Food fortification saves lives on a population scale, but it does not affect everyone equally. Certain groups face heightened risk from fortification programs, either because they receive too little of the added nutrient to matter or because they receive enough to cause harm. Pregnant women, young infants, people with underlying thyroid or metabolic conditions, and communities too poor to buy commercially processed staples all occupy different corners of this problem, and each for different reasons.
Why Fortification Creates Winners and Losers
Large-scale food fortification is often described as a population-wide intervention, but in practice its effects are uneven across subgroups. People with limited access to commercially processed foods, or who simply cannot afford them, may get little benefit. At the same time, people with higher physiological requirements, such as pregnant and lactating women, may not get enough of a nutrient even from a fortified diet to meet their needs.1Europe PMC / Nutrients. Aligning the Epidemiology of Malnutrition with Food Fortification: Grasp Versus Reach This is the central tension: a single fortification level baked into a country’s flour or salt supply has to work for millions of people whose diets, body sizes, life stages, and health conditions vary enormously.
Tolerable upper intake levels are set with the goal of protecting all members of the general population, including sensitive individuals, throughout their lifetime. Regulatory bodies try to account for the range of individual thresholds at which a nutrient tips from beneficial to harmful, and they set separate limits for infants, children, adults, older adults, and pregnant or lactating women where needed.2PubMed Central. Guidance for establishing and applying tolerable upper intake levels for vitamins and essential minerals But those limits are modeled from available data, and the data for some populations, particularly infants layering multiple fortified products, are thin.
Pregnant Women and Folic Acid
The clearest success story in food fortification is folic acid added to flour to prevent neural tube defects. In the United States and Canada, adding roughly 100 to 150 micrograms a day of folic acid through fortified grain products raised blood folate levels and cut the number of babies born with neural tube defects.3PubMed. Fortification of flour with folic acid A U.S. study found that after mandatory fortification began in 1998, birth prevalence of neural tube defects dropped about 19%, from roughly 38 per 100,000 live births to about 31.4JAMA. Impact of Folic Acid Fortification of the US Food Supply on the Occurrence of Neural Tube Defects In countries that fortified at somewhat higher levels, the reductions were even steeper. Costa Rica saw about a 60% drop, and Chile saw roughly a 55% reduction between 1999 and 2009.5PubMed Central. Impact of folic acid fortification of flour on neural tube defects: a systematic review
Yet pregnant women remain a “risk group” even in countries with mandatory folic acid fortification, because the amount delivered through flour may not fully close the gap for a woman whose folate needs spike early in pregnancy, often before she knows she is pregnant. This is why public health agencies still recommend that women who could become pregnant take a separate folic acid supplement on top of whatever they get from fortified foods. Fortification brings up the population floor but does not necessarily push the most vulnerable subgroup past the threshold that prevents birth defects on its own.
Iron Fortification and the Double-Edged Sword
Iron deficiency is the most common micronutrient deficiency worldwide, and fortifying wheat flour with iron has been a standard public health tool for decades. A Cochrane review of the evidence estimated that iron-fortified wheat flour may reduce the risk of anemia by about 27% compared with unfortified flour.6PubMed Central. Wheat flour fortification with iron and other micronutrients for reducing anaemia and improving iron status in populations For people who are genuinely iron-deficient, that is a meaningful benefit.
The problem emerges when iron-fortified foods reach people who are not deficient. Elevated iron levels can shift the composition of gut bacteria, favoring harmful species while suppressing protective ones like bifidobacteria and lactobacilli. The resulting imbalance has been linked to gastrointestinal problems, inflammatory bowel disease, and metabolic disturbances.7PubMed. Current iron therapy in the light of regulation, intestinal microbiome, and toxicity: are we prescribing too much iron? This is not a theoretical concern. A scenario analysis modeling the effects of adding 10 milligrams of iron per day through fortification in India estimated it could increase the prevalence of high fasting blood glucose by 2 to 14% across different states, with similar bumps expected in high blood pressure and cholesterol.8European Journal of Clinical Nutrition. Is iron status associated with markers of non-communicable disease in adolescent Indian children?
