Nutrients US Women Fall Short On: Iron, Folate, D

What the latest US national survey shows about iron, folate, calcium, vitamin D, fiber and iodine in women, which everyday American foods supply them, and when to talk to a doctor.

The most recent national survey, What We Eat in America (NHANES, August 2021 to August 2023), found that women aged 20 and over took in about 11 mg of iron, 803 mg of calcium, 4 mcg of vitamin D and 15 g of fiber a day from food and drink ^[2]. For iron, calcium and vitamin D, those amounts fall below what adult women are advised to get ^[5,7,8]. The Dietary Guidelines for Americans 2020-2025 named calcium, vitamin D, fiber and potassium as nutrients of public health concern for the whole population, and called iron critical in pregnancy ^[3]. In the same survey period, 14.0% of women aged 20 to 59 had anemia ^[1]. Folate and iodine matter most for women who could become pregnant ^[4,6,9]. If your periods are heavy or you feel worn out most of the time, ask your primary care doctor or OB-GYN about a blood test rather than guessing.

What does the national survey actually measure?

What We Eat in America is the dietary part of NHANES, run by the USDA and CDC. Interviewers ask people to recall everything they ate and drank the day before. The figures below come from that first-day recall and cover food and beverages only, so vitamins and other supplements are not counted ^[2].

Nutrient	Average intake, women 20+ (food and drinks) ^[2]	Recommended daily amount, women 19-50
Iron	11.0 mg	18 mg (8 mg from age 51) ^[5]
Folate	383 mcg DFE	400 mcg DFE ^[6]
Calcium	803 mg	1,000 mg (1,200 mg from age 51) ^[7]
Vitamin D	4.0 mcg	15 mcg, or 600 IU ^[8]
Fiber	15.0 g	see the fiber section below

An average below the recommended amount does not mean every woman is short, and some people close the gap with supplements. It does show where the typical diet tends to land.

Why iron runs low during the years you have periods

Women between 19 and 50 are advised to get 18 mg of iron a day, more than twice the 8 mg recommended after age 50, because monthly bleeding means iron is lost on a regular basis ^[5]. Needs rise to 27 mg a day in pregnancy ^[5]. Average intake from food among women 20 and older was 11.0 mg in the 2021-2023 survey ^[2].

The CDC's latest data brief reported that 13.0% of females aged 2 and over had anemia in August 2021 to August 2023, compared with 5.5% of males. The figure was 17.4% among girls aged 12 to 19 and 14.0% among women aged 20 to 59 ^[1]. The survey defined anemia in women as hemoglobin below 12.0 g/dL ^[1]. Not all anemia comes from low iron, but iron deficiency is one of the main causes.

The 2025-2030 edition of the Dietary Guidelines, published in January 2026, notes that adolescent girls have higher iron needs because of menstruation ^[4]. NIH's Office of Dietary Supplements also lists pregnancy and frequent blood donation as reasons iron stores run down ^[5].

Where iron comes from in an American diet

About half of the iron Americans eat comes from bread, cereal and other grain products ^[5]. That's because enriched flour, white rice and breakfast cereals have iron added. A serving of cereal fortified with 100% of the Daily Value provides 18 mg, while a slice of white or whole wheat bread or half a cup of enriched white rice gives about 1 mg ^[5].

Beans are the other big plant source. A cup of canned white beans has about 8 mg, and half a cup of lentils, chickpeas or canned kidney beans has 2 to 3 mg ^[5]. Among animal foods, 3 ounces of cooked oysters provide 8 mg, beef liver 5 mg, and a 3-ounce portion of braised beef about 2 mg, while roast chicken and turkey give closer to 1 mg ^[5].

The iron in meat, poultry and seafood (heme iron) is absorbed more easily than the iron in grains, beans and vegetables (nonheme iron) ^[5]. Vitamin C helps with nonheme iron, so beans with salsa or tomatoes, or cereal with a glass of orange juice, is a reasonable pairing ^[5]. Tea and coffee work the other way. In a classic absorption study, black tea served with a bread meal cut iron absorption by 79 to 94%, coffee and cocoa also reduced it, and adding milk made little difference ^[15]. If you drink iced tea or coffee with lunch, having it between meals instead is a simple change. Because plant iron is harder to absorb, NIH sets the recommendation for vegetarians at 1.8 times that for people who eat meat ^[5]. In a 2023 Gallup poll, 6% of US women said they eat a vegetarian diet, compared with 2% of men ^[13].

When should you see a doctor?

The CDC suggests seeing a healthcare provider if you need to change a pad or tampon after less than 2 hours, if your period lasts more than 7 days, or if you pass clots the size of a quarter or larger ^[10]. Soaking through protection every hour for several hours, needing to change it during the night, and feeling tired, low on energy or short of breath are also listed as signs ^[10].

A blood test can show whether your iron is low and whether something else is going on. Your primary care doctor, OB-GYN or a clinic can order one. Please don't start high-dose iron on your own. The upper limit for adults is 45 mg a day from food and supplements combined, and too much can cause stomach problems ^[5].

