Nutrition: The Complete Guide

Key numbers at a glance

What good nutrition actually means

Nutrition is the process of getting from food the energy and raw materials your body needs to run, repair and defend itself. Energy is measured in calories and comes from three macronutrients: carbohydrate, protein and fat. Alongside them come micronutrients, the vitamins and minerals needed in small amounts, plus fiber, water and thousands of plant compounds that do not fit neatly into either group. No single food supplies all of this, which is the simplest argument for variety.

The Dietary Guidelines for Americans, the federal advice that shapes school meals, food labels and most of what your doctor will tell you, has moved away from single nutrients toward eating patterns. The reason is practical. People do not eat nutrients; they eat meals, and the effect of a food depends on what it replaces. Swapping butter for olive oil does something different from swapping butter for white bread, even though both cut saturated fat. Looking at the whole pattern over weeks matters far more than any single meal or any single ingredient.

A healthy pattern, in the language of the Guidelines, is built mostly from vegetables, fruit, whole grains, dairy or fortified soy alternatives, a variety of protein foods and oils, while keeping added sugars, saturated fat and sodium low and alcohol limited. That description fits many cuisines. You do not need to adopt someone else's diet to eat well; you can usually adjust the meals you already enjoy by changing proportions, ingredients and portion sizes.

How much energy you need

Calorie needs depend on age, sex, body size and how active you are. The Guidelines estimate roughly 1,600 to 2,400 calories a day for adult women and 2,000 to 3,000 for adult men, with needs generally falling as you get older. The 2,000-calorie figure on food labels is a reference point for comparing products, not a personal target. If your weight is stable, you are broadly meeting your energy needs; the question then is the quality of what supplies them.

Carbohydrate, protein and fat: the macronutrients

Federal guidance gives broad ranges rather than a single ideal split. For adults, carbohydrate is suggested at 45 to 65 percent of calories, fat at 20 to 35 percent and protein at 10 to 35 percent. The ranges are wide on purpose: many different combinations can support good health, and the type of each macronutrient tends to matter more than the exact proportion. A low-fat diet built on sugary snacks and a higher-fat diet built on nuts, fish and olive oil are not equivalent, even if their calorie totals match.

Carbohydrate

Carbohydrate is the body's preferred fuel for the brain and for hard exercise. It comes packaged very differently in different foods. In beans, whole grains, fruit and vegetables it arrives with fiber, water, vitamins and minerals and is digested more slowly. In soda, candy and many baked goods it arrives as refined starch or added sugar with little else. The practical aim is not to cut carbohydrate as a category but to shift most of it toward minimally processed sources, which also happens to be the easiest way to raise your fiber intake.

Protein

Protein supplies amino acids for building and repairing muscle, skin, enzymes and immune cells. The Recommended Dietary Allowance for adults is 0.8 g per kg of body weight a day, about 0.36 g per pound, so a 150-pound (68 kg) adult needs roughly 54 g. Most Americans already meet this. Sports nutrition guidance for athletes in training suggests 1.2 to 2.0 g per kg a day, and older adults may benefit from more than the baseline; your doctor or a registered dietitian can advise. A 3-ounce (85 g) serving of cooked chicken breast provides about 26 g.

Where people fall short is usually distribution rather than total. A typical American day puts little protein at breakfast and a large amount at dinner. Spreading it across meals, using inexpensive sources such as eggs, canned fish, lentils, beans, milk and yogurt, makes it easier to reach your needs without supplements. If you have chronic kidney disease or liver disease, do not raise your protein intake without talking to your care team first, as you may have been advised to limit it.

Fat

Fat carries the fat-soluble vitamins A, D, E and K, supplies essential fatty acids your body cannot make, and makes food satisfying. The distinction that matters is between unsaturated fats, found in olive, canola and other vegetable oils, nuts, seeds, avocado and fish, and saturated fat, found mainly in butter, fatty meat, cheese, cream, coconut oil and palm oil. Replacing saturated fat with unsaturated fat lowers LDL cholesterol, the type that builds up in artery walls. Artificial trans fats, once common in margarine and fried snacks, have been removed from the US food supply by the FDA.

