What Are Vitamins and Which Foods Provide Them?
Vitamins are organic compounds your body needs in small amounts to function, and it cannot make most of them on its own—so they have to come from food. The main exceptions are vitamin D, which your skin synthesizes in response to sunlight, and vitamin K, which gut bacteria produce in limited amounts. If you eat a varied diet, you likely cover most of your needs; if you're tracking what you eat, a food log can show where the gaps are. This guide covers what each vitamin does, where to find it, and who tends to fall short.
Vitamins vs. minerals vs. macronutrients
These three categories are often lumped together, but they work differently:
- Macronutrients — carbohydrates, protein, and fat. You need them in large amounts for energy and structure.
- Vitamins — organic compounds (they contain carbon) needed in small amounts. They mostly act as coenzymes, helping chemical reactions happen.
- Minerals — inorganic elements like calcium, iron, and zinc. They don't contain carbon and play structural and regulatory roles.
The key practical difference: vitamins are fragile. Heat, light, air, and water can destroy them during cooking and storage, which is why cooking method affects how much you actually get.
The essential vitamins and what they do
There are 13 essential vitamins. Here's what each one does and where to find it.
| Vitamin | Main role | Common food sources |
|---|---|---|
| A | Vision, immune function, skin | Liver, carrots, sweet potato, spinach, eggs |
| C | Collagen formation, antioxidant, iron absorption | Citrus, bell peppers, broccoli, strawberries |
| D | Calcium absorption, bone health | Fatty fish, egg yolks, fortified milk, sunlight |
| E | Antioxidant, protects cell membranes | Nuts, seeds, vegetable oils, spinach |
| K | Blood clotting, bone health | Kale, spinach, broccoli, Brussels sprouts |
| B1 (thiamine) | Energy metabolism, nerve function | Whole grains, pork, legumes, sunflower seeds |
| B2 (riboflavin) | Energy metabolism, cell growth | Milk, eggs, lean meat, almonds |
| B3 (niacin) | Energy metabolism, DNA repair | Poultry, fish, peanuts, whole grains |
| B5 (pantothenic acid) | Energy metabolism, hormone synthesis | Widespread—meat, mushrooms, avocado, eggs |
| B6 (pyridoxine) | Protein metabolism, neurotransmitter synthesis | Poultry, fish, potatoes, chickpeas, bananas |
| B7 (biotin) | Fat and carbohydrate metabolism | Eggs, nuts, seeds, sweet potato |
| B9 (folate) | Cell division, DNA synthesis | Leafy greens, legumes, fortified grains, asparagus |
| B12 (cobalamin) | Red blood cell formation, nerve function | Animal products only—meat, fish, dairy, eggs |
The B vitamins work as a team; a shortfall in one often signals a shortfall in others, since they cluster in similar foods.
Fat-soluble vs. water-soluble: why it matters
This distinction affects how you absorb, store, and lose each vitamin.
Fat-soluble (A, D, E, K): Absorbed with dietary fat, stored in your liver and fatty tissue, and not easily excreted. You don't need them daily—your body draws on reserves. But because they accumulate, very high doses from supplements can reach toxic levels.
Water-soluble (C and all B vitamins): Dissolved in water, not stored in meaningful amounts, and excreted in urine. You need them more regularly. They're also more easily lost during cooking—boiling vegetables leaches B vitamins and C into the water, so steaming or stir-frying preserves more.
A practical takeaway: eat fat-soluble vitamins with some fat. A spinach salad with olive oil absorbs more vitamin K and A than plain spinach.
Who tends to fall short
Deficiency is uncommon in people eating a varied diet, but certain groups are at higher risk:
- Vegans and strict vegetarians — vitamin B12, since it occurs naturally only in animal products. Fortified foods or supplements are typically needed.
- Older adults — reduced stomach acid impairs B12 absorption, and skin makes less vitamin D with age.
- People with limited sun exposure — vitamin D, especially in winter at higher latitudes or with covered skin.
- Pregnant people — increased need for folate, which is why folic acid is recommended before and during early pregnancy.
- People with malabsorption conditions — celiac disease, Crohn's disease, or after bariatric surgery, where fat-soluble vitamins are poorly absorbed.
- Heavy alcohol use — depletes several B vitamins, particularly thiamine and folate.
Signs of deficiency vary by vitamin: fatigue and pale skin (B12, iron), bleeding gums (C), bone pain (D), night blindness (A), and easy bruising (K) are common examples. These symptoms overlap with many other conditions, so a diagnosis needs a clinician, not self-assessment.
How to check whether your diet covers them
The most reliable way to know if you're meeting your needs is to track intake against reference values. A food log that breaks out individual micronutrients—rather than just calories and macros—shows which vitamins you're consistently under on.
MyFoodData, for example, tracks 30+ nutrients and offers free micronutrient breakdowns, with verified badges marking foods that have the most complete data. Its comparison tools let you see how different foods stack up side by side, which is useful when you're trying to close a specific gap—say, swapping a low-folate grain for a higher one. The site also notes that its core tracking, recipes, and barcode scanning are free, with a Premium tier that removes ads and adds features like unlimited photo scanning and profile sharing.
To use any tracker well:
- Log a few typical days, not your best days—you want an honest baseline.
- Check the micronutrient view, not just calories.
- Look for patterns, not single-day dips. One low day doesn't matter; a consistent shortfall does.
- Adjust with whole foods first before reaching for supplements.
- Re-check after a few weeks to confirm the change worked.
If you find a persistent gap—especially B12, D, or iron—talk to a healthcare provider before supplementing, since dosing and interactions depend on your situation.