Nutrients that are at risk for depletion in long term vegetarian diets are iron, Vitamin D, Vitamin B12, selenium, zinc, taurine and Omega 3 oils (due to heavier use of the Omega 6 soy and corn oils in vegetarian diets). Females who had been on a vegetarian diet for greater than 6 years had the most severe depletion of Vitamin B12. The beneficial antioxidant vitamins beta-carotene, vitamins E and C and folic acid levels however are significantly higher in a vegetarian diet that is vegetable (not grain) based.
It is difficult to generalize about vegetarian diets as some are high in quality with a large variety of vegetables, high quality oils and adequate protein sources, while others are mainly composed of wheat, corn and high in sugar and low in vegetables. After all, Pepsi, potato chips and M&M’s is technically a vegetarian diet. It is prudent to recognize that a high quality vegetarian diet is more involved than simply not eating meat and is more likely the result of planning, study, and time spent in the kitchen. Essential Fatty Acid (EFA) testing at GSMC however is finding more depletion of Omega 6 oils occurring in vegetarians, likely due to the fact that the Omega 3 (flax oil) supplementation is practiced because of the coverage it gets in the media. Vegetarian diets can lead to nutrient deficiencies (selenium and essential fatty acids specifically) that may increase cancer risk. It seems wise to consider vitamin, mineral and fatty acid supplementation if you are vegetarian, unless you consistently eat a high quality vegetarian diet with adequate protein and essential fatty acids from nuts and seeds and their oils. Given enough time, nutrient deficiencies contribute to chronic illness.