Folic acid if you could become pregnant

Adult women are advised to get 400 mcg DFE of folate a day, rising to 600 mcg DFE in pregnancy ^[6]. On top of food folate, anyone who could become pregnant is advised to get 400 mcg of folic acid daily from supplements, fortified foods or both ^[6]. The US Preventive Services Task Force recommends a daily supplement with 400 to 800 mcg of folic acid, starting at least one month before conception and continuing through the first two to three months of pregnancy ^[6].

The reason for starting early is that the neural tube, which becomes the baby's brain and spine, forms in the first weeks, often before a pregnancy is known. Since January 1998, enriched grain products in the US have been fortified with folic acid, and NIH reports that neural tube defect rates have dropped by 28% since then ^[6].

That fortification is why so much ordinary American food carries folic acid. Bread, cereal, flour, cornmeal, pasta and rice are fortified, and since 2016 manufacturers have been allowed to add folic acid to corn masa flour, the base of tortillas and tamales ^[6]. Half a cup of cooked enriched rice provides 54 mcg and a slice of white bread 32 mcg ^[6]. Natural folate comes from foods such as spinach (131 mcg in half a cup cooked), black-eyed peas (105 mcg in half a cup), asparagus, Brussels sprouts, romaine lettuce and avocado ^[6]. The Nutrition Facts label shows whether a product has folic acid added, and it's worth checking, because not every bread, pasta or cereal on the shelf is fortified ^[14].

Even counting supplements, NHANES data show that 17% of women aged 19 to 30 and 19% of girls aged 14 to 18 do not reach the average requirement for folate ^[6]. Inadequate intake was reported in 23% of non-Hispanic Black women compared with 13% of non-Hispanic White women ^[6].

Folic acid supplements and multivitamins are sold at most pharmacies and grocery stores, and under the Affordable Care Act, health insurance plans must cover folic acid supplements for women who may become pregnant, so you may be able to get them at no cost ^[14]. If you are thinking about pregnancy, raise it with your doctor or pharmacist at a preconception visit, especially if you have had a pregnancy affected by a neural tube defect or take medicines for epilepsy, since you may need a different dose.

Calcium through the life stages

Women need 1,000 mg of calcium a day until 50 and 1,200 mg after that ^[7]. In the 2021-2023 survey, average calcium intake from food and drinks was 803 mg among women 20 and older, and 776 mg among women aged 50 to 59 ^[2]. An earlier NHANES analysis found that about 32% of women took a supplement containing calcium ^[7].

In the US, about 72% of calcium comes from dairy products and foods with dairy ingredients added ^[7]. Eight ounces of plain low-fat yogurt has about 415 mg, a cup of milk 276 to 299 mg, and 1.5 ounces of part-skim mozzarella 333 mg ^[7]. If you don't eat dairy, a cup of calcium-fortified orange juice provides about 349 mg, half a cup of firm tofu made with calcium sulfate 253 mg, and 3 ounces of canned sardines with bones 325 mg ^[7]. A 6-inch corn tortilla has 46 mg ^[7]. Plant milks vary, so the label is the only way to know how much calcium a carton has.

After menopause, falling estrogen reduces how much calcium the body absorbs and increases how much is lost in urine ^[7]. NIH notes that about 30% of postmenopausal women in the US and Europe have osteoporosis ^[7]. People who are lactose intolerant or who avoid dairy are also more likely to fall short, and lactose-free milk contains the same calcium as regular milk ^[7].

Vitamin D is hard to get from food alone

The recommended amount for women aged 19 to 70 is 15 mcg (600 IU) a day ^[8]. Women averaged 4.0 mcg from food and drinks in the latest survey ^[2]. Looking at 2013-2016 data, NIH reports that more than 97% of women got less than the average requirement of 10 mcg (400 IU) from food and drinks ^[8].

Almost all milk sold in the US is voluntarily fortified with about 3 mcg (120 IU) per cup, and soy, almond and oat milks are often fortified to a similar level ^[8]. Many breakfast cereals and some orange juices also have vitamin D added ^[8]. Fish is the main natural source: 3 ounces of farmed rainbow trout gives about 16 mcg and sockeye salmon about 14 mcg, while a large egg has about 1 mcg ^[8]. Cheese contains very little, so a diet heavy in cheese but light on milk doesn't add much.

Diet is only part of the story, because skin also makes vitamin D in sunlight. How much depends on where you live and the time of year. A study in Boston, at about 42 degrees north, found that winter sunlight produced no vitamin D in skin from November through February, while at 34 degrees north (roughly the latitude of Los Angeles) it still did in midwinter ^[16]. So in much of the northern US, winter sun can't be counted on. Sunlight through a window doesn't help either, since UVB doesn't pass through glass ^[8].

Blood tests give a fuller picture. In NHANES 2011-2014, 5% of people aged 1 and older were at risk of deficiency and 18% were at risk of inadequacy, based on blood levels of 25-hydroxyvitamin D ^[8]. People with limited sun exposure, darker skin, obesity, or conditions that affect fat absorption are more likely to run low ^[8].

