Essential Vitamins: A Complete Nutritionist's Guide
Article is a full overview of all 13 vitamins, with links to in-depth guides on each one and related topics.
Table of Contents
- What Are Vitamins?
- Two Types of Vitamins
- Water-Soluble Vitamins
- Fat-Soluble Vitamins
- How Your Body Manages Vitamin Stores
- Who Is at Risk for Deficiencies?
- How to Check Your Vitamin Levels
- Daily Vitamin Requirements
- Food vs. Supplements
- Practical Checklist
- Key Takeaways
1. What Are Vitamins?
The Simple Definition
Vitamins are nutrients your body needs to work properly — but can't make enough of on its own. That's why you have to get them from food. You don't need large amounts (we're talking milligrams or even micrograms per day), but every single vitamin plays a role in keeping you healthy — from producing energy to fighting infection to building strong bones.
Vitamins aren't magic pills or "superfoods." They're essential tools your body uses every day to run basic processes. Without them, things start to break down.
A Quick History
In 1911, Polish biochemist Casimir Funk isolated the first vitamin — B1 — and coined the word "vitamine," from the Latin vita, meaning life. Before that, scientists had noticed strange diseases like scurvy, rickets, and beriberi for centuries but didn't know what caused them. The answer, it turned out, was missing vitamins.
By the end of the 20th century, all 13 known vitamins had been discovered, isolated, and synthesized. It's one of the biggest breakthroughs in the history of nutrition and medicine.
Why Vitamins Matter
Vitamins are involved in hundreds of chemical reactions in your body every day. Here's what they do:
- Help convert food into energy (most B vitamins)
- Protect your cells from damage (vitamins C, E, and beta-carotene)
- Support healthy cell growth (vitamins A and D)
- Help your blood clot properly (vitamin K)
- Keep your nervous system running (vitamins B1, B6, B12)
- Help build DNA (vitamins B9 and B12)
When you're low on a vitamin, you usually don't feel dramatically sick right away. More often, you just feel off — tired, foggy, run-down. That's why it's worth paying attention to your diet and checking in with your doctor.
2. Two Types of Vitamins
All 13 vitamins fall into one of two groups based on how they dissolve in the body.
Water-Soluble vs. Fat-Soluble
Water-soluble vitamins (9 total): vitamin C and all the B vitamins (B1, B2, B3, B5, B6, B7, B9, B12). These dissolve in water and travel through your bloodstream. Your body doesn't store most of them — any extra gets flushed out through your urine. So you need a regular supply from food.
Fat-soluble vitamins (4 total): vitamins A, D, E, and K. These dissolve in fat and get stored in your body's fatty tissue and liver. Because they build up over time, taking too many supplements can lead to toxic levels — especially with vitamins A and D.
Why Does This Matter?
The difference shapes how you should think about getting enough of each vitamin:
| Water-Soluble | Fat-Soluble | |
|---|---|---|
| Stored in the body? | No (except B12) | Yes — in fat and liver |
| Can you overdose? | Rarely from food | Yes, with excess supplements |
| How often do you need them? | Every day | Less often |
| Need fat to absorb? | No | Yes |
| How are they removed? | Through urine | Slowly, through bile |
📌 Want to go deeper? Water-Soluble vs. Fat-Soluble Vitamins: What's the Difference? (link to separate article)
3. Water-Soluble Vitamins
Vitamin C (Ascorbic Acid)
What it does: Vitamin C is best known for its role in immune health — but it does a lot more than fight colds. It's essential for making collagen, the protein that holds your skin, joints, blood vessels, and bones together. It also helps your body absorb iron from plant foods, supports wound healing, and acts as a powerful antioxidant that protects your cells from damage.
Where to find it: Bell peppers (especially red ones), citrus fruits, strawberries, kiwi, broccoli, Brussels sprouts, and rosehips are all great sources. One important note: vitamin C breaks down with heat, so the less you cook these foods, the more vitamin C you keep.
