This post is an update on my experiments measuring the effect of low-carb foods and dietary supplements on blood sugar.
I’m still working my way through low-carb flour replacements, but since I’m running the vinegar experiment in parallel, it’s going to take a while to get through all of them.
In the meantime, I wanted to share my preliminary results and see if anyone has suggestions for additional low-carb flours to add to the study.
If you have any low-carb flour replacements you like or would like to see tested, please post it in the comments or send me a PM (contact form on the right).
Next week I’ll have an update on the vinegar experiments.
Historically, there hasn’t been a lot of low-carb replacements for flour available, mostly almond flour, coconut flour, and resistant starches. Similar to other low-carb products, a ton of new flour replacements have hit the market in the last few years. As always, the net carb counts look good, but I wanted to test them to see if they really hold up (see evidence of blood glucose impact of dietary fibers here & here).
So far, I’ve found 11 flours to test:
Baseline:
Wheat flour
Modified starches
Carbalose flour
Carbquick
Freekeh flour
Nuts:
Almond flour
Hazelnut flour
Beans:
Lupin flour
Okara flour (from soybeans)
Other seeds:
Coconut flour
Hemp protein powder
Flaxseed meal
Psyllium husk powder
I’ve gotten through 7 so far and all have been pretty good, with peak ∆BG of 16-29% of wheat flour by weight and 9-23% by volume (see chart below).
As mentioned above, since I’m running the vinegar experiment in parallel, it’s going to take a while to get through the remaining flours. Once I do, I’ll post a full update with more detail on taste, texture, and the full blood glucose analysis.
If you have any low-carb flour replacements you like or would like to see tested, please post it in the comments or send me a PM (contact form on the right).
I’ll test all the requests over the next couple weeks and post the results.
Thanks to the team for all the work they put in figuring out the protocol, running the experiments, and analyzing the data: /u/genetastic and /u/kabong!
Summary
A reader, /u/genetastic, reached out about collaborating on experiments to determine the effect of vinegar on blood glucose after meal consumption.
Like most of you, I had heard all the nigh-magical, pseudoscience claims about using apple cider vinegar to treat diabetes. However, when you dig into the literature, there’s a sizable number of peer-reviewed studies, including several decent meta-analyses, showing that consumption of vinegar with a meal can reduce the blood glucose impact in both diabetic and non-diabetic subjects (see background below for details). There’s also a lot of open questions, including:
Is the effect large enough to matter for practical meals?
What types of meals does vinegar affect?
What is the best protocol to get a large effect without unpleasant side effects?
What’s the underlying mechanism?
Is the effect specific to vinegar or do other acids work?
/u/genetastic, a third collaborator /u/kabong, and I decided to answer these questions with community self-experiment.
For the first phase of this experiment, we wanted to check that we could observe the reported impact of vinegar on blood sugar and that the effect size was large enough to be worth further study.
Towards this end, all three experimenters tested consuming regular white bread with and without apple cider vinegar (the most commonly tested meal and vinegar source in the literature).
Here’s a summary of the results & next steps (full details below):
We observed a similar effect of vinegar on blood glucose as that reported in the literature.
The effect was both statistically significant and meaningful in magnitude, justifying further study of the scope, mechanism, and optimal protocol.
Peak change in blood glucose & iAuC were reduced by 20% and time to peak blood glucose & initial rise were slowed by 15-20 min. (30-50%).
P-values were all <0.05, with the exception of the drop in iAuC, which was 0.12
Next, we will be looking at the following:
Diluting vinegar to make it more palatable
Alternate macronutrients (simple sugars, proteins) to determine scope of the effect
Alternate acid sources to test the amylase-inhibition hypothesis
All-in-all, a good start to the study. The effect seems to be real and likely caused by a slowing of the initial rise/rate of metabolism.
We’re also see a lot of value to running the experiment as a team rather than my more typical N=1 study. With most of my experiments, there’s always a concern that the results are specific to my body chemistry and won’t generalize to others. Having data from multiple people significantly reduces that risk.
That said, having data from multiple participants significantly complicates the analysis. Luckily, /u/genetastic is much better at statistics than I am and was able to handle it.
It would significantly improve the study to have a larger number of participants. If you’re interested in collaborating on this or other scientifically rigorous self-experiments with low-carb foods, supplements, or other health interventions, please let me know in the comments or via the contact form on the right.
