Table of Contents
At this point we have talked about 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 we 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 are one of the reasons why certain food groups exert significant health benefits. This is discussed further in Lesson 10.
Tip: This is where 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, 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:
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.
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.
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 UL, the potential risk of adverse effects may increase.
To be clear, more scientific evidence is required to establish an EAR and RDA level than needed to establish an AI. 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 in large part 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, 202)
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 will be 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.(Blumberg, 2018; Biesalski, 2017) However, there is potential harm in taking some of the mega dose supplements, specifically vitamin A, vitamin E, and beta-carotene.(Schwingshackl, 2017) 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) 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
- todders: iron
- adolescent males: phosphorus, choline, magnesium
- adolescent females: phosphous, choline, magnesium, iron, folate, B6, B12
- pregnant women: iron, folate, iodine, choline
- elderly: B12
- B12 is additionally of concerns for individuals who do not consume animal products
They additionally mention 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 one must be careful to also consider how much salt they use to season food.
In 2019 guidelines for sodium intake were updated to state that an adequate intake level is 1500mg daily for people aged 14 years or older while for health benefits trying to stay <2300mg 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 an ideal sodium intake is <1500mg/d. 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)
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 at what level may salt intake be too low. Some data suggests better outcomes with salt intake at 3000-5000mg/d(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) 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 some people are affected to different degrees by similar sodium intake.(Farquhar, 2015)
With all of this controversy in mind, I suggest people with elevated blood pressure decrease sodium intake to <2300mg daily if possible, whereas people with normal blood pressure can likely consume up to 5000mg daily without significant increased risk of other issues, assuming this does not cause a significant increase in their blood pressure.
Tip: One additional consideration is sodium lost in sweat. For people who sweat a large amount (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 one’s blood pressure) should be a suitable strategy.
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 one’s potassium level gets too high, it’s extremely difficult to achieve this from food intake and thus as long as one is not taking potassium supplements this is generally not a concern.
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/d 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 publication 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 cardiovascular disease. 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 age 14 years and older 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.
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.
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 IU daily should be a safe amount and help prevent deficiency or insufficiency. The below research does not consider COVID-19.
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 or all-cause mortality.(Zhang, 2019) A separate systematic review 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 or fractures or for other nonskeletal health outcomes.(Pilz, 2019)
Note: See below in the Calcium section for additional discussion on 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 benefit of vitamin D supplementation or otherwise raising one’s 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), and 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 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 obtain 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)
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 700mg daily age 1-3 years old, 1000mg daily age 4-8, 1300mg daily age 9-18, 1000mg daily age 19-70 in males and age 19-50 in females, 1200mg daily age 51-70 in females (due to increased need associated with menopause), and 1200mg daily if >70 years old. The TUL is based on a relatively sparse literature base primarily focused on risk of kidney stones and is set at 2500mg daily age 1-8, 3000mg daily age 9-18, 2500mg daily age 19-50, and 2000mg daily age 51+. Of note, it is rather difficult to achieve this limit with food intake alone.
Evidence for fracture risk reduction
Since the time of those guidelines more research has been done. A recent systematic review and meta-analysis 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. A separate recent systematic review did not find any significant benefit 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)
Evidence for harm
There have also been concerns of increased calcium intake potentially having a negative impact on cardiovascular health. In 2016 a systematic review and meta-analysis concluded that calcium intake below the TUL is not associated with increased cardiovascular risks in generally healthy adults and the data indicating concern came mostly from individuals with impaired kidney function.(Chung, 2017) 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 indicate a potential negative effect on cardiovascular risk, while a 2019 review takes 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) think the majority of the negative association with CVD is due to methodological confounding, while a separate recent editorial(Morelli, 2020) still suggests there are unresolved concerns. Finally, a 2020 systematic review and meta-analysis of cohort studies and randomized controlled trials evaluating dietary & supplemental calcium intake and the risk of cardiovascular disease shows that increased dietary calcium does not increase the risk of cardiovascular disease while calcium supplements do seem to increase the risk of coronary heart disease, especially myocardial infarction.(Yang, 2020)
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 to make up a dietary deficiency especially in individuals at higher risk of fractures.
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 also seen not uncommonly 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) 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 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 is difficult to determine one’s 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 proving effective.
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. 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. However, it is worth noting that low ferritin levels can contribute to poorer sleep.
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 (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 one’s health. In general when one is meeting the RDA additional supplementation tends to not prove very helpful for the average individual without specific medical conditions. Eating a variety of nutritious foods can aid in achieving a rich supply of micronutrients and phytonutrients to aid one’s health. Cronometer.com is a great starting point to assess one’s intake, supplementing a generic multivitamin/multimineral supplement is likely safe for anyone with concerns, and beyond that altering one’s diet to help achieve desirable quantities will likely prove beneficial, while individual supplements can be considered for specific situations.
- 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
- 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
- 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
- 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
- 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
- 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
- Cormick G, Belizán JM. Calcium Intake and Health. Nutrients. 2019;11(7):1606. Published 2019 Jul 15. doi:10.3390/nu11071606
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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.
- 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
- 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
- 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
- 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
- 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
- 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.
- 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
- 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
- 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.
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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.
- 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
- 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
- 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
- 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
- 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
- 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
- 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