Thursday, June 4, 2015

Are unsustainable agriculture practices contributing to ALS and Alzheimer's?

I've always been told that no one knows what potential causes exist for ALS (amyotrophic lateral sclerosis, AKA Lou Gehrig's Disease) or Alzheimer's disease (with the exception of a relatively rare genetic form of ALS). So the idea that there is at least a plausible hypothesis as to what may be behind these terrible diseases caught my interest when I watched Dr. Michael Greger's excellent review of the issue in these two videos:
http://nutritionfacts.org/video/als-lou-gehrigs-disease-fishing-for-answers/
http://nutritionfacts.org/video/diet-and-amyotrophic-lateral-sclerosis-als/

He does an excellent job telling the story of how the research has progressed and the evidence started coming together, and reviews quite a few more articles than I do here. But I wanted to produce a short written summary for those who don't like videos, and to highlight where I think the data is relatively strong and weak.

Since my professional research focuses primarily on sustainable agriculture, my mother died from ALS, and my grandfather died from Alzheimer's, I have a strong interest in how these topics might intersect. That also means I likely lack the objectivity needed to review this from a completely neutral perspective, but I think the data paint a compelling picture that merits further study.

The basic hypothesis here is that BMAA (β-N-methylamino-L-alanine, a toxin created by cyanobacteria, AKA blue-green algae) forms when algae thrive (often due to excessive nutrient runoff from agriculture), accumulates in seafood, and can cause neurological damage including ALS, Alzheimer's, Parkinson's disease, and similar symptoms. Note that concern over microcystin, which is another toxin produced by cyanobacteria, led to the residents of Toledo being unable to drink their tap water for 48 hours in August of 2014.

Let's take a look at each of the steps in that theory.


Cyanobacteria in Lake Littoistenjärvi
Cyanobacteria in Lake Littoistenjärvi, Flickr user Stefe

First, there is strong evidence that consumption of high levels of BMAA is associated with ALS / Alzheimer's. The classic case is in Guam, where incidence of ALS, Alzheimer's, and Parkinson's (referred to collectively as ALS-parkinsonism-dementia complex or ALS-PDC) was abnormally high among the Chamarro people there. These people eat flying foxes (a kind of bat), which in turn eat cycad seeds which are high in BMAA, and the BMAA accumulates in flying fox flesh at levels around 3,500 ug of BMAA per g of flesh (Cox et al. 2003). When you feed BMAA to macaques, they develop similar symptoms (Spencer et al. 1987), and BMAA was detected in brains of people in who died from ALS / Alzheimer's but not in brains of people who died of other causes (Cox et al. 2003, Pablo et al. 2009).

In addition to directly showing high levels of BMAA in the diet and presence of BMAA in brain tissue of symptomatic patients, there is some additional weaker correlative evidence. Torbick et al. 2014 found a correlation between hotspots of ALS and proximity to lakes with high nitrogen and turbidity. This may sound like a stretch, but there is solid evidence showing how nutrient and sediment runoff from agriculture leads to eutrophication and algal blooms in lakes and streams (in addition to hypoxia in the Gulf of Mexico), and since BMAA is produced by blue-green algae this is at least interesting data. Another very small study (Field et al. 2013) looked at three patients who lived on the same short street and all developed ALS (raising the possibility of an environmental trigger given the rarity of ALS). In looking for common factors, they found that all three patients consumed Chesapeake blue crab on a weekly basis, and they verified that these blue crabs had BMAA. However, the levels found (0-115 ug/g in the claws) were significantly lower than in the flying foxes, and some of the BMAA leaches into cooking water meaning the absorbed dose should be lower unless the broth is consumed.

This raises the question of how common seafood with potentially dangerous levels of BMAA is, and the evidence is mixed. On the one hand, Brand et al. 2010 measured BMAA concentrations in several types of seafood in S Florida and found high levels (up to 7,351 ug/g) in some samples of some species (with other samples having lower values or none). They found the highest levels in blue crab, pink shrimp, and one sample of pufferfish), and indeed those levels were higher than that of the flying foxes in Guam. On the other hand, Jiang et al. found BMAA at levels less than 1 ug/g in locally-caught Swedish seafood (although they did find detectable levels in about half of tested samples), and review the results and methods of a few other studies where BMAA levels were much lower than those found by Brand et al. This is an area where we really need more research; both measuring levels of BMAA in seafood, and determining how those concentrations relate to an increased risk of disease.