Since I’ve started posting these food-effect studies, one of the most requested products has been low-carb chocolate. As with other low-carb products, a ton of new low-carb chocolates have become available. Initially, most used a simple substitution of a non-nutritive sweetener, like erythritol, for sugar. However, I’ve noticed in the last few years, a number of high cocoa/low sugar chocolates that use regular sugar, just in very low quantities (90-100% cocoa).
In both cases, the net carb count can be very low, though this largely relies on subtracting the high fiber content of the cocoa. Since I’ve had very mixed results with the blood glucose impact of dietary fiber (see here & here), I tested them myself.
Towards that end, I tested 13 chocolates from 4 different categories (grouped by sweetener). Here’s my overall conclusions:
Lowest BG impact: Lily’s Almond Dark & The Good Chocolate Signature Dark
~65% of the impact of 100% cocoa bars
Best combination of taste & impact: Taza Wicked Dark & Trendz Bar
Chocolate with added fiber shows much higher blood glucose impact
There’s a significant variation between brands
This could be due to different fiber type or quantity
Watch out for the ChocZero chocolate, which gave ~2x the BG impact of the next highest chocolate.
Evidence continues to pile up that there’s a large variation in the impact of different fibers, even ones with the same name listed on the nutrition label. I’m going to see whether I can source a decent variety to test.
If anyone knows where to get the fibers and resistant starches that are used in low-carb prepared foods (especially from the actual manufacturers), please let me know in the comments or by PM.
As always, please let me know if you have any thoughts, suggestions, or anything else you’d like to see me test.
This week in my low-carb food study, I have Reader Requests!
For the past 6 weeks, I’ve been posting a series of studies on the blood glucose impact of low-carb foods (tortillas, cereal, ice-cream, bread). In the comments for each of these posts, I’ve been getting some great recommendations for other foods to try, so I decided to do a “Reader Requests” study where I measured the BG impact of the recommended foods.
The results were really interesting. In every category, there was a Reader Request that either had a much lower BG impact than what I had found or gave significant insight into the BG impact of different ingredients.
Here’s what I found:
Summary
Tortillas
The regular flour tortillas were much lower impact than I expected (30% peak BG & 70% iAuC vs. glucose), similar to that of the resistant wheat starch tortillas. This makes the resistant starch tortillas look even worse than I originally thought. Definitely never going to eat those again.
Neither of the recommended low-carb tortillas (Mr. Tortilla & A La Madre) beat out La Tortilla Factory for taste, texture, and BG impact, so I’m going to stick with La Tortilla Factory for personal meals.
Ice Cream
All three of the requested low-carb brands had lower BG impact than any of the brands I’d previously tested. The Two Spoons brand, in particular, was extremely good and has the only fruit-flavored low-carb ice cream I’ve seen. The Two Spoons Strawberry and Brownie Fudge flavors are my new favorite by a pretty wide margin.
Breads
The Julian Bakery breads were very low carb, but didn’t taste much like regular bread. They were interesting, but if I’m looking for a bread replacement, I’d pick something else.
Yogurt
Two Good Strawberry Yogurt had good texture and low BG impact, but the flavor was too mild and had a stevia aftertaste I didn’t like.
I would prefer to eat their plain yogurt and add my own mix-ins, maybe some nuts or chopped chocolate for a dessert.
Note: Readers also recommended several of the best breads that were included in the original bread post, including: Carb0naut (Can’t find the original request, sorry), Unbun Unbread (u/fawkesandholly, u/Impressive_Citron_84), Kiss My Keto (u/justjules83), and Base Culture (u/Spell_Chick).
If there’s anything else you want to see me test, please let me know in the comments.
– QD
Details
Tortillas
Tortillas tested. New requests in orange.Blood glucose impact of tortillas.
Summary: Nothing spectacular here, but the Mr. Tortilla could be good if you prefer smaller size tortillas/soft tacos.
La Tortilla Factory Flour Tortilla (not low-carb, as a control) (Can’t find the original request, sorry)
Much lower impact than I expected (30% peak BG & 70% iAuC vs. glucose), similar to that of the resistant wheat starch tortillas. This makes the resistant starch tortillas look even worse than I originally thought. Definitely never going to eat those again.
About the same BG impact as the regular flour tortillas (23% peak BG & 63% iAuC vs. glucose). Not great and not consistent with the claimed net carbs.
Taste was only ok, too. Will not use again.
Mr. Tortilla 1 Net Carb Tortilla (Can’t find the original request, sorry)
About the same BG impact as the best-in-class La Tortilla Factory tortillas (14% peak BG & 40% iAuC vs. glucose, or about half the LTF flour tortillas)
I didn’t like the taste as much as the LTF low-carb tortillas (bit too gritty), but they’re taco sized, which is very convenient for some recipes.
