Overall adherence to the US Dietary Guidelines is low: the majority of Americans do not follow a healthy eating pattern. Together with physical inactivity, eating an energy-rich, nutrient-poor diet predisposes one to many chronic diseases, including type 2 diabetes mellitus, cardiovascular disease, cancer, and osteoporosis. Approximately one-half of American adults have at least one preventable chronic disease (1), and additionally, obesity is a major public health problem in the US, with more than one-third of adults (2) and 17% of children and adolescents (3) classified as obese. Decades of public health messages to eat a balanced diet have not resulted in behavior change — energy-rich, nutrient-poor foods comprise an estimated 27% of daily caloric intake in the American diet, and alcohol constitutes an additional 4% of daily caloric intake (4). Many Americans are exceeding energy (caloric) needs but not meeting micronutrient (vitamin and nutritionally essential mineral) requirements. One analysis of US national survey data (National Health and Nutrition Examination Survey 2003-2006) found that children and adults with high intakes of added sugars (>25% of energy intake; the upper limit recommended by the National Academy of Medicine) had lower dietary intakes of several micronutrients, especially vitamins A, C, and E, as well as magnesium (5). An estimated 13% of the US population have added sugar intakes above this cutoff level for added sugars (5) and may be at risk for micronutrient inadequacies. In fact, National Health and Nutrition Examination Surveys (NHANES) that assess the nutritional and health status of a nationally representative sample of the civilian, non-institutionalized US population have reported a high prevalence of select micronutrient inadequacies in the US population (see Tables 1-3).

Assessing Nutrient Intake

Nutritional assessments in populations are typically done by measuring nutrient intake through dietary surveys and comparing mean intake with the age- and gender-specific nutrient requirements. Although more difficult and costly to do in entire populations, nutritional biomarkers — biochemical indicators that give more objective and reliable measures of dietary exposure and nutrient body status — are sometimes also employed (6, 7).

US national dietary surveys

“What We Eat in America” (WWEIA), the dietary assessment component of NHANES, is a joint effort of the US Department of Health and Human Services and the US Department of Agriculture. Nutrition data are collected during both in-depth household interviews and medical examinations; food intake is assessed by completing two 24-hour dietary recalls, the first being conducted at a mobile examination center and the second being a telephone interview 3 to 10 days later (8). Details on the information collected during the interviews can be found on the USDA website. Intake of 65 nutrients and food components is derived from dietary assessment information using the USDA's Food and Nutrient Database for Dietary Studies (FNDDS). FNDDS and WWEIA datasets are released every two years. NHANES also assesses dietary supplement use in the US population, so total nutrient intake from dietary and supplemental sources can be determined.

To assess nutrient intake and derive an estimate of the prevalence of nutrient inadequacy in the US population, the mean intake of an age- or gender-specific group is compared to the corresponding Estimated Average Requirement (EAR) for a particular nutrient. Like the other Dietary Reference Intakes (DRIs), the EARs are determined by expert panels appointed by the Food and Nutrition Board of the National Academy of Medicine (formerly the Institute of Medicine). The DRIs are nutrient-based reference values for the US and Canadian populations; in addition to the EAR, the DRIs include the Adequate Intake (AI), which is used to estimate prevalence of inadequacy in a population when a requirement has not been set; the Recommended Dietary Allowance (RDA; see HIGHLIGHT); and the Tolerable Upper Intake Level (UL; see HIGHLIGHT). The EAR is the DRI that should be used to assess nutrient intake of an individual or of a group. Using the RDA to assess nutrient intake is not appropriate; the RDA should instead be used in the planning of diets for individuals (9).

HIGHLIGHT: DIETARY REFERENCE INTAKES (9)

Estimated Average Requirement (EAR) - a nutrient intake value that is estimated to meet the requirement of half the healthy individuals in a particular life stage and gender group.

Recommended Dietary Allowance (RDA) - the dietary intake level that is sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group.

Adequate Intake (AI) - a recommended intake value based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of healthy people that are assumed to be adequate — used when an RDA cannot be determined.