Fruit, vegetables, whole grains and fiber

If one change does the most good for the most people, it is eating more plants. Higher intakes of fruit and vegetables are linked to lower rates of heart disease and some cancers, yet only about 1 in 10 American adults eats the recommended amount. At 2,000 calories a day that amount is 2 cups of fruit and 2 1/2 cups of vegetables. One cup of fruit means 1 cup fresh, frozen or canned, 1/2 cup dried, or 1 cup of 100% juice; one cup of vegetables means 1 cup raw or cooked, or 2 cups of raw leafy greens. At least half of your fruit should come as whole fruit rather than juice.

Frozen and canned produce counts and is nutritionally comparable to fresh. Frozen vegetables are picked and frozen quickly, keep for months and are often cheaper, which makes them one of the most useful items in a busy kitchen. With canned food, choose fruit packed in water or juice rather than heavy syrup, and vegetables or beans labeled low sodium or no salt added, or rinse them before use.

Whole grains keep all three parts of the kernel: the bran, the germ and the endosperm. Refined grains keep only the endosperm and lose most of the fiber and many micronutrients. The Guidelines recommend making at least half your grains whole, which at 2,000 calories means at least 3 of the 6 ounce-equivalents a day. An ounce-equivalent is 1 slice of bread, 1/2 cup of cooked rice, pasta or oatmeal, or 1 cup of ready-to-eat cereal. On the label, the first ingredient should say whole; a brown color alone can come from molasses or caramel coloring.

Why fiber deserves its own attention

Fiber is the part of plant food that the small intestine cannot digest. It passes into the colon, where it adds bulk, holds water and feeds gut bacteria. Higher intakes are linked to lower rates of heart disease, type 2 diabetes and colorectal cancer, yet more than 90 percent of women and 97 percent of men in the US fall short. The Guidelines base the target on 14 g per 1,000 calories, which works out at about 25 to 28 g a day for women aged 19 to 50 and about 31 to 34 g for men of the same age. The Daily Value on food labels is 28 g.

Beans, peas and lentils are the richest everyday source, followed by whole grains, vegetables, fruit and nuts. Raise your intake gradually over a few weeks, and drink more fluid as you do, because fiber works by holding water; doubling it in one day reliably causes bloating and gas. Food is usually a cheaper and more complete source than fiber supplements.

The three things to limit: sodium, added sugars and saturated fat

Most of the gap between how Americans eat and what the Guidelines recommend comes down to three things that arrive largely through packaged, restaurant and fast food. Understanding where they hide is more useful than trying to avoid them by willpower alone. Because these foods are designed to taste good and are eaten often, small changes to the products you buy every week usually do more than occasional strict days.

Sodium

Higher sodium intake raises blood pressure, one of the strongest modifiable risk factors for stroke and heart disease. The Guidelines advise adults to keep sodium below 2,300 mg a day, about the amount in one teaspoon of table salt, and the American Heart Association suggests an ideal limit of 1,500 mg for most adults. The average American eats about 3,400 mg a day, and more than 70 percent of it comes from packaged and restaurant food rather than the salt shaker. Bread, pizza, sandwiches, deli meats, soups and sauces are major contributors, and the range between brands of the same product can be large.

Your sense of taste adapts to less salt over a few weeks, so gradual reductions are easier to sustain than drastic ones. Acid, herbs and toasted spices can replace some of what salt adds. Sea salt and pink salt are not meaningfully lower in sodium. Potassium-based salt substitutes can be dangerous if you have kidney disease, heart failure or diabetes, or take ACE inhibitors, angiotensin receptor blockers or potassium-sparing diuretics, so ask your doctor first.