How much you need per day:
- Women: 75 mg
- Men: 90 mg
- Pregnant women: 85–120 mg
- Smokers: add 35 mg (smoking burns through vitamin C faster)
- Upper safe limit: 2,000 mg/day
Signs of deficiency: Classic vitamin C deficiency causes scurvy — bleeding gums, slow-healing wounds, joint pain, and weakness. Most people today don't get full-blown scurvy, but lower-than-optimal levels can show up as frequent infections, tiredness, and dull or rough skin.
Getting too much from food is essentially impossible. Very high supplement doses (over 2,000 mg/day) can cause digestive issues and, in some people, raise the risk of kidney stones.
Interesting fact: Most animals make their own vitamin C. Humans lost that ability through an ancient genetic mutation — probably because our early ancestors ate enough fruits and vegetables to cover their needs. We're in the same boat as guinea pigs and great apes.
📌 Want to go deeper? Vitamin C: Sources, Benefits, and Dosage Guide (link to separate article)
Vitamin B1 (Thiamine)
What it does: Thiamine helps your body turn carbohydrates into energy. It's especially important for your nervous system and heart muscle. If you're very active or eat a lot of carbs, your thiamine needs go up.
Where to find it: Whole grains (oatmeal, brown rice), legumes, pork, sunflower seeds, nuts, and nutritional yeast. Refined grains like white bread and white rice have very little — the outer bran layer, where thiamine lives, gets stripped away during processing.
How much you need per day:
- Women: 1.1 mg
- Men: 1.2 mg
- Pregnant or breastfeeding: 1.4 mg
Signs of deficiency: Severe deficiency causes beriberi — a disease that damages the nervous system and heart, causing weakness, numbness, and heart failure. In people who drink heavily, low B1 can lead to a serious brain disorder called Wernicke-Korsakoff syndrome. Milder deficiency often shows up as irritability, trouble focusing, and ongoing fatigue.
Vitamin B2 (Riboflavin)
What it does: Riboflavin helps your body produce energy from the food you eat — carbs, fats, and proteins. It also supports the function of other B vitamins, protects cells from oxidative damage, and helps maintain good eyesight.
Where to find it: Dairy products, eggs, meat, liver, dark leafy greens, almonds, and fortified cereals. One quirky detail: riboflavin breaks down in sunlight, so milk stored in clear bottles or jugs left in bright light loses a significant amount.
How much you need per day:
- Women: 1.1 mg
- Men: 1.3 mg
- Pregnant: 1.4 mg
- Breastfeeding: 1.6 mg
Signs of deficiency: Cracks at the corners of your mouth, a swollen or sore tongue, flaky skin around the nose and mouth, and sensitivity to bright light are typical signs. Low riboflavin also interferes with iron absorption and can raise homocysteine — a marker linked to heart disease risk.
Vitamin B3 (Niacin)
What it does: Niacin is needed for over 400 different reactions in your body, including turning food into energy, repairing DNA, and keeping your nervous system working. At high prescription doses, it can also lower triglycerides and raise HDL ("good") cholesterol — though this use is tightly controlled medically.
Where to find it: Chicken, beef, tuna, salmon, peanuts, whole grains, and mushrooms. Your body can also convert the amino acid tryptophan into niacin — roughly 60 mg of tryptophan makes 1 mg of niacin.
How much you need per day:
- Women: 14 mg NE (niacin equivalents)
- Men: 16 mg NE
- Upper limit from supplements: 35 mg/day (for nicotinic acid form)
Signs of deficiency and excess: Severe niacin deficiency causes pellagra — a condition known for the "four Ds": dermatitis, diarrhea, dementia, and (if untreated) death. Today in the U.S., it's rare but can appear in people with severe alcohol use disorders, certain malabsorption conditions, or very limited diets.
Taking high-dose niacin supplements can cause "niacin flush" — a harmless but uncomfortable wave of redness and heat in the skin. Chronic high doses can also stress the liver.
Vitamin B5 (Pantothenic Acid)
What it does: B5 is a building block of Coenzyme A (CoA) — a molecule your body absolutely needs to break down fats, make cholesterol and steroid hormones, and produce energy. It's also involved in building red blood cells and repairing cells throughout the body.
