Summary: PD prevalence rates appear higher in areas with acidic soils. A possible route is Aluminium -> Grass -> Cow -> Milk

In the past few months I've started a couple of threads suggesting an association between PD and:
- serum metal levels [1];
- the fungus histoplasma capsulatum [2]

In this post I present evidence that links together these two theories by suggesting that soil type is the common feature for both of them.

While writing this post I came across a thread started by Ron in 2009, "Chemical from Soil Bacteria Shows Potential Neuron Toxicity" [3]. Ron reported work done at the University of Alabama which implicated the bacterium streptomyces, which "is frequently found in dirt".

As with most of my posts the approach will be mainly epidemiological. We start with maps showing spatial variations in the prevalence of Parkinson's:
- US, Willis et al.[4]
- England, my mapping of relative prevalence inferred using NHS prescription data [5].

The US PD data has a similar distribution to that of soils with pH less than 6. An exception is that the two distributions diverge south of the Great Lakes. See the map by BONAP [6], and compare with [1].

The British Geological Survey produce a map of topsoil pH values [7], compare with [2]. The PD data from England shows an apparent relationship, albeit far from perfect, between high levels of PD and low topsoil pH values (in Dartmoor, the Welsh borders, the Lake District and the Scottish Borders) and low levels of PD and high topsoil pH (in the area from London north to the Humber). On the other hand, the similarity between the two factors is not seen in the zone from Manchester to Liverpool.

So, we have an apparent association between PD and acidic soil, let's go on to look at possible causal mechanisms.

Faltmarsch et al. [8] report aluminium concentrations of up to 50 times higher in the milk of cows fed on vegetation grown in acid sulphate soils. They go on to discuss the impact this could have on health, particularly Alzheimer's and Parkinson's.

Chen et al. [9] report "The meta-analysis of all prospective studies confirmed a moderately elevated risk of Parkinson’s disease among individuals with high dairy consumption: the RRs between extreme intake categories were 1.6 (95 percent CI: 1.3–2.0) for men and women combined, 1.8 for men (95 percent CI: 1.4–2.4), and 1.3 for women (95 percent CI: 0.8–2.1)." This does not seem a large impact, but aluminium could be a confounding factor. If the problem wasn't the milk per se, but the aluminium in the milk then the relative risk for people drinking milk from non-acidic areas would be lower, while people drinking milk from acidic areas would have a higher relative risk.

How does histoplasma capsulatum fit into the picture. In the thread [2] we gave links to maps showing the distribution of the the associated disease histoplasmosis, which closely followed that of PD in the US. We add here that histoplasma is a "Soil-based fungus that thrives in moist, acidic soil w/ a high nitrogen content". [10]

A difficuly with the hypothesis that histoplasma is a major cause of PD is that it is rare in the UK, yet PD prevalence levels are similar. This suggests that if fungi do play a role in PD, it is across a number of related species. It would be worth investigating other acid soil liking fungi, such as Blastomyces.

References

[1] http://neurotalk.psychcentral.com/thread175864.html

[2] http://neurotalk.psychcentral.com/thread170268.html

[3] http://neurotalk.psychcentral.com/sh...highlight=soil

[4] "Geographic and Ethnic Variation in Parkinson Disease: A Population-Based Study of US Medicare Beneficiaries"
Willis A., Evanoff B., Lian M., Criswell S., Racette B.
Neuroepidemiology. 2010 April; 34(3): 143–151.
Published online 2010 January 15. doi: 10.1159/000275491
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2865395/

[5]http://www.parkinsonsmeasurement.org/Epidemiology/EnglandPrescription/prevalenceEngland1.htm

[6] http://www.bonap.org/2008_Soil/SoilT...latedMaps.html

[7] http://www.bgs.ac.uk/nercsoilportal/maps.html

[8] "Envionmental risks of metals mobilised from acid sulphate soils in Finland: a literature review"
R. Faltmarsch, M. Astrom, K. Vuori
Boreal Environment Research 13:444-456, 2008

