Make sure to consume some of these ingredients when doing vegetarian diet / less meat diet, so that you can get the nutrients without eating much meat.
Fat: Diary products, nuts, cooking oils.
Protein: Diary products, soy foods, legumes (beans), eggs.
Zinc: Dairy products, soy foods, nuts & seeds & legumes.
Iron: Beans, soy foods, dark leafy greens.
- Pair with foods rich in vitamin C for better absorpsion.
Calcium: Diary products.
Vitamin D: Eggs. And sunshine. No really, get outside once in a while!
Vitamin B12: Diary products, eggs.
Omega–3 Fatty Acids: Eggs, soy products, (some) nuts & seeds.
Iodine: Seaweed & other sea products.
For the "semi-vegetarians", who don't refrain completely from eating meat but rather just reduces the amount of consumption, seafood and animal organs can supplement the nutrients lacking in plant-based diet very efficiently - especially for some vitamins, minerals, and essential amino acids.