Saturday, September 30, 2017

Photosynthesis, Carbon Dioxide and Higher Alcohol Wines

Let me preface this piece by saying that I'm a fan of lower alcohol wines. I was first introduced to wine in 1980s Upstate New York, drinking 11.5% Rieslings and, yes, Cayuga Whites. Red wines from the area, like Marechal Foch and De Chaunac (for an overview of hybrid varieties like Cayuga White, Marechal Foch and De Chaunac, see here) were in the range of 12-12.5%. At the time, this wasn't considered low alcohol, it was considered the norm.

Perhaps because of this early exposure to lower alcohol wines, I've always preferred them, and I actively look for them when considering a purchase. New Zealand, despite being a cool climate winegrowing region, now regularly produces 13-13.5% whites and Pinot noirs are often seen with 14.5%. This goes against my, personal, ideas of what these wines should be.

I look forward to wines from the really challenging vintages where grapes struggle to get as ripe as the winemakers want them. The 2012 vintage in Hawkes Bay had a really cool and extended ripening period and grapes were brought in at much lower sugar levels (measured in degrees Brix in New Zealand and other places) than usual, but it resulted in some very good, and more elegant, in my opinion, wines as a result, with the alcohol being in balance with the other aspects of the palate. New Zealand's most recent vintage was also a challenge due to rainfall in the ripening period, resulting in grapes being brought in before target Brix were hit. I tasted my first of this vintage's wine in August, a Marlborough Sauvignon blanc, that had all the hallmarks of the region, but with only 12% alcohol: it was a much more harmonious assemblage than with the usual higher alcohol wines of the region.

Having got that out of the way, what about climbing alcohol percentages in wine?

Rising average alcohol levels in wines has been a topic of discussion for some time, and various reasons for this have been put forth over the years. A useful study to look at was published in 2011 by Alston et al. where data from California was examined to show that average harvest Brix levels between 1980 and 2010 increased. Sugars in red wine varieties increased by an average of 0.23% per year over that period, and notably, in their Figure 1, Brix for red varieties was pretty much flat from 1980 to the mid 1990s, rising from there to the 2010 average of around 23.8°. This was particularly noticeable for the North /Central Coast and Delta regions, where the rate of increase was 0.72, 0.75, and 0.96%, respectively, between 1990 and 2008, compared to 0.53% for California as a whole (Alston et al. 2011 Table 1).

So fruit sugars are going up (at least in California) and the wines made therefore have higher alcohol. But why are the sugars going up?

A different take on this has come about recently, where people are starting to look at rising carbon dioxide (CO2) concentrations in the atmosphere and linking this to increased plant productivity (e.g. here and here). This isn't a difficult link to make, as the process of photosynthesis takes CO2 and water and with the help of the enzyme Rubisco, releases oxygen and sugar (in the form of glucose). It stands to reason that if you increase the availability of a starting material, you can end up with more product. This is assuming that other starting materials (Rubisco, water, sufficiently warm temperatures and light energy in this case) aren't limiting, and that the products don't start piling up in the area where they're being produced - if glucose and oxygen keep building up in the cell, the rate of photosynthesis will slow through a process called feedback inhibition.

So increasing CO2 should mean more efficient photosynthesis and more sugars to go around? As we usually find, things aren't that simple.

There has been plenty of research into the effects of raising CO2 concentration and its positive effects on plant growth and productivity, however, much of this has been with relatively short duration experiments. When plants have a longer time and a chance to adapt to the changed conditions there is more talk of photosynthetic down-regulation, or acclimation, resulting in relatively little change.

A review by Makino and Mae notes that longer term plant adjustment is a complicated system. For example, if sugar is being produced more quickly, but the plant does not have the capability of moving the sugars out of the cell fast enough, photosynthesis will be slowed by feedback inhibition. This kind of makes sense, too, as the plant would change things so that a balance remains between production and utilisation of photosynthetic products.

There is also a suggestion that seedlings have a greater response to high CO2 compared to older plants, possibly because seedlings are generally carbohydrate supply limited, whereas older plants have a store of carbohydrates that are used when needed. Grapevines, being perennial plants, have decent carbohydrate stores even from a reasonably young age.

It's not just photosynthesis that can change, either - under climate change scenarios, increasing temperatures will also increase the respiratory activity of Rubisco. Yes, this enzyme goes both ways: it can help convert CO2 into sugar, but the same enzyme also latches onto oxygen in the process of photorespiration. This opposes photosynthesis and makes the process less efficient. Photorespiration increases faster than photosynthesis as temperatures increase, so photosynthetic efficiency suffers.

And as Jamie Goode has pointed out (here in an article where he points out a whole bunch of interesting things on the subject) with higher CO2 plants don't need to open their stomatal pores as much, because a lesser amount of air holds the same amount of CO2. This can lead to less water use, as with less air movement in and out of the leaf, there is less water vapour lost, too. A side effect of this, however, would be a rise in leaf temperature due to less evaporative cooling (you can experience this by spraying your arm with water - it feels cooler right away because the water is evaporating, and to do that your body heat is used). Higher leaf temperatures could mean more photorespiration, and more time when the leaf gets too hot to keep the enzymatic machinery going. Higher temperatures, associated with climate change, will only make this problem worse.

The multiple changes to the environment will cause plants to respond, but exactly how they respond is really too complex for us to say at the moment, especially when you start to take into account that these changes will have an influence on all the other living creatures around and on the vine (disease organisms, insect pests, and don't forget the soil ecosystem!).