Tolerable Upper Intake Level (UL) - the highest level of nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals in the general population.

Like all studies that assess dietary exposure using self-reported data, the NHANES analyses are subject to systematic bias and have some limitations. For example, the 24-hour dietary recall method relies on a person’s memory of food eaten and estimated portion size (10). A type of measurement error called recall bias can occur if the recollections of study participants are inaccurate. Also, a single-day assessment of food intake may not reflect usual dietary intake of participants (10). In a study that examined the validity of energy (caloric) intake data from NHANES 1971-2010 (28,993 men and 34,369 women), underreporting of caloric intake was found in 58.7% of men and 67.3% of women; underreporting of calories was even higher among obese individuals (11). Misreporting of dietary intake, including underreporting of intake, appears to also be common among children and, particularly, among adolescents (12). Thus, it is important to keep in mind that NHANES data of usual daily intakes of micronutrients may also be incorrectly estimated; the accuracy of micronutrient intake data of NHANES also depends on that of the FNDDS. In addition to collection of dietary data, some NHANES data include biochemical assessments that function as objective indicators of dietary intake and inform on participants’ nutritional status. Lastly, all the NHANES data are cross-sectional in nature and thus cannot provide any information about the causality of diet-health relationships.

Nutritional biomarkers

To avoid the bias associated with self-reporting of dietary intake, nutritional biomarkers can be used to evaluate dietary exposure and nutrient intake. Nutritional biomarkers are considered objective biochemical indicators of past dietary exposure and help inform nutrient body status (7, 13). To measure nutrient exposure and estimate body status, plasma or serum concentrations of certain nutrients (e.g., folate, vitamin B6, vitamin B12, vitamin C, vitamin D, vitamin E, copper, selenium, zinc) are measured in NHANES analyses. Concentration of folate in red blood cells — a better biomarker of long-term intake and body stores compared to blood levels (14) — has also been employed, and urinary iodine has been used as an indicator of recent iodine intake in NHANES participants (4 years and older). Moreover, no single biomarker captures body iron status, and NHANES analyses rely on the use and interpretation of several different measures, including serum iron, serum ferritin (the iron-storage protein), saturation of transferrin (the main carrier of iron in blood), transferrin receptor, and total iron-binding capacity.

It is important, however, to recognize the limitations of the biomarker used. For example, circulating levels are poor indicators of nutrient body status when the blood concentration of a nutrient is homeostatically regulated (e.g., vitamin A, calcium, zinc). Biomarkers are not available for every nutrient, and some are affected by disease states, including inflammation and infection, and also by kidney function or age (15).

Thus, dietary surveys and nutritional biomarkers are two methods used to assess dietary exposure of a population. Each has its advantages and limitations but can be used in combination to better estimate dietary intake and inform on nutritional status.

Micronutrient Deficiencies and Inadequacies 

Very low dietary intake of a vitamin or nutritionally essential mineral can result in deficiency disease, termed micronutrient deficiency. Micronutrient deficiencies, especially iron, vitamin A, zinc, iodine, and folate, are prevalent in the developing world, affecting an estimated 2 billion people worldwide. They are a major contributor to infections and associated with severe illness and death (16). Subpopulations most at risk for micronutrient deficiencies include pregnant women and children five years and younger (15). Primarily affecting the underdeveloped world, micronutrient deficiencies are rare, but not absent, in populations residing in industrialized nations.

However, micronutrient inadequacies — defined as nutrient intake less than the EAR — are common in the United States and other developed countries. Such inadequacies may occur when micronutrient intake is above the level associated with deficiency but below dietary intake recommendations (17). In contrast to micronutrient deficiencies that result in clinically overt symptoms, micronutrient inadequacies may cause covert symptoms only that are difficult to detect clinically. For example, micronutrient inadequacies could elicit symptoms of general fatigue (18), reduced ability to fight infections (19), or impaired cognitive function (i.e., attention [concentration and focus], memory, and mood) (19). Micronutrient inadequacies may also have important implications for long-term health and increase one’s risk for chronic diseases like cancer (17, 20), cardiovascular disease (20), type 2 diabetes mellitus (21), osteoporosis (20, 22), and age-related eye disease (23).

