People on a plant-based diet but also omnivores should be on guard against nutrient deficiencies. Below I listed a few examples. Do not stress over it too much, though. If you miss a serving of legumes now and then, or fall a little short on your calcium-rich foods once in a while, it is not a big deal.
Proteins. You need about one gram of protein per kilogram of body weight per day. Much of this protein should come from lysine-rich foods like beans (e.g. kidney beans, soybeans), legumes (e.g. chickpeas, lentils), vegetables (e.g. spinach, broccoli, Brussel sprout, cauliflower, peas), champignons, nuts (e.g. pumpkin seeds, peanuts, walnuts), seeds, and grains (e.g. quinoa, buckwheat, millet).
Fats. Maximum 30% of your energy demand. Nuts, seeds, avocado and vegetable oils. Needed to transport fat-soluble vitamins, to form steroid hormones and provide a natural feeling of satiety.
Amino Acids. Eight are essential and must come from food. Grains, legumes, vegetables, nuts, and seeds provide all essential amino acids, but are low in one or more. E.g. quinoa, chia seeds, goji berries, seitan, and germinated lentils contain all 8 amino acids. They are used to build new proteins in the body.
Calcium. Leafy greens (e.g. Bok choy, collard, kale, turnip greens, broccoli, leek, okra), legumes (e.g. soybeans, tofu, white beans), nuts/seeds (e.g. almonds, sesame, sunflower seeds, pumpkin seeds, poppy seed), fruits (e.g. figs)
Magnesium. Amaranth, millet, quinoa, nuts (e.g. almonds, hazelnuts, pumpkin seeds, walnuts, sunflower seeds, sesame, poppy seed, flaxseed), legumes (e.g. white beans, chickpeas, peas, soybeans, lentils), cacao, fruits (e.g. bananas, raspberries, blackberries, kiwi, pineapple, apricots, dates), dried fruits (often more magnesium than fresh ones), avocado, vegetables (e.g. spinach, broccoli, kohlrabies, okra)
Iron. dried apricots, amaranth, millet, cacao, goji berries, seaweed, sourdough bread, white beans, soybeans, Black-eyed peas, lentils, parsley, cinnamon, turmeric, yeast, nuts (e.g. pistachios, sunflower seeds, pumpkin seeds), black salsifies, spinach, and okra. Young women with heavy periods may have a tough time keeping up with iron needs. This is not a problem that is specific to vegans. It can help to take a low dose supplement (30-60 mins preprandial) with vitamin C (e.g. orange juice) to boost absorption. There is some evidence that taking supplements of the amino acid L-lysine boosts absorption as well. There can be negative health consequences to taking in too much iron.
Iodine: Iodized salt (¼ teaspoon per day), sunflower seeds.
Potassium. Not a problem if eating enough vegetables (e.g. potatoes, spinach, okra), beans, lentils, mushrooms, fruits (e.g. bananas), avocados, whole grains and nuts (e.g. walnuts).
Folate. walnuts, chickpeas, sojabeans, yeast, cabbage and leafy greens.
Zinc. Nuts/seeds (e.g. walnuts, pumpkin seeds).
Vitamin B12. If eating vegan you cannot get enough by eating unwashed organic produce, mushrooms grown in B12-rich soil, sauerkraut or fortified foods (e.g. soymilk). Everyone over the age of 50 should add vitamin B12 supplements (not vegan) to their diet since it becomes increasingly difficult to digest and absorb it in animal foods with aging.
Vitamin A (fat-soluble). Carrots, sweet potatoes, pumpkin (e.g. butternut), spinach, collards, kale, sunflower seeds, goji berries, rock melon.
Vitamin D (fat-soluble). Only a small amount can absorbed with food (e.g. mushrooms). Largely is produced in the skin with the help of ultraviolet beta rays. 15 minutes direct sunlight (not behind a window) per day on your face and hands are enough. Solarium light consists mainly of ultraviolet alpha rays which does not support the vitamin D synthesis. Smog, clouds, sunscreen, darker skin, age and weak sunlight (northern latitudes in winter) reduce vitamin D synthesis. It is recommended to supplement then.
Vitamin E (fat-soluble). Vegetable oils, nuts (e.g. walnuts, sunflower seeds, hazelnuts), goji berries.
Vitamin K (fat-soluble). Leafy greens, cabbage, sauerkraut, olive oil, champignons, strawberries, Brussel sprout, chives, asparagus, potatoes.
Vitamin C (sensitive to heat, light and oxygen). Improves our immune system. Kiwi, sea buckthorn, citrus fruits (e.g. lemon; not the one in the plastic bottle (E 300), orange, grapefruit), Strawberries, bananas, goji berries, okra, green leafy vegetables (e.g. kale), peppers, cauliflower, cabbage, broccoli. We need around 1000 mg per day. Our body cannot store more than 200 mg. That’s why repeat. Since it has a stimulating effect some people cannot sleep if taking in the evening.
Omega-3 fats (DHA/EPA). nuts/seeds (e.g. walnuts, chia seeds, flaxseed and to a lesser extent hemp and pumpkin seeds. Of these, walnuts and chia are probably the most convenient sources. Even if you are getting plenty of Omega-3s, your body may not be properly converting these fats to provide sufficient levels of DHA and EPA. It is rare for men to be able to convert ALA from flax seeds into DHA/EPA. So I supplement (e.g. micro algae oil; not on an empty stomach).
Niacin (Vitamin B3). Reduces anxiety and depression. Avocado, broccoli, tomatoes, dates, mushrooms, asparagus, Swiss chard, pumpkin seeds, sweet potatoes, carrots, okra, almonds, and spinach.