There are data suggesting that smoking, head trauma and lead exposure are linked with an increased ALS risk, and vitamin E with reduced risk, but none of these associations has been conclusively established.
Research from the Harvard School of Public Health (HSPH)
has found that the onset of amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, could be delayed or even prevented by some of the naturally occurring carotenoids in brightly-coloured fruit and vegetables. Reported in the journal Annals of Neurology
, the study suggests that beta-carotene and lutein are particularly effective in reducing the risk of ALS, whereas other nutrients – such as vitamin C, lycopene and beta-cryptoxanthin – confer no discernible advantage.
Carotenoids are the organic pigments which give many fruits and vegetables their characteristic bright red, orange, yellow and green colours. First author Kathryn Fitzgerald was able to shed more light on the research for ScienceOmega.com
ALS affects around 5,000 people in the United Kingdom and between 20-30,000 people in the United States. More common in men than women, onset generally occurs between the ages of 40 and 70. ALS is a progressive neurological disease which causes muscle degeneration and eventually paralysis through its attack on the nervous system. Approximately ten per cent of the cases occur in individuals with a family history of the disease, with several genetic mutations having been identified as causing ALS.
"On the whole, very little is known about risk factors for the remaining 90 per cent of cases," Fitzgerald explained. "There are data suggesting that smoking, head trauma and lead exposure are linked with an increased ALS risk, and vitamin E with reduced risk, but none of these associations has been conclusively established."
It has been hypothesised that one of the biologic properties of carotenoids is to function as an antioxidant. As prior research has suggested the potential role of oxidative stress in ALS pathogenesis, the Harvard team were encouraged to investigate the relationship these nutrients have with the risk of ALS.
"Our research group has also found that long term users of vitamin E supplements have a reduced ALS risk," stated Fitzgerald. "As a result, we wanted to see whether other dietary antioxidants would also be associated with reduced ALS risk."
As a basis for the analysis, data were examined from the NIH-AARP Diet and Health Study
, the Cancer Prevention Study II Nutrition Cohort
, the Multiethnic Cohort
, the Health Professionals Follow-up Study
, and the Nurses' Health Study
, with a total of 1093 ALS cases identified after excluding those with unlikely food consumption. It was found that those individuals with higher consumption of carotenoids were also more likely to take regular exercise, have higher vitamin C consumption, and take supplements of vitamins C and E. Those with diets rich in beta-carotene and lutein were less likely to develop ALS. I asked Fitzgerald if it is possible to discount the effect of other factors, such as the high likelihood of exercise and vitamin supplements, in those with a lower risk of developing the disease.
"Our analyses account for exercise and use of vitamin supplements, and we still observe a strong association between carotenoid intake and lower ALS risk," she replied. "However, we can’t entirely rule out the role of other compounds explicitly."
The significant effect consuming larger amounts of beta-carotene and lutein was not shared by lycopene, beta-cryptoxanthin and vitamin C, however.
"Individual carotenoids have different biologic properties, and these properties can affect the molecules’ orientation in the cell membrane and how they react with various oxidative radicals," Fitzgerald remarked.
In addition, it is likely that vitamin C has different biologic effects than fat-soluble antioxidants like carotenoids as it is a water-soluble antioxidant. This is one potential explanation for the different effects that different nutrients have. Further research is anticipated to find out more about the impact of dietary nutrients on ALS, as Fitzgerald related.
"We have plans to look at more food-based analyses and other dietary nutrients such as fibre and omega-3 fatty acid intake, which could also be related to ALS risk."