If you are a Type 1 diabetic then you will know the truth is there is a myriad of things which can affect your blood sugars and they are inherently unpredictable. It reminds me a little of the stock market. It is impossible to predict what the final price of a stock will be on a given day but you can predict the trend over time. Anyone that tells you differently is, most likely, trying to sell you something.
So too with with blood glucose. It is very hard to accurately predict your body’s reaction to the various forces acting on your blood on a given day but, over time, you can get an idea of the trends and general principles. Anyone that tells you otherwise is probably selling a book or supplements.
The upshot of this is that you should never beat yourself up for having a bad day with your blood sugar. Focus on the game and not a given play. Let measures such as your HbA1c, percentage in range, and the standard deviation be your guide more than a moment in time on your glucometer.
Knowing how different forces act on your blood glucose can help you manage these long term trends so here are some of the big influences on your blood sugar. As usual, there is a tl;dr summary at the end for the time deprived.
Clearly one of the biggest forces on blood glucose are carbohydrates. We can divide carbohydrates into three categories for this discussion:
- Fast Acting: Sugars/Simple Carbohydrates/High Glycemic Index (GI) Foods
- Slow Acting: Starches/Complex Carbohydrates/Low GI Foods
- No Acting: Inedible Carbohydrates/Fiber
Fast acting carbohydrates will spike the blood and make it very difficult to manage. If you take insulin you will need to try and match the insulin activity with the blood sugar spike. Get this wrong and your blood sugar starts roller-coasting. For the diabetics who can still produce their own insulin, fast acting sugars in sufficient quantities can overwhelm your pancreas and spike your blood.
Slower acting carbohydrates still need to be covered by insulin but the slower rise can make it easier to manage. The slower rise also means those with an impaired pancreas may be able to produce enough insulin to stop them spiking too high.
Fiber, by definition, is not broken down by the body so it is physically impossible for it to directly affect blood sugars. This being said, there are insulin dependent diabetics who factor fiber in their calculations. My guess is because, in certain countries like the USA, food labeling puts fiber in with the rest of the carbohydrates so it simply makes things easier to calculate a ratio including the fiber, even if it makes no metabolic sense.
Indirectly, fiber (especially soluble fiber) does have an effect on blood sugar in slowing down the absorption of digestible carbohydrates and widening the glucose response curve.
There is no direct metabolic path to convert digested fat into glucose so eating fat will not raise your blood sugars. However, like fiber, it will slow down the absorption of carbohydrates. Also, digested fats readily enter the bloodstream, temporarily increasing insulin resistance. This leads to some people concluding it raises blood sugar when the reality is their insulin is simply not as effective.
As an example, let us consider a slice of toast with 15g of carbohydrates. While this may normally require ‘x’ units of insulin to be covered, if it is eaten with avocado on top, which is 15% fat, this may raise insulin resistance and the normal amount of insulin will be insufficient, leading to a spike. It is not the fat turning to glucose which causes this spike, it is the temporary increase in insulin resistance. Also the insulin resistance may influence the effectiveness of a Type 1’s basal insulin leading to increased glucose output by the liver.
Finally, given fats have an effect on how the body processes carbohydrates, it does not take much to realise the order in which we eat foods will have an effect on how they affect our blood glucose; if we eat the fattier foods on our plate first, this will slow absorption of the carbohydrates whereas eating the carbohydrates first means they are initially unhindered in entering the bloodstream.
Usually proteins will not significantly affect your glucose as the body does not convert a lot of protein to glucose but, for someone eating a low carbohydrate diet, the body ramps up a metabolic process called gluconeogenesis which is the one which converts protein to glucose. There is no hard rule for bolusing for proteins under these circumstances but some find success by finding a ‘protein ratio’ similar to their insulin to carbohydrate ratio.
This is a bottle of almost pure alcohol (95% alcohol by volume, I use it to make sugar-free liqueurs). Like fats, alcohol does not convert directly to glucose so, in principle, it will not affect blood sugar. However, also like fats, this is not the full story.
Alcohol is seen as a poison in the body so the liver will drop everything to remove it from the blood. This includes releasing glucose into the blood which, usually, the liver does constantly and is the reason Type 1 diabetics use a long acting insulin to keep their liver from releasing too much glucose (basal insulin).
So, in theory, alcohol will lead to a drop in blood glucose but no one drinks pure alcohol. Liqueurs usually contain sugar syrup (sugar dissolved in water) and the fermentation process demands the use of sugars to feed the yeast and residual sugars often end up in the final product.
So alcoholic drinks are a mixed bag. The alcohol has the potential to lower blood sugar but the things it is mixed with may raise blood sugars. This makes alcoholic drinks quite dangerous for Type 1s in large quantities because the effects are inherently unpredictable.
