That was the conclusion of a paper published in the Annals of Neurology. The researchers brought together data from multiple studies looking at onset of Amyotrophic Lateral Sclerosis (ALS) or motor neuron disease and compared this to Vitamin C and carotene intake.
Their findings? Vitamin C supplements did not have an effect on the incidence of ALS but carotenes did. On an individual basis, people who ate a large amount of β-carotene (predominantly from carrots) and lutein (from green leafy vegetables) had a reduced risk of ALS. No such correlation was found for the other carotenes tested: α-carotene, β-cryptoxanthin and lycopene.
The publication is available on the Wiley Online Library website.