Citrus fruit and carrots protect against Alzheimer’s disease, a press release recently published by the University of Ulm suggests. A closer look at the language used though reveals the statement to be rather hypothetical. However, accuracy does not seem to be a concern of articles aimed at the general public, and this is exactly how expectations and hype are created. The neurologist Christine von Arnim now faces the - not inconsiderable - task of having to scale down expectations and put the Ulm researchers’ work into its correct context.
The facts behind the story are that two researchers from Ulm – epidemiologist Professor Gabriele Nagel and neurologist Christine von Arnim – have examined the blood of people suffering from mild dementia for the presence of antioxidants and compared their values to those of healthy people. The researchers carried out a cross-sectional study and have come up with two values that could be of major interest to the scientific world, to the extent that the Journal of Alzheimer’s Disease considered the study worth publishing. What they found is this: the concentration of the antioxidants vitamin C and beta-carotene in the serum of early-stage Alzheimer’s disease (AD) patients was significantly lower than in the blood of control subjects.
The press release makes it appear that the publication of partially positive headlines immediately prior to world Alzheimer’s Day (21st September 2012) is all it takes: job over. However, the reality is that although thousands of researchers and developers around the world are permanently working on the accumulation of knowledge about the disease, the causes of AD are not yet known. And such knowledge is exactly what is needed to develop an efficient Alzheimer’s drug that treats the underlying disease, rather than targets the symptoms. Currently, five approved drugs target the symptoms of AD. Numerous clinical trials have been abandoned. Since 1998, there have been 101 unsuccessful attempts to develop drugs to treat Alzheimer’s (see report from the Pharmaceutical Research and Manufacturers of America “Researching Alzheimer’s Medicines: Setbacks and Stepping Stones”).
Scientists have long suggested oxidative stress as one of the major causes of both the ageing processes and of all known neurodegenerative diseases, including Alzheimer’s. Oxidative stress develops when the body is no longer able to degrade high enough quantities of free radicals (short-lived, reactive oxygen species). These dangerous by-products of the human metabolism damage cells and important proteins.
The recently published study was initiated on the back of epidemiological data that suggested that healthy nutrition, i.e. food rich in antioxidants, was associated with a slightly reduced risk of developing AD. Antioxidants (also known as radical catchers) such as vitamin C and E as well as provitamin A (beta-carotene) have been found to have a protective effect on cells.
However, studies investigating the association of increased vitamin uptake (i.e. the consumption of fruit and vegetables) and the risk of developing Alzheimer’s have not yet reached a clear result. They suggest that the risk of developing AD can be reduced, but final evidence to substantiate the findings is still lacking (Boeing et al., 2012). According to Professor von Arnim, in vitro and cell culture experiments have shown that amyloid beta protein found in the brains of AD patients, which is the hallmark of AD, triggers the formation of free radicals and hence contributes to oxidative stress.
In their study, von Arnim and Nagel have investigated whether the serum levels of vitamin C and E, beta-carotene, lycopene and coenzyme Q10 are significantly lower in the blood of AD patients. “In order to possibly influence the onset and development of Alzheimer’s disease, we need to be aware of potential risk factors,” Gabriele Nagel says.
Participants were recruited from the cross-sectional study IMCA ActiFE (Activity and Function in the Elderly in Ulm) for which a representative population-based sample of around 1500 senior citizens was examined. The 65 to 90-year-olds from Ulm and the surrounding area underwent neuropsychological testing and answered a series of lifestyle questions. In addition, their blood was examined and their body mass index (BMI) was calculated. For the present study, scientists compared 74 patients (average age: 78.9 years) with mild dementia with a control group consisting of 158 healthy persons of the same age.
Christine von Arnim deduces from the data that there is a link between nutrition and AD and she and her colleagues will carry out further investigations to find out more. However, she is careful to point out that the study does not allow any deductions to be made as to cause and effect, and that a study carried out over a longer period of time is necessary to confirm the result that vitamin C and beta-carotene might prevent AD. A prospective study needs to be conducted to find out which volunteers develop dementia over the next five to ten years and whether a bad antioxidative status promotes the development of AD.
Von Arnim also pointed out that even an expensive longitudinal study, for which it is difficult to acquire funding (pharma sponsoring is not available), would not be sufficient to come up with practical recommendations on food that could possibly prevent the onset and development of AD. As von Arnim explained, a placebo-controlled, prospective double-blind study would be required. She also made it clear that a study that assessed whether vitamin E protects against Alzheimer’s, could not provide evidence that this is actually the case.
“We are a long way from being able to give practical recommendations,” said von Arnim summarising the current state of AD knowledge. The neurologist believes that AD, which affects around 1.2 million people in Germany, is not the result of one single cause and her objective is to find numerous parameters that might help people to avoid dementia as they get older.
Von Arnim is currently involved in a joint project with colleagues from the Department of Geriatrics that focuses on the relationship between physical activity and cognitive performance. She will also analyse ActiFE data relating to social isolation in order to find out whether there is an association with the development of Alzheimer’s disease.
von Arnim C. et al.: Dietary Antioxidants and Dementia in a Population-Based Case-Control Study among Older People in South Germany. Journal of Alzheimer's Disease. DOI:10.3233/JAD-2012-120634
Boeing, H. et al.: Critical review: Vegetables and Fruit in the Prevention of Chronic Diseases. Eur. J. Nutr. 2012: 637-663
Vitamin C and and beta-carotene might protect against demention, press release University of Ulm, 11. Sept. 2012
Studies related to unsuccessful attempts to develop drugs to treat Alzheimer's:
Pharmaceutical Research and Manufacturers of America (ed.): Researching Alzheimer's Medicines. Setbacks and Stepping Stones, 13. Sept. 2012
Cabut, S.: Maladie d'Alzheimer: des espoirs déçus : Le Monde, 19. Sept. 2012