Thiamine Intake of More Than 0.68 mg Is Linked to Cognitive Decline in Older Adults

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Thiamine intake may help with energy metabolism and neurotransmitter activity, but the water-soluble B vitamin can lead to cognitive decline among cognitively healthy older adults, a new study found.¹

Particularly, an older adult who takes > 0.68 mg/day can experience cognitive decline—the study suggests a dose of 0.68 mg/day for older adults is the “sweet spot.”²

Dietary thiamine is found in whole grains, fortified breakfast cereals, legumes, liver, and salmon. A few small studies found having dietary thiamine in high doses (5 – 600 mg/day) can improve cognitive function with mild cognitive impairment or early-stage dementia (n = 70).¹ Investigators, led by Chengzhang Liu, from the department of epidemiology and biostatistics at Anhui Medical University in China, conducted an observation study to see if the previous findings would apply to cognitively healthy older adults—if dietary thiamine intake was linked with slowing or quickening cognitive decline.

“Thiamine deficiency may lead to an insufficient supply of energy to the neurons of the brain and decreased acetylcholine signaling in the brain, which may impair cognitive function,” investigators wrote.

Liu and colleagues leveraged data from the China Health and Nutrition Survey, a long-term ongoing multipurpose study beginning in 1989 with nearly half of China’s population by 2011. The survey collected data on mental acuity for cognitively healthy adults aged ≥ 55 years in 1997, 2000, 2004, and 2006. The current study assessed 3106 participants with a mean age of 63 years and who had ≥ 2 rounds of survey data.

Although the survey collected data on diet, trained investigators collected detailed data on personal dietary intake over 24 hours on 3 consecutive days in person. The team assessed nutrient intake with the Chinese food composition tables.

Participants also had 3 cognitive tests of immediate and delayed recall, obtained from the Telephone Interview for Cognitive Status-modified. They had to remember a 10-word list to assess verbal memory, count backgrounds from 20 to assess attention, and serial substructions of 7 five times from 100 to assess numerical fluency. A greater score indicated a better cognitive function.

The mean monitoring period was approximately 6 years, and the team observed a J-shaped association between dietary thiamine intake and the speed of cognitive decline over 5 years.

On average, older adults took 0.93 mg of thiamine daily. However, the threshold, marking the highest dose of dietary thiamine to bring benefits without cognitive decline, was 0.68 mg (95% confidence interval [CI], 0.56 – 0.80). The dose ≤ 0.68 mg/day was not linked to cognitive decline.

In contrast, for older adults taking > 0.68 mg/day, a daily unit (1 mg/day) increase in thiamine intake was linked to a significant drop of 4.24 in the global cognitive score (95% CI, 2.22 – 6.27) and 0.49 units in the composite score (95% CI, 0.23 – 0.76) within 5 years. The decline of approximately 4 points in the global cognitive score equates to roughly a 15% decline in cognitive function.

The team noted associations between high thiamine dose and cognitive decline were stronger among participants who were obese (P < .05). They observed a stronger association for participants with hypertension and non-smokers (P < .05), but the association was statistically insignificant after a depth analysis.

To find the optimal dose of dietary thiamine range for preserving cognitive function, investigators assessed the doses of 0.4, 0.6, 0.8, 1, 1.2, and 1.4 mg/day. Ultimately, they found the ultimate dose range was 0.6 mg/day to < 1 mg/day. Similar observations were made when evaluating the daily intake of other B vitamins including riboflavin and niacin and other foods including red or processed meat.

Limitations mentioned by the investigators included only collecting data on a 24-hour dietary recall which only showcases specific days and could lead to inaccuracies. Additionally, participants were older adults in China, so the study may not apply to other nationalities or age groups.

“If substantiated by further research, our study highlights the importance of maintaining optimal dietary thiamine intake levels in the general older population to prevent cognitive decline,” investigators wrote.

^References

1. ^{Liu C, Meng Q, Wei Y, et al. J- shaped association between dietary thiamine intake and the risk of cognitive decline in cognitively healthy, older Chinese individuals. General Psychiatry 2024;37:e101311. doi:10.1136/ gpsych-2023-101311}
2. ^{J-Shaped Curve Apparent Between Dietary Thiamine and Worsening Mental Acuity. EurekAlert! February 20, 2024. https://www.eurekalert.org/news-releases/1034703?. Accessed February 20, 2024.}