Where to find it: Almost everywhere — pantothenic acid gets its name from the Greek word pantothen, meaning "from all sides." Some of the best sources are liver, eggs, mushrooms, avocado, legumes, whole grains, and yogurt.
How much you need per day:
- Adults: 5 mg
- Pregnant: 6 mg
- Breastfeeding: 7 mg
Deficiency is extremely uncommon and only happens with severe malnutrition. There's also no known toxicity from food or normal supplement amounts.
Vitamin B6 (Pyridoxine)
What it does: B6 is involved in more than 100 reactions related to breaking down amino acids (the building blocks of protein). It's essential for making brain chemicals like serotonin, dopamine, and GABA, producing hemoglobin, and keeping your immune system strong. It also helps regulate homocysteine, high levels of which are linked to heart disease.
Where to find it: Chicken, tuna, salmon, liver, potatoes, bananas, chickpeas, sunflower seeds, avocado, and dark leafy greens.
How much you need per day:
- Adults under 50: 1.3 mg
- Women over 50: 1.5 mg
- Men over 50: 1.7 mg
- Pregnant: 1.9 mg
- Upper limit: 100 mg/day
Signs of deficiency: On its own, B6 deficiency is rare — it usually shows up alongside low levels of other B vitamins. Signs include mood changes, depression, confusion, skin rashes, and a sore tongue. Taking very high doses from supplements (over 200 mg/day long-term) can cause nerve damage in the hands and feet.
Vitamin B7 (Biotin)
What it does: Biotin helps your body process fats, carbohydrates, and amino acids. It's involved in producing glucose when your body needs it and plays a role in how your genes are expressed. It also supports healthy skin, hair, and nails — which is why biotin supplements are so popular in beauty products.
Where to find it: Egg yolks, liver, salmon, avocado, sunflower seeds, sweet potatoes, nuts, and yeast. Heads up: raw egg whites contain a protein called avidin that actually blocks biotin absorption. Cooking the egg solves this — heat breaks avidin down.
How much you need per day:
- Adults: 30 mcg
- Pregnant: 30 mcg
- Breastfeeding: 35 mcg
Biotin deficiency is rare. It can happen if someone eats a lot of raw egg whites regularly, or has a certain genetic condition. Symptoms include hair loss, a skin rash around the eyes and mouth, and neurological issues.
Vitamin B9 (Folate / Folic Acid)
What it does: Folate (from food) and folic acid (the synthetic version used in supplements and fortified foods) are critical for making and repairing DNA, dividing cells properly, and producing red blood cells. They're also needed for making neurotransmitters and keeping homocysteine levels in check.
Where to find it: Spinach, romaine lettuce, arugula, lentils, chickpeas, black beans, asparagus, broccoli, avocado, eggs, and fortified grain products (like many cereals and breads in the U.S.).
How much you need per day:
- Adults: 400 mcg DFE (dietary folate equivalents)
- Pregnant: 600 mcg DFE
- Breastfeeding: 500 mcg DFE
Why it matters during pregnancy: This is one of the most important nutrients if you're pregnant or planning to become pregnant. In the first 28 days after conception — often before a woman even knows she's pregnant — folate is critical for forming the baby's neural tube. Low levels during this window significantly raise the risk of neural tube defects like spina bifida and anencephaly. Getting enough folate can reduce that risk by 50–70%.
Because many pregnancies are unplanned, the CDC and most major health organizations recommend that all women who could become pregnant take 400 mcg of folic acid every day.
Worth knowing: about 10–15% of people have a variation in the MTHFR gene that makes it harder for their body to convert folic acid into its usable form. If this applies to you, a methylfolate supplement (L-5-MTHF) may work better. Talk to your doctor.
