Overall adherence to the US Dietary Guidelines is low: the majority of Americans do not follow a healthy eating pattern. 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).
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.
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).
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.
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).
Like all studies that assess dietary exposure using self-reported data, the NHANES analyses are subject to 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).
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).
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).
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 developing 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).
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).
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).
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. 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).
Referência :
https://lpi.oregonstate.edu/mic/micronutrient-inadequacies/overview
