One of the reasons I decided to switch from the Slow Carb Diet that I followed since the beginning of 2011 to nutritional ketosis was because I had a blood test that showed my HbA1c level to be 5.7% which placed me at an “increased risk for diabetes.”
- < 5.7% is normal
- 5.7% to 6.4% means you have a higher risk of diabetes
- > 6.4% means you HAVE diabetes
I was surprised by having such a high HbA1c, especially since the main idea behind the Slow Carb Diet was to maintain glycemic control to decrease the amount of insulin fluctuations with the exception of one cheat day. Since I was strictly adherent to the diet, the only possible explanation that I could come up with was that my cheat days exposed me to so much glucose, that it actually raised my HbA1c, placing me at increased risk for diabetes. I chose my diet so that I could lose weight AND be healthier… but if it placed me at increased risk for diabetes, then the whole thing was pointless.
So when I came across the idea of nutritional ketosis which espouses even stricter control of glucose and subsequently insulin release WITHOUT the benefit of cheat days, I was ready to jump on the bandwagon.
Before I go forward, I should explain what HbA1c actually is and to do that I have to go into some basic biology.
- Everyday your body makes new red blood cells (RBCs) and breaks down old RBCS at an equal rate so you have a constant number of RBCs (assuming you are healthy).
- The lifespan of a RBC is somewhere between 100 – 120 days.
- The main function of the RBC is to bring oxygen to your body by using an oxygen carrying protein called hemoglobin
- When your RBCs are exposed to glucose, some of this glucose sticks onto the hemoglobin protein forming a sugar-hemoglobin
- The more glucose there is, the more hemoglobin proteins it sticks to, forming more sugar-hemoglobins
- Also, the longer your RBC is alive, the more it is exposed to glucose, hence it will have more sugar-hemoglobins
- The HbA1c test measures the average percentage of sugar-hemoglobins of ALL the RBCs in your body, giving you an idea of how much sugar they’ve been exposed to in the past 90ish days.
- So if you are diabetic, and your blood sugar is high all the time, you will have more sugar-hemoglobins, and thus a higher HbA1c.
- This is an important tool that doctors use to track diabetics because even though they can have a normal blood sugar measurement (which is a snapshot in time), if their HbA1c is high, it tells the doctor that their blood sugar has been poorly controlled on average in the past 3 months.
- HbA1c is a function of your blood glucose level and how long your red blood cells live. If this were put into an equation it would look something like this:
- HbA1c ~ (RBC lifespan) x (avg blood glucose concentration)
So now that I’ve gotten all of that out of the way and bored you death I can go into what my HbA1c was after 72 days of nutritional ketosis.
- Before starting nutritional ketosis my HbA1c was 5.7% which equates to an average blood glucose of 117 mg/dL (according to this calculator)
- My average fasting AM blood glucose during 72 days of nutritional ketosis was 83.8 mg/dL which equates to an expected HbA1c of 4.5% (according to this calculator).
- My HbA1c after 72 days of nutritional ketosis was 5.7%!!!!
When I saw that I was like WTF!!!!!!!! WHY DIDN’T IT GO DOWN!?!?!
Possible explanations that crossed my mind were:
- Maybe there was a lab error
- Maybe my glucose is actually bouncing around a lot higher than it is when I measure it in the morning
- Maybe I’m still eating too much protein leading to increased gluconeogenesis
- Maybe I’m eating more carbs than I think, since I know that food labels can be way off
- Maybe there’s something else going on with me (like a glucagonoma) causing me to have a higher glucose throughout the day even though I was eating very low carb and having a normal fasting AM level
I couldn’t believe that I was still at “increased risk of diabetes” despite being in prolonged ketosis confirmed with blood ketone measurements! It didn’t make any sense at all! If I was exposed to enough glucose to average 117 mg/dL, that means that I was also exposed to a lot of insulin which would then prevent me from reaching ketosis! These are two mutually exclusive things! HOW CAN THIS BE?!?!?!?
So I did what any rational person would do. I went to google and found out that there were a few people out there who ate low carb with the same issue which you can see here and here, which made me feel better since I wasn’t the only person in the world to experience this.
Then I came across this article which offered the best explanation and helped me put 2 and 2 together. He basically said that HbA1c can be an unreliable test because “there is actually a wide variation in how long red blood cells survive in different people.” I actually found evidence in the scientific literature to support this, where they observed that there is a wide variation in RBC lifespans in normal people that actually can have a clinically significant impact on their HbA1cs. Then there’s this paper showing that RBCs die faster when they are exposed to more glucose, which can also be interpreted as RBCs live longer when they are exposed to less glucose.
In my case, this all started to make sense, particularly when taking into account the HbA1c equation above:
HbA1c ~ (RBC lifespan) x (avg blood glucose concentration)
Since my HbA1c was high and I know from my measurements that my blood glucose concentration was normal if not on the low end, that means the reason for my elevated HbA1c must be that my RBCs are living longer.
Whew… what a sigh of relief. My low carb diet and subsequent low blood sugars actually help my RBCs to live longer. RBCs that live longer are then exposed to blood glucose for a longer period of time causing me to have a higher HbA1c. My ABNORMAL lab result actually reflects a HEALTHIER change in my body.
The curious thing is, there is virtually no data out there in the scientific literature examining the effects of a low carb or ketogenic diet on HbA1cs.
Inuitively it should look something like this:
- Low Carb -> Lower Blood Glucose -> Lower HbA1c
But from all the data I’ve just presented, it looks like it’s actually more like:
- Low Carb -> Lower Blood Glucose -> Longer RBC lifespan -> Higher HbA1c
This means that all the reference ranges for HbA1c that we are currently using don’t necessarily apply to people who eat low carb or have good glycemic control.
In part 2, I start another n=1 experiment to prove this to my self with actual measurements.