefits of vegetarian diets is unclear, but it is worth noting that low ferritin levels can contribute to poorer sleep.

Iron conclusion

Overall, I recommended plugging your regular diet into cronometer.com to see if your iron intake seems deficient or excessive, and if you have any specific concern discuss with your medical provider and consider having a ferritin level checked (of note, it is important to check when healthy as ferritin can be artificially elevated when ill or when the body undergoes acute stress).


Micronutrients are easy to ignore but deficiencies can make a significant impact on your well-being. In general, when you are meeting the RDA then additional supplementation tends to not prove very helpful and is likely a waste of money (though there may be exceptions for people with known deficiencies or certain medical conditions). Eating a variety of nutritious foods can aid in accumulating a rich supply of micronutrients and phytonutrients to aid one’s health. Cronometer.com is a great starting point to assess your intake, supplementing a generic multivitamin/multimineral supplement is likely safe if you have concerns, and beyond that altering your diet to help achieve desirable quantities of various micronutrients will likely prove beneficial, while individual supplements can be considered for specific situations.

Click here to proceed to Lesson 10


  1. Baker LB. Sweating Rate and Sweat Sodium Concentration in Athletes: A Review of Methodology and Intra/Interindividual Variability. Sports Med. 2017;47(Suppl 1):111-128. doi:10.1007/s40279-017-0691-5
  2. Bates GP, Miller VS. Sweat rate and sodium loss during work in the heat. J Occup Med Toxicol. 2008;3:4. Published 2008 Jan 29. doi:10.1186/1745-6673-3-4
  3. Biesalski H & Tinz J. Micronutrients in the life cycle: Requirements and sufficient supply. NFS Journal. 2018;11:1-11. doi:11. 10.1016/j.nfs.2018.03.001
  4. Biesalski HK, Tinz J. Multivitamin/mineral supplements: Rationale and safety – A systematic review. Nutrition. 2017;33:76-82. doi:10.1016/j.nut.2016.02.013
  5. Blumberg JB, Bailey RL, Sesso HD, Ulrich CM. The Evolving Role of Multivitamin/Multimineral Supplement Use among Adults in the Age of Personalized Nutrition. Nutrients. 2018;10(2):248. Published 2018 Feb 22. doi:10.3390/nu10020248
  6. Bouillon R, Manousaki D, Rosen C, Trajanoska K, Rivadeneira F, Richards JB. The health effects of vitamin D supplementation: evidence from human studies. Nat Rev Endocrinol. 2022 Feb;18(2):96-110. doi: 10.1038/s41574-021-00593-z. Epub 2021 Nov 23. PMID: 34815552; PMCID: PMC8609267.
  7. Cappuccio FP, Campbell NRC, He FJ, Jacobson MF, MacGregor GA, Antman E, Appel LJ, Arcand J, Blanco-Metzler A, Cook NR, Guichon JR, L’Abbè MR, Lackland DT, Lang T, McLean RM, Miglinas M, Mitchell I, Sacks FM, Sever PS, Stampfer M, Strazzullo P, Sunman W, Webster J, Whelton PK, Willett W. Sodium and Health: Old Myths and a Controversy Based on Denial. Curr Nutr Rep. 2022 Jun;11(2):172-184. doi: 10.1007/s13668-021-00383-z. Epub 2022 Feb 14. PMID: 35165869; PMCID: PMC9174123.
  8. Chung M, Tang AM, Fu Z, Wang DD, Newberry SJ. Calcium Intake and Cardiovascular Disease Risk: An Updated Systematic Review and Meta-analysis [published correction appears in Ann Intern Med. 2017 May 2;166(9):687]. Ann Intern Med. 2016;165(12):856-866. doi:10.7326/M16-1165
  9. Cook NR, He FJ, MacGregor GA, Graudal N. Sodium and health-concordance and controversy. BMJ. 2020 Jun 26;369:m2440. doi: 10.1136/bmj.m2440. Erratum in: BMJ. 2020 Jun 29;369:m2608. He, J [corrected to He, Feng J]. PMID: 32591335; PMCID: PMC7318881.
