It is estimated that about 2 billion people live primarily on a meat-based diet worldwide, while 4 billion focus on a plant-based diet.
A plant-based diet has smaller quantities of bioavailable iron when compared to meat, poultry, and fish eaters. Iron in heme form is better absorbed when compared to non-heme form iron. Plant-based food or non-heme iron absorption is inhibited by phytic acid present in these foods.
And, although vegetarians have lower iron stores because of low quantities of it in their diets, the adverse health impact of lower iron and zinc absorption was not seen. (Hunt, 2002). In fact, in some cases, a plant-based diet combined with stress reduction led to a decrease in recurrent prostate cancer (Saxe et al., 2006).
Zinc deficiency can occur in diets low in bioavailable zinc food, like red meat and unrefined cereals rich in phytate and dietary fibers. In US diets, more than half of Zinc comes from animal food. Vegetarian diets contain legumes, whole grains, nuts, and seeds; while they have adequate Zinc quantities, the bioavailability is restricted due to phytic acid present in these foods. High levels of calcium can also reduce the bioavailability of Zinc.
Elimination of meat and increased intake of phytate-containing legumes and whole grains leads to lower absorption of trace elements iron and Zinc. However, the consequences of lower bioavailability are still not completely understood (Hunt, 2003).
Zinc is a non-toxic element. Excessive supplementation can lead to copper deficiency (Sandstead, 1995). The best sources for Zinc are red meats, liver, shellfish, nuts, whole grains, and legumes.
Plant-based sources of Omega3 are flaxseed, chia seeds, canola, walnut and soybean oils, leafy and green vegetables. These are short-chain omega 3 molecules that need to be converted in the body into long-chained fatty acids. Converting plant-based omega3 foods into a nutritionally useful form is an inefficient metabolic process. The absorption levels of this type of fatty acid are quite low.
Natural food-based nutrition will continue to be attractive, and these are best obtained from organically raised fatty fish. It will need to come from less efficient Omega3s sources like flaxseed, chia seeds, canola, and walnut for vegans.
Vitamin B12 supplementation may occur in vegans. Excess supplementation can lead to difficulty in sleeping and other side effects.
Replacing animal protein with plant protein will likely reduce mortality rates, lower cholesterol levels, and higher health benefits.
I have only provided an overview. Minerals, supplements, and nutrition is a vast subject, and it is best to take the help of a nutrition expert.