A fully plant-based diet can absolutely provide everything the body needs, but it does take a bit more deliberate planning than a diet that includes animal products. A handful of nutrients are either missing from plants entirely or harder to absorb from them, and knowing which ones matters more than counting every gram.

Vitamin B12 is the one non-negotiable

Vitamin B12 is really the only nutrient that’s practically impossible to get in reliable amounts from unfortified plant foods. It occurs naturally in animal products, and its presence in the plant world is scarce and inconsistent at best. That’s why the near-universal recommendation for vegans is to eat B12-fortified foods regularly — some plant milks, breakfast cereals, and nutritional yeast are fortified — or to take a supplement. B12 deficiency develops slowly, sometimes over years, but its effects on the nervous system and blood cell production are serious enough that this isn’t the nutrient to leave to chance.

Iron: absorption matters as much as amount

Plant foods contain what’s called non-heme iron, which the body absorbs less efficiently than the heme iron found in meat. Good plant sources include legumes, tofu, buckwheat, pumpkin seeds, and leafy greens like spinach. Pairing these foods with a source of vitamin C noticeably improves absorption — a squeeze of lemon over a lentil dish or a side of citrus with a bowl of grains both help. Tea and coffee right after a meal work the other way, reducing iron absorption, so it’s worth spacing them out by an hour or so.

Calcium beyond dairy

Without dairy, calcium can come from tofu (especially when set with calcium sulfate), fortified plant milks, sesame seeds and tahini, and some leafy greens like kale and bok choy. Spinach and chard do contain calcium too, but it’s absorbed less efficiently there because of their high oxalic acid content, which binds up some of the mineral.

Plant-based omega-3s

Plant-based alpha-linolenic acid (ALA) shows up in flaxseed, chia seeds, walnuts, and canola oil, but the body only converts a modest fraction of it into the more active omega-3 forms. Anyone who wants extra assurance here can look at algae-based omega-3 supplements — a plant source of the same fatty acids usually obtained from fish.

Protein is more about habit than availability

With enough overall calories, hitting a solid protein target on a vegan diet usually isn’t hard — legumes, soy foods like tofu and tempeh, whole grains, and nuts add up quickly. The bigger factor is variety rather than sheer quantity, since spreading protein sources across the day helps cover the full range of essential amino acids, and it helps to include a protein source at each meal rather than just one.

Zinc and iodine

Zinc is found in legumes, nuts, whole grains, and seeds, but like iron, it’s somewhat less bioavailable from plant sources. Iodine is another nutrient that’s easy to underestimate on a plant-based diet, particularly if the diet skips iodized salt and seaweed; in some cases it’s worth discussing a supplement with a doctor.

Putting it into practice

It helps to think less about individual nutrients and more about overall variety: different types of legumes and grains, a mix of nuts and seeds, vegetables and greens in a range of colors, and fortified foods where useful. Periodic blood work, especially for B12, ferritin, and vitamin D, makes it easier to catch a shortfall early and adjust the diet or supplements before any symptoms show up.