American Health & Medical Research Association
Practical guide

Shortfalls in vitamins and minerals are common, but true deficiencies are not

Many Americans eat less than they need of a few nutrients, yet blood tests find few are deficient. Below, we look at who should pay attention, which supplements make sense and where more becomes too much.

By the Health Research USA editorial team

Published Last updated October 2026

Written from the sources listed below; links checked October 2026. It touches on medicines, doses or health conditions and has not yet been reviewed by a licensed clinician, so use it to prepare for a conversation with yours. How we research and review

Sources15, listed below Reading time15 minutes

Where the evidence stands

  • Strong evidence Folic acid before and in early pregnancy prevents neural tube defects
  • Promising but early Zinc shortens a cold
  • Not enough evidence A daily multivitamin prevents heart disease or cancer
  • Evidence says no, or unsafe Vitamin D pills prevent cancer, heart disease or fractures in healthy older adultsBeta-carotene or vitamin E pills prevent cancer or heart diseaseRegular vitamin C prevents colds for most people

Each use is rated separately, from the scorecard in this guide. Safety cautions are spelled out in the guide itself. How we grade

On this page
  1. Five jobs that vitamins and minerals do
  2. A shortfall in your diet isn't the same as a deficiency in your blood
  3. The 2026 national report shows some gaps widening
  4. What the Dietary Guidelines flag, then and now
  5. Fortification: three public health fixes most people never notice
  6. The 12-nutrient table
  7. When a supplement clearly makes sense
  8. More isn't better: upper limits and real harms
  9. What the evidence says
  10. Questions readers ask
  11. The bottom line

Key takeaways

  • More than 9 in 10 Americans get less vitamin D from food than the average requirement, yet in 2011–2014 only about 5% had blood levels in the deficiency range5.
  • About 48% of Americans get less magnesium from food than the average requirement, and 39% of people 4 and older fall short on calcium even counting supplements6.
  • CDC’s 2026 nutrition report found low iron stores, a sign of iron deficiency, in about 18% of females ages 12 to 49 in 2021–2023, up from about 13% in 2003–20041.
  • Since folic acid was added to enriched grains in 1998, about 1,300 fewer U.S. babies a year are born with neural tube defects, a CDC analysis estimated11.
  • Too much is a growing problem too: the share of Americans 6 and older with excess vitamin D in their blood rose from under 1% in 2001–2002 to 8% in 2021–20231.

On May 1, 1924, a new product reached grocery shelves in Michigan: table salt with iodine added14.

Michigan sat in the Great Lakes goiter belt. Goiter is a visibly swollen thyroid gland, and before the 1920s it showed up in roughly a quarter to seven in ten children across that region, Appalachia and the Northwest14. Salt iodization was voluntary then, and it still is14.

A century later, most Americans aren’t deficient in most nutrients2, and about 60% of U.S. adults reported taking a dietary supplement in 2017–20201. Yet national data still show real, specific shortfalls, and they cluster in predictable groups.

Below, we look at where the gaps are, who benefits from which supplements, and where more becomes too much.

Five jobs that vitamins and minerals do

Here are the main ones, grouped by the work they do.

  • Building blood. Iron sits at the core of hemoglobin, the protein that carries oxygen from your lungs to your tissues9. Folate and vitamin B12 help make DNA and new red blood cells78.
  • Building bone. Vitamin D helps your gut absorb calcium, and calcium gives bones and teeth their structure56. About half or more of your body’s magnesium is in bone6.
  • Running nerves and muscles. Potassium and calcium help nerves fire and muscles contract6. B12 helps build the central nervous system8.
  • Setting your metabolism and growth. Iodine is part of thyroid hormones, which help regulate metabolism and guide a baby’s brain and bone development10. Zinc helps hundreds of enzymes work and supports growth6.
  • Defending and repairing. Vitamin C helps make collagen, and vitamins A and C and zinc support immune function6. Vitamin E works as an antioxidant6.

A shortfall in your diet isn’t the same as a deficiency in your blood

Two kinds of numbers describe nutrition, and they often disagree.

Intake numbers compare what people eat with the Estimated Average Requirement (EAR), the amount that meets the needs of half of healthy people. The Recommended Dietary Allowance (RDA) is set higher, to cover 97% to 98% of them7. Our adequacy guide covers these yardsticks.

