Beef liver is highly nutritious, providing protein, iron, B vitamins, and is especially rich in vitamin A. One serving of beef liver can meet more than 100% of your daily vitamin A requirement. It's also a good source of vitamin K, which is important for bone health. However, beef liver is high in cholesterol and excessive consumption can lead to vitamin A toxicity and copper toxicity. Symptoms of vitamin A toxicity include nausea, headache, and bone weakness. Symptoms of copper toxicity include nausea, belly pain, and severe cases can cause liver damage. It's best to eat liver in moderation, usually no more than one serving per week, and consult with a doctor if you have health conditions or are on medications that interact with vitamin A.