Finally we have the question of to what degree algal blooms are really associated with BMAA. Scott et al. (2014) found that 70% of the cyanobacteria blooms they sampled had BMAA (compared to 50% with microcystin). Apparently BMAA is produced more under low-nitrogen conditions, while microcystin is produced more under high-N conditions, but interestingly large algal blooms allow both to form simultaneously due to nutrient gradients within the bloom. Again we need more study to determine what drives BMAA production in the first place, and what nutrient levels we should aspire to achieve.

This leads to an alarming possibility: in addition to the potential risk from seafood, the fact that drinking water is generally not tested for BMAA and BMAA can occur even when microcystin levels (which are tested more frequently) are low means we could be missing a risk factor for some serious diseases.

So what are the implications of all this? First, there is enough evidence to raise concerns that consumption of BMAA could be a contributing factor to developing ALS and Alzheimer's disease. Second, while the wide variation in measured levels of BMAA in seafood means more study is needed, the fact that Brand et al. found some levels comparable to the infamous flying foxes in Guam should be motivation to look seriously at this. Third, since eutrophic waters are associated with BMAA production (and thus perhaps with ALS as indicated in the Torbick study), this is one more reason to work on improving agricultural practices to reduce nutrient and sediment runoff.

There are many promising possibilities to reduce nutrient runoff (precision agriculture, riparian buffers and wetlands, changes in cropping systems, changes in irrigation and drainage, and more) and the research is clear that we need different approaches in different contexts. If evidence continues to grow about the link between the way we grow our food and the incidence of ALS and Alzheimer's disease, so will our motivation to take swift and effective action to solve our nutrient runoff problem. Hopefully farmers, conservationists, and health professionals can come together to make that happen.



Brand, L. E., Pablo, J., Compton, A., Hammerschlag, N., & Mash, D. C. (2010). Cyanobacterial blooms and the occurrence of the neurotoxin, beta-N-methylamino-l-alanine (BMAA), in South Florida aquatic food webs. Harmful Algae, 9(6), 620–635. doi:10.1016/j.hal.2010.05.002

Cox, P. A., Banack, S. A., & Murch, S. J. (2003). Biomagnification of cyanobacterial neurotoxins and neurodegenerative disease among the Chamorro people of Guam. Proceedings of the National Academy of Sciences of the United States of America, 100(23), 13380–13383. doi:10.1073/pnas.2235808100

Pablo, J., Banack, S. A., Cox, P. A., Johnson, T. E., Papapetropoulos, S., Bradley, W. G., … Mash, D. C. (2009). Cyanobacterial neurotoxin BMAA in ALS and Alzheimer’s disease. Acta Neurologica Scandinavica, 120(4), 216–25. doi:10.1111/j.1600-0404.2008.01150.x

Scott, L. L., Downing, S., Phelan, R. R., & Downing, T. G. (2014). Environmental modulation of microcystin and β-N-methylamino-l-alanine as a function of nitrogen availability. Toxicon, 87, 1–5. doi:10.1016/j.toxicon.2014.05.001

Spencer, P., Nunn, P., Hugon, J., Ludolph, A., Ross, S., Roy, D., & Robertson, R. (1987). Guam amyotrophic lateral sclerosis-parkinsonism-dementia linked to a plant excitant neurotoxin. Science, 237(4814), 517–522. doi:10.1126/science.3603037

Torbick, N., Hession, S., Stommel, E., & Caller, T. (2014). Mapping amyotrophic lateral sclerosis lake risk factors across northern New England Mapping amyotrophic lateral sclerosis lake risk factors across northern New England.

Thursday, February 12, 2015

Clever Hans: or when horses do math, check your science


My latest blog post is about the challenge of overcoming bias in scientific studies, as illustrated by the wonderful story of Clever Hans, the horse who supposedly could do math and other impressive feats:
http://blog.nature.org/science/2015/02/12/horses-doing-math-clever-hans-lessons-conservation-science/

Monday, December 22, 2014

Double-blind taste test party

While this is pretty light on the science, we did have a science-esque double-blind taste test party which involved randomly generated numeric labels and a fun decoding step at the end where we found out what we liked and what the odd patterns were. Anyway, our blog post about the experience is here:
http://veganladyeats.blogspot.com/2014/12/double-blind-taste-test-party.html
and the raw data (without any well-designed charts, sorry) is here:
http://fish.freeshell.org/events/BlindTastingPartyData.xlsx

Friday, September 19, 2014

Reforestation to reduce ozone without costing businesses extra money



A new paper (on which I'm an author) was just published in PNAS on our collaboration with Dow. In particular, we looked at reforestation as a tool for ozone abatement, with the key finding that in Houston reforestation was cost-competitive with building scrubbers (which has a high initial capital cost and cannot readily be adjusted to a precise need for removal) and NOx allowances. If carbon credits could be sold it would be cheaper.

