Vitamin A deficiency linked to Alzheimer’s disease – NHS Choices
This article has been reproduced from the NHS Choices website.
“Alzheimer’s may begin in the womb because mums are short of crucial vitamin, scientists warn,” the Daily Mirror reports
Vitamin A deficiency linked to Alzheimer’s disease – NHS Choices
This article has been reproduced from the NHS Choices website.
“Alzheimer’s may begin in the womb because mums are short of crucial vitamin, scientists warn,” the Daily Mirror reports.
New research involving both mice and humans looked at the link between vitamin A deficiency, brain development and Alzheimer’s risk. Vitamin A helps boost the immune system and is mainly found in animal sources, including dairy, eggs, meat and oily fish, and some fruits and leafy vegetables.
Researchers assessed mice who were genetically engineered to develop an Alzheimer’s-like condition. They found feeding mice vitamin A-deficient diets increased the development of abnormal clumps of protein associated with the condition.
They further found the offspring of these mice performed poorly on a maze test designed to assess memory and situational awareness.
Researchers also took blood samples from around 300 older adults in Chinese care homes and found vitamin A levels were linked with cognitive impairment.
But this one-off cross-assessment of a specific population sample doesn’t prove cause and effect. It could be the case that whatever factors lead to cognitive impairment in adults could also lower vitamin A levels.
And as vitamin A deficiency is more of a recognised problem in non-Western countries, levels in this Chinese population may not be the same as the UK.
All people should be able to get enough vitamin A by eating a healthy diet. Pregnant women in particular should not take vitamin A supplements or eat foods known to have a very high vitamin A content, like liver, as excessive vitamin A can cause birth defects. Similarly, older adults should not routinely take vitamin A supplements as they can increase the risk of osteoporosis and fractures.
Where did the story come from?
The study was carried out by researchers from the Children’s Hospital of Chongqing Medical University in China and the University of British Columbia in Canada. Funding was provided by the National Natural Science Foundation of China and the Canadian Institutes of Health Research. It was published in the peer-reviewed journal, Acta Neuropathologica.
The Mirror and The Sun did provide warnings about the risks of taking vitamin A supplements, but they probably would have been better positioned at the top, not the bottom, of their articles.
What kind of research was this?
This study in both humans and mice aimed to see whether vitamin A deficiency may have a role in the development of Alzheimer’s disease.
The causes of Alzheimer’s, aside from known risk factors like older age and possibly genetics, remain largely unknown. As the researchers say, vitamin A deficiency is a problem in the developing world, particularly among pregnant women, the elderly and young children.
Some studies have observed decreased vitamin A levels in people with Alzheimer’s, and there has been speculation that this could lead to increased amyloid protein plaque deposits characteristic of the disease.
This study aimed to look at the correlation between vitamin A deficiency and cognitive decline in elderly adults. The researchers also used a mouse model of Alzheimer’s to see whether vitamin A deficiency is linked with accumulation of protein plaques and memory deficits, and whether this could be reversed by taking supplements.
What did the researchers do?
The human study involved a sample of older adults (average age 77) from 15 care homes in China. They were assessed on how they performed everyday activities, and their cognitive function was measured using several well-validated assessments:
- the Mini-Mental State Examination (MMSE)
- the Cognitive subscale of the Alzheimer’s Disease Assessment Scale (ADAS-Cog)
- the Clinical Dementia Rating Scale (CDR)
The participants also provided blood samples for analysis of vitamin A. Researchers excluded people with anxiety, depression, severe dementia, Parkinson’s, diabetes or who were receiving vitamin A supplements. Of 650 potential adults, full data was available for 330 people.
The animal study involved mice genetically engineered to produce an enzyme involved in the production of amyloid beta protein plaques who then developed an Alzheimer’s-like condition. The mice were split into two groups and fed for four weeks with either normal diets or a diet deficient in vitamin A.
At the same time, breeding was allowed. Six months after birth, the researchers tested the behaviour of the mouse pups using the water maze test. They then analysed their blood samples.
They also carried out subsequent tests looking at the effect of switching between diets – for example, switching the vitamin A-deficient mums and their pups to a diet with normal vitamin A content immediately after birth, and vice versa. After death, the researchers also analysed the mice brain tissue samples.
What did they find?
The majority of older adults (61%) had normal blood vitamin A levels (defined as a level of 1.05 micromols or greater). A quarter (26%) had marginal deficiency (0.70 to 1.05) and 13% were vitamin A deficient (less than 0.70).
Researchers found CDR and ADAS-Cog scores were significantly higher (worse) in those with deficiency or marginal deficiency compared with those with normal vitamin A levels. There was no difference in MMSE scores or how they performed daily activities. However, when researchers pooled the deficient and marginally deficient groups, these people also had lower MMSE s