Glass half full? How wine glass size affects consumption and what it means for health studies

You probably know the joke: The pessimist says the glass is half empty, the optimist half full; the chemist sees the glass completely full but half in the liquid state and half in the vapor state; your IT support person recommends emptying the glass and then refilling it; and an engineer will say that the glass is 2 times bigger than it needs to be. Wine glass size – more specifically the amount of wine per serving – has important implications for studies on the health effects of drinking. The reference serving size has long been set at 5 ounces (150 ml), but wine glasses have been getting bigger. And since virtually all studies on wine and health are based on self-reported levels of consumption (as opposed to, say placing human subjects in a lab for 10 years with strictly portioned wine allocations), it is possible that we are trying to hit a moving target when trying to figure out what’s healthy and what isn’t.

Does the engineer have the correct answer? Wine glasses have been getting larger for quite a long time, and maybe they have gotten too large. According to an analysis by scientists at the University of Cambridge, wine glasses are gargantuan compared to what our forebears tipped back a few hundred years ago. By calculating the volumes of stemware from the 1800’s in museums to averages today, they determined that capacity has multiplied 7-fold, now approaching nearly a pint. Historically there are several reasons for the diminutive dimensions; smaller glasses were likely less fragile, and a glass excise tax from mid-1700’s Britain was a disincentive to go big. But by the mid 1800’s glass production became more automated, methods of manufacturing improved, and the tax was dropped. Volumes have continued to balloon ever since.

Of course the chemist has a point too. One reason for increasing the volume is to accommodate the vapor state, the bouquet that so enhances the wine drinking experience. As any self-respecting wine aficionado knows, bowl shapes and sizes have been tweaked to optimize for each varietal. While there is plenty of room for debate on the subject, there is some scientific validation. One thing is certain: If you order wine by the glass and you get 5 oz. in a 6 oz. glass, that’s a sure sign that it’s not intended for swirling and savoring.

Which brings us to the IT support theory: Drinking the contents of the glass to prepare it for another fill, and hence another reflection on the question, may lead to excess consumption (you weren’t going to just dump it out were you?) Or more simply put, does the trend to larger glasses translate to increased drinking? The Cambridge group decided to test the hypothesis in a local watering hole, convincing the owners to agree to an experiment: Keeping the serving size constant, the glassware was changed out every 2 weeks to increasingly larger sizes. “By the glass” wine sales rose by nearly 10%, leading the authors to conclude that when it comes to wine glasses, size matters.

In attempting to replicate the findings and understand the reasons behind them however, their next study found the opposite. Using video recordings, subjects were again given the same serving portion in two different sized glasses on different occasions. In this more controlled setting, wine drunk from the larger glasses was actually sipped more slowly, and the researchers found “no support for the hypothesized mechanism” of increased wine consumption due to larger glasses.

There are other factors at play here, such as rising alcohol content in modern wines compared to traditional ones. People still perceive and report a portion of wine as the same regardless of the vessel. But I see another explanation: It’s usually wine connoisseurs who want their wine in the larger glass so they can appreciate it more. Wine quality is better across the board, and rising prices for the good stuff discourage guzzling. Half full or half empty is all the same to me: just right.

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