This is the “dual burden” problem in compressed form. A country dealing with widespread iron-deficiency anemia also has growing rates of diabetes and heart disease. Fortification that helps one subgroup may nudge another toward metabolic trouble. Populations where iron deficiency and non-communicable diseases coexist in the same communities are at particular risk from one-size-fits-all iron fortification.
Iodized Salt and Thyroid Complications
Universal salt iodization is among the most successful public health measures ever implemented. But the introduction of iodized salt can cause problems in populations that were previously severely iodine-deficient. When iodine intake rises rapidly from very low levels, some people develop iodine-induced hyperthyroidism, a condition where the thyroid goes into overdrive. Reports from Zimbabwe and the Democratic Republic of Congo documented biochemical and sometimes clinically severe hyperthyroidism shortly after iodized salt was introduced, including cases that were potentially lethal.9PubMed. Risks of iodine-induced hyperthyroidism after correction of iodine deficiency by iodized salt
The risk is highest in the first couple of years after iodized salt enters a previously deficient market, and it concentrates among people who already have underlying thyroid disease, such as nodular goiter, which is itself a consequence of long-term iodine deficiency.10PubMed Central. Iodine-induced thyroid dysfunction In other words, the people most harmed by the correction are those who were most harmed by the original deficiency. Most individuals tolerate the extra iodine without problems, but in areas where deficiency has been entrenched for generations and goiter rates are high, rollout of iodized salt calls for monitoring thyroid outcomes alongside iodine status.
Vitamin A and Pregnancy Risk
Vitamin A fortification is common in staple foods like sugar and cooking oil in parts of sub-Saharan Africa, Central America, and South Asia. In populations with widespread deficiency, adding vitamin A to foods that everyone eats makes epidemiological sense. But preformed vitamin A (retinol) is one of the few vitamins where the gap between “enough” and “too much” is narrow enough to cause real harm, especially in early pregnancy.
A landmark study found that women who consumed more than 10,000 IU per day of supplemental vitamin A had nearly five times the prevalence of birth defects involving cranial-neural-crest tissue compared with women who consumed 5,000 IU or less per day. The risk appeared to have a threshold near 10,000 IU of supplemental vitamin A, and the increased defect rate was concentrated among women who consumed high levels before the seventh week of gestation.11PubMed. Teratogenicity of high vitamin A intake The European Food Safety Authority has set the tolerable upper intake level for preformed vitamin A at 3,000 micrograms per day for all adults, including pregnant and lactating women, with lower limits scaled down for children and infants.12PubMed Central. Scientific opinion on the tolerable upper intake level for preformed vitamin A and β-carotene
The risk group here is women in early pregnancy who layer fortified foods on top of supplements or a diet already high in liver and other retinol-rich animal foods. In countries where vitamin A is added to multiple food vehicles, the possibility of a pregnant woman exceeding safe levels without realizing it is not negligible. This is a place where total-diet monitoring matters more than just tracking a single food.
Infants at the Intersection of Multiple Fortified Products
Babies occupy a unique risk position because they are small, their nutrient needs change rapidly month by month, and they often receive nutrients from several fortified sources at once: infant formula, fortified cereals, vitamin drops, and sometimes micronutrient powders. A Dutch study that tracked vitamin D intake in infants from the combination of fortified foods, formula, and supplements found that about 4 to 12% of infants aged 7 to 11 months exceeded the tolerable upper intake level for vitamin D. At the 99th percentile, intake was 2 to 4 micrograms above the upper limit depending on age.13PubMed Central. Vitamin D intake of Dutch infants from the combination of (fortified) foods, infant formula, and dietary supplements
This pattern is called “stacking,” and it is difficult for parents to manage because the nutrient content of individual products looks safe on its own. A bottle of formula at 100% of the daily value, plus a fortified cereal at 50%, plus a vitamin drop at 100%, can easily push total intake past the ceiling without any single product being obviously problematic. Infants are also more sensitive to excess doses per kilogram of body weight than adults. The risk is most acute for fat-soluble vitamins like A and D, which accumulate in the body rather than being flushed out in urine.
