Chronic fatigue is becoming increasingly common in modern life as people juggle heavier workloads with less downtime. Fatigue is often caused by stress and lack of sleep, but nutritional deficiencies may also play a role, researchers say.
A research team led by Professor Hiroaki Shikauchi of the Graduate School of Human Life Ecology at Osaka Metropolitan University investigated whether deficiencies in certain vitamins could be related to fatigue and motivation levels. Scientists focused on folic acid (B9) and vitamin B12. These two nutrients help regulate homocysteine (Hcy), a substance that increases in the blood when these vitamins are deficient.
Blood markers associated with fatigue and motivation
Approximately 600 healthy Japanese adults participated in this study. The researchers measured blood levels of homocysteine, folate, and vitamin B12, and assessed participants’ fatigue and motivation using the Calder Fatigue Scale questionnaire and visual analogue scales.
The research team found that participants with higher homocysteine levels generally had lower levels of folate and vitamin B12, regardless of gender.
The researchers then looked more closely at how homocysteine levels were related to fatigue in men and women separately. Their analysis also took into account factors that can influence fatigue, such as age, sleep duration, workload, and eating habits.
The results showed that men with higher homocysteine levels were more likely to report greater physical fatigue. In women, elevated homocysteine levels were associated with decreased motivation.
Vitamin deficiencies can affect energy levels
“These results suggesting a relationship between vitamin B12, folic acid, and fatigue in healthy people may be the first report of this kind,” Professor Kanouchi said.
“Blood homocysteine levels have traditionally been a concern due to their association with cardiovascular disease, dementia, and bone fractures. However, the results of this study suggest that future attention should also be paid to fatigue and motivation. To prevent elevated homocysteine levels, it is important to avoid vitamin B12 and folic acid deficiencies. Maintaining a balanced diet each day is essential.”
The research results were published in a magazine nutrients.