📌 Want to go deeper? Folic Acid During Pregnancy: How Much, When to Start, and Which Form to Take (link to separate article)
Vitamin B12 (Cobalamin)
What it does: B12 is essential for making DNA, forming healthy red blood cells, and protecting the myelin sheath — the coating around your nerve fibers that helps signals travel properly. It works closely with folate and B6 to manage homocysteine levels. It's also the only vitamin that contains a metal (cobalt) in its structure.
Where to find it: B12 is found only in animal products: meat, fish, shellfish, eggs, and dairy. The richest sources are clams, beef liver, mackerel, salmon, and beef.
How much you need per day:
- Adults: 2.4 mcg
- Pregnant: 2.6 mcg
- Breastfeeding: 2.8 mcg
If you follow a plant-based diet: Plant foods don't contain B12 in a form your body can use. Algae, miso, and tempeh are sometimes marketed as sources, but they're not reliable. If you're vegan — or vegetarian and skipping eggs and dairy — you need a B12 supplement or fortified foods. This isn't optional. Long-term B12 deficiency causes irreversible nerve damage.
Signs of deficiency: B12 is stored in the liver, so deficiency builds up slowly — it can take months or even years to show up after cutting out animal foods. When it does, symptoms include fatigue, weakness, numbness or tingling in the hands and feet, memory problems, depression, and a specific type of anemia where red blood cells are abnormally large but don't work properly.
It's not just vegans who are at risk. Adults over 50 often absorb B12 poorly because their stomachs produce less acid and less "intrinsic factor" — a protein needed to absorb B12. People with Crohn's disease, celiac disease, or those taking metformin or acid-reducing medications (like omeprazole) long-term are also at risk.
📌 Want to go deeper? Vitamin B12: Deficiency Signs, Testing, and the Best Supplement Forms (link to separate article)
4. Fat-Soluble Vitamins
Vitamin A (Retinol)
What it does: Vitamin A comes in two forms. Retinol comes from animal foods and is ready for your body to use right away. Beta-carotene comes from plants and gets converted into vitamin A as needed. Both forms support your eyesight (especially in low light), keep skin and mucous membranes healthy, regulate cell growth, and support a strong immune system and reproductive health.
Where to find it: Retinol: beef liver, cod liver oil, eggs, and dairy products. Beta-carotene: carrots, pumpkin, sweet potatoes, spinach, kale, apricots, and mangoes. Eating these with a little fat — like olive oil or avocado — boosts how much beta-carotene your body actually absorbs.
How much you need per day:
- Women: 700 mcg RAE (retinol activity equivalents)
- Men: 900 mcg RAE
- Pregnant: 770 mcg RAE
- Upper safe limit: 3,000 mcg RAE/day — for retinol only, not beta-carotene
Signs of deficiency and risk of overdose: Deficiency is rare in the U.S. but common globally. The first sign is usually night blindness — difficulty seeing in dim light. Severe deficiency can damage the cornea.
Too much retinol from supplements is a real concern. Acute toxicity causes headaches, nausea, and blurred vision. Long-term excess can damage the liver, cause bone pain, and is dangerous during pregnancy because it can harm the developing baby. This is why prenatal vitamins use beta-carotene instead of high-dose retinol.
Beta-carotene doesn't cause toxicity — at very high amounts, it can turn your skin slightly orange, which is harmless and goes away when you cut back.
📌 Want to go deeper? Vitamin A: Retinol vs. Beta-Carotene, Daily Needs, and Safety (link to separate article)
Vitamin D (Calciferol)
What it does: Technically, vitamin D is a hormone, not just a vitamin. Once activated in your kidneys, it binds to receptors in more than 30 different tissues. Its most well-known job is helping your body absorb calcium and keep bones strong. But it also plays a role in immune function, muscle strength, mood regulation, and reducing inflammation.
Where to find it: Sunlight: your skin makes vitamin D when exposed to UVB rays — this is the main source for most people in sunny regions. Food: fatty fish (salmon, mackerel, herring), cod liver oil, egg yolks, and fortified foods like milk, orange juice, and cereals. Natural food sources alone are rarely enough to meet your full daily needs.