Micronutrient Powders for Young Children
Point-of-use fortification with micronutrient powders, small sachets of vitamins and minerals that caregivers sprinkle onto home-prepared food, has become a popular strategy for reaching children who do not eat commercially fortified products. A review of the evidence found that home fortification with these powders reduced anemia by about 31% and iron deficiency by about 51% in infants and young children compared with no intervention, though there was no effect on growth.14PubMed. Home fortification of foods with multiple micronutrient powders for health and nutrition in children under two years of age These products fill a genuine gap, especially in low-income settings where families rely on unfortified staples. But they also add another variable to the stacking problem: a child receiving micronutrient powders at home may also be eating commercially fortified porridge and getting periodic high-dose vitamin A supplements through government campaigns.
Genetics and Individual Variation
Not everyone metabolizes the same nutrient the same way, and genetic variation can turn a population-level benefit into an individual-level risk. One well-studied example involves folate and a common genetic variant in the MTHFR gene. People who carry two copies of a particular variant (known as the TT genotype) appear to get a cancer-protective benefit from adequate folate intake. Among men with normal folate status, the TT genotype was associated with a threefold decrease in cancer risk compared with other genotypes. But that protection disappeared in men whose folate status was deficient, and people with the TT genotype who had low intakes of folate and related B vitamins were at elevated risk for colorectal adenomas compared with TT individuals who ate more of these nutrients.15Oxford Academic (The Journal of Nutrition). Folate, Methyl-Related Nutrients, Alcohol, and the MTHFR 677C→T Polymorphism Affect Cancer Risk: Intake Recommendations
The implication is that a fortification program designed to raise folate intake population-wide might help most people while failing to protect a genetically defined subgroup that also has poor dietary intake. Conversely, high folic acid intake has drawn concern (still debated in the literature) about potentially accelerating existing precancerous growths in some individuals. Genetics adds a layer of risk stratification that blanket fortification cannot accommodate.
When the Fortified Product Never Reaches the People Who Need It
Even a perfectly designed fortification policy does nothing for people who do not eat the fortified food. Micronutrient malnutrition is shaped by living conditions, income, cultural norms, and the food systems people can actually access.16PubMed Central. Equity in access to fortified maize flour and corn meal In many low- and middle-income countries, the poorest households buy grain from local mills that are not part of the fortification system, or they grow and process their own staples. These households are typically the ones with the highest rates of deficiency, creating a paradox where the intervention misses the people it was designed for.
Consumer behavior research underscores this gap. A study on fortified wheat flour found that about a third of respondents bought it from physical stores, but purchasing rates varied sharply by income. Among upper-class respondents, roughly 38% bought fortified flour in stores and 45% bought it online. Among lower-middle-class respondents, only about 22% bought it in stores and just 7% bought it online.17Scientific Reports. Consumer awareness, perceptions and purchasing behaviour regarding fortified wheat flour available in the market The people who can most easily buy fortified products are the people who least need them nutritionally. This is the access gap that population-level fortification statistics often mask.
Vitamin D Fortification and Global Variation
Vitamin D deficiency is widespread in many parts of the world, especially at higher latitudes where sunlight exposure is limited for much of the year. Countries like the United States, Canada, India, and Finland have adopted systematic vitamin D food fortification, with evidence supporting it as a cost-effective way to improve population vitamin D status.18PubMed Central. Rationale and Plan for Vitamin D Food Fortification: A Review and Guidance Paper Finland’s experience has been particularly instructive: after expanding vitamin D fortification of dairy products and fat spreads, the country saw meaningful improvements in population-level vitamin D levels.
But the risk-group issue persists. People who avoid dairy (whether for lactose intolerance, allergy, or dietary choice) miss most fortified vitamin D in countries that use milk as the primary vehicle. Older adults, who both need more vitamin D and tend to eat less overall, may not get enough from fortification alone. And dark-skinned individuals living at high latitudes produce less vitamin D from sunlight, compounding the challenge. These are the subgroups where fortification narrowly misses, and where targeted supplementation still matters.
Quality Control Failures on the Supply Side
A fortification policy is only as good as its enforcement. Data from 20 national fortification programs across 12 countries found that fewer than half of tested samples were adequately fortified according to the country’s own standards.19PubMed Central. Regulatory Monitoring of Fortified Foods: Identifying Barriers and Good Practices That means consumers who believe they are eating fortified food may be getting substantially less of the added nutrient than expected, or in some cases more. Both failures create risk: under-fortification defeats the purpose, while over-fortification can push intake past safe limits, particularly for people who eat large quantities of the fortified staple.