Added sugars

Added sugars are sugars and syrups put into food during processing or preparation, including table sugar, honey and corn syrup. They supply calories without other nutrients and are a major cause of tooth decay. The Guidelines recommend keeping them below 10 percent of calories from age 2 onward, which at 2,000 calories is under 50 g, about 12 teaspoons. The American Heart Association suggests a lower limit of about 25 g for women and 36 g for men. Children under 2 should avoid added sugars entirely.

Sugar-sweetened drinks are the largest single source in the American diet. A 12 fl oz (355 ml) can of regular cola contains about 39 g, close to a full day's limit by itself, so drinks are the obvious first target. The sugars naturally present in whole fruit and plain milk do not count as added sugars. Liquid calories also tend not to make you feel full, so they add to rather than replace what you eat.

Saturated fat

The Guidelines recommend keeping saturated fat below 10 percent of calories, which at 2,000 calories is under about 22 g a day. If you have been told to lower your LDL cholesterol, the American Heart Association suggests aiming for about 5 to 6 percent. What you replace it with matters as much as the cut: replacing saturated fat with unsaturated fat lowers LDL, while replacing it with refined carbohydrate achieves little. Coconut oil is not an exception to this advice; it is high in saturated fat. Read the saturated fat line on the label rather than total fat.

Vitamins, minerals and supplements

A varied diet supplies most people with the vitamins and minerals they need, but a few nutrients are commonly short in American diets or needed in larger amounts at particular life stages. These include vitamin D, calcium, fiber and potassium for the general population, iron for some women and children, folic acid before and during early pregnancy, and vitamin B12 for older adults and people who eat no animal foods.

Vitamin D helps the body absorb calcium and phosphorus. Skin makes it from sunlight, but season, latitude, darker skin, sunscreen and age all reduce how much, so many people depend on fortified milk and plant milks, fortified cereals, fatty fish such as salmon and trout, and egg yolks. The Recommended Dietary Allowance is 15 mcg (600 IU) a day for adults aged 19 to 70 and 20 mcg (800 IU) over 70. The adult upper limit is 100 mcg (4,000 IU) a day. Because vitamin D is stored in the body, high-dose products taken without advice can accumulate to harmful levels.

Calcium needs are 1,000 mg a day for most adults aged 19 to 50, rising to 1,200 mg for women over 50 and men over 70. Dairy foods, fortified soy beverages, canned fish with soft bones, tofu made with calcium and some leafy greens are good sources. Iron needs are higher in women of reproductive age than in men, and higher again in pregnancy. Absorption of vitamin B12 from food tends to decline with age, which is why adults over 50 are advised to get much of it from fortified foods or supplements.

• Check how much you already get from fortified foods before adding a supplement
• Ask your doctor whether you need vitamin D if you are rarely outdoors, cover your skin, have darker skin or are over 70
• Talk to your doctor before supplementing vitamin D if you have sarcoidosis, kidney disease, a parathyroid disorder, or a history of high blood calcium or kidney stones
• Bring your supplement bottles to appointments so your doctor can see the actual doses

How supplements are regulated

In the US, dietary supplements do not need FDA approval before they are sold. Manufacturers are responsible for safety and labeling, and the FDA acts mainly after problems appear. Doses on the shelf vary widely; vitamin D products, for example, range from 10 mcg (400 IU) to many times the upper limit. Supplements can also interact with prescription medicines, and some interfere with lab tests. Tell your doctor and pharmacist everything you take, check the dose against the upper limit, and treat a supplement as a way to fill a known gap rather than as insurance against a poor diet.

How to read a food label

The Nutrition Facts label, the ingredients list and the allergen statement answer almost every question a shopper has, and most people read the marketing on the front of the package instead. Learning to read three or four lines takes a few minutes and pays off at every shopping trip. Here is the order that works for most shoppers. It takes less than a minute per product.