How much you need per day:
- Adults up to age 70: 600 IU (15 mcg)
- Adults over 70: 800 IU (20 mcg)
- Upper safe limit: 4,000 IU/day
- Optimal blood level (25(OH)D): 40–60 ng/mL, though many experts consider 30 ng/mL an acceptable minimum
The vitamin D gap in the U.S.: Studies estimate that 35–40% of American adults have low vitamin D levels. The problem is especially common among people who live in northern states (think Boston, Chicago, or Seattle), work indoors, have darker skin (which produces less vitamin D from sunlight), or are older — because skin produces less vitamin D with age.
Above roughly the 37th parallel — which runs through Northern California, Kansas, and Virginia — UVB rays are too weak from November through March to trigger meaningful vitamin D production, no matter how much time you spend outside.
Sun or supplements? In summer, 15–30 minutes of midday sun with exposed arms and legs can produce enough vitamin D for many fair-skinned people. But for anyone who lives in northern states, uses sunscreen consistently, or spends most of their time indoors, supplementation is a smart and well-supported choice. The right dose is best guided by a blood test (25(OH)D) rather than guesswork.
📌 Want to go deeper? Vitamin D: How to Test, What Your Levels Mean, and How Much to Take (link to separate article)
Vitamin E (Tocopherol)
What it does: "Vitamin E" is actually a group of eight related compounds, but alpha-tocopherol is the most active form in the human body. It's a fat-soluble antioxidant that protects the fatty membranes of your cells from being damaged by free radicals. It also helps regulate immune responses and supports healthy blood flow.
Where to find it: Sunflower oil, wheat germ oil, almonds, hazelnuts, sunflower seeds, spinach, broccoli, avocado, and olive oil. Keep in mind that vitamin E degrades when oils are stored for a long time or heated at high temperatures.
How much you need per day:
- Adults: 15 mg
- Breastfeeding: 19 mg
- Upper limit from supplements: 1,000 mg/day
Signs of deficiency: Vitamin E deficiency on its own is very rare in healthy people. It usually only occurs with conditions that impair fat absorption — like celiac disease, Crohn's disease, or cystic fibrosis. When it does happen, it can cause nerve damage, muscle weakness, balance problems, and vision issues.
Vitamin K (K1 and K2)
What it does: Vitamin K activates proteins your body needs for two important jobs: clotting blood (K1's main role) and directing calcium to the right places — into bones, not artery walls (K2's main role). Without enough vitamin K, even minor cuts could bleed for longer, and over time, calcium can end up in blood vessels instead of your skeleton.
Where to find it: K1 (phylloquinone): spinach, kale, broccoli, Brussels sprouts, and parsley. Eating these with a bit of fat significantly improves absorption. K2 (menaquinones): fermented foods like natto (a Japanese soybean dish) and sauerkraut, hard cheeses, egg yolks, and meat. Your gut bacteria also produce some K2.
How much you need per day:
- Women: 90 mcg
- Men: 120 mcg (There's no established upper limit — vitamin K toxicity from food hasn't been reported)
K1 vs. K2 — what's the difference? Both forms share a similar core structure but have different "tails" that affect where they end up in the body. K1 mostly goes to the liver and supports blood clotting factors. K2 — particularly the MK-4 and MK-7 forms — is better at reaching bones and blood vessels, which is why researchers are increasingly interested in K2 for bone density and cardiovascular health. Studies are still ongoing.
Important: if you take blood thinners like warfarin, big changes in your vitamin K1 intake can affect how well the medication works. Always check with your doctor before dramatically changing how many leafy greens you eat.
