Monday, September 11, 2017

How a simple blood test will make you rethink the carbs you eat

What if you could figure out the optimal carbohydrates for your body? The 7-Day Carb Test explained in Robb Wolf's book “Wired to Eat” (available in the Barbell Strategy lending library) is a tool to essentially do just that. 

As an athlete, I’ve found that eating some carbohydrate works really well for me. I typically do high-intensity and/or anaerobic sports like weightlifting and bouldering, and have noticed markedly better performance when I’m eating carbs than when I’ve eaten low-carb, high-fat, moderate protein. But I've also noticed I feel better on specific carbs compared to others. Oatmeal, for example, tends to lead to crankiness and frantic snack scavenging only a couple of hours after breakfast, while yams and sweet potatoes give me good energy without the crashes.

So when Mike offered to get a blood glucometer for the gym (#nerdgym), I jumped at the chance to do the 7-Day Carb Test and learn more about exactly which carbs work for me and which don't. 

How the 7-Day Carb Test works

The 7-Day Carb Test is fairly straightforward: Eat 50 grams of effective carbohydrate first thing in the morning, wait two hours and then test your blood glucose. For reference, Wolf suggests 90 to 115 mg/dL as an ideal blood glucose range at the two-hour mark.

There are a lot of nuances and frequently asked questions that come up, which Wolf addresses on his website, but the most important thing is to be consistent with how you run your experiment each day. 

Here are the variables I kept constant:
  • Drink black coffee (the first thing I do every morning) along with my test meal.
  • Set my timer for two hours immediately after finishing the test meal (versus starting the timer with my first bite or midway through the meal).
I also tested my fasting blood glucose one day to get a baseline of where I typically start out on a given morning. 

The carbs I tested and my hypotheses

In his book, Wolf includes charts with common carbohydrates and the amount you’d need to eat to get 50 grams of effective carbohydrate (NOT the same thing, as 50 grams of sweet potato doesn't contain 50 grams of actual carbohydrate, for example). However, you can test any carb you wish as long as you figure out how much you’d need to eat to get 50 grams of effective carbohydrate (remember cross-multiplying fractions?).

For obvious reasons, I decided to pick carbohydrates I eat fairly frequently or would consider eating if my glycemic response was favorable. They were:
  • White rice
  • Gluten-free oatmeal
  • Gluten-free bread (Kim and Jake’s)
  • Yams (garnet)
  • White potatoes (Yukon Gold)
  • Corn tortillas
  • Brown rice
Based on my subjective experience with each, yams were the only carb I predicted would give me a favorable glycemic response. Oatmeal and white rice usually make me feel like I haven't eaten anything in days, and the other four carbs don't seem to make me feel particularly good or bad.

Day 1: White rice


glucometer reading for white rice version 2
White rice, take 2
glucometer reading for white rice version 1
White rice, take 1
I eat white rice mostly post-workout because it’s easily digestible (no fiber) and helps replenish muscle glycogen. But for the same reasons, it sucks as a food for other times of day, and I’m usually hungry again pretty soon after I eat it, despite adding fat to it to help slow digestion (and make it more delicious).

Since this was literally the only thing I ate for breakfast, I was hungry within an hour and eagerly anticipating a real breakfast after testing my blood glucose. Instead of giving me an actual reading, however, the glucometer simply displayed “Lo” on screen. WTF? According to the user manual, any reading below 20 mgl/dL would produce a "Lo" display (it also warned I might have a seizure and shouldn’t operate machinery). I tried again with another test strip, and this time got a reading of 27 mg/dL — EXTREMELY low blood glucose. Hang on to your @%#$ing hats, coworkers!

Day 2: Gluten-free oatmeal


For about a year, Bob’s gluten-free oatmeal had been one of my breakfast standbys. Typically, I’d have a bowl of the stuff with coconut oil and cinnamon added, plus turkey bacon or some other meat for protein. Despite trying to fortify my oatmeal against blood sugar annihilation, I’d nevertheless noticed I’d usually crash about two hours after breakfast and NEED A SNACK to get me to lunch. Now my usual breakfast is solely fat- and protein-based, and I’m finding I can usually go until lunch without feeling hungry or experiencing the typical headaches and crankiness of low blood sugar. 

Anyway, just like white rice, oatmeal gave me a "Lo" reading. I didn't retest with a different strip because I actually tested on the shoulder of highway 36 (hey, I was stuck in traffic and the timer went off). Not the best science here, but for my purposes, sufficient enough to rule out oatmeal as a good carb source for me.

Day 3: Gluten-free bread

fasting blood glucose on glucometer
Fasting blood glucose

After two days of very, very low readings, I was a little suspicious of the glucometer — could it be it wasn’t working properly? So on Day 3, I decided to take my fasting blood glucose before eating my test meal and got a nice, reasonable 76 mg/dL. Normal fasting blood glucose is between 75 and 100 mg/dL, according to Dr. Peter Attia. This was also a good personal reference point since the last time I had my fasting blood glucose tested (as part of a full panel via WellnessFx) I was closer to 90 mg/dL. 

Heartened, I ate my dosage of Kim and Jake’s gluten-free bread, which I also ate fairly often as a former Cured employee. Since it’s bread, I wasn’t expecting a good glycemic response but my reading two hours later was surprising: 74 mg/dL, not far off from my fasting blood glucose earlier that morning.