Start with servings per container and the serving size. Serving sizes are based on the amounts people typically eat, not on a recommendation, and two products with different serving sizes cannot be compared without adjusting. Next, use the percent Daily Value column: 5 percent or less of a nutrient per serving is low and 20 percent or more is high. That single rule lets you compare two cans of soup in seconds. The Daily Values used on the label are 2,300 mg for sodium, 20 g for saturated fat, 50 g for added sugars and 28 g for dietary fiber.

Look for the Includes Added Sugars line rather than total sugars alone, since total sugars also counts the natural sugar in milk and fruit. Then read the first three ingredients, because ingredients are listed by weight, heaviest first. Finally, check the allergen statement if you or anyone you cook for has a food allergy. US law requires the major food allergens to be declared: milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, soybeans and sesame.

• Do not treat front-of-package words such as natural, multigrain or made with whole grain as a nutrition verdict
• Do not assume a high-protein product is low in sugar or sodium
• Do not read no added sugar as meaning low in sugar; check total sugars too
• Do compare brands of bread, broth, sauce and cereal, where sodium and sugar vary widely

Planning, shopping and keeping food safe

Most poor food decisions are made hungry, tired and short of time. Planning works because it moves the decision to a calmer moment. You do not need a seven-day menu; planning three dinners you will actually cook is more useful than an ambitious plan you abandon by Wednesday. Many people find it easier to cook components rather than identical finished meals: a pot of grain, a tray of roasted vegetables, a batch of beans or lentils, a cooked protein and a sauce can be combined in different ways across several days.

A stable shopping list helps too. Keep the staples the same each week and vary the vegetable or fruit according to what is in season or on sale. A well-stocked pantry, with oats, canned beans and fish, frozen vegetables, whole-grain pasta and brown rice, eggs and a good oil, means that the default meal on a bad evening is still a reasonable one. Oats in particular are one of the cheapest whole-grain breakfasts available, and oat beta-glucan at 3 g a day is the basis of an FDA-authorized health claim about heart disease risk.

Batch cooking needs attention to food safety. Refrigerate cooked food within 2 hours, or within 1 hour when the air temperature is above 90°F (32°C). Keep your refrigerator at 40°F (4°C) or below, eat cooked leftovers within 3 to 4 days, and reheat them to 165°F (74°C), checked with a food thermometer. Divide large batches into shallow containers so they cool quickly. Do not taste food to decide whether it is still safe; when in doubt, throw it out.

• Clean: wash hands, cutting boards and counters often
• Separate: keep raw meat, poultry, seafood and eggs away from ready-to-eat food
• Cook: use a food thermometer to reach safe internal temperatures
• Chill: refrigerate promptly and keep the refrigerator at 40°F (4°C) or below

Nutrition at different stages of life

The basic pattern applies across life, but some groups have specific needs or specific risks, and generic advice can be wrong or even unsafe for them. The sections below cover the most common situations; your own care team's advice always takes priority over general guidance, because they know your history, your medicines and your test results. Bring questions to every visit.

Before and during pregnancy

Anyone who could become pregnant is advised to take 400 mcg of folic acid every day, because it helps prevent serious birth defects of the brain and spine that develop very early, often before a pregnancy is known. During pregnancy, iron needs rise and a prenatal vitamin is commonly recommended; your obstetric provider will advise on the right product. The FDA and EPA advise eating 8 to 12 ounces a week of a variety of fish lower in mercury, such as salmon, shrimp, canned light tuna and cod, and avoiding high-mercury fish such as shark, swordfish, king mackerel and bigeye tuna. Caffeine should also be limited; ask your obstetric provider how much is right for you.

Pregnancy also raises the risk from foodborne illness, including listeria. Avoid unpasteurized milk and cheeses made from it, and heat deli meats and hot dogs until steaming. Your obstetrician, midwife or a registered dietitian can tailor advice if you have gestational diabetes, a restrictive diet or nausea that limits what you can eat. Wash produce, cook meat, poultry and eggs thoroughly, and follow the cooling and storage times above closely.

