In a thread started in 2014 by badboy99 [1], to whom my thanks, the benefits of D-lactic acid are commented on.

For instance, a report from the Max Planck Institute says that D-lactate or glycolate "can stop or even counteract" the process of neuronal death in the substantia nigra. And, "Both glycolic and D-lactic acids occur naturally in unripe fruits and certain kinds of yoghurt." [2]

This raises the question of whether the fermentation done by me and others has been creating D- or L- lactate or a mixture of the two.

Lactic acid is chiral: L and D. That is, it can have versions that are mirror images of each other. And, the important point is that the types can have different effects. (Incidently, it is the same with Dopa, L-Dopa works for PD, D-Dopa doesn't [3]).

The relative amounts of the two types depends on what is being fermented, the bacteria used and the process used. An analysis of various commercial yogurts found D/L ratios ranging from 0.02 to 1.64 [4].

A final point is that high yogurt consumption may contribute to potentially fatal acidosis. However, Vrese and Barth report that [5]:
"the consumption of foods containing D-lactic acid gives no reason for concern in healthy adults."
Whether this applies to PwP, I don't know. I work on the principle that if something can have a large benefit, something very close to it can have a large negative effect.

References

[1] http://neurotalk.psychcentral.com/sh...ight=d-lactate

[2]"Potential basis for the treatment and prevention of Parkinson’s disease"
Max Planck Institute, July 2014
http://www.mpg.de/8334548/Parkinson-yoghurt

[3] http://en.wikipedia.org/wiki/D-DOPA

[4] "Dietary Sugars: Chemistry, Analysis, Function and Effects"
ed. Preedy V.

[5] "Postprandial plasma D-lactate concentrations after yogurt ingestion."
de Vrese M1, Barth CA.
Z Ernahrungswiss. 1991 Jun;30(2):131-7.
http://www.ncbi.nlm.nih.gov/pubmed/1897274

John