Nutrients

General information for healthy adults, not personal advice and not a diagnosis. Amounts and needs differ. For a supplement decision, talk with a doctor or a qualified dietitian.

Often discussed on a vegan diet

Vitamin B12. No unprocessed plant reliably covers it. Useful sources are fortified plant milk, fortified breakfast cereals and a supplement.
Vitamin D. Sunlight depending on season and latitude, fortified plant milk, and vegan D3.
Iodine. Iodised salt. Seaweed only in small amounts, because the iodine content swings widely.
Omega-3 (EPA/DHA). Algae oil supplies EPA and DHA. Flax, chia and walnuts supply ALA, and the body converts only a little of it.
Iron. Lentils, pumpkin seeds, oats and tofu, plus vitamin C from pepper or lemon in the same meal.
Calcium. Tofu set with calcium sulfate, fortified plant milk, kale, broccoli, tahini and calcium-rich mineral water.
Zinc. Legumes, oats, seeds and whole grains.
Selenium. One or two Brazil nuts, and whole grains depending on the soil.

Often short in mixed diets in Germany

Population data often show low intakes of fibre, folate, iodine, vitamin D, magnesium, calcium and, in women, iron. The same plant foods cover much of that: legumes, whole grains, leafy greens, seeds, nuts, fortified plant milk and iodised salt. Fibre is the clearest gap that a plant-heavy plate closes.

Compounds in animal foods linked to disease

These are mechanisms and study grades, not a claim that every portion causes illness.

Heme iron. In red meat. In the gut it favours nitrosating reactions and is linked to colorectal cancer. This is one of the stronger mechanistic stories behind the IARC rating of red meat.
Nitrite curing salt. In processed meat it can form nitrosamines. IARC classifies processed meat as carcinogenic to humans (Group 1) and red meat as probably carcinogenic (Group 2A), mainly for colorectal cancer. The working group estimated that each daily 50 gram portion of processed meat raises colorectal cancer risk by about 18 percent. For one person that increase starts from a small baseline risk. Across the population it matters.
Heterocyclic amines and polycyclic aromatic hydrocarbons. They form when muscle meat is fried or grilled hard. Lower heat and less browning mean less of them.
Saturated fat. From meat, sausage and butter they raise LDL cholesterol. That pathway is well supported for cardiovascular risk.
Carnitine and choline. Gut bacteria can turn them into TMAO. Observational studies link higher TMAO with cardiovascular risk. Fish can raise TMAO as well, so the picture is not “meat only”.
Secondary bile acids. A diet high in fat and meat produces more of them. They can irritate the gut lining. This is a supporting mechanism, not a stand-alone proof.
AGEs. Advanced glycation end products form especially when animal foods are cooked dry and hot. They are discussed in connection with inflammation and blood vessels.
IGF-1. High milk intake can raise IGF-1. A link with prostate cancer is being studied and is less settled than processed meat or heme iron.

Sources: IARC press release 240 (26 October 2015) on red and processed meat; DGE food-based dietary guidelines, March 2024.