There are plenty of caveats (the legal framework to actually do this is not in place yet, we assume land owners exist who want their lands reforested (as opposed to having to buy land), it only works in places with NOx-limited ozone and ozone non-attainment areas, etc. Also, the national map I made (above) is a coarse analysis showing where this could be replicated, but does not include factors like the current drought in California (the intent is to flag areas deserving a closer look if the policy piece goes through). For the paper, I did a more rigorous habitat assessment about where within the study area a specific type of bottomland hardwood forest could likely be planted successfully.
 
Nonetheless, it is exciting that in this case we found that a natural solution could be appealing to businesses, while also providing benefits to others (habitat, recreation, etc.). I was only peripherally involved (in the mapping out of where this could work), but I'm still pretty proud.

There is a blog post about why this paper is arguably significant here:

and more details here:

and the actual paper is here:

More information: Reforestation as a novel abatement and compliance measure for ground-level ozone, Timm Kroeger, PNAS, DOI: 10.1073/pnas.1409785111

Read more at: http://phys.org/news/2014-09-reforestation-urban-areas-ozone.html#jCp


Monday, June 23, 2014

Do the Rumble-Rump with Peacock Spiders

My latest blog piece is fluff, but still pretty and interesting.
http://blog.nature.org/science/2014/06/23/do-the-rumble-rump-with-peacock-spiders/
The highlight (other than pics and videos) is that the researchers of one study I refer to documented several key dance moves, including "crunch-rolls," "grind-revs", and "rumble-rumps." And yes, I already have worked out the human equivalent of each, and stand ready to shoot the video once we have critical mass.

Wednesday, June 18, 2014

Global Agriculture Trends: Are We Actually Using Less Land?

A colleague of mine recently alluded to the "rapidly accelerating conversion of natural habitat for agriculture," which got me curious how fast agricultural area was really growing globally. I was pretty surprised to find out that it is actually shrinking! This doesn't mean conversion isn't happening, but it still makes for a pretty interesting story (with a few pretty important caveats). Read about it here:
http://blog.nature.org/science/2014/06/18/global-agriculture-land-sustainability-deforestation-foodsecurity/

Here is the map showing where ag land is expanding and where it is contracting:
And for those hesitant to click, here are the other charts:


Some of the most important caveats are: the data has some known issues, we don't have data on how sustainable the increased productivity is, and projected supply is not expected to keep up with projected demand.

The book chapter can be cited as follows for now:
Fisher, J.R.B. and Kareiva, P. Ecosystem-service based metrics of sustainability as tools for promoting conservation and food security. 2014. In Gardner et al. (Eds), Agricultural Resilience: Perspectives from Ecology and Economics. Cambridge University Press. Manuscript submitted for publication.

Saturday, June 14, 2014

Is pollen flammable?

A few weeks ago, there was a post on XCKD's "what if" asking what would happen if all of the pollen on earth was ignited: http://what-if.xkcd.com/97/

As evidence that pollen is actually flammable, the author pointed to youtube videos labeles "burning pollen" but which are actually not of pollen at all. Rather, they are the fluff from cottonwood seeds: https://www.youtube.com/watch?v=aKra62IC-_w

This got me curious: is real pollen also flammable? It is denser so I figured it wouldn't naturally catch on fire to the same degree, but I still wanted to see for myself.

I gathered up a ton of pollen (from red flower carpet rose), and held a lit match against it.


 I did the same thing with sawdust as a reference, as I just had them in a little pile on top of concrete (rather than trying to ignite with a specific dispersal pattern in the air which would have been harder and more dangerous). The idea is that sawdust is accepted to be flammable (or inflammable if you like), even though it may not catch on fire the same way a piece of paper would depending on the conditions. But I figured this would be comparable to what is already online with cottonwood fluff, but for actual pollen (e.g. if a bunch of pollen fell from the flowers and accumulated on the ground). Note that oak catkins or other flower structures don't count as pollen either.

I found that pollen is roughly as flammable as sawdust, perhaps a bit more. Here are the videos:

Sawdust:

Pollen:

Here's what the pollen looked like at the end: