Which vitamin has an increased risk of causing toxicity?

The vitamin that has an increased risk of causing toxicity is Vitamin A. This is primarily due to its fat-soluble nature, which means that the body can store it in fatty tissues and the liver. When consumed in excessive amounts over time, fat-soluble vitamins like Vitamin A can accumulate to toxic levels, leading to hypervitaminosis A. Toxicity symptoms can include nausea, headaches, dizziness, and even more severe impacts such as liver damage and central nervous system disorders.

In contrast, vitamins such as Vitamin C and the B-vitamins (including Vitamin B12) are water-soluble. This means they are generally excreted through urine when consumed in excess, making toxicity less likely. Though it's still possible to experience adverse effects from excessive supplementation of water-soluble vitamins, the risk is significantly lower compared to fat-soluble vitamins. This distinction highlights why Vitamin A is particularly notable for its potential toxicity in higher doses.