  10. Cormick G, Belizán JM. Calcium Intake and Health. Nutrients. 2019;11(7):1606. Published 2019 Jul 15. doi:10.3390/nu11071606
  11. Curtis EM, Cooper C, Harvey NC. Cardiovascular safety of calcium, magnesium and strontium: what does the evidence say? Aging Clin Exp Res. 2021 Mar;33(3):479-494. doi: 10.1007/s40520-021-01799-x. Epub 2021 Feb 9. PMID: 33565045; PMCID: PMC7943433.
  12. de la Guía-Galipienso F, Martínez-Ferran M, Vallecillo N, Lavie CJ, Sanchis-Gomar F, Pareja-Galeano H. Vitamin D and cardiovascular health. Clin Nutr. 2021 May;40(5):2946-2957. doi: 10.1016/j.clnu.2020.12.025. Epub 2020 Dec 29. PMID: 33397599; PMCID: PMC7770490.
  13. Farquhar WB, Edwards DG, Jurkovitz CT, Weintraub WS. Dietary sodium and health: more than just blood pressure. J Am Coll Cardiol. 2015;65(10):1042-1050. doi:10.1016/j.jacc.2014.12.039
  14. Ferruzzi MG, Tanprasertsuk J, Kris-Etherton P, Weaver CM, Johnson EJ. Perspective: The Role of Beverages as a Source of Nutrients and Phytonutrients. Adv Nutr. 2020;11(3):507-523. doi:10.1093/advances/nmz115
  15. Filippini T, Malavolti M, Whelton PK, Naska A, Orsini N, Vinceti M. Blood Pressure Effects of Sodium Reduction: Dose-Response Meta-Analysis of Experimental Studies. Circulation. 2021 Apr 20;143(16):1542-1567. doi: 10.1161/CIRCULATIONAHA.120.050371. Epub 2021 Feb 15. PMID: 33586450; PMCID: PMC8055199.
  16. Filippini T, Malavolti M, Whelton PK, Vinceti M. Sodium Intake and Risk of Hypertension: A Systematic Review and Dose-Response Meta-analysis of Observational Cohort Studies. Curr Hypertens Rep. 2022 May;24(5):133-144. doi: 10.1007/s11906-022-01182-9. Epub 2022 Mar 4. PMID: 35246796.
  17. Georgieff MK, Krebs NF, Cusick SE. The Benefits and Risks of Iron Supplementation in Pregnancy and Childhood. Annu Rev Nutr. 2019;39:121-146. doi:10.1146/annurev-nutr-082018-124213
  18. Graudal NA, Hubeck-Graudal T, Jurgens G. Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol, and triglyceride. Cochrane Database Syst Rev. 2017;4(4):CD004022. Published 2017 Apr 9. doi:10.1002/14651858.CD004022.pub4
  19. Haider LM, Schwingshackl L, Hoffmann G, Ekmekcioglu C. The effect of vegetarian diets on iron status in adults: A systematic review and meta-analysis. Crit Rev Food Sci Nutr. 2018;58(8):1359-1374. doi:10.1080/10408398.2016.1259210
  20. He FJ, Li J, Macgregor GA. Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. BMJ. 2013;346:f1325. Published 2013 Apr 3. doi:10.1136/bmj.f1325
  21. He FJ, Tan M, Ma Y, MacGregor GA. Salt Reduction to Prevent Hypertension and Cardiovascular Disease: JACC State-of-the-Art Review. J Am Coll Cardiol. 2020 Feb 18;75(6):632-647. doi: 10.1016/j.jacc.2019.11.055. PMID: 32057379.
  22. He FJ, Campbell NRC, Woodward M, MacGregor GA. Salt reduction to prevent hypertension: the reasons of the controversy. Eur Heart J. 2021 Jul 1;42(25):2501-2505. doi: 10.1093/eurheartj/ehab274. PMID: 34117487.
