"Vegetarian and vegan diets have been followed for thousands of years for spiritual, ethical, health, and environmental reasons. When a food system is heavily focused on meat production, there may be deforestation, overgrazing of land and pasturage, and animal abuses. By avoiding animal flesh, vegetarians hope to support their own health and that of the planet. Broadly speaking, vegetarians eat beans, grains, fruits, and vegetables and do not eat red meat, poultry, seafood, or other animal flesh. Lactovegetarians eat dairy products, while lacto-ovo vegetarians eat dairy products and eggs. A vegan diet is the most restrictive vegetarian diet; vegans do not eat dairy, eggs, or other animal products, and some do not eat honey. Well-balanced vegetarian diets can lower the risk of chronic conditions including heart disease, diabetes, and obesity, and they can promote sustainable agriculture. However, diets that lack variety may be insufficient in calcium, iron, omega-3 fatty acids, zinc, and vitamin B12. People who do not plan their meals may also gravitate toward foods high in fat. Vegetarianism and veganism may reduce cancer, heart disease, obesity, and Type 2 diabetes risks and may help with weight reduction and weight maintenance. These diets require attention to fat and nutrient consumption, vigilance for hidden animal products, and negotiation of meals and holidays with meat-eating friends and family."