Final answer:
Sodium is not touted as providing antioxidant protection from harmful free radicals, unlike β-carotene, Vitamin C, and Vitamin E, which are well-known antioxidants.
Step-by-step explanation:
The question asks which nutrient is not known for providing antioxidant protection against harmful free radicals. The options provided are β-carotene, Vitamin C, Sodium, and Vitamin E. Of these, β-carotene (a provitamin that can be converted to vitamin A), Vitamin C, and Vitamin E are all acknowledged for their antioxidant properties. These antioxidants are beneficial as they neutralize free radicals, preventing them from causing cellular damage. The most studied antioxidants include the "big three" vitamin antioxidants: Vitamins E, A (for which β-carotene is a precursor), and C. On the other hand, Sodium is not recognized as an antioxidant and does not offer protection from free radicals. Therefore, the correct answer is Sodium.