  23. Heath AK, Kim IY, Hodge AM, English DR, Muller DC. Vitamin D Status and Mortality: A Systematic Review of Observational Studies. Int J Environ Res Public Health. 2019;16(3):383. Published 2019 Jan 29. doi:10.3390/ijerph16030383
  24. Henry ME, Appel LJ. Potassium-enriched salt substitutes: benefits, risks, and a “trolley problem” in public health. Am J Clin Nutr. 2021 Jul 1;114(1):12-13. doi: 10.1093/ajcn/nqab153. PMID: 33963732.
  25. Huang L, Trieu K, Yoshimura S, et al. Effect of dose and duration of reduction in dietary sodium on blood pressure levels: systematic review and meta-analysis of randomised trials. BMJ. 2020;368:m315. Published 2020 Feb 24. doi:10.1136/bmj.m315
  26. Huo X, Clarke R, Halsey J, Jackson R, Lehman A, Prince R, Lewis J, Baron J, Kroger H, Sund R, Armitage J. Calcium Supplements and Risk of CVD: A Meta-Analysis of Randomized Trials. Current Developments in Nutrition. 2023;7(3). doi: 10.1016/j.cdnut.2023.100046.
  27. Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, Ross AC, Taylor CL, Yaktine AL, Del Valle HB, eds. Dietary Reference Intakes for Calcium and Vitamin D. Washington (DC): National Academies Press (US); 2011.
  28. Kahwati LC, Weber RP, Pan H, et al. Vitamin D, Calcium, or Combined Supplementation for the Primary Prevention of Fractures in Community-Dwelling Adults: Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA. 2018;319(15):1600-1612. doi:10.1001/jama.2017.21640
  29. Kim J, Choi J, Kwon SY, et al. Association of Multivitamin and Mineral Supplementation and Risk of Cardiovascular Disease: A Systematic Review and Meta-Analysis. Circ Cardiovasc Qual Outcomes. 2018;11(7):e004224. doi:10.1161/CIRCOUTCOMES.117.004224
  30. Książek A, Zagrodna A, Słowińska-Lisowska M. Vitamin D, Skeletal Muscle Function and Athletic Performance in Athletes-A Narrative Review. Nutrients. 2019;11(8):1800. Published 2019 Aug 4. doi:10.3390/nu11081800
  31. Lerchl K, Rakova N, Dahlmann A, et al. Agreement between 24-hour salt ingestion and sodium excretion in a controlled environment. Hypertension. 2015;66(4):850-857. doi:10.1161/HYPERTENSIONAHA.115.05851
  32. Li K, Wang XF, Li DY, et al. The good, the bad, and the ugly of calcium supplementation: a review of calcium intake on human health. Clin Interv Aging. 2018;13:2443-2452. Published 2018 Nov 28. doi:10.2147/CIA.S157523
  33. McMillen SA, Dean R, Dihardja E, Ji P, Lönnerdal B. Benefits and Risks of Early Life Iron Supplementation. Nutrients. 2022 Oct 19;14(20):4380. doi: 10.3390/nu14204380. PMID: 36297062; PMCID: PMC9608469.
  34. Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. J Acad Nutr Diet. 2016 Dec;116(12):1970-1980. doi: 10.1016/j.jand.2016.09.025. PMID: 27886704.
  35. Melse-Boonstra A. Bioavailability of Micronutrients From Nutrient-Dense Whole Foods: Zooming in on Dairy, Vegetables, and Fruits. Front Nutr. 2020 Jul 24;7:101. doi: 10.3389/fnut.2020.00101. PMID: 32793622; PMCID: PMC7393990.
  36. Messerli FH, Hofstetter L, Syrogiannouli L, Rexhaj E, Siontis GCM, Seiler C, Bangalore S. Sodium intake, life expectancy, and all-cause mortality. Eur Heart J. 2021 Jun 1;42(21):2103-2112. doi: 10.1093/eurheartj/ehaa947. PMID: 33351135; PMCID: PMC8169157.
  37. Michos ED, Cainzos-Achirica M, Heravi AS, Appel LJ. Vitamin D, Calcium Supplements, and Implications for Cardiovascular Health: JACC Focus Seminar. J Am Coll Cardiol. 2021 Feb 2;77(4):437-449. doi: 10.1016/j.jacc.2020.09.617. PMID: 33509400.