All-in-all, I found these to be ok, but will continue to buying the La Tortilla Factory low-carb tortillas going forward
Ice Cream
Ice cream tested. New requests in orange.Blood glucose impact of ice cream per gram.Blood glucose impact of ice cream per gram, zoomed in to only show low-carb ice creams.Blood glucose impact of ice cream per cup, zoomed in to only show low-carb ice creams.
Summary: All three of the requested low-carb brands had lower BG impact than any of the brands I’d previously tested. The Two Spoons brand, in particular, was extremely good and has the only fruit-flavored low-carb ice cream I’ve seen. The Two Spoons Strawberry and Brownie Fudge flavors are my new favorite by a pretty wide margin.
Talenti Double Dark Chocolate (not low-carb, as a control) (Can’t find the original request, sorry)
BG impact was consistent with the carb count (peak BG 27% of glucose, total carbs 31% of mass), and way higher than any of the keto brands. Not surprising.
Lower BG impact than any of the original brands I tested (2.0% peak BG & 5.5% iAuC vs. glucose)
Much harder texture out of the freezer than heavy cream-based ice cream. Even after sitting out for 35 min., I had to microwave it to get to my desired softness.
Had a strong chocolate and coconut taste. A lot lighter/airy than the heavy cream based brands, but still had a “creamy” texture.
Overall, I didn’t like it as much as the other brands, but I could see some people preferring it.
Lower BG impact than any of the original brands I tested (2.5% peak BG & 5.9% iAuC vs. glucose)
Softest texture of any of the brands. This and Two Spoons were the only keto ice creams that could be “scooped” straight from the freezer.
The Coffee Karamell flavor is more mild than I’d like, but it’s ok. I’d really like to try some of their other flavors, but this is the only one in my grocery that’s low-carb.
Way lower calories than other brands (240 kcal/pint vs. 470-680 kcal for other brands). Not sure why, though maybe it’s got a higher water content with more stabilizers & emulsifiers to soften.
Warning: The nutrition label on their website doesn’t match with what I found in the store. The BG impact matches up with the label, so if you’re buying this, make sure you read the label carefully.
The lowest BG impact of any ice cream I’ve tested:
Chocolate: 1.8% peak BG & 4.2% iAuC vs. glucose
Strawberry: 2.0% peak BG & 4.9% iAuC vs. glucose
This has the most similar texture to regular ice cream of all the brands I’ve tried. Scoopable, but a bit hard straight from the freezer. 1 min. in the microwave at 30% power got it to my preferred texture.
The chocolate flavor was good, though I’d prefer a stronger flavor.
The strawberry was amazing. Extremely smooth, creamy taste and the strawberry mix-ins taste like firm strawberry jam. This is the only keto fruit flavored ice cream I’ve found. I’ve always preferred fruit-flavored ice-creams and this was a great example.
I also tried their Brownie Fudge & Coffee Toffee flavors, but didn’t do a BG test
Brownie fudge: My second favorite after strawberry. A stronger chocolate flavor than chocolate and the brownies gave a nice flavor and textural contrast (even stronger chocolate flavor & soft chewy texture).
Coffee Toffee: Very strong coffee flavor with a great texture contrast from chocolate chips and toffee. If you like coffee ice cream, I’d definitely recommend it.
Breads
Bread tested. New requests in orange.Blood glucose impact of bread.
Summary: The Julian Bakery breads were very low carb, but didn’t taste much like regular bread. They were interesting, but if I’m looking for a bread replacement, I’d pick something else.
Julian Bakery KetoThin Bread (Can’t find the original request, sorry)
The lowest BG impact of any of the breads I’ve tested (3% peak BG & 8% iAuC vs. glucose)
This one was a bit odd. It was soft, moist, and tasted pretty good, but not at all like bread. You can really taste the cream cheese in it.
When toasted or fried, it became slightly crispy and the cream cheese taste was much less noticeable.
Julian Bakery PaleoThin Sandwich Bread (Can’t find the original request, sorry)
3rd lowest BG impact, after Julian Bakery KetoThin & UnBun UnBread (6% peak BG & 10% iAuC vs. glucose)
The bread was a little wet when I opened it and tasted slightly sour. Taste was not that great, though maybe it was starting to spoil? I ate it right after opening the sealed package and 3 days after it arrived, so if it was spoiled, that’s not a good sign.
Yogurt
Blood glucose impact of Two Good Strawberry Yogurt.
