1) Iron. Plant sources contain a significant amount of iron, but in non heme form, which is more sensitive to inhibitors than iron that comes from animal products. You should do two things to increase your blood-iron levels: 1) consume more plant iron; and 2) avoid absorption inhibitors, such as red wine, tea, coffee, and fiber.
2) Zinc. Whereas non-vegetarian diets seem to enhance the absorption of zinc, vegetarian and vegan diets do the exact opposite–they inhibit it. Nutritionists suggest that you can overcome this by consuming more foods that contain zinc, such as soybeans, cashews, and sunflower seeds while reducing your intake of inhibitors by washing vegetables and grains.
3) Calcium. Vegetarians can easily consume an adequate amount of calcium without any dietary additions, but it is also important that vegetarians avoid consuming certain foods that are high in oxalates, which inhibit calcium absorption. There is a suggestion from some dieticians that vegetarians should not consume spinach, beet greens, and swiss chard as the calcium component of a meal plan. While they are rich in calcium, they also contain high amounts of oxalates.
Rather than consuming those foods for calcium, vegetarians should consider other options, such as soy yogurt, tofu, beans, almonds, and calcium-fortified foods.
Many vegetarians lack vitamin B-12, simply because it does not exist naturally in any non-animal forms. Vegetarians should seek out vitamin B-12 fortified foods, such as certain soy milks and cereals to supplement what they lack.
As outlined earlier, there are a number of essential nutrients vegetarians can overlook of they do not research and plan their diet properly. This information is not meant to discourage you from considering becoming a vegetarian, but instead to encourage you to spend a little time planning a healthy approach to your vegetarian diet before starting it.
If properly thought out and planned adequately, a vegetarian diet can not only make up for what it lacks from animal products, but it can far exceed the healthfulness of most non-vegetarian diets.