Babies, children and teens

The American Academy of Pediatrics recommends exclusive breastfeeding for about the first 6 months where possible, with iron-fortified infant formula as the alternative, followed by the introduction of solid foods alongside continued breast milk or formula. Children under 2 should have no added sugars. Older children need the same overall pattern as adults in smaller portions, with plenty of calcium and vitamin D for growing bones. Juice should be limited and whole fruit preferred. Eating together as a family, offering new foods repeatedly without pressure and keeping sweetened drinks out of the home are some of the most practical things parents can do.

Older adults

Calorie needs fall with age while the need for many nutrients does not, so each meal has to carry more nutrition per bite. Protein helps preserve muscle, especially alongside strength training, and older adults may benefit from more than the baseline amount. Vitamin B12 absorption tends to decline, calcium and vitamin D needs rise, and thirst becomes a less reliable signal, which increases the risk of dehydration. Unintended weight loss, poor appetite, difficulty chewing or swallowing, or trouble shopping and cooking all deserve a conversation with your doctor rather than being accepted as part of getting older.

People with long-term conditions

If you live with diabetes, chronic kidney disease, heart failure, celiac disease, inflammatory bowel disease or a food allergy, general advice may not fit. Kidney disease can require limits on protein, potassium, phosphorus or fluid. People taking warfarin should keep vitamin K intake from leafy greens consistent rather than avoiding them. People with celiac disease must avoid wheat, barley and rye entirely and should choose oats labeled gluten-free, but should be tested before removing gluten, as going gluten-free first can make the test unreliable. In all of these cases, your own care team's advice comes first.

Cost and access to healthy food in the US

Eating well does not have to cost more, but it does take some knowledge of where the value is. Per serving, dried and canned beans and lentils, oats, brown rice, eggs, frozen vegetables, bananas, carrots, cabbage, canned fish and plain yogurt are among the most nutritious foods in any grocery store. Buying produce in season and freezing it, shopping with a list, comparing unit prices on the shelf tag and choosing store brands all stretch a budget further than most specialty health foods.

Several federal programs help people who are struggling to afford food. The Supplemental Nutrition Assistance Program (SNAP) helps eligible households buy groceries, and WIC provides supplemental foods, nutrition education and breastfeeding support to eligible pregnant and postpartum women, infants and children under 5. School breakfast and lunch programs reach millions of children, and many areas also have food banks and food pantries. Eligibility rules vary by state, so your local social services office or a hospital social worker is a good place to start.

Professional nutrition advice can also be covered. Many insurance plans cover visits with a registered dietitian for certain conditions, and Medicare Part B covers medical nutrition therapy for people with diabetes or kidney disease when referred by a doctor. Ask your plan what is covered before booking, and ask your doctor for a referral if you have a condition where diet is a central part of treatment.

Common nutrition myths, and what the guidance says

Nutrition attracts more confident misinformation than almost any other area of health, partly because everyone eats and partly because single studies are easy to overstate. A few principles help you sort claims. Be wary of anything that promises a dramatic result from one food or one supplement, that blames a single nutrient for most of your problems, or that is sold by the person making the claim. Real dietary guidance changes slowly, because it rests on many studies pointing in the same direction.

• Myth: carbohydrate makes you gain weight. Guidance: weight depends on total energy over time; whole grains, beans and fruit are linked to better health outcomes
• Myth: fresh produce is always better than frozen. Guidance: frozen and canned fruit and vegetables count and are nutritionally comparable
• Myth: you need a detox. Guidance: your liver and kidneys clear waste continuously; no juice or cleanse has been shown to improve on them
• Myth: more protein is always better. Guidance: beyond your requirement, surplus protein is simply used as energy
• Myth: sea salt is healthier than table salt. Guidance: they contain similar amounts of sodium by weight
• Myth: a supplement can make up for a poor diet. Guidance: supplements can fill specific gaps but do not reproduce the benefits of whole foods
• Myth: you must cut out all treats. Guidance: an occasional treat fits within a healthy pattern; it is the daily default that matters

Working with your doctor and a dietitian

Your doctor can check the things diet affects, including blood pressure, cholesterol, blood glucose and weight, and can look for medical reasons behind symptoms you might otherwise try to fix with food. A registered dietitian, sometimes listed as a registered dietitian nutritionist, is a credentialed professional trained to translate medical needs into an eating plan that fits your budget, culture and routine. The title nutritionist on its own is not regulated in the same way everywhere, so check credentials.