📌 Want to go deeper? Vitamin K2: What the Science Says About Bones and Heart Health (link to separate article)
5. How Your Body Manages Vitamin Stores
Not All Vitamins Are Stored the Same Way
Your body does its best to hold onto vitamins when your intake drops — but it can only do so much. Here's roughly how long your stored vitamins would last without any new intake:
| Vitamin | Where it's stored | Time before deficiency without intake |
|---|---|---|
| B12 | Liver (3–5 mg) | 2–5 years |
| A | Liver | 1–2 years |
| D | Fat tissue | Several months |
| B9 (folate) | Liver, red blood cells | 3–6 months |
| E | Fat tissue | Several months |
| K | Minimal | Days to weeks |
| C | Blood and tissues | 1–3 months |
| B1, B2, B6 | Very little | Weeks to months |
Your Body Tries to Adapt
When your vitamin intake drops, your body compensates — it absorbs more from food, reduces how much it excretes through urine, and pulls stored vitamins from different tissues as needed. These are smart survival mechanisms, but they have real limits. If intake stays low for a long time, stores eventually run out.
Deficiency Happens in Stages
Vitamin deficiency doesn't usually strike suddenly. It develops in four gradual stages:
- Stores get low — tissue levels drop, but you feel and function normally
- Subclinical deficiency — lab results look off, but symptoms are vague: tired, moody, not quite right
- Clinical deficiency — clear, recognizable symptoms appear
- Severe deficiency — serious or potentially irreversible damage (such as nerve damage from long-term B12 deficiency)
Most people who have low vitamin levels are somewhere in stages 1 or 2 — and have no idea. That's what makes regular checkups and dietary awareness so valuable.
6. Who Is at Higher Risk for Vitamin Deficiencies?
Some people are more likely to run low on certain vitamins based on their diet, lifestyle, age, or health conditions.
Pregnant and Breastfeeding Women
During pregnancy, your need for folate, iron, vitamin D, iodine, choline, and B12 goes up significantly. It's hard to get enough of all of these from food alone — especially when nausea limits what you can eat in the first trimester. A quality prenatal vitamin and personalized guidance from your OB and a registered dietitian can help fill the gaps.
Older Adults (65+)
Getting older changes how your body absorbs and uses vitamins. Appetite often decreases, stomach acid production drops (reducing B12 absorption), and skin produces less vitamin D from sunlight. Older adults are especially at risk for low vitamin D, B12, calcium, and magnesium.
People on Special Diets
- Vegans: B12 (critical — must supplement), vitamin D, iron, zinc, omega-3s, iodine, calcium
- Vegetarians (who eat eggs and dairy): moderate risk for B12, vitamin D, iron, zinc
- Gluten-free diets: B vitamins (if fortified grains are excluded), iron, calcium
- Very low-calorie diets: risk of deficiency across the board
People with Certain Health Conditions
Digestive diseases like celiac disease, Crohn's disease, and other malabsorption conditions reduce how well your gut absorbs vitamins. Liver disease interferes with activating vitamins B12, D, and A, and with producing clotting factors (vitamin K). Kidney disease impairs the body's ability to activate vitamin D.
People Taking Certain Medications
Some very common medications can interfere with vitamin absorption or metabolism:
- Metformin (for diabetes) → reduces B12 absorption
- Proton pump inhibitors like omeprazole (for acid reflux) → reduce B12, magnesium, and calcium
- Warfarin (blood thinner) → interacts with vitamin K
- Isoniazid (for tuberculosis) → reduces B6
- Birth control pills → can lower folate, B6, and B12
- Statins (for cholesterol) → may reduce CoQ10
If you take any of these regularly, ask your doctor whether you should monitor specific vitamin levels.
📌 Want to go deeper? Who's Most at Risk for Vitamin Deficiencies — and What to Do About It (link to separate article)
7. How to Check Your Vitamin Levels
Blood Tests
A blood test is the most reliable way to find out if you're actually low in a vitamin. But not every vitamin can be tested with equal accuracy.
Here are the most useful lab markers:
- Vitamin D: 25-hydroxyvitamin D (25(OH)D) — the standard and very reliable
- B12: serum B12 gives a rough idea; holotranscobalamin (active B12) and methylmalonic acid are more precise
- Folate: red blood cell folate is more stable and accurate than serum folate
- Vitamin A: serum retinol
- Iron status: ferritin, transferrin, and total iron-binding capacity (TIBC)
Vitamins like C, E, K, and most B vitamins aren't routinely tested. Doctors usually assess them based on symptoms and eating habits.
