A recent study examining the diet of an isolated Japanese community provides clues to their increased longevity and lack of neurodegenerative disease.
The Ogimi people on the Japanese island of Okinawa have been the subject of intense study owing to their increased lifespan and apparent lack of neurodegenerative diseases. Okinawan women have an average life expectancy of 85.08 years, exceeding the average Japanese women’s life expectancy of 83.99 years. A suggestion that caloric restriction during world war II resulting in increased longevity has been largely dismissed as an explanation given Europeans also suffered from the same fate without the associated increased longevity.
The major source of calories in the Ogimi diet come from seaweeds and tofu based products which is in contrast to the rest of Japan where rice is the major staple. An analysis of the Ogimi diet shows it is remarkably rich in amino acids, particularly L-serine, of which tofu, edamame, seaweed and pork have the highest L-serine content.
On average, the total L-serine content of the Ogimi diet for women over the age of 70 is in excess of 8 g/day which is about 6 g/day above the daily L-serine intake (2.53 g/day) from all sources consumed by women in the USA and twice the L-serine intake (7.15 g/day) consumed by the 99th percentile of US women age 71+.
Interestingly, the Ogimis also make flour from the seeds of the cycad, a plant that has been directly linked to neurodegenerative diseases owing to the toxic amino acid derived from cyanobacteria – BMAA – that resides in the seeds. Studies examining BMAA toxicity have shown L-serine to be neuroprotective against BMAA in cell cultures, fruit flies, and monkeys.
A recent clinical trial of ALS patients who were supplemented with 30g/day of L-serine showed a slowing of disease progression by 85%.
The unique nature of the Ogimi diet, being rich in seaweeds and tofu, all of which have high serine content, may explain the lack of neurodegenerative disease and increased longevity in this community.
This suggests a diet high in serine or serine supplementation throughout life may be beneficial in preventing progression to neurodegeneration.
The study by Cox and Metcalf is open access and available here