Fiber, and iodine during pregnancy

Fiber is on the 2020-2025 list of nutrients of public health concern ^[3]. US women aged 20 and older averaged 15.0 g a day in the 2021-2023 survey ^[2]. The 2025-2030 guidelines encourage fiber-rich whole grains ^[4]. Beans, lentils and whole grain bread are the same foods that help with iron and folate.

Iodine is the nutrient the US data flag specifically for pregnancy. The recommended amount goes from 150 mcg a day to 220 mcg in pregnancy and 290 mcg while breastfeeding ^[9]. In NHANES 2007-2014, the median urinary iodine level of pregnant women was 144 mcg/L, below the 150 mcg/L that WHO uses as the lower end of the adequate range in pregnancy, and NIH describes a substantial portion of pregnant women in the US as iodine insufficient ^[9].

Part of the reason is how salt works in the US. Iodizing table salt has been voluntary since the 1920s, and a quarter teaspoon of iodized salt has about 78 mcg ^[9]. But most of the salt Americans eat comes from processed and restaurant food, and manufacturers almost always use noniodized salt ^[9]. If the salt you cook with doesn't say iodized on the label, it isn't adding iodine. Most store-bought bread contains very little iodine ^[9]. Dairy, seafood and eggs are the main food sources: 3 ounces of baked cod has about 146 mcg, three-quarters of a cup of plain Greek yogurt 87 mcg, a cup of nonfat milk 84 mcg, and a hard-boiled egg 31 mcg ^[9]. Plant milks contain little iodine, so vegans and people who avoid dairy may need to pay more attention ^[9].

The American Thyroid Association advises women planning a pregnancy, pregnant or breastfeeding to take 150 mcg of iodine a day as potassium iodide, yet only 34 of 59 best-selling prenatal vitamins checked in 2016-2017 contained any iodine ^[9]. If you take a prenatal vitamin, check the label and ask your doctor. The 2025-2030 guidelines list iron, folate and iodine as top nutrient priorities in pregnancy ^[4].

How does the US compare with other countries?

Each country runs its own nutrition survey, with different years, age ranges, methods and reference values, so intake percentages can't be lined up side by side. A shared yardstick helps. WHO publishes modeled estimates of anemia in women aged 15 to 49 for almost every country, using the same hemoglobin thresholds (below 120 g/L if not pregnant, below 110 g/L if pregnant) ^[11]. For 2023, the estimate for the US was 15.0%, compared with 30.7% worldwide ^[11,12].

The CDC's measured figure for US women aged 20 to 59 was 14.0%, close to but not the same as WHO's 15.0%, partly because the age range, years and adjustments differ ^[1,11]. We look at how the US sits next to Canada, Mexico, the UK, Japan and several European countries, and why food habits might explain some of the gaps, in How US women compare with other countries.

Common questions

Q1. Should I take an iron supplement if I have heavy periods?

Not without a blood test first. Heavy periods are a common reason for low iron, but a doctor can check your hemoglobin and iron stores, look for the cause of the bleeding, and tell you whether you need iron and how much ^[5,10]. Taking more than the 45 mg upper limit without medical advice can cause stomach problems ^[5].

Q2. When should I start folic acid if I'm planning a pregnancy?

The USPSTF recommends starting a daily supplement with 400 to 800 mcg of folic acid at least one month before conception and continuing through the first two to three months of pregnancy ^[6]. Because many pregnancies are unplanned, the general advice is that anyone who could become pregnant gets 400 mcg of folic acid daily ^[6].

Q3. Doesn't enriched bread and cereal already give me enough folic acid?

Fortified grains help, but they don't replace the advice to get 400 mcg of folic acid a day if you could become pregnant ^[6]. How much you get depends on what you eat, and not every grain product is fortified, so the label is worth a look. Insurance plans must cover folic acid supplements for women who may become pregnant ^[14].

Q4. Does a low vitamin D intake mean I'm deficient?

Not necessarily. Most women get less vitamin D from food than recommended, but the body also makes it in sunlight ^[8]. Only a blood test shows your actual level, so ask your doctor if you have risk factors such as little time outdoors, living in the northern half of the country, or a condition that affects absorption ^[8,16].

Q5. Do I need extra iodine?

Most adults don't need to think about it, but needs rise in pregnancy and breastfeeding ^[9]. The American Thyroid Association recommends 150 mcg of iodine a day for women planning a pregnancy, pregnant or breastfeeding, and not every prenatal vitamin contains it ^[9]. Talk to your doctor before starting any supplement, especially if you have a thyroid condition.

Q6. Why do the US numbers differ from WHO's?

The CDC measures hemoglobin directly in a sample of the population, while WHO combines survey data in a statistical model to produce comparable estimates for every country ^[1,11]. The two use different age ranges and years, so small differences are expected.

References

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This article provides general health information and is not a substitute for diagnosis or treatment. If you have symptoms that concern you, please see a healthcare provider.

This article is general information and doesn't replace advice from a doctor or dietitian.

Which nutrients do American women most often fall short on?