By intake, the shortfalls look large. From 2013 to 2016, 94% of Americans age 1 and older got less vitamin D from food and drinks than the EAR5. Magnesium intakes from food fell below the EAR for 48% of people of all ages6. Counting food and supplements, 39% of people 4 and older fell short on calcium in 2007–2010, including 49% of children 4 to 186.

About 15% of adults fall below the EAR for zinc6. About 17% to 19% of teen girls and women 19 to 30 fall short on folate, even with supplements7.

Blood tests tell a calmer story. In NHANES, the national survey that draws blood from a sample of Americans, only about 5% had vitamin D levels in the deficiency range in 2011–20145. Sunlight and supplements likely fill much of the gap that food leaves. Your skin makes vitamin D when ultraviolet light hits it, and 28% of people 2 and older took a vitamin D supplement in 2015–20165.

CDC’s 2012 national nutrition report put it plainly: for most nutrients it tracked, 10% or less of the U.S. population was deficient in 2003–20062. The highest rates were for vitamin B6, at about 10.5%; iron in women 12 to 49, at about 9.5%; and vitamin D, at about 8.1%2.

Averages hide big differences. In that report, 31% of non-Hispanic Black Americans were deficient in vitamin D, compared with 3% of non-Hispanic White Americans2. NIH lists people with dark skin among those at higher risk of low vitamin D5.

The 2026 national report shows some gaps widening

CDC’s newest report, released in June 2026, tracks nutrient levels in blood and urine from 1999 through August 20231. Highlights:

  • Iron: Low iron stores among females 12 to 49 rose from about 13% in 2003–2004 to about 18% in 2021–20231. Among Mexican-American women, the rate climbed from 15% to 28%1.
  • Folate: Among women 12 to 49 who were not pregnant, the share with red blood cell folate below the World Health Organization’s target for preventing neural tube defects rose from about 16% to 21%1.
  • Vitamin d: Between 2001–2002 and 2021–2023, insufficient levels fell from 28% to 22%, while excess levels rose from under 1% to 8%, with the biggest rise among adult supplement users1.
  • Vitamin B12: From 1999–2000 to 2013–2014, deficiency held steady at about 2% to 4%, but borderline levels rose from about 7% to 10%1.

Supplement users had vitamin levels 10% to 60% higher than nonusers1. CDC notes that the comparison describes a difference and doesn’t prove the pills caused it.

What the Dietary Guidelines flag, then and now

The 2020–2025 Dietary Guidelines named four “dietary components of public health concern” for the general population: calcium, potassium, fiber and vitamin D3. They also flagged iron for infants fed mostly breast milk3.

The 2025–2030 Guidelines, released in January 2026, drop that formal list4. Instead, they point out nutrients by life stage and diet:

  • Older adults need as much or more of key nutrients, including B12, even when they need fewer calories4.
  • Pregnancy makes folate, iron and iodine top priorities, and the Guidelines suggest discussing a prenatal vitamin with a clinician4.
  • Breastfed babies, and those drinking less than 32 ounces of formula a day, should get 400 IU of vitamin D daily4.
  • Vegan diets show broad shortfalls, from vitamins A, D, E, B6 and B12 to calcium, iron, zinc and protein. For plant-based eaters, the Guidelines advise periodic checks of iron, B12, vitamin D, calcium and iodine4.

Fortification: three public health fixes most people never notice

Iodine in salt. Since the 1950s, roughly three in four U.S. households (70% to 76%) have cooked with iodized salt alone, according to a 2012 review14. But most of the salt Americans eat comes from processed foods, and manufacturers almost always use salt without iodine10. From 2007 to 2014, pregnant women’s median urine iodine was 144 micrograms per liter, below the World Health Organization’s cutoff of 15010.

Folic acid in grains. Since 1998, enriched grain products must carry 140 micrograms of folic acid per 100 grams11. The target is neural tube defects, serious defects of a baby’s developing brain or spinal cord.

A CDC analysis compared births in 1995–1996 with 1999–2011. Where programs also counted prenatal diagnoses, the rate fell from 10.7 to 7.0 per 10,000 live births, a 35% drop; across all programs, it fell 28%11. CDC’s 2026 report puts the decline at 19% to 32%1. Folate deficiency in women of reproductive age, 10% to 12% before fortification, fell below 1%1.

