Final answer:
Most water-soluble vitamins are not highly toxic when consumed in excess because they are excreted in the urine, making the statement false. Toxicity is more of a concern with fat-soluble vitamins.
Step-by-step explanation:
The statement that 'most water-soluble vitamins are highly toxic when consumed in excess' is false. Water-soluble vitamins, which include vitamin C and the B-complex vitamins, are not stored in the body and are excreted in the urine if taken in excess. It is rare for hypervitaminosis, or vitamin toxicity, to occur with water-soluble vitamins unless high dosages are taken through supplements.
In contrast, fat-soluble vitamins, such as vitamins A, D, E, and K, can accumulate in the body's fatty tissues, potentially leading to toxicity if consumed in excess.