Vegetables deliver a wide range of essential nutrients, including fiber, potassium, vitamins A, C, and K, B vitamins, minerals like magnesium and calcium, and protective plant compounds you won’t find in any other food group. The specific mix varies dramatically depending on the type of vegetable, which is why eating a variety matters more than zeroing in on any single one.
Fiber and Carbohydrates
Most of the calories in vegetables come from carbohydrates, but the amounts are modest compared to grains or fruit. A medium potato has about 26 grams of carbohydrates and 110 calories, while a full stalk of broccoli has just 8 grams and 45 calories. Leafy greens sit at the low end: a serving of leaf lettuce has roughly 2 grams of carbohydrates and only 15 calories.
Fiber is one of the biggest nutritional selling points of vegetables. A medium sweet potato provides about 4 grams of fiber (16% of the daily value), and a stalk of broccoli delivers 3 grams (12% DV). Root vegetables and cruciferous vegetables tend to be the richest sources, while watery greens like iceberg lettuce contribute very little. Most adults fall short of the recommended 25 to 30 grams of fiber per day, and adding a few servings of vegetables is one of the easiest ways to close that gap.
Vitamins: What Each Type Provides
Vitamin A and Beta-Carotene
Orange and deep-green vegetables are loaded with beta-carotene, a pigment your body converts into vitamin A. A single baked sweet potato provides about 1,403 micrograms of vitamin A, which is 156% of the daily value. Carrots are another standout, delivering 110% DV per medium carrot. Leaf lettuce, despite being light on most nutrients, still provides 130% DV of vitamin A per serving. Your body uses vitamin A for vision, immune function, and skin health.
Vitamin C
Red bell peppers are one of the richest vitamin C sources in the entire produce aisle. One cup of chopped raw red bell pepper contains 191 milligrams, or 212% of the daily value. That’s roughly triple what you’d get from an orange. Broccoli delivers 220% DV per stalk, and even a medium potato provides 45% DV. Brussels sprouts, tomatoes, and spinach are also solid sources. Vitamin C supports your immune system and helps your body absorb iron from plant foods.
Vitamin K
Dark leafy greens and cruciferous vegetables are the primary dietary sources of vitamin K, which your body needs for blood clotting and bone metabolism. Spinach, kale, broccoli, and cabbage are all rich in it. If you take blood-thinning medication, these are the vegetables your doctor has likely flagged, because vitamin K directly affects how those drugs work.
B Vitamins
Different vegetables contribute different B vitamins. Spinach, asparagus, and broccoli are among the best sources of folate (B-9), which is critical for cell growth and especially important during pregnancy. Potatoes and mushrooms supply niacin (B-3). Broccoli, avocados, and mushrooms provide pantothenic acid (B-5). Acorn squash is a notable source of thiamin (B-1). No single vegetable covers all the B vitamins, which is another reason variety matters.
Key Minerals
Potassium is the mineral vegetables deliver most generously. Acorn squash leads the pack with 749 mg per half cup (baked), followed by avocado at 604 mg and potato at 504 mg. Carrots, spinach, broccoli, and tomatoes all contribute meaningful amounts as well. Potassium helps regulate blood pressure and fluid balance, and most people don’t get enough of it.
Vegetables also supply calcium, magnesium, and iron, though generally in smaller amounts than dairy or meat. Broccoli and kale provide calcium that your body absorbs relatively well. However, not all vegetable minerals are equally available to your body, a topic covered in more detail below.
Protective Plant Compounds
Beyond the standard vitamins and minerals, vegetables contain thousands of compounds called phytonutrients that act as antioxidants and support long-term health in ways that isolated supplements don’t replicate.
Cruciferous vegetables like broccoli, Brussels sprouts, kale, cabbage, cauliflower, and arugula contain compounds called glucosinolates. When you chop or chew these vegetables, the glucosinolates break down into active compounds, the most studied being sulforaphane (from broccoli and Brussels sprouts). Preclinical and clinical research has identified glucosinolates as potentially protective against chronic disease, and they’re found almost exclusively in this vegetable family.
Garlic and onions belong to the allium family and are rich in organosulfur compounds. Garlic’s signature compound, allicin, has demonstrated anti-inflammatory and antimicrobial properties. One study of 146 participants found that taking an allicin-containing supplement for 12 weeks reduced the incidence and symptoms of the common cold. Onions contain a related compound called propiin, which breaks down into substances with their own anti-inflammatory and antimicrobial effects. These sulfur compounds are what give alliums their pungent smell.
Orange and red vegetables get their color from carotenoids like beta-carotene (carrots, sweet potatoes), lycopene (tomatoes), and lutein (spinach, kale). These pigments function as antioxidants and are particularly associated with eye health and skin protection.
How Cooking Changes the Nutrient Profile
Cooking can either boost or reduce the nutrients you get from vegetables, depending on the method. Boiling causes the biggest losses in vitamin C, reducing it by anywhere from 10% to 71% depending on the vegetable. Spinach loses the most. The vitamin leaches into the cooking water, so if you’re making soup, you still capture it, but if you drain the water, it’s gone.
Microwaving preserves the most vitamin C, retaining over 90% of the original content. Steaming falls in the middle, with moderate nutrient loss. For carotenoids like beta-carotene and lycopene, cooking actually improves absorption by breaking down plant cell walls and making these compounds easier for your gut to take up. This is why cooked tomatoes deliver more usable lycopene than raw ones.
The practical takeaway: there’s no single best cooking method. Eating a mix of raw and lightly cooked vegetables gives you the broadest nutrient benefit.
Why Some Nutrients Are Harder to Absorb
Spinach is often promoted as a great source of calcium and iron, but it also contains very high levels of oxalates, compounds that bind to these minerals and prevent your body from absorbing them. Raw spinach contains up to 2,350 mg of total oxalates per 100 grams of fresh weight. When oxalates encounter calcium, iron, or magnesium in your digestive tract, they form insoluble compounds that pass through you without being absorbed.
Boiling does help. Cooked spinach drops from roughly 2,350 mg to about 477 mg of total oxalates per 100 grams, because much of it dissolves into the water. Beetroot and Swiss chard also contain notable oxalate levels, though beetroot is considerably lower than spinach.
This doesn’t make spinach a bad choice. It’s still packed with folate, vitamin A, vitamin K, and potassium. But if you’re relying on vegetables for calcium or iron, low-oxalate options like broccoli, kale, and bok choy deliver those minerals in a form your body can actually use. Pairing iron-rich vegetables with a vitamin C source (like bell peppers or tomatoes) also significantly improves iron absorption.
Getting the Most From Your Vegetables
Different vegetable families bring different strengths to your plate. Orange and red vegetables are your best sources of vitamin A and lycopene. Cruciferous vegetables deliver vitamin C, vitamin K, and unique protective compounds like sulforaphane. Leafy greens provide folate and vitamin K. Root vegetables supply potassium and fiber. Alliums contribute sulfur compounds with antimicrobial and anti-inflammatory properties.
Eating across these categories, rather than relying on one or two favorites, is the most reliable way to cover your nutritional bases. Color is a useful shortcut: a plate with three or four different colored vegetables almost always delivers a broader nutrient profile than one dominated by a single type.