Food Journaling
Tracking what you eat for 3–7 days — including weekends — gives a registered dietitian a clear picture of your typical diet. This can reveal nutritional gaps sometimes before any symptoms even show up.
Key things to look at: how nutrient-dense your diet is overall, how varied your food choices are, which food groups you eat regularly, and whether anything you're eating or avoiding affects absorption.
Nutrition Tracking Apps
Apps like Cronometer or MyFitnessPal let you log your meals and see a breakdown of your nutrient intake. They're a helpful starting point but aren't perfect — food databases have gaps, they don't account for cooking losses, and they can't factor in your individual absorption rate.
📌 Want to go deeper? Which Vitamin Tests Should You Ask Your Doctor For? (link to separate article)
8. Daily Vitamin Requirements
Where Do These Numbers Come From?
In the United States, the main reference is the Recommended Dietary Allowance (RDA) — set by the National Academies of Sciences. It represents the daily intake that meets the needs of 97.5% of healthy adults. The numbers are updated as new research becomes available.
The EU and WHO publish their own slightly different guidelines, but for most vitamins, the numbers are in the same range.
Daily Vitamin Reference Chart (Adults)
| Vitamin | Women | Men | Pregnant | Upper Safe Limit |
|---|---|---|---|---|
| C | 75 mg | 90 mg | 85 mg | 2,000 mg |
| B1 | 1.1 mg | 1.2 mg | 1.4 mg | — |
| B2 | 1.1 mg | 1.3 mg | 1.4 mg | — |
| B3 | 14 mg | 16 mg | 18 mg | 35 mg |
| B5 | 5 mg | 5 mg | 6 mg | — |
| B6 | 1.3 mg | 1.3 mg | 1.9 mg | 100 mg |
| B7 | 30 mcg | 30 mcg | 30 mcg | — |
| B9 | 400 mcg | 400 mcg | 600 mcg | 1,000 mcg |
| B12 | 2.4 mcg | 2.4 mcg | 2.6 mcg | — |
| A | 700 mcg RAE | 900 mcg RAE | 770 mcg RAE | 3,000 mcg |
| D | 600 IU | 600 IU | 600 IU | 4,000 IU |
| E | 15 mg | 15 mg | 15 mg | 1,000 mg |
| K | 90 mcg | 120 mcg | 90 mcg | — |
Source: National Academies of Sciences, DRI 2023. These are general guidelines for healthy adults. If you have a health condition or take medications, your personal needs may differ — check with your doctor.
9. Food vs. Supplements
Can You Get Everything from Food?
For most healthy adults eating a varied, balanced diet — yes, mostly. A diet with plenty of vegetables, fruits, whole grains, legumes, quality protein, and healthy fats covers the needs for most vitamins, most of the time.
And food has a real edge over supplements: vitamins in whole foods come packaged with other nutrients that help your body absorb and use them better. This is sometimes called the "food matrix effect." A vitamin C capsule isn't quite the same as eating a bell pepper — the nutrients in real food work together in ways that isolated supplements simply can't replicate.
When Do Supplements Make Sense?
Supplements are a good idea when:
- You have a confirmed deficiency from a blood test
- Your needs are higher — during pregnancy, when training hard, or recovering from illness
- Your diet is restricted — if you're vegan, on a very low-calorie diet, or dealing with appetite issues
- You have absorption problems — from a digestive condition, surgery, or a medication that interferes
- You don't get enough sun — especially for vitamin D if you live in a northern state or work indoors
- You're over 50 — B12 and vitamin D absorption both naturally decline with age
The Vitamins Hardest to Get from Food Alone
- Vitamin D — even a solid diet can't fully compensate for limited sun exposure
- B12 — if you're vegan or have absorption problems
- Folate — hitting 600 mcg during pregnancy through food alone is very difficult
- Iodine — if you don't use iodized table salt (note: sea salt, kosher salt, and most specialty salts are not iodized)
📌 Want to go deeper? Vitamin Supplements: When You Actually Need Them and How to Choose (link to separate article)
10. Practical Checklist
Take a Quick Look at Your Diet
Answer these honestly:
On most days, do you eat:
- 3–5 servings of vegetables in different colors?