Go to an appointment prepared. Keep a simple food diary for three or four typical days, including drinks, snacks and weekend meals. Bring your supplement bottles and a list of your medications. Say what you actually want to change and what has made it hard before. Questions worth asking include whether any of your results suggest you should change your diet, whether any of your medicines interact with food or supplements, whether you need any nutrient tests, and whether a referral to a dietitian would be covered by your insurance.

A practical four-week plan

Large overnight changes are hard to sustain. This plan makes one change a week, each built on the last, so that by the end of the month several new habits are running without much effort. If a week does not go to plan, repeat it rather than abandoning the whole thing. Keep notes on what you changed and how it felt.

Week 1: drinks and breakfast

Replace sugar-sweetened drinks with water, plain sparkling water, unsweetened tea or coffee, or milk. Then build a breakfast that includes some protein and some fiber, such as oatmeal with milk and fruit, eggs with whole-grain toast, or plain yogurt with nuts and berries. These two changes alone often remove a large share of added sugars from a typical day. Keep a jug of water in the refrigerator.

Week 2: half the plate

Aim to fill half your plate with vegetables and fruit at lunch and dinner. Stock frozen vegetables so this is possible on busy nights, and add a can of rinsed beans to a soup, sauce or salad at least twice. Raise fiber gradually and drink more water as you do. Choose one new vegetable to try this week. Roasting is an easy start.

Week 3: grains, fats and labels

Swap two refined grain foods you eat often for whole-grain versions, such as bread and pasta, or mix brown and white rice half and half to start. Cook with olive or canola oil instead of butter. On each shopping trip, compare the sodium and added sugars of two brands of one product you buy regularly and switch to the lower one.

Week 4: plan and batch

Plan three dinners on the weekend, write one shopping list, and cook two components in advance, such as a grain and a tray of roasted vegetables. Store them in shallow containers in the refrigerator and use them within 3 to 4 days. At the end of the week, review what worked, keep it, and choose the next change. Repeat the plan in later weeks.

Every guide in this topic

• Vitamin D: What the Evidence Actually Says
• The Evidence on Dietary Fiber, Without the Hype
• Dietary Protein: What the Evidence Actually Says
• The Evidence on Dietary Salt, Without the Hype
• Added Sugar: What the Evidence Actually Says
• Saturated Fat: Sorting the Evidence From the Noise
• What the Guidance Really Says About Fruit and Vegetables
• The Evidence on Whole Grains, Without the Hype
• The Evidence on Food Labels, Without the Hype
• What the Guidance Really Says About Meal Planning

Frequently asked questions

What is the single most useful change I can make to my diet?

For most Americans it is eating more vegetables, fruit, beans and whole grains, ideally in place of refined grains, sugary drinks and processed meats. That one shift raises fiber, potassium and many vitamins while lowering added sugars, sodium and saturated fat at the same time. If you drink soda or sweetened coffee drinks daily, replacing them is often the quickest single win.

Do I need to count calories to eat healthily?

Not usually. Calorie counting can be a useful short-term tool for some people, but the quality of your diet matters as well as the quantity, and many people find it hard to sustain. Building meals around vegetables, protein foods and whole grains, limiting sugary drinks and watching portion sizes tends to keep calories in a sensible range without constant tracking.

Is it better to buy organic food?

The Dietary Guidelines do not recommend organic over conventional food for health reasons. Both must meet the same federal safety standards for pesticide residues. The bigger health gain comes from eating more fruit and vegetables of any kind, so if organic prices mean you buy less produce, conventional, frozen or canned is the better choice. Wash fresh produce under running water before eating.

