B in AD spells good news

Patients genetically predisposed to Alzheimer's could improve their memory with vitamin B

By Graham Furness

Charmaine Hendrickson, a 75-year-old retired biology professor, had always thought of herself as a scatterbrain, but in recent years her memory seemed to be failing. She was afraid that this was an early sign of dementia, which ran in her family. But surprisingly, her memory improved in the last three months � she hadn't missed any of her chess club meetings and kept all her appointments with her doctor. She wondered what had brought on the change. Could it be her vitamin B supplements? She keeps a bottle of them on her bedside table and started taking them almost six months ago.

New research now points to evidence that Ms Hendrickson's supplements may be doing the trick � vitamin B₁₂ may be of particular benefit to those genetically predisposed to Alzheimer's disease (AD), according to Swedish research published in an April issue of Neuropsychology.

Scientists already knew of a genetic predisposition for AD, and that low levels of two B vitamins � B₁₂ and folate � were also linked to problems. However, few had examined how nutrition and genotype together affect cognition to reflect what people really carry into old age � a mix of inborn traits and environmental factors, including undiagnosed vitamin B deficiencies.

The apolipoprotein E (Apo E) gene regulates proteins that transport cholesterol in the body. About 15% of the population carries a version called the epsilon4 allele, which is a known risk factor for dementia. Nearly one out of four carriers who have one copy of this allele and nearly half with two copies will develop AD.

Carriers of the epsilon4 allele have smaller hippocampi, which are associated with memory. The researchers wanted to measure how an additional shortfall, such as low vitamin B, affected this particular group. The study was part of a long-term project that followed 167 healthy people averaging nearly 83 years of age. Some 82 participants had low B₁₂, 28 of whom carried the epsilon4 allele and 54 didn't. The researchers then tested episodic memory by using a list of words to remember as their test.

Among carriers of the epsilon4 allele, people with normal B₁₂ levels recalled a greater number of words. When subjects were given five, as opposed to two seconds to encode their memories, scores naturally went up. The extra time appeared more helpful to the low-vitamin B₁₂ patients with the epsilon4 allele, suggesting that the deficit is partly a problem with storing memories rather than retrieving them.

A significant difference showed up when participants had just two seconds to encode words. In that situation, those with the high-risk genotype plus low B₁₂ levels exhibited poorer memory.

The findings suggest a complex interaction of genetic and non-genetic factors. According to the authors, "epsilon4 Apo E carriers may derive relatively greater cognitive benefits from B₁₂ and folate supplements. Supplement treatment is relatively inexpensive and may be required as part of preventive health regimes for older persons."