Low BG impact (4% peak BG & 7% iAuC vs. glucose), a little higher than its net carb count (2% of mass)
Strawberry flavor is very mild and has a stevia aftertaste that I don’t like.
Texture is great, creamy and not chalky like some greek yogurts
I didn’t like this and would prefer to eat their plain yogurt and add my own mix-ins, maybe some nuts or chopped chocolate for a dessert.
Design/Methods
Foods. Full nutrient and ingredient info here. Key nutrition facts in the tables in above.
Procedure. At 5:00a, I took 4.5u of Novolog (fast acting insulin, duration of 2-4h), then drank a Ketochow shake (website, BG testing) at 5:30a. After that, no food or calorie-containing drinks were consumed and no exercise was performed. Non-calorie-containing drinks were consumed as desired (water or caffeine-free tea). At 10:30am-12 pm, the substance to be tested was eaten as rapidly as comfortable and notes on taste and texture were recorded (before observing any change in blood sugar).
Blood sugar was monitored for 5h using a Dexcom G6. Calibration was performed 15-30 min. before the start of each experiment.
Separately, all breads were toasted using a Brava oven (wheat toast, setting 7). Taste and texture were recorded.
Data Processing & Visualization. iAUC was calculated using the trapezoid method (see data spreadsheet for details). Data was visualized using Tableau.
Medication. During these experiments, I took long-acting basal insulin each evening at 9pm (Lantus, 1.5u) and 2000 mg of metformin and multivitamin each morning at 5am. I did not dose for the experimental food ingested.
About a week ago a reader, /u/genetastic, reached out about collaborating on experiments to determine the effect of vinegar on blood glucose after meal consumption.
Like most of you, I had heard all the nigh-magical, pseudoscience claims about using apple cider vinegar to treat diabetes. However, when you dig into the literature, there’s a sizable number of peer-reviewed studies, including several decent meta-analyses, showing that consumption of vinegar with a meal can reduce the blood glucose impact in both diabetic and non-diabetic subjects (see background below for details). There’s also a lot of open questions, including:
Is the effect large enough to matter for practical meals?
What types of meals does vinegar affect?
What is the best protocol to get a large effect without unpleasant side effects?
What’s the underlying mechanism?
Is the effect specific to vinegar or do other acids work?
/u/genetastic, a third collaborator /u/kabong, and I decided to answer these questions with community self-experiment.
Below, I give more details on the background literature and pre-register our protocol and analyses.
It would significantly improve the study to have a larger number of participants. If you’re interested in collaborating on this or other scientifically rigorous self-experiments with low-carb foods, supplements, or other health interventions, please let me know in the comments or via the contact form on the right.
Details
Purpose
To replicate (or fail to replicate) the existing literature and quantify the effect of vinegar on blood glucose level after consumption of complex carbohydrates.
To better understand the underlying mechanism by determining how this effect varies with person/metabolic status, dose, source of calories, and type of acid.
Figure 1. Forest plot showing individual and pooled random effect standard mean difference (95% CI) of trials testing the effect of vinegar on glucose area under the curve. Test of overall effect: z = 2.42, p = 0.01.Figure 2. Forest plot showing individual and pooled random effect standard mean difference (95% CI) of trials testing the effect of vinegar on insulin area under the curve. Test of overall effect: z = 3.73, p < 0.001.
All together this is decent evidence for the acid as inhibitor of alpha-amylase as mechanism hypothesis
One of the biggest challenges in the vinegar/acid literature is that all of the experiments were done with different meals, protocols, and doses, making it difficult to integrate data from multiple studies. To address this issue and answer some of the open questions about this effect, /u/genetastic, /u/kabong, and I decided to do a series of community self-experiments.
While we each have different motivations and interests, overall, the questions we’re looking to answer are:
Is the effect large enough to matter for practical meals?
What types of meals does vinegar affect?
What is the best protocol to get a large effect without unpleasant side effects?
What’s the underlying mechanism?
Is the effect specific to vinegar or do other acids work?
To answer these questions, we will be conducting experiments using the protocol below.
Methods
Materials
Meals:
white bread (starch)
dried dates (simple sugars)
tortilla with beans, salsa, & avocado (starch, fat, and protein)
Vinegar:
Apple cider or white vinegar
As large a quantity as comfortable, not to exceed 30g
Diluted in as little water as tolerable
Blinding
Vinegar supplementation will not be blinded
However, the protocol was established in advance and adhered to without modification once experiments started.
Procedure
Each participant is using a slightly different procedure
