Persistent fatigue: what if it was a lack of B vitamins?

A Japanese study suggests that a deficiency in vitamin B12 and folate could contribute to fatigue and loss of motivation.

Homocysteine: a marker of deficiency

Chronic fatigue is often attributed to stress or lack of sleep. But a team of researchers from Osaka Metropolitan University, led by Professor Hiroaki Kanouchi, wanted to test another hypothesis: that of a link between nutritional status and the fatigue experienced on a daily basis.

To do this, researchers measured blood concentrations of homocysteine, vitamin B12 and folate (B9) in nearly 600 healthy Japanese adults. Homocysteine is an amino acid whose level increases in the blood when these two vitamins are deficient. Usually, homocysteine levels are mostly monitored in the context of cardiovascular disease and dementia.

Participants’ fatigue and motivation were assessed using questionnaires. The results appeared in the journal Nutrients.

Results: Individuals with high homocysteine levels also had lower levels of vitamin B12 and folate, regardless of gender. There were differences between men and women: high homocysteine levels were associated with greater physical fatigue in men, and with lower motivation in women.

Why are these vitamins important?

Vitamin B12 and folate (B9) are involved in the synthesis of neurotransmitters and the formation of myelin, the protective sheath that surrounds neurons. In his Practical guide to nootropic supplementsAnne-Laure Denans, doctor of pharmacy, recalls the action of folate on mood and cognition: “Folate helps reduce depression. Low folate concentrations in the blood and cerebrospinal fluid are associated with depression and dementia. » In addition, a B12 deficiency, if it persists over time, can lead to more severe neurological and psychiatric symptoms: cognitive disorders, neuropathy, and in advanced cases, dementia.

Where to find these vitamins in food?

Vitamin B12 is present in products of animal origin:

meats (beef, poultry, offal such as liver);
fish and seafood (sardines, tuna, mussels, oysters);
eggs and dairy products (cheese, milk, yogurt).

Read: The foods richest in vitamin B12

People following a strict vegan diet are at particular risk of deficiency. Supplementation is then generally recommended.

For folate (B9), the best food sources are:

green leafy vegetables (spinach, watercress, arugula);
legumes (lentils, chickpeas, beans);
asparagus, broccoli, avocado;
offal (particularly poultry liver).

Supplement: what form and doses?

Reference doses (ANSES)

ANSES sets the reference nutritional intakes for a healthy adult at 4 µg per day for vitamin B12, and 330 µg per day for folate (B9). These values correspond to the minimum requirements to avoid a deficiency, not necessarily at therapeutic doses.

Needs increase in certain situations: pregnant women need 4.5 mcg per day of B12 and 600 mcg per day of folate; breastfeeding women, 5 µg per day of B12 and 500 µg per day of folate.

Which form to favor?

For vitamin B12, Anne-Laure Denans recommends methylcobalamin rather than cyanocobalamin: “Methylcobalamin, which is an active form of vitamin B12, has the advantage of being a form directly usable by the body and could be more interesting than the cyanocobalamin form. » Some people absorb vitamin B12 poorly through the digestive system, especially those with gastrointestinal disorders or taking proton pump inhibitors (PPIs). Higher doses can then be considered.

For folate, the active form 5-MTHF (5-methylfetrahedrofolate) is preferred.

Finally, it is recommended to combine B6, B9 and B12 for best results.

Read: B vitamins: the B6-B9-B12 trio at the heart of the prevention of cognitive decline (subscribers)

To remember

A Japanese study links high homocysteine levels, reflecting a B12 and folate deficiency, to physical fatigue or loss of motivation.
These vitamins play a role in the synthesis of neurotransmitters and the protection of neurons.
In food, they are found respectively in animal products (B12) and green vegetables and legumes (B9).
As a supplement, prefer methylcobalamin (B12) and 5-MTHF (B9).