Many Americans are not reaching micronutrient intake requirements from food alone (24, 25), presumably due to eating an energy-rich, nutrient-poor diet. About 75% of the US population (ages ≥1 year) do not consume the recommended intake of fruit, and more than 80% do not consume the recommended intake of vegetables (1). Intakes of whole grains are also well below current recommendations for all age groups, and dairy intake is below recommendations for those ages 4 years and older (1). The 2015-2020 Dietary Guidelines for Americans highlighted the nutrients that are underconsumed in the US population, i.e., "shortfall nutrients," labeling a few as "nutrients of public health concern" because low intake may lead to adverse health effects: Vitamin D (adverse health effect: osteoporosis), calcium (osteoporosis), potassium (hypertension and cardiovascular disease), dietary fiber (poor colonic health), and iron (anemia in young children, women of childbearing age, and pregnant women) were such labeled (1). Other nutrients, including vitamins A, C, and E; choline, and magnesium, were identified as also being underconsumed by the US population (1).

A recent US national survey, NHANES 2007-2010, which surveyed 16,444 individuals four years and older, reported a high prevalence of inadequacies for multiple micronutrients (see Table 1). Specifically, 94.3% of the US population do not meet the daily requirement for vitamin D, 88.5% for vitamin E, 52.2% for magnesium, 44.1% for calcium, 43.0% for vitamin A, and 38.9% for vitamin C. For the nutrients in which a requirement has not been set, 100% of the population had intakes lower than the AI for potassium, 91.7% for choline, and 66.9% for vitamin K. The prevalence of inadequacies was low for all of the B vitamins and several minerals, including copper, iron, phosphorus, selenium, sodium, and zinc (see Table 1). Moreover, more than 97% of the population had excessive intakes of sodium, defined as daily intakes greater than the age-specific UL (26).

Table 1. NHANES 2007-2010: Usual Micronutrient Intake from Food Sources and Prevalence of Micronutrient Inadequacies Among US Residents Ages ≥4 Years (26)
Micronutrient Mean Daily Intake from Food* % < EAR
 Folate 542 μg DFE
9.5
 Niacin 24.7 mg
1.1
 Riboflavin 2.2 mg
2.1
 Thiamin 1.6 mg
4.7
 Vitamin A 621 μg RAE
43.0
 Vitamin B6 2.0 mg
9.5
 Vitamin B12 5.3 μg 2.5
 Vitamin C 84.0 mg 38.9
 Vitamin D 4.9 μg 94.3
 Vitamin E# 7.4 mg 88.5
 Vitamin K 85.2 μg 66.9
 Calcium 987 mg 44.1
 Copper 1.3 μg 4.2
 Iron 15.1 mg 7.4
 Magnesium 286 mg 52.2
 Phosphorus 1,350 mg 1.0
 Potassium 2,595 mg 100
 Selenium 108 μg
0.3
 Sodium 3,433 mg
0.1
 Zinc 11.7 mg
11.7
 Choline†† 315 mg 91.7
*includes enriched and fortified food
#α-tocopherol
% < AI; DFE, dietary folate equivalents
††considered an essential nutrient but not strictly a micronutrient
Abbreviations: DFE, dietary folate equivalents; RAE, retinol activity equivalents

It is important to note that the abovementioned data include micronutrient intake from enriched and fortified food and thus represent micronutrient intakes from all food sources. Enrichment is the addition of nutrients to replace losses that may occur in food processing, and fortification is the addition of nutrients to food to prevent or correct a nutritional deficiency, to balance the total nutrient profile of food, or to restore nutrients lost in processing. Fortified and enriched food help Americans — both children and adults — meet dietary requirements of many micronutrients, especially for folate, niacin, riboflavin, thiamin, vitamin A, vitamin D, and iron (see Table 2 and Table 3 below and the separate article on Micronutrient Inadequacies: the Remedy) (24).