  38. Milajerdi A, Djafarian K, Shab-Bidar S. Dose-response association of dietary sodium intake with all-cause and cardiovascular mortality: a systematic review and meta-analysis of prospective studies. Public Health Nutr. 2019;22(2):295-306. doi:10.1017/S1368980018002112
  39. Morelli MB, Santulli G, Gambardella J. Calcium supplements: Good for the bone, bad for the heart? A systematic updated appraisal. Atherosclerosis. 2020;296:68-73. doi:10.1016/j.atherosclerosis.2020.01.008
  40. Myung SK, Kim HB, Lee YJ, Choi YJ, Oh SW. Calcium Supplements and Risk of Cardiovascular Disease: A Meta-Analysis of Clinical Trials. Nutrients. 2021 Jan 26;13(2):368. doi: 10.3390/nu13020368. PMID: 33530332; PMCID: PMC7910980.
  41. National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Food and Nutrition Board; Committee to Review the Dietary Reference Intakes for Sodium and Potassium, Oria M, Harrison M, Stallings VA, eds. Dietary Reference Intakes for Sodium and Potassium. Washington (DC): National Academies Press (US); 2019.
  42. O’Connor EA, Evans CV, Ivlev I, Rushkin MC, Thomas RG, Martin A, Lin JS. Vitamin and Mineral Supplements for the Primary Prevention of Cardiovascular Disease and Cancer: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA. 2022 Jun 21;327(23):2334-2347. doi: 10.1001/jama.2021.15650. PMID: 35727272.
  43. O’Donnell M, Mente A, Yusuf S. Sodium intake and cardiovascular health. Circ Res. 2015;116(6):1046-1057. doi:10.1161/CIRCRESAHA.116.303771
  44. O’Donnell M, Mente A, Alderman MH, Brady AJB, Diaz R, Gupta R, López-Jaramillo P, Luft FC, Lüscher TF, Mancia G, Mann JFE, McCarron D, McKee M, Messerli FH, Moore LL, Narula J, Oparil S, Packer M, Prabhakaran D, Schutte A, Sliwa K, Staessen JA, Yancy C, Yusuf S. Salt and cardiovascular disease: insufficient evidence to recommend low sodium intake. Eur Heart J. 2020 Sep 14;41(35):3363-3373. doi: 10.1093/eurheartj/ehaa586. PMID: 33011774.
  45. Olde Engberink RHG, van den Hoek TC, van Noordenne ND, van den Born BH, Peters-Sengers H, Vogt L. Use of a Single Baseline Versus Multiyear 24-Hour Urine Collection for Estimation of Long-Term Sodium Intake and Associated Cardiovascular and Renal Risk. Circulation. 2017;136(10):917-926. doi:10.1161/CIRCULATIONAHA.117.029028
  46. Perna S. Is Vitamin D Supplementation Useful for Weight Loss Programs? A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Medicina (Kaunas). 2019;55(7):368. Published 2019 Jul 12. doi:10.3390/medicina55070368
  47. Pilz S, Zittermann A, Trummer C, et al. Vitamin D testing and treatment: a narrative review of current evidence. Endocr Connect. 2019;8(2):R27-R43. doi:10.1530/EC-18-0432
  48. Rakova N, Jüttner K, Dahlmann A, et al. Long-term space flight simulation reveals infradian rhythmicity in human Na(+) balance. Cell Metab. 2013;17(1):125-131. doi:10.1016/j.cmet.2012.11.013
  49. Reid IR, Bristow SM, Bolland MJ. Calcium and Cardiovascular Disease. Endocrinology and Metabolism. 2017;32:339-349. doi:10.3803/EnM.2017.32.3.339
  50. Reijven PLM, Soeters PB. Vitamin D: A magic bullet or a myth? Clin Nutr. 2020 Sep;39(9):2663-2674. doi: 10.1016/j.clnu.2019.12.028. Epub 2020 Jan 10. PMID: 31959477.
