The findings, based on studies of genetically-engineered mice, also show that supplements given to newborns with low levels of vitamin A could be effective in slowing the degenerative brain disease.
"Our study clearly shows that marginal deficiency of vitamin A, even as early as in pregnancy, has a detrimental effect on brain development and has long-lasting effect that may facilitate Alzheimer's disease in later life," said Weihong Song, a professor at the University of British Columbia in Canada.
They examined the effects of vitamin A deprivation in the womb and infancy on Alzheimer's model mice.
These early developmental stages are crucial periods during which brain tissue is "programmed" for the rest of a person's life.
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The researchers found that even a mild vitamin A deficiency increased the production of amyloid beta, the protein that forms plaques that smother and ultimately kill neurons in Alzheimer's disease.
They also found that these mice, when deprived of vitamin A, performed worse as adults on a standard test of learning and memory.
Still, researchers showed that some reversal is possible. Mice who were deprived in utero but then given supplements immediately after birth performed better on the tests than mice who were not given such supplements.
"In some cases, providing supplements to the newborn Alzheimer's disease model mice could reduce the amyloid beta level and improve learning and memory deficits," said Song.
Examining 330 elderly people researchers found that 75 per cent of those with either mild or significant vitamin A deficiency had cognitive impairment, compared to 47 per cent of those with normal vitamin A levels.
The study was published in the journal Acta Neuropathologica.