Table 2. NHANES 2003-2006: Usual Micronutrient Intake from Food Sources and Prevalence of Micronutrient Inadequacies Among US Children and Adolescents (ages 2-18 Years) (24)
Micronutrient Mean Daily Intake from Food (naturally occurring) Mean Daily Intake from Food (naturally occurring + enriched/fortified) % < EAR when Accounting for Intake from All Food Sources
Folate 159 μg DFE 550 μg DFE 4.1
Niacin 13.9 mg 21.9 mg 0.8
Riboflavin 1.6 mg 2.2 mg 1.1
Thiamin 0.8 mg 1.6 mg 2.0
Vitamin A 377 μg RAE 604 μg RAE 5.7
Vitamin B6 1.3 mg 1.8 mg 3.8
Vitamin B12 4.3 μg 5.6 μg 1.1
Vitamin C 66.2 mg 84.8 mg 19.2
Vitamin D 1.7 μg 6.1 μg 86.8
Vitamin E* 5.7 mg 5.9 mg 81.4
Vitamin K 55.8 μg 56.2 μg 62.4#
Calcium 963 mg 1,025 mg 47.2
Copper 1.1 μg 1.1 μg 3.0
Iron 8.4 mg 15.3 mg 2.1
Magnesium 229 mg 236 mg 35.5
Phosphorus 1,257 mg 1,280 mg 16.8
Potassium 2,288 mg 2,301 mg 97.6#
Selenium 95.7 μg 96.4 μg 0.4
Zinc 9.8 mg 11.5 mg 6.5
*α-tocopherol
#% ≤AI (adequate intake)
Abbreviations: DFE, dietary folate equivalents; EAR, estimated average requirement; RAE, retinol activity equivalents
Table 3. NHANES 2003-2006: Usual Micronutrient Intake from Food Sources and Prevalence of Micronutrient Inadequacies Among US Adults (ages ≥19 Years) (24)
Micronutrient Mean Daily Intake from Food (naturally occurring) Mean Daily Intake from Food (naturally occurring + enriched/fortified) % < EAR when Accounting for Intake from All Food Sources
Folate 213 μg DFE 540 μg DFE 12.8
Niacin 18.5 mg 25.1 mg 2.0
Riboflavin 1.7 mg 2.3 mg 2.4
Thiamin 0.9 mg 1.7 mg 7.2
Vitamin A 424 μg RAE 600 μg RAE 51.0
Vitamin B6 1.6 mg 2.0 mg 15.1
Vitamin B12 4.3 μg 5.2 μg 3.9
Vitamin C 74.4 mg 85.4 mg 42.9
Vitamin D 2.0 μg 4.5 μg 95.4
Vitamin E* 6.8 mg 7.2 mg 93.9
Vitamin K 86.7 μg 88.2 μg 71.1#
Calcium 856 mg 911 mg 49.4
Copper 1.3 μg 1.3 μg 4.7
Iron 10.3 mg 16.0 mg 7.8
Magnesium 278 mg 290 mg 60.9
Phosphorus 1,308 mg 1,342 mg 1.8
Potassium 2,695 mg 2,717 mg 97.6#
Selenium 109 μg 110 μg 1.1
Zinc 11.2 mg 12.3 mg 11.9
*α-tocopherol
#% ≤AI (adequate intake)
Abbreviations: DFE, dietary folate equivalents; EAR, estimated average requirement; RAE, retinol activity equivalents

Shortfall Micronutrients

Calcium

Calcium is designated a nutrient of public health concern in the 2015-2020 Dietary Guidelines for Americans because it is underconsumed by certain subpopulations and because of its importance in bone health (see the article on Bone Health) (1). Calcium status must be assessed through dietary intake surveys because blood concentrations of calcium are tightly regulated at 2.5 mM (27). Dietary surveys show that many Americans are not meeting the dietary requirements for calcium, especially older children, adolescents, and women (including pregnant women), and some older adults. Overall, more than 40% of the US population do not meet the calcium requirement from diet alone (28). When accounting for intake from all sources, including calcium or multi-nutrient supplements (calcium-containing supplements are taken by 26% of the population), total usual calcium intakes for female adolescents (ages 12-19 years) and older women (ages ≥60 years) were still below the age-specific EAR (NHANES 2009-2010) (29). Compiling intake data from all age groups (2 years and older), males had higher daily intakes, but when adjusting for total caloric intake, females had a higher calcium "density" than the males (29). Dairy products, which represent rich and absorbable sources of calcium, comprised at least 37% of total calcium intake in this analysis (29).