- 1–2 servings of fruit?
- A good source of protein — meat, fish, eggs, or legumes?
- Whole grains, not just white bread and white rice?
- Enough fluids — about 6–8 cups of water per day?
On a regular basis, do you eat:
- Fatty fish like salmon or mackerel (at least twice a week)?
- Dark leafy greens — spinach, kale, broccoli?
- Legumes — lentils, chickpeas, black beans?
- Nuts and seeds?
Do any of these apply to you?
- You don't eat meat or animal products
- You rarely spend time outdoors in sunlight
- You're over 50
- You have a chronic digestive condition
- You take metformin, a proton pump inhibitor, or another long-term medication
- You're pregnant or planning to become pregnant
If you checked 3 or more risk factors — or fewer than half of the items in the first section — it's worth having a conversation with a registered dietitian.
The Most Common Vitamin Deficiencies in the U.S.
Based on national survey data (NHANES) and clinical practice, the most frequent low-grade deficiencies among American adults are:
- Vitamin D — affects an estimated 35–40% of adults; more common in northern states, among older adults, and in people with darker skin tones
- Magnesium — over 45% of Americans don't meet the average daily requirement through diet alone
- Vitamin B12 — particularly in adults over 50, vegans, and those taking metformin or acid-suppressing medications
- Iron — especially in women of reproductive age and endurance athletes
- Folate — most often low in women of reproductive age who aren't supplementing
Simple First Steps
- Get a few basic blood tests: ask your primary care provider about vitamin D (25(OH)D), a complete blood count (CBC), ferritin, and B12
- Track your food for 3–5 days — including at least one weekend day
- Talk to a registered dietitian (RD) for a full dietary review
- Don't self-prescribe supplements without testing first — especially fat-soluble vitamins A, D, E, and K, which can build up to harmful levels
11. Key Takeaways
Here's the short version of everything above:
- All 13 vitamins are essential. Your body can't run basic processes without them.
- Water-soluble vitamins need regular daily replenishment. Fat-soluble ones build up in your body — which means too many supplements can reach toxic levels.
- Deficiency usually doesn't look dramatic. It most often feels like persistent fatigue, low mood, getting sick too often, or poor skin and hair quality.
- Vitamin D and B12 are the two most commonly deficient vitamins in the U.S. — and the two most likely to need supplementation even in people who eat well.
- The best way to understand your vitamin status: blood tests + dietary analysis + a conversation with your doctor or dietitian.
- Food comes first. Use supplements as a targeted tool — not as a default daily routine for everyone.
What Should You Do Next?
Getting your vitamins right isn't about memorizing a list of 13 and buying 13 bottles. It's about understanding how your daily food choices, lifestyle habits, and health situation affect what your body actually gets at the cellular level.
If you're wondering about your vitamin status, the smartest starting point is a conversation with your doctor and some basic lab work — not a shopping trip to the supplement aisle.
This article is written by a nutritionist for informational purposes only. Before starting any supplements or making major dietary changes — especially if you have a health condition or take prescription medications — talk to your doctor or a registered dietitian.
Related articles:
- Essential Vitamins — Complete Guide (you are here)
- Water-Soluble vs. Fat-Soluble Vitamins: What's the Difference?
- Vitamin D: How to Test, What Your Levels Mean, and How Much to Take
- Vitamin B12: Signs of Deficiency, Testing, and Best Supplement Forms
- Folic Acid During Pregnancy: How Much, When to Start, and Which Form
- Vitamin A: Retinol vs. Beta-Carotene — What You Need to Know
- Vitamin K2: What the Science Says About Bones and Heart Health
- Who's Most at Risk for Vitamin Deficiencies?
- Which Vitamin Tests Should You Ask Your Doctor For?
- Vitamin Supplements: When You Need Them and How to Choose