Should I take a multivitamin?

Most healthy adults who eat a varied diet do not need one, but some people may benefit, including those who could become pregnant (for folic acid), older adults (for vitamin B12 and vitamin D), and people on very restricted diets. Ask your doctor whether you have a specific gap, and choose a product that does not exceed upper limits.

How much water should I drink each day?

There is no single figure that fits everyone, because needs vary with body size, activity, heat and health conditions, and food supplies some of your fluid. For most healthy people, drinking when thirsty and having water with meals is enough, and pale yellow urine is a reasonable sign. People with heart failure or kidney disease may have fluid limits and should follow their care team.

Are eggs bad for my cholesterol?

For most people, eggs can be part of a healthy eating pattern. Saturated fat has a larger effect on blood LDL cholesterol than the cholesterol in food for most people. What you eat with eggs matters too: eggs with vegetables and whole-grain toast differ from eggs with bacon and sausage. If you have high LDL cholesterol or diabetes, ask your doctor what fits your plan.

Are plant-based diets healthy?

Well-planned vegetarian and vegan diets can meet nutrient needs at every life stage, according to dietitian guidance. The Guidelines include a healthy vegetarian pattern. People who eat no animal foods need a reliable source of vitamin B12 from fortified foods or a supplement, and should pay attention to iron, calcium, vitamin D, zinc and omega-3 fats. A dietitian can help, especially during pregnancy or for children.

Is intermittent fasting a good idea?

Time-restricted eating is not part of the Dietary Guidelines, and current evidence does not show it works better than other ways of reducing calories. Some people find it a convenient structure. It is not suitable without medical advice if you take insulin or other diabetes medicines that can cause low blood sugar, are pregnant or breastfeeding, or have a history of an eating disorder.

How can I tell if a food is ultra-processed or unhealthy?

Rather than relying on a label like processed, look at the Nutrition Facts panel and the ingredients list. A product high in added sugars, sodium or saturated fat (20 percent Daily Value or more per serving) and low in fiber deserves a second look. Many processed foods, such as canned beans, frozen vegetables and plain yogurt, are excellent choices.

When should I see a registered dietitian?

A dietitian is worth seeing if you have a condition where food is part of treatment, such as diabetes, kidney disease, celiac disease or a food allergy; if you are pregnant and have a restricted diet; if you have unintended weight loss; or if you have tried to change your eating several times without success. Ask your doctor for a referral and check your insurance coverage.

When to speak to a doctor

See your doctor if you have unintended weight loss, a change in bowel habits lasting three weeks or more, blood in your stool, ongoing abdominal pain, persistent bloating or diarrhea after eating grains, or unusual thirst and frequent urination, and before taking high-dose supplements or making major dietary changes if you have kidney disease, liver disease, heart failure, diabetes or are pregnant. Call 911 for trouble breathing, throat swelling or fainting after eating (use prescribed epinephrine first), severe abdominal pain with vomiting and a swollen belly, signs of severe dehydration such as confusion or very little urine, or chest pain lasting more than a few minutes. If someone has swallowed too many vitamins or iron tablets, especially a child, call Poison Control at 1-800-222-1222.

Where this comes from

• Dietary Guidelines for Americans — Dietary Guidelines for Americans, 2020-2025
• NIH Office of Dietary Supplements — Vitamin D: Fact Sheet for Consumers
• NIH Office of Dietary Supplements — Calcium: Fact Sheet for Consumers
• FDA — How to Understand and Use the Nutrition Facts Label
• FDA — Advice about Eating Fish
• American Heart Association — How much sodium should I eat per day?
• Medicare.gov — Medical nutrition therapy services
• CDC — Folic Acid
• CDC — Four Steps to Food Safety
• Academy of Nutrition and Dietetics — Nutrition and Athletic Performance

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.