Iron

The Dietary Guidelines for Americans 2015-2020 highlights iron as a nutrient of public health concern for certain subgroups of the population, including young children, women who may become pregnant, and pregnant women.

Dietary surveys have estimated usual iron intake and the prevalence of iron inadequacy among young children in the US. A report from NHANES 2009-2012 found that 10% of infants ages 6 to 11 months (n=381) had dietary iron intakes less than the EAR (30), and the prevalence of iron inadequacy for toddlers ages 12 to 23 months (n=516) was estimated to be only 1% (30). Similar results were found in a study that examined intake of 3,022 US infants and toddlers: 7.5% of infants (7-11 months) and less than 1% of toddlers (12-24 months) had intakes below the EAR (31). Additionally, compiling data from NHANES releases from 2003-2012, less than 1% of toddlers (n=1122) ages 12-23 months had intakes below the EAR for iron (32).

Because iron content of breast milk is low, the American Academy of Pediatrics recommends that breast-fed infants be given 1 mg/kg/day of supplemental iron beginning at 4 months of age until complementary foods, including iron-fortified cereal, are introduced (see the American Academy of Pediatrics website for age-specific recommendations regarding iron intake) (33). Fortified and enriched food are significant sources of dietary iron for older children and adolescents (34).

Adolescents have increased requirements for iron due to rapid growth. In particular, adolescent girls are at a heightened risk of iron deficiency due to inadequate intake of dietary iron, especially heme iron; increased demands of growth; and iron loss that occurs with menstruation. NHANES 2001-2002 found that 16% of US adolescent girls had iron intakes below the EAR, whereas fewer than 5% of adolescent boys were considered to have inadequate iron intake (35).

Multiple biomarkers, including serum iron, red blood cell hemoglobin, serum ferritin, transferrin saturation, soluble transferrin receptor (sTfR), and total iron-binding capacity, have been used to assess iron status at the population level. However, these are often used to assess iron deficiency rather than dietary iron inadequacy. The CDC’s Second National Report on Biochemical Indicators of Diet and Nutrition in the US Population reported data from NHANES 2003-2006 using biochemical cutoffs for iron inadequacy in children, adolescents, and adults (36). In particular, the prevalence of iron inadequacy assessed by serum ferritin (cutoffs of <12 ng/mL for children and <15 ng/mL for adolescents and adults) was 8.9% in US children ages 1-5 years, 15.2% in adolescent females ages 12-19 years, and 13.2% in nonpregnant women of childbearing age (ages 20-49 years) (36). Additionally, 16.9% of adolescent females and 19.4% of nonpregnant women of childbearing age were found to have high serum sTfR concentrations (>4.4 mg/L), another biomarker of iron inadequacy (36). In an analysis of NHANES 1999-2006 data that used various markers of iron deficiency, 9.8% of nonpregnant women (ages 18-49 years) and 25.4% of pregnant women were considered to be iron deficient, i.e., with values below at least two of the three iron deficiency cutoffs: hemoglobin concentration <12 g/dL, ferritin concentration <12 ng/mL, and transferrin saturation <16% (37). Another analysis of these NHANES data, examining prevalence of iron deficiency among 1,171 pregnant women, found that 17.4% were deficient by sTfR concentrations and 18.0% by total body iron, a value that is calculated using serum ferritin and sTfR concentrations (38). Not surprisingly, the prevalence of iron deficiency in the second, and especially, the third trimester of pregnancy was greater than in the first trimester (38); intake requirements for dietary iron increase starting in the second trimester despite an increase in intestinal iron absorption (39).

For more information on life stage-specific needs for iron, see the article on Iron.