Vitamin D in milk. Almost all U.S. milk is voluntarily fortified with about 3 micrograms (120 IU) of vitamin D per cup5.

Many natural-health readers prefer food as nature made it, and that’s a reasonable starting point. You can get iodine from seafood, dairy and eggs, folate from greens and beans, and vitamin D from fatty fish. Just know which nutrients you’ve been getting from fortified foods, so you can replace them if you cut those foods out.

The 12-nutrient table

All values are for adults and come from NIH’s Office of Dietary Supplements. Amounts are approximate per serving. “UL” is the Tolerable Upper Intake Level, the most you can take daily without likely harm7.

Nutrient Main jobs Good food sources Adult RDA or AI Upper limit Pay attention if you…
Vitamin A Vision, immunity, growth Baked sweet potato 1,403 mcg; ½ cup raw carrots 459 mcg 900 mcg (men), 700 mcg (women) 3,000 mcg preformed Are pregnant; avoid high-dose preformed A6
Vitamin C Collagen, immunity, iron absorption ½ cup raw red pepper 95 mg; orange 70 mg 90 mg (men), 75 mg (women) 2,000 mg Smoke; you need 35 mg more6
Vitamin D Calcium absorption, bone 3 oz sockeye salmon 14.2 mcg; 1 cup milk 2.9 mcg 15 mcg (600 IU); 20 mcg after 70 100 mcg (4,000 IU) Are older, have dark skin, get little sun, or have obesity5
Vitamin E Antioxidant, immunity 1 oz sunflower seeds 7.4 mg; 1 oz almonds 6.8 mg 15 mg 1,000 mg from supplements Most diets fall below the RDA, though true deficiency is rare6
Folate DNA, cell division ½ cup cooked spinach 131 mcg; ½ cup black-eyed peas 105 mcg 400 mcg DFE; 600 in pregnancy 1,000 mcg folic acid Could become pregnant712
Vitamin B12 Nerves, red blood cells 3 oz clams 17 mcg; 1 cup milk 1.3 mcg 2.4 mcg None set Are over 50, vegan, or take metformin or acid reducers18
Calcium Bones and teeth, muscles, nerves 8 oz plain low-fat yogurt 415 mg; ½ cup calcium-set tofu 253 mg 1,000 mg; 1,200 for women over 50 and men over 70 2,500 mg; 2,000 after 50 Are past menopause or avoid dairy6
Iron Carries oxygen in blood 3 oz cooked oysters 8 mg; 1 cup canned white beans 8 mg 18 mg (women 19 to 50); 8 mg (men, women over 50); 27 in pregnancy 45 mg Are pregnant, have heavy periods, give blood often, or eat no meat9
Iodine Thyroid hormones 3 oz cod 146 mcg; ¼ tsp iodized salt 78 mcg 150 mcg; 220 in pregnancy 1,100 mcg Are pregnant or vegan, or skip dairy, seafood and iodized salt10
Magnesium 300-plus enzyme systems, muscles, nerves, blood sugar 1 oz pumpkin seeds 156 mg; ½ cup black beans 60 mg 400 to 420 mg (men); 310 to 320 mg (women) 350 mg, from supplements and medicines only Have type 2 diabetes, a gut disease or heavy alcohol use, or are older6
Potassium Fluid balance, nerves, muscles 1 cup cooked lentils 731 mg; banana 422 mg 3,400 mg (men), 2,600 mg (women) None set Have kidney disease; ask before adding more6
Zinc Enzymes, immunity, wound healing 3 oz cooked Pacific oysters 28 mg; 3 oz beef sirloin 3.8 mg 11 mg (men), 8 mg (women) 40 mg Are vegetarian, had weight-loss surgery, or drink heavily6

When a supplement clearly makes sense

Food comes first, but for some people the evidence for a specific supplement is strong. Use this table to start a conversation with your clinician.