Storage and packaging add another layer of uncertainty. Vitamin A in fortified flour degrades rapidly under poor conditions. One study found that more than 45% of the added vitamin A was lost within three months even under mild storage conditions, and over 85% was lost in more extreme heat and humidity.20PubMed. Storage conditions and packaging greatly affects the stability of fortified wheat flour: Influence on vitamin A, iron, zinc, and oxidation Vitamin C in fortified milk is similarly fragile. In one experiment, the type of bottle determined whether the vitamin survived at all: in packaging without an oxygen barrier, vitamin C was completely oxidized within a month.21PubMed. Effects of sterilization, packaging, and storage on vitamin C degradation, protein denaturation, and glycation in fortified milks Temperature-driven degradation also affects vitamins D, B1, and pantothenic acid in various product formats.22PubMed Central. Stability of nutrients in complex liquid and powder food matrices: learnings from shelf-life studies in foods for special medical purposes
In tropical climates with weak cold chains, the vitamin A that was supposedly added to a bag of flour may be largely gone by the time it reaches a household. The label says “fortified,” but the biology says otherwise. This turns an apparent population benefit into an invisible risk-group failure, because the very regions that need fortification most are often the ones where storage conditions destroy it fastest.
Biofortification as an Alternative for Hard-to-Reach Groups
One response to the access problem has been biofortification: breeding or engineering staple crops to contain higher levels of vitamins and minerals in the plant itself, rather than adding nutrients at the processing stage. Orange-fleshed sweet potato (rich in beta-carotene), iron-enriched beans, and zinc-enriched wheat are among the products that have been developed and distributed in parts of Africa and South Asia.23PubMed Central. Biofortification: an approach to eradicate micronutrient deficiency The advantage is that the nutrient is already in the food when it is harvested, so it reaches people who grow their own staples or buy from local markets outside the industrial food chain.
Evidence so far suggests that biofortification can contribute to improved micronutrient intakes and status, though the effect sizes depend heavily on how much of the biofortified crop people actually eat and how well the added nutrients survive cooking and digestion.24PubMed. From harvest to health: challenges for developing biofortified staple foods and determining their impact on micronutrient status Biofortification does not solve the over-exposure problem for people at the high end of intake, but it addresses the other side of the risk equation: the populations that industrial fortification systematically misses.
Monitoring Gaps and How They Affect Risk Judgments
Much of the difficulty in protecting fortification risk groups comes from incomplete data. Total dietary intake data, biomarker surveys, and voluntary supplement use are rarely collected in a way that lets public health officials compare the risks of deficiency against the risks of excess for a specific subgroup in a specific country. A framework proposed by nutrition researchers recommends assessing total dietary intakes and nutritional status, building rapid screening tools into routine surveillance, improving biomarkers of excess (not just deficiency), and developing methods for predicting and comparing the risks and benefits of fortification programs.25PubMed Central. Weighing the risks of high intakes of selected micronutrients compared with the risks of deficiencies
Without that data infrastructure, fortification programs fly somewhat blind. They know the national average is moving in the right direction, but they cannot see whether pockets of the population are being left behind or pushed into excess. The risk groups exist in the shadows of population averages.
Consumer Perception and Who Opts Out
There is also a behavioral dimension. Focus group research with consumers in the UK found that informing people about fortification in food products created trade-offs in their minds between taste, health benefits, price, and familiarity. Trust in labeling and product claims was a recurring concern.26PubMed. Exploring consumer beliefs about novel fortified foods: A focus group study with UK-based older and younger adult consumers If a fortified product tastes different, costs more, or feels unfamiliar, some consumers will avoid it. In mandatory fortification programs (where the nutrient is added to a staple like flour or salt), opting out is harder but not impossible: people can switch to unfortified artisanal products or imports. In voluntary programs, where companies choose whether to add nutrients, opting out is as easy as picking a different brand. The consumers most likely to opt out on taste or price grounds tend to be the ones who would benefit most from the added nutrients, reinforcing the access gap from another direction.