Magnesium

The 2015-2020 Dietary Guidelines state that magnesium is underconsumed in the US (1); however, it was not labeled as a "nutrient of public health concern" despite low intake of magnesium being associated with increased risks of several chronic diseases, including cardiovascular disease, type 2 diabetes, and potentially, osteoporosis (40, 41). According to dietary surveys, more than one-half of the US population (ages ≥4 years) has intakes below the EAR for magnesium (see Table 1) (26) — NHANES 2003-2006 found that about 36% of children and adolescents and 61% of adults had intakes lower than the EAR for magnesium (24). Reliable biomarkers of magnesium intake are not available (40), and data assessing magnesium status in the US population are lacking. Blood concentrations of magnesium are tightly regulated and cannot be used to assess magnesium nutritional status (41).

Good sources of magnesium include green leafy vegetables, whole grains, beans, and nuts; consumption of whole grains, dark-green vegetables, and beans among Americans is well below intake recommendations (1).

Potassium

The US Dietary Guidelines 2015-2020 highlights potassium as a nutrient of public health concern because it is underconsumed by Americans (1). US national surveys indicate that the vast majority of the US population does not meet intake recommendations for potassium. Among US adults (ages ≥20 years) surveyed in NHANES 2011-2012 (n=4,730), fewer than 3% had potassium intakes greater than the adequate intake of 4,700 mg/day (42). According to NHANES 2009-2010, average potassium intakes are well below the AI for all age groups assessed (2 years and older), with the potassium density of the diet being higher in females versus males (43). Fruit and vegetables were the main dietary source of the mineral, comprising 20% of total potassium intake, about half of which came from white potatoes. Additionally, another NHANES analysis (2003-2010) found that almost all (97%) infants ages 7 to 11 months reached the AI for potassium, presumably because breast milk and infant formula provide sufficient amounts of potassium (44, 45) and because younger children have higher fruit intakes (1). However, only ~5% of children ages 1 to 3 years and less than 1% of children ages 4 to 5 years met the age-specific AI (46).

The richest sources of potassium are fruit and vegetables; approximately three-quarters of the US population do not meet intake recommendations for fruit and vegetables (1).

Vitamin A

Dietary surveys indicate that many US adults are not meeting dietary requirements for vitamin A: Even when accounting for vitamin A from fortified food, which is significant, 51% of adults fall short of the EAR (24). In contrast, more than 94% of children and adolescents (ages 2-18 years) have vitamin A intakes equivalent to the requirement or higher (24). Fortified, ready-to-eat cereal and fortified milk are important sources of vitamin A for children and adolescents (34). NHANES has also reported serum retinol concentrations: less than 1% of the US population is deficient in vitamin A (36). Serum retinol concentrations can be used to assess deficiency in a population (47), but this assay cannot assess vitamin A inadequacy because retinol concentrations decline only once liver reserves are depleted (48). Moreover, serum retinol concentrations are decreased by inflammation and infection (47-49).

Vitamin C

Dietary intake surveys have found a higher prevalence of vitamin C inadequacy among adults (43%) compared to children and adolescents (19% for ages 2-18 years) (24). Biomarker data confirm that adults are at an increased risk for vitamin C deficiency. Serum ascorbic acid concentrations are often used to assess vitamin C status; concentrations between 11.4 and 23 μmol/L may be considered low, and concentrations lower than 11.4 μmol/L are generally considered deficient (36). Based on data from NHANES 2003-2006, 6% of the US population (≥6 years) were severely deficient in vitamin C. The prevalence of vitamin C deficiency and low vitamin C concentrations was lower among children ages 6 to 11 years compared to adolescents and adults; greater than 6% of adults ages 20 to 59 years were considered vitamin C deficient and greater than 10% had low serum vitamin C concentrations (36). Females had higher concentrations than males (36).

Previous NHANES analyses have reported a higher prevalence of severe vitamin C deficiency in the US population (50), suggesting that vitamin C status has improved in the US population over the past two decades.