If you… Consider Why
Could become pregnant 400 to 800 mcg of folic acid a day, from at least a month before conception through the first 2 to 3 months The U.S. Preventive Services Task Force gives this its top grade, A12
Are planning a pregnancy, pregnant or breastfeeding A daily supplement or prenatal vitamin with 150 mcg of iodine The American Thyroid Association advises it; in a 2016–2017 check, only 34 of 59 best-selling prenatals contained iodine10
Are over 50 B12 from fortified foods or a supplement CDC estimates that 10% to 30% of older people may not absorb the B12 found naturally in food1
Take metformin or an acid reducer long term, or eat vegan Ask about B12 levels and a supplement These drugs may cut B12 absorption, and only animal foods contain it naturally8
Are 1 to 18, 75 or older, pregnant, or have high-risk prediabetes Vitamin D The Endocrine Society’s 2024 guideline suggests it for these groups13
Have a breastfed baby 400 IU of vitamin D daily for the baby The 2025–2030 Guidelines recommend it4
Have iron deficiency confirmed by a blood test Iron, at the dose your clinician sets Extra iron can build up in people with hemochromatosis, and overdoses can poison children9

The Endocrine Society also suggests against vitamin D beyond the standard intake for healthy adults under 75, and against routine blood testing for vitamin D in healthy people13. All of its recommendations are conditional, so each is phrased as a suggestion rather than a firm rule13.

If you’ve had a pregnancy affected by a neural tube defect or take certain seizure medicines, ask your clinician whether you need more folic acid12.

More isn’t better: upper limits and real harms

The upper limit is a safety ceiling, not a goal7.

About 5% of adults 51 to 70 take in more folic acid than the upper limit, mainly from supplements7. Among children 1 to 13 who take folic acid supplements, 30% to 66% exceed their age’s limit7.

Iron pills are a real danger in a house with small children. At least 43 U.S. children died from accidental iron supplement overdoses between 1983 and 2000, which is why FDA requires a warning on the label9. If a child swallows iron pills, call Poison Control at 1-800-222-1222, or 911 if the child is very sick.

Some pills failed their big tests. In large trials, beta-carotene supplements raised lung cancer risk in smokers and asbestos-exposed workers, by 28% in one study and 18% in another615. In the SELECT trial, men taking vitamin E had a 17% higher risk of prostate cancer6. The U.S. Preventive Services Task Force recommends against both for preventing heart disease or cancer15.

Iron and calcium can blunt levothyroxine, a thyroid drug, so labels advise taking them 4 hours apart69. Magnesium can interfere with some antibiotics and osteoporosis drugs6. Tell your clinician and pharmacist about every supplement you take.

Apply the same skepticism to supplement makers that you’d apply to a drug company. Our articles on supplement stacks and third-party testing can help you shop.

What the evidence says

Claim Evidence rating What it rests on
Folic acid before and in early pregnancy prevents neural tube defects Strong evidence Task Force grade A; national birth data since fortification1112
Vitamin D pills prevent cancer, heart disease or fractures in healthy older adults Evidence says no, or unsafe The VITAL trial gave 2,000 IU a day to 25,871 older adults and found no significant reduction5
A daily multivitamin prevents heart disease or cancer Not enough evidence Task Force found the evidence insufficient15
Beta-carotene or vitamin E pills prevent cancer or heart disease Evidence says no, or unsafe Large trials found harm; Task Force recommends against615
Zinc shortens a cold Promising but early 2024 Cochrane review: about 2 days shorter, but low- to very-low-certainty evidence6
Regular vitamin C prevents colds for most people Evidence says no, or unsafe No drop in how often colds start; slightly shorter colds6

Questions readers ask

Should I take a multivitamin just in case?

The Task Force found too little evidence to say a multivitamin prevents heart disease or cancer15. It can’t replace food. If you take one, add up what’s in all your products so you stay under the upper limits7.

Should I get my vitamin levels tested?

For healthy people, the Endocrine Society suggests skipping routine vitamin D tests13. Testing makes more sense when you have symptoms, a condition that affects absorption, or a medicine known to lower a nutrient, such as metformin and B128. Our article on lab ranges explains why one number out of range often means little.

Is synthetic folic acid worse than natural folate?

Not for this job. Your body absorbs folic acid better than food folate: 1 microgram taken with food counts as about 1.7 micrograms of food folate7. The pregnancy evidence comes from folic acid12. The upper limit applies only to the synthetic form, not to folate in greens and beans7.

I eat a whole-food vegan diet. What should I watch?

B12 first, because only animal foods supply it naturally, so you need fortified foods or a supplement8. The Guidelines also advise periodic checks of iron, vitamin D, calcium and iodine for plant-based eaters4. Vegetarians need about 1.8 times as much iron as meat eaters, and zinc can run low too69.

