A new review reveals how smarter supplement strategies and cutting-edge diagnostics could tackle hidden vitamin and mineral deficiencies worldwide—who needs them and what works?
Review: Micronutrients — Assessment, Requirements, Deficiencies, and Interventions. Image Credit: Fida Olga / Shutterstock
In a recent review article published in The New England Journal of Medicine, the author describes the current state of knowledge regarding the body’s requirements for various micronutrients and how deficiencies can be treated.
The focus is on current issues and emerging research, particularly of interest to healthcare practitioners. The author Lindsay H. Allen, Ph.D. at the University of California at Davis, also notes that supplements should be used cautiously and targeted to at-risk groups, as routine supplementation for chronic disease prevention is not supported by current evidence, and that while micronutrient deficiencies are known to cause acute health problems, evidence for their role in chronic disease prevention through supplementation remains limited and sometimes inconclusive, though some studies suggest possible benefits in specific cases such as cancer mortality reduction with vitamin D.
Micronutrients and their medical history
Micronutrients are essential nutrients that humans need in small amounts. They include trace minerals and fat-soluble and water-soluble vitamins. They do not include sodium or calcium, which are macrominerals.
Deficiencies in one or more of the 20 essential micronutrients can affect the body’s genes, proteins, and metabolism. Some common deficiencies include anemia (caused by the lack of vitamin B12 or iron), night blindness (lack of vitamin A), rickets (lack of vitamin D), and scurvy (lack of vitamin C).
The term ‘vitamin’ was introduced in the early 1900s, with their discovery involving animal models to understand how different nutrients prevent deficiency. While widespread recognition of the importance of micronutrients came early on due to severe deficiency symptoms, it took centuries before physicians identified specific essential nutrients.It was not until the 1980s that the adverse effects of mild (as opposed to acute) micronutrient depletion without clinical symptoms were recognized.
More recently, randomized controlled trials in low—and middle-income countries (LMICs) have established the need to monitor micronutrient status and the effectiveness of interventions. Many countries have now implemented programs to monitor and control micronutrient deficiencies.
Assessing micronutrient status
Bodies such as the European Food Safety Authority set recommendations for micronutrient intake. They use reference values such as the estimated average requirement (EAR), defined as the median intake necessary for a particular group; the recommended dietary allowance (RDA, the amount needed to meet 97.5% of a group’s needs); and the tolerable upper intake level (UL, the most a person can consume without harm).
Consuming a micronutrient below the EAR indicates an increased probability of deficiency, while the RDA is often used for dietary planning. The UL is important to avoid overconsumption of supplements or fortified foods.
Assessing micronutrient status to identify deficiencies can involve collecting information on food consumed or biochemical markers. The cutoff values for these ‘biomarkers’ help medical professionals determine deficiencies, but errors may arise due to poor absorption, inflammation, or disease. Serum retinol is used to assess vitamin A status, while serum 25(OH)D, serum ferritin, and plasma zinc are used to determine vitamin D, iron, and zinc, respectively.
Estimating micronutrient intake can be challenging as dietary patterns vary, as does the use of supplements and fortified foods. However, dietary patterns can help identify risk – for example, individuals who avoid animal-based foods are at higher risk of iron, zinc, and vitamin B12 deficiencies.
Some tools use 24-hour dietary recalls and food diaries to collect information on what people are eating to assess their deficiency risk. By allowing for data collection over multiple periods, they can reduce errors and inaccuracies. However, intake data and biochemical assessments may not always align due to factors like poor absorption, inflammation, or underlying health conditions, complicating diagnosis and intervention decisions.
Current status in high-income countries
Higher-income countries, including the United States, often have reliable sources of information on micronutrient needs and supplements. Fortified foods are readily available, and supplement use is common. Multivitamin-mineral supplements are the most common supplement products; users generally follow healthier diets than non-users.
Often recommended supplements include vitamins C, D, and E, calcium, omega-3s, and folic acid. These are used to slow age-related eye degeneration, prevent congenital disabilities, prevent heart disease, and improve bone health. Despite trials, antioxidants like vitamins C and E have not been proven to reduce risks for chronic diseases and may have adverse effects at high doses, including increased risks of prostate cancer, respiratory infections, and even increased mortality associated with vitamin E, as well as a higher risk of hip fractures linked to high-dose vitamin A.
Although most micronutrient deficiencies are uncommon in high-income countries, certain groups remain at risk, including older adults (vitamin D, B6, choline), pregnant women (iron), and those with restricted diets such as vegans.
Vitamin D deficiency is common, particularly among non-Hispanic Black Americans and women; severe deficiencies are often linked to low exposure to sunlight.
Calcium and vitamin D supplements are critical for pregnant or lactating individuals with higher nutrient requirements. Iron deficiency anemia is also a concern for women, particularly during pregnancy. While iron supplementation can address this issue, high doses have been linked to side effects such as constipation and nausea. Folic acid fortification in foods has greatly reduced neural tube defects and deficiencies are rare, but high doses can impair vitamin B12 status.
Micronutrients in the global south
Vitamin A, iron, and iodine deficiencies became an important focus of global nutrition activities in the 1980s, particularly after research showed that vitamin A supplementation could lower preschooler mortality by 34%.
Since then, various interventions, including nutrition education, crop biofortification, food fortification, and supplements, have been used to address micronutrient deficiencies in LMICs through efforts such as the Food Fortification Initiative. Today, 94 countries have laws that require the fortification of grains like rice, maize, and wheat.
Supplementation often targets young children and pregnant women, as they are easily reached through health systems. Recent strategies increasingly favor multiple micronutrient supplements over single-nutrient approaches, often combining up to 15 nutrients to address coexisting deficiencies. Research has shown that supplements with multiple micronutrients, often containing 15 nutrients, can be more beneficial than single-nutrient supplements, for this group. However, the World Health Organization currently recommends multiple micronutrient supplementation during pregnancy, primarily within research contexts, until more definitive evidence is available.
Conclusions
Micronutrient deficiencies remain a significant public health concern, particularly in low- and middle-income countries and various monitoring efforts and interventions have been implemented to address them. Although widespread deficiencies are less common in high-income countries, targeted efforts are still needed for specific at-risk groups.
Emerging research using advanced "omics" technologies—such as genomics, proteomics, and metabolomics—is uncovering new biomarkers of deficiency (e.g., GSTO1 for zinc, plasmalogens for B12) and may reveal subtle, non-clinical impacts of marginal deficiencies, especially in vulnerable populations.
Ongoing research into improved biomarkers and more advanced metabolomics and genomics studies can improve our understanding of these deficiencies and optimize interventions for those who need them.