Vitamin D

Dietary intake surveys indicate a high prevalence of vitamin D inadequacy in the US population, with 81% of children and adolescents (age 2-18 years) and 95% of adults not meeting the EAR (24). Fortified food substantially contribute to total vitamin D intake from the diet, especially among children and adolescents where intake from fortified food is 2.5 times that from natural sources (Table 2) (24).

However, surveys of dietary intake are not very informative because sunlight is the primary source of vitamin D (see the article on Vitamin D). Measuring total serum 25-hydroxyvitamin D concentration (1 ng/mL corresponds to 2.5 nmol/L) is considered the best indicator to evaluate vitamin D status. Yet, high-quality evidence is still needed to ensure that the current cutoff values are optimal to define states of insufficiency and deficiency (51). According to the National Academy of Medicine (NAM) (formerly the Institute of Medicine), dietary intake at a level equivalent to the EAR corresponds to a 25-hydroxyvitamin D concentration of 16 ng/mL (40 nmol/L) (52); thus, concentrations below that cutoff are considered inadequate. The IOM cutoff for vitamin D deficiency is 12 ng/mL or 30 nmol/L; 25-hydroxyvitamin D concentrations greater than 20 ng/mL (50 nmol/L) are considered adequate for bone health by the NAM (52). Using these cutoffs, NHANES 2003-2006 found 17.2% and 8.1% of the US population (ages ≥1 year) to be inadequate or deficient in vitamin D, respectively (36). Sharp differences were found when the data were examined by ethnicity, with vitamin D inadequacy and deficiency being quite prevalent among Non-Hispanic blacks (see Table 4) (36). Additionally, obesity (body mass index [BMI] ≥30 kg/m2) — affecting more than one-third of US adults (53)  — is known to increase one’s risk for vitamin D deficiency (54).

Table 4. Prevalence of Vitamin D Inadequacy and Deficiency in the US Population by Ethnicity (ages ≥1 year), NHANES 2003-2006 (36)
Ethnicity Prevalence (%) of Inadequacy* Prevalence (%) of Deficiency#
Non-Hispanic blacks 51.6
31.1
Mexican Americans 24.4
11.3
Non-Hispanic whites 9.4
3.6
*NAM cutoff for inadequacy, 25-hydroxyvitamin D concentrations <16 ng/mL (40 nmol/L)
#NAM cutoff for deficiency, 25-hydroxyvitamin D concentrations <12 ng/mL (30 nmol/L)

An analysis of NHANES 2003-2006 data examining vitamin D status among US children and adolescents (ages 6-18 years), found that 10.3% were inadequate and 4.6% were deficient according to the NAM cutoffs (55). Stratifying the data by age group showed a lower prevalence of vitamin D insufficiency in younger children compared to older children and adolescents (see Table 5). Among children and adolescents considered obese (>95% BMI percentile), 17.8% had inadequate vitamin D status and 8.2% had vitamin D deficiency (55).

Table 5. Prevalence of Vitamin D Inadequacy and Deficiency in US Children and Adolescents, NHANES 2003-2006 (55)
Age Prevalence (%) of Inadequacy* Prevalence (%) of Deficiency#
6-8 years 2.7
1.2
9-13 years 10.0
3.9
14-18 years 16.2
8.1
*NAM cutoff for inadequacy, 25-hydroxyvitamin D concentrations <16 ng/mL (40 nmol/L)
#NAM cutoff for deficiency, 25-hydroxyvitamin D concentrations <12 ng/mL (30 nmol/L)

Overall, the prevalence of vitamin D inadequacy measured by biomarker data is much lower than the prevalence assessed by dietary intake surveys for all age groups. As stated above, dietary surveys poorly assess vitamin D body status. Sun exposure, skin color, and BMI have variable, substantial impact on vitamin D status; thus, examining circulating 25-hydroxyvitamin D concentrations is the most reliable way to assess vitamin D status in a population.