  51. Rizzoli R. Vitamin D supplementation: upper limit for safety revisited? Aging Clin Exp Res. 2021 Jan;33(1):19-24. doi: 10.1007/s40520-020-01678-x. Epub 2020 Aug 28. PMID: 32857334; PMCID: PMC7897606.
  52. Ruiz-García A, Pallarés-Carratalá V, Turégano-Yedro M, Torres F, Sapena V, Martin-Gorgojo A, Martin-Moreno JM. Vitamin D Supplementation and Its Impact on Mortality and Cardiovascular Outcomes: Systematic Review and Meta-Analysis of 80 Randomized Clinical Trials. Nutrients. 2023 Apr 7;15(8):1810. doi: 10.3390/nu15081810. PMID: 37111028; PMCID: PMC10146299.
  53. Schwingshackl L, Boeing H, Stelmach-Mardas M, et al. Dietary Supplements and Risk of Cause-Specific Death, Cardiovascular Disease, and Cancer: A Systematic Review and Meta-Analysis of Primary Prevention Trials. Adv Nutr. 2017;8(1):27-39. Published 2017 Jan 17. doi:10.3945/an.116.013516
  54. Sim M, Garvican-Lewis LA, Cox GR, Govus A, McKay AKA, Stellingwerff T, Peeling P. Iron considerations for the athlete: a narrative review. Eur J Appl Physiol. 2019 Jul;119(7):1463-1478. doi: 10.1007/s00421-019-04157-y. Epub 2019 May 4. PMID: 31055680.
  55. Tankeu AT, Ndip Agbor V, Noubiap JJ. Calcium supplementation and cardiovascular risk: A rising concern. J Clin Hypertens (Greenwich). 2017;19(6):640-646. doi:10.1111/jch.13010
  56. Thakur N, Raigond P, Singh Y, Mishra T, Singh B, Lal M, Dutt S. Recent Updates on Bioaccessibility of Phytonutrients. Trends in Food Science & Technology. 2020;97:366-380
  57. Trinquart L, Johns DM, Galea S. Why do we think we know what we know? A metaknowledge analysis of the salt controversy. Int J Epidemiol. 2016;45(1):251-260. doi:10.1093/ije/dyv184
  58. Wallace T, Weaver C. Calcium Supplementation and Coronary Artery Disease: A methodological Confound? Journal of the American College of Nutrition. 2020;39(5):383-387. doi:10.1080/07315724.2019.1681202
  59. Wang YJ, Yeh TL, Shih MC, Tu YK, Chien KL. Dietary Sodium Intake and Risk of Cardiovascular Disease: A Systematic Review and Dose-Response Meta-Analysis. Nutrients. 2020 Sep 25;12(10):2934. doi: 10.3390/nu12102934. PMID: 32992705; PMCID: PMC7601012.
  60. Yang C, Shi X, Xia H, et al. The Evidence and Controversy Between Dietary Calcium Intake and Calcium Supplementation and the Risk of Cardiovascular Disease: A Systematic Review and Meta-Analysis of Cohort Studies and Randomized Controlled Trials. J Am Coll Nutr. 2020;39(4):352-370. doi:10.1080/07315724.2019.1649219
  61. Yao P, Bennett D, Mafham M, et al. Vitamin D and Calcium for the Prevention of Fracture: A Systematic Review and Meta-analysis. JAMA Netw Open. 2019;2(12):e1917789. Published 2019 Dec 2. doi:10.1001/jamanetworkopen.2019.17789
  62. Zhang FF, Barr SI, McNulty H, Li D, Blumberg JB. Health effects of vitamin and mineral supplements. BMJ. 2020 Jun 29;369:m2511. doi: 10.1136/bmj.m2511. PMID: 32601065; PMCID: PMC7322674.
  63. Zhang Y, Fang F, Tang J, et al. Association between vitamin D supplementation and mortality: systematic review and meta-analysis. BMJ. 2019;366:l4673. Published 2019 Aug 12. doi:10.1136/bmj.l4673
Scroll to Top