So the overall effect on grapes and wine gets hazy pretty quickly, with lots of factors, and responses, involved. Having said this, I agree with Jamie in that the rise in CO2 concentration is not really what's responsible for increasing wine alcohol - that has more to do with consumer preference and technological advances.

For those that are thinking about strategies for dealing with high Brix and high alcohol wines, we have a number of tools in the viticultural toolbox, but this is a topic for another article!

Tuesday, July 4, 2017

"Heavy" Drinking and Cancer Risk

I saw a recent headline about alcohol consumption that concerned me a bit, and because so many editors skew research report findings to get more clicks, I thought I'd take a closer look.

The article in question is titled "Heavy drinking Europeans most prone to digestive cancers." The information itself isn't too extraordinary - if you consume excessive amounts of alcohol, there are bound to be issues, much like if you consume too much of anything.

However, what worried me are two things: 1) what is considered heavy drinking and 2) at the end of the article was a quote from Richard Gardner, who is the CEO of the British Society of Gastroenterology. He said "Fundamentally, there’s no such thing as no-risk drinking."

As a scientist, I know that there is very rarely anything that is black and white, and I have some interest in the area of wine consumption and health issues (having followed in my father's footsteps with research into resveratrol production by grapevines). I have posted on this subject before (see here) and my views on moderate wine consumption and health have not changed in the intervening years...

So the undefined statement about heavy drinking and that about all alcohol consumption being bad immediately rang some alarm bells and got me more interested.

For starters, to be completely pedantic, there is no such thing as no risk anything. Every time we walk out the door, our odds of being injured increase, not to mention all the potential dangers in the home itself! So everything we do is a calculated risk - we have to make the decision, does the risk of a bad thing happening outweigh the benefits of the activity?

For alcohol consumption, there are many examples of research reports that indicate possible health issues generated by excessive drinking, but the key there is "excessive." The article above uses the phrase "heavy drinking." I do not think anyone would argue that consuming too much alcohol is bad for your health - the real question is, in terms of understanding the article, how much is too much and also, and a bit separately, is less than that beneficial or not?

Let's drill down and do some investigative reading of the article....

The headline I saw was on The Drinks Business, and most of the article is fair, noting that there is a range of consumption across the different countries. However, "heavy drinking" is defined as having "more than four alcoholic drinks at least once a week." This can be a bit confusing, as it could be interpreted as more than four drinks per week, but also as more than four drinks a day at least once a week. Without clarity around this, it's difficult to know how to interpret the information.

Because there can be losses or alterations to information as it gets transmitted around (see Chinese Whispers), it would be a good idea to go direct to the source, rather than relying on someone else's interpretation of the information (a very important component of reviewing scientific information, too).

The Drinks Business got their information from Bloomberg, who published "Europeans are drinking themselves to death."

In reading this article, we see a bit more detailed information, with a focus on the average number of drinks per day people consume in various countries.They also report that drinking "heavily" means "more than four alcoholic drinks - at least once a week," which still doesn't help us in interpreting what the data actually mean.

So the next step is to go back to the original source, United European Gastroenterology. Their press release is "Alcohol consumption putting vast majority of Europeans at risk of digestive cancers, report reveals." There, "people that consume 4 or more drinks per day" are considered to be heavy drinkers. This clarifies what they are really talking about, and makes sense - with that much alcohol per day, it's no wonder there is a health impact!

But the original report's version of "heavy" drinking differs considerably from what the editors at Bloomberg used - there is a definite alteration to how people might interpret what "heavy" drinking is with the Bloomberg version.

Lesson: If you can, don't trust the reporting - go back to the source!

Getting back to Richard Gardner's statement, "Fundamentally, there’s no such thing as no-risk drinking," let's take a closer look at that...

Currently, the American Cancer Society (see "Colorectal Cancer Risk Factors") recommends avoiding "heavy alcohol use" and recommends "no more than 2 drinks a day for men and 1 drink a day for women," adding that this "could have many health benefits, including a lower risk of colorectal cancer" (note that the Bloomberg article also points this out).

They're not the only ones saying that moderate consumption of alcohol can be beneficial. The National Institute on Alcohol Abuse and Alcoholism says this "may protect healthy adults from developing coronary heart disease."

The Centre for Disease Control and Prevention has a nice summary of what is considered excessive consumption (here) as does the NIAAA (here)

Not all agencies have quite the same take. The National Health Service (England) suggests that new research shows that "evidence on a protective effect from moderate drinking is less strong than previously thought"(source here). They state that fewer than 14 units of alcohol per week puts you in a "low risk"category as "there is no safe drinking level."

And that brings us back to the risks versus benefits. Saying that "there is no safe drinking level" is misleading because it implies that people should not consume alcohol at all. The fact remains that there is no completely "safe" level of anything. Equally valid, but useless statements could be "there is no safe amount of driving" or "there is no safe amount of sugary drink consumption."

 As the saying goes, "health is simply the slowest possible way to die..." 

We all make choices that have an effect on our health - some are worse, but some can be better.

So for me, I'm happy being in the "low risk" group the National Health Service identifies because based on my reading of the research, there is support for both positive aspects of the risk and for negative ones. 

I believe the positives outweigh the negatives by a large margin, and not just from a health standpoint, but just as importantly from a lifestyle standpoint. Wine gives me so much pleasure in life! Wine is part of a meal - it is part of a discussion - it is part of intellectual stimulation. 

For some, alcohol in whatever form may be a means to get drunk, but that is not at all how I view alcohol - alcohol to me is a component of a beverage that (in wine, at least) is complex, varied, nuanced and something to be thought about, discussed and most of all, enjoyed.