[9] "Dairy products and risk of Parkinson’s disease"
Honglei Chen,1 Eilis O’Reilly,2 Marjorie L. McCullough,3 Carmen Rodriguez,3 Michael A. Schwarzschild,4 Eugenia E. Calle,3 Michael J. Thun,3 and Alberto Ascherio2,5
Am J Epidemiol. 2007 May 1; 165(9): 998–1006
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2232901/

[10] John Hopkins POC-IT Guide: Histoplasmosis
http://www.hopkinsguides.com/hopkins...Histoplasmosis

John

Unfortunately it's behind a pay wall, but Kyrozis et al. report [1]:

" incident PD exhibited strong positive association with consumption of milk, but not cheese or yoghurt. This finding may help narrow down the search for potential dairy product components with a facilitatory role in PD. Concerning other dietary components, inverse association was found between polyunsaturated fat intake and incident PD. Also, inverse association was found with tobacco smoking, in line with previous studies, but not with caffeine."

I find the distinction between milk and yogurt and cheese interesting. Greek yoghurt is drained of most of the whey. Does this leave a lower fraction of any of the milk's aluminium content remaining in the curds?

Reference:

[1] "Dietary and lifestyle variables in relation to incidence of Parkinson’s disease in Greece"
Andreas Kyrozis, Apostolia Ghika, Panayiotis Stathopoulos, Dimitris Vassilopoulos, Dimitrios Trichopoulos, Antonia Trichopoulou
European Journal of Epidemiology,vol 28, issue 1, pp 67-77, 2013-01-01
http://link.springer.com/article/10....654-012-9760-0

John

John -
An interesting topic. Regarding the question about the effect of cow's milk I have run across the following but have not verified:
1) If you drink milk before bed and don't brush the resulting increase in acidity of saliva increases cavities. However, if you consume cheese instead the opposite effect is true. I don't know if this relates to different types of cheese or not but it would be interesting to see some numbers from cultures with homogenous type. ("Hey. What is the PH for Cheez Whiz anyway? ")

2) Regarding soil PH- Tea lovers often express concern about exposure to flouride leached from the soil of the plantations where their favorite brew is grown. But it seems to me that it might be more exciting to look at the state of the PH of the rain at a given site since that would reflect the conditions over time. But we still have a problem with the lack of geographical clustering. There is something that resists in one individual but not in his (seemingly) identical neighbor.

3) As I have noted before, I have some serious doubts about the general assumption that PD is an old problem due to the lack of description of such a destinctive late-stage patient. They should be stiff and rigid, not shaky. The advent of the Industrial Revolution would have greatly increased the acid-rain effect in England and might even have produced great effect within short distances.

There is much interest at the moment in the role of alpha-synuclein in the pathogenesis of PD. I thought it would be interesting to go through my posts, most of which were based on epidemiological evidence, and see if there were any evidence of an involvement of alpha-synuclein.

Acidic soils increase the amount of aluminium in food and water.

Ulversky, Li and Fink write [1]:
"We examined the effect of various metals on the kinetics of fibrillation of recombinant α-synuclein and in inducing conformational changes, as monitored by biophysical techniques. Several di- and trivalent metal ions caused significant accelerations in the rate of α-synuclein fibril formation. Aluminum was the most effective, along with copper(II), iron(III), cobalt(III), and manganese(II)."

tag johnt:alpha-synuclein

References:

[1] "Metal-triggered Structural Transformations, Aggregation, and Fibrillation of Human α-Synuclein
A POSSIBLE MOLECULAR LINK BETWEEN PARKINSON′S DISEASE AND HEAVY METAL EXPOSURE"
November 23, 2001 The Journal of Biological Chemistry, 276, 44284-44296
Vladimir N. Uversky,Jie Li and Anthony L. Fink
http://www.jbc.org/content/276/47/44284.full

John