The bottom line

Most Americans aren’t deficient in most vitamins and minerals, but many eat less than they need of vitamin D, magnesium, calcium and a few others. The real gaps cluster in predictable groups: people who could become pregnant, older adults, vegans, people on certain medicines, and women with low iron.

Start with food, because it brings fiber and other nutrients along with the vitamins. Add a supplement when your life stage, diet or test results point to one, and keep the total under the upper limit. When in doubt, bring your bottles to your clinician or pharmacist.

About this article

This article was researched using federal health agency data, NIH Office of Dietary Supplements fact sheets, national guidelines and peer-reviewed research, listed below, and was reviewed in October 2026. It is general education, not medical, legal or financial advice..

Sources

  1. Centers for Disease Control and Prevention. “2026 CDC Nutrition Report: A Comprehensive Biochemical Study of the Nutrition Status of the U.S. Population Based on 24 Years of NHANES Data.” CDC, June 24, 2026. Three parts of the report were used: (a) “At a Glance” summary (vitamin D, folate, supplement use), cdc.gov ; (b) iron fact sheet, cdc.gov ; (c) “B Vitamins and Related Biochemical Compounds” chapter (B12, folate, neural tube defects), cdc.gov
  2. Centers for Disease Control and Prevention. “Second National Report on Biochemical Indicators of Diet and Nutrition in the U.S. Population,” Executive Summary. CDC, 2012. cdc.gov
  3. de Jesus JM, Office of Disease Prevention and Health Promotion. “Make Every Bite Count During National Nutrition Month.” HHS, March 2021.
  4. U.S. Department of Health and Human Services and U.S. Department of Agriculture. “Dietary Guidelines for Americans, 2025–2030.” January 2026. cdn.realfood.gov
  5. NIH Office of Dietary Supplements. “Vitamin D: Fact Sheet for Health Professionals.” ODS, accessed October 2026. ods.od.nih.gov
  6. NIH Office of Dietary Supplements. Fact sheets for health professionals, one per nutrient; each claim cited6 comes from the sheet for the nutrient named. “Vitamin A and Carotenoids” (updated March 10, 2025), ods.od.nih.gov ; “Vitamin C” (July 31, 2025), ods.od.nih.gov ; “Vitamin E” (March 26, 2021), ods.od.nih.gov ; “Calcium” (accessed October 2026), ods.od.nih.gov ; “Magnesium” (January 6, 2026), ods.od.nih.gov ; “Potassium” (June 2, 2022), ods.od.nih.gov ; “Zinc” (January 6, 2026), ods.od.nih.gov
  7. NIH Office of Dietary Supplements. “Folate: Fact Sheet for Health Professionals.” ODS, accessed October 2026. ods.od.nih.gov
  8. NIH Office of Dietary Supplements. “Vitamin B12: Fact Sheet for Health Professionals.” ODS, updated July 2, 2025. ods.od.nih.gov
  9. NIH Office of Dietary Supplements. “Iron: Fact Sheet for Health Professionals.” ODS, updated September 4, 2025. ods.od.nih.gov
  10. NIH Office of Dietary Supplements. “Iodine: Fact Sheet for Health Professionals.” ODS, updated November 5, 2024. ods.od.nih.gov
  11. Williams J, Mai CT, Mulinare J, et al. “Updated Estimates of Neural Tube Defects Prevented by Mandatory Folic Acid Fortification — United States, 1995–2011.” Morbidity and Mortality Weekly Report, 2015;64(1):1–5. cdc.gov
  12. U.S. Preventive Services Task Force. “Folic Acid Supplementation to Prevent Neural Tube Defects: Preventive Medication.” Final recommendation, August 1, 2023. uspreventiveservicestaskforce.org
  13. Endocrine Society (Demay MB, Pittas AG, et al.). “Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline.” Journal of Clinical Endocrinology and Metabolism, 2024. endocrine.org
  14. Leung AM, Braverman LE, Pearce EN. “History of U.S. Iodine Fortification and Supplementation.” Nutrients, 2012;4(11):1740–1746. pubmed.ncbi.nlm.nih.gov
  15. U.S. Preventive Services Task Force. “Vitamin, Mineral, and Multivitamin Supplementation to Prevent Cardiovascular Disease and Cancer: Preventive Medication.” Final recommendation, June 21, 2022. uspreventiveservicestaskforce.org