The above-discussed biomarker data use the NAM cutoffs for inadequacy and deficiency. Others have used higher cutoffs to evaluate vitamin D status in a population. For example, the US Endocrine Society has suggested that vitamin D deficiency and insufficiency should be defined as serum 25-hydroxyvitamin D values of ≤20 ng/mL (≤50 nmol/L) and <30 ng/mL (75 nmol/L), respectively (51). The Linus Pauling Institute recommends that individuals aim for serum 25-hydroxyvitamin D concentrations of at least 30 ng/mL (75 nmol/L). Using such cutoffs would result in higher estimates of the prevalence of vitamin D deficiency and inadequacy in a population.

Vitamin E

Severe vitamin E deficiency rarely occurs in humans but has been observed as a result of malnutrition, from genetic defects affecting the transport of α-tocopherol (i.e., defects of the α-tocopherol transfer protein [α-TTP] or of apolipoprotein B), and in fat malabsorption syndromes (56). Circulating levels of α-tocopherol are often used to assess vitamin E status, although concentrations should be adjusted for plasma lipid concentrations when elevated (57). According to the US National Academy of Medicine, plasma α-tocopherol concentrations less than 12 μmol/L (516 μg/dL) in adults are indicative of vitamin E inadequacy (58). Using this cutoff, data from NHANES 2005-2006 based on plasma concentrations show that the prevalence of vitamin E inadequacy among US adults (≥20 years), excluding pregnant and lactating women, is extremely low (<1% of the population) (36). Past NHANES analyses have found a similar low prevalence of vitamin E inadequacy among US adults (36). This contrasts with the data from dietary surveys that suggest vitamin E inadequacy in the US is widespread. Discrepancies may be due to a number of factors, including underreporting of fat and fat-soluble vitamin intake, inaccuracies in the food composition database that lists nutrient values of foods, and/or lack of correction of circulating vitamin E concentrations to lipid concentrations (36). Some have questioned whether the nutritional requirement of vitamin E needs to be reevaluated (57).

Micronutrient Excess

Sodium

According to dietary surveys, almost all Americans meet the AI for sodium (1.2-1.5 g/day). In fact, sodium is overconsumed by the US population: 90% of US adults surveyed in NHANES 2011-2012 had daily sodium intakes in excess of the UL of 2.3 g/day (42). Several surveys have found that more than 99% of US adults have intakes in excess of the AI for all age and gender groups examined (26, 59). Combined data from NHANES 2007-2008 and 2009-2010 indicated that average dietary sodium intakes were 3.1 g/day in children (ages, 3-18 years), 3.8 g/day in adults ages 19-50 years, and 3.3 g/day in older adults (>50 years) (60). All of these intakes are well above the UL — only about 22% of children, 8% of adults, and 15% of older adults consume less than the life stage-specific UL for sodium (60). A more recent assessment from NHANES 2011-2012 examined sodium intakes of children by age group, finding average intakes of 3.1 g/day in children (ages, 6-10 years), 3.1 g/day in preadolescents (ages, 11-13 years), and 3.6 g/day in adolescents (ages, 14-18 years) — intakes all above the UL (61). Overconsumption of sodium is apparent among younger children as well: A compilation of data from NHANES 2003-2010 found that 79% of children ages 1 to 3 years and 87% of children ages 4 to 5 years had sodium intakes in excess of the UL (46). A UL has not been established for infants, but average sodium intake in infants ages 7 to 11 months was 500 mg/day (AI, 370 mg/day) (46).

While dietary recall methods like those employed in NHANES are not the best measure of sodium intake due to day-to-day variations (24-hour urinary excretion is the gold standard), they likely underestimate intake in populations because of underreporting of food (62). Thus, overconsumption of sodium, which is linked to adverse health outcomes (hypertension, cardiovascular disease), is a major public health concern in the US (see the article on Sodium).


Authors and Reviewers

Written in November 2017 by:
Victoria J. Drake, Ph.D.
Linus Pauling Institute
Oregon State University

Reviewed in March 2018 by:
Balz Frei, Ph.D.
Former Director, Linus Pauling Institute
Distinguished Professor Emeritus, Dept. of Biochemistry and Biophysics
Oregon State University

The writing of this article was supported by a grant from Pfizer Inc.

Copyright 2018  Linus Pauling Institute


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