Day 4: Yams


As I mentioned, I eat yams (and sweet potatoes) probably more than any other carb. I love them and I feel good with them, and it’s super easy to bake off a bunch of them and have them on hand for the week. In retrospect, I should have tested both yams and sweet potatoes to see if there are any differences in my glycemic response to each, but since I eat yams more frequently, I tested only them.

Again, a nice 75 mg/dL, almost identical to my fasting blood glucose.

Day 5: White potatoes

50 grams of effective carbohydrate in white potatoes on food scale
Saddest breakfast ever

I love potatoes, period, and generally feel fine eating white potatoes, but because I know they’re typically higher glycemic, I usually eat them less than yams or sweet potatoes. But I love making homemade fried potatoes with Yukon Gold potatoes and lots of ghee, so I figured it’d be worth testing.

Eating dry, cold potato was pretty gross and it took me a while to get through this meal. Two hours later, my blood glucose was 105 mg/dL — not amazing but within Wolf's range.

Day 6: Corn tortillas


Tacos are the best and since I try to eat gluten-light, testing corn tortillas was a must. Eating five cold, dry corn tortillas first thing the morning definitely was not the most fun experience, but sometimes you gotta do one for science.

This was another day where I took a couple of readings, as I initially got the "Lo" display but then 39 mg/dL with a second test.

A breakfast of sausage, eggs with Parm Reg, avocado and kimchi immediately followed…

Day 7: Brown rice


I don’t typically eat brown rice because if I eat rice at all, it’s to get straight carb into my body quickly and white rice is better suited for this job. But I had some brown rice in my cupboard and decided to go for it.

breakfast of eggs, sausage, avocado and kimchi
Typical post-test breakfast
So much for brown rice being the “healthier” choice — my blood glucose was at 31 mg/dL, a mere four points higher than my reading after eating white rice. If you’re looking for fiber, just eat more vegetables. Brown rice is basically just as “bad” as white rice (at least for me).

Googling hypoglycemia, or why I won’t be eating rice that often anymore


Honestly, the results of these tests surprised me. From reading Wolf’s account of how certain carbs affected his blood glucose, I was expecting my most antagonistic carbs to spike my blood glucose and keep it elevated at the time of my test. For me, it appeared to be the opposite: the carbs that seem to have the biggest negative impact gave me hypoglycemic blood glucose readings. 

In trying to make sense of what’s happening I reviewed some articles on Dr. Attia’s blog. (Side note: I love this dude. He’s one of the best resources for not only explaining very complex biological processes in plain English, but he’s an athlete who's experimented with nutritional ketosis and has experience with using it in clinical settings as well.) His primer on insulin is quite helpful, particularly this: “Carbohydrates stimulate insulin more than any other food. And even within carbohydrates, there are different amounts of insulin stimulus that result from them, depending on the simplicity of them.” Perhaps the rice, oatmeal and corn — all simple carbohydrates — elicit a strong (perhaps too strong) insulin response, which subsequently puts me into a hypoglycemic state?

I’m not sure if that’s what’s happening and would welcome the thoughts of someone more knowledgeable on the subject (or perhaps I’ll research this more for a future blog post). Regardless, it’s clear that certain carbohydrates put my blood glucose out of the sweet spot and I should probably avoid them most of the time. 

Final thoughts

  • I'm just one person. As with a lot of health recommendations, what works for some (or even many) might not work for you. Glucometers are fairly inexpensive, and blood testing is also pretty cheap and available directly to you without having to go through your doctor or an insurance company. It’s thus easier and cheaper than ever to get a lot of data on what’s going on in your body and how your lifestyle choices affect your health. Take advantage of it! Knowing what works best for you through experimentation is better than blindly following conventional medical or public advice, which is often too vague to be helpful and inevitably geared toward the safety of masses rather than to you.  
  • It’s really hard to do good nutrition science. There are so many variables you need to control, and because it’s food and we’re finicky animals, it’s not straightforward or convenient. I mean, every day I tested myself I had to predict where I’d be in two hours, and as I mentioned, one day I was stuck in traffic on a highway. Not ideal for participant compliance. The difficulty of designing good clinical nutrition studies is part of the reason we don’t have definitive research on a lot of nutrition-related questions. Another is that they’re really expensive and depending on who you are and what you want to test, it can be very hard to get sufficient funding (please go read Nina Teicholz’s “The Big Fat Surprise” for a fascinating and disturbing history of nutrition science and policy in the US). All this to say, you can either wait for perfect nutrition research, or you can use yourself as an N of 1 and get actionable results a lot sooner.
  • Try to avoid diabetes. Testing your blood glucose is annoying, and while that inconvenience is probably minor compared to the other reasons you don't want to have diabetes, every day of this experiment I thought, "I can't imagine having to do this every day!" All facetiousness aside, remember type 2 diabetes is preventable and learning what foods sends your blood glucose to the extremes is key to prevention.

Melissa Komadina is a copy writer and recent Barbell Strategy member who lives in Denver. Her favorite carbs are beer and donuts, and she is blissfully unaware of her blood glucose response to either.



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