Ask Pete: Should You Carbo-Load on Beer?

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QUESTION #1: Is drinking beer a good way to carbo-load the night before a race? – Ken

ANSWER:

Okay, first a confession. Ken is a clubmate of mine, and he posed this question on behalf of most of my Cal Coast Track Club masters clubmates—many of whom I’ve seen take this question out of the realm of the hypothetical and put into actual practice. So I’m sorry, Ken, but I have some bad news.

First, alcohol is not a carbohydrate (or a fat or a protein). It’s alcohol. A beer has about 12 grams of carbohydrates. Each gram of carbohydrate contains about 4 calories of energy. Alcohol has about 7 calories per gram, and a “standard” drink (12 oz of 5% alcohol beer) has 14 grams of alcohol. So most of your beer calories are alcohol—two-thirds or more!

Most alcohol gets broken down in the liver. This is important. Because while your liver is breaking down alcohol, it’s neglecting its normal duty of maintaining your blood glucose levels. When your blood glucose levels drop, your muscles start burning stored glycogen (increasing stored glycogen is the whole point of carbo-loading), leading to reduced glycogen levels—in turn leading to reduced running performance.

Alcohol simultaneously interrupts the metabolizing of other important nutrients. And it inhibits the release of a hormone (ADH) that regulates urination. For every 10 ounces of beer you drink, you’ll urinate about 16 ounces. Yikes! Honestly, a beer the night before a race probably won’t hurt, but beer as your energy prep plan, well, that leads to dehydration, less race-time energy, and decreased performance. Plus, there’s little reason to carbo-load for races under 90 minutes, anyway, but that’s for another Q & A.

QUESTION #2: I’ve been reading about “heat camps,” where runners train in the heat to get the same benefits as training at altitude, only more quickly. What are your thoughts? – Michael

ANSWER:

Both altitude training and heat training can benefit runners. But they benefit us in different ways. Altitude training generally requires a minimum of three weeks, and it stimulates the production of the hormone erythropoietin (EPO), which in turn—in runners who aren’t overly fatigued—leads to the creation of more red blood cells (RBCs). RBCs carry oxygen to the muscles in your body, so altitude training theoretically leads to an increase in oxygen-dependent, aerobic energy production.

Heat training, on the other hand, can stimulate an increase of up to 12% in plasma volume, the non-RBC part of your blood, as long as you train while mildly dehydrated (no more than 2%). Greater plasma volume helps maintain a high stroke volume (the amount of blood your heart pumps per beat) and lowers blood viscosity (i.e., thickness), which allows it to flow more smoothly while delivering the afore-mentioned RBCs to your muscles. Plasma volume can expand in days, versus the weeks and months it takes RBCs. Both types of training lead to better running economy and improved performance.

So what you should do? Given the opportunity, do both. Or, do whichever one you can. This isn’t an either/or training decision. There are no single-workout, silver bullets in running.

QUESTION #3: During a long run, does energy come just from glycogen stored in the muscle you’re using, or does it also come from glycogen stored in the liver and other muscles? – Bill

ANSWER:

Lucky for you, Bill, energy is generated by multiple sources during your long run. First, let’s clarify that human muscles are powered by only one energy source: energy from the molecule ATP (adenosine triphosphate). We break down carbohydrates, fats, and sometimes (as a last resort) protein during the process of creating ATP. On your long runs, about 50% of the ATP you generate comes from the breakdown of fat. The other 50% comes from carbohydrates. The primary source of those carbs is muscle glycogen, with each of your muscle cells having its own glycogen “tank”—actually, a collection of glycogen granules, each of which contains a boatload of glucose molecules.

At the same time, your muscle fibers can import the carb glucose from your blood, with your liver breaking down its own glycogen stores to maintain blood glucose levels. But here’s the thing: Only about 5 grams of glucose circulate in your blood, while your muscles can store up to 800 grams of glycogen. So it’s glycogen that dictates how energetic you’ll feel during your run. You’ll also use some anaerobic energy, which, as a byproduct, produces lactate, another great carbohydrate source for creating ATP. Bottom line: Between fat, glycogen, glucose, and lactate, you can complete your long run without fear of running low on fuel. See this great 2018 article for a more science-y breakdown of energy use during exercise.

WHO ASKED YOU, ANYWAY?

Pete’s freebee training tip: Since it’s summer, here’s some more advice about training in heat: Don’t overhydrate on runs, even when it’s hot, even when you’re sweating. Training triggers adaptations in response to the stimuli we receive during workouts. If you want the benefits of heat training—e.g., increased plasma volume—you’ll need the stimulus of slight dehydration.

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