In the short term, aerobic exercise will lower blood glucose as the body makes use of it to run muscles. Moreover, it is believed that the glucose enters the muscles through pathways opened up by exercise which do not require insulin. Short term anaerobic exercise (more strenuous exercise) can raise blood sugar as the liver releases glucose into the blood to help feed the muscles.
Also, the effects of exercise on the blood can continue well after exercise has stopped so monitoring of blood glucose is very important.
In the long term, exercise can reduce fat stores in the body, lowering insulin resistance, as well as increasing muscle mass to store glucose.
The human body is a complex interplay of hormones so when one increases or decreases, this has an effect on others. Insulin is no exception. For diabetics going through puberty this is a minefield. For women, their monthly cycle can also cause insulin resistance to fluctuate, throwing out insulin ratios and interfering with blood glucose management.
Stress and Illness
Given both stress and illness affect hormones in the body, it is unsurprising that they affect blood sugar levels. Try to avoid unnecessary stress and carefully check blood glucose levels during illness. Strategies which work to reduce stress hormones and lower blood glucose for some include meditation and massage.
The act of going to sleep can affect your blood sugar or, more accurately, the act of the waking up. Dawn phenomenon is an increase in blood sugar (probably) due to the shifts in hormones as someone moves from sleep to being awake. There is not a huge amount that can be done about the dawn phenomenon but, if it is causing blood glucose to be consistently high in the mornings at a level to potentially cause long damage to the body, it may be worth discussing, with your health care team, changing your basal insulin routine.
Medications can affect blood sugars with a common complaint coming from the injection or ingestion of steroids for medical treatment. Steroids tend to spike the blood, especially if injected. If you are taking a new medication, it makes sense to ask your health care team how it may affect your blood sugar and insulin resistance.
Strategies For Management
As you can see above, there are a range of factors which can affect blood glucose levels. For this reason, an approach which primarily relies on looking at food, such as Dr Bernstein and Forks Over Knives, may well work for some but has no guarantee of working for everyone.
In my opinion, a better approach is to adjust insulin, rather than trying to adjust everything else. Looping (the linking of a continuous glucose monitor and an insulin pump for automatic blood glucose management) and books like Sugar Surfing or Think Like a Pancreas adopt this approach.
This being said, diet moderation still has a place. Modern insulins have their limitations so it make sense to be careful not to test those limitations with a diet filled with fast-acting carbohydrates.
A healthy human body does a remarkable job of keeping blood sugars in check. For those of us with impaired or non-existent insulin production replicating this job can be very hard. With so many factors affecting blood sugar levels, it is impossible to have perfect management every day. Therefore, it is better to manage glucose levels for the long term, rather than fixating on how your levels are on a given day.
Some of the factors affecting blood glucose are:
- Fast and slow acting carbohydrates: Increase blood glucose
- Fiber: No direct effect on glucose levels but can slow the absorption of digestible carbohydrates, stretching out the blood glucose response curve
- Fats: No direct effect on glucose levels but they can temporarily increase insulin resistance leading to increased liver glucose production, and a spike in blood glucose in response to food as the on board insulin proves to be not as effective as it otherwise would be. In contrast, like fiber, fats can slow the digestion of glucose, widening the response curve.
- Proteins: No direct effect unless the person is not eating enough carbohydrate for their body’s needs. In this case, the body uses gluconeogenesis to directly convert proteins to glucose, raising blood glucose levels
- Alcohol: While pure alcohol has the potential to lower glucose, not many people drink pure alcohol. Many people drink either a fermented drink like beer which has sugar as an integral part of the process or they drink liqueurs which are a combination of alcohol, sugar syrup and flavoring. Therefore, depending on the alcoholic drink at hand, it can raise or lower blood glucose levels
- Exercise: Gentle (aerobic) exercise usually lowers blood glucose while more strenuous (anaerobic) exercise can raise blood glucose levels. In the long term exercise can be beneficial in reducing insulin resistance and increasing muscle mass, used for glucose storage.
- Hormones: Different hormones of the body can also affect insulin resistance and, therefore, blood glucose levels. This is especially problematic for diabetics going through puberty and for women who are menstruating
- Stress, Illness, and the Dawn Phenomenon: As all of these affect the body’s hormones, it is no surprise they also affect blood glucose levels
- Medications: These can affect the body and blood glucose levels. If you are unsure if a specific medication will affect you, talk to your health care team
There are a range of factors which can influence blood glucose levels and, often, in unpredictable ways. While some advocate for strictly controlling major factors, such as food, others advocate adjusting insulin to accommodate all of these influencing factors. Every person is different so it will be a case of taking the elements from both approaches which work for you.
Thank you for an extremely informative article, useful for young and older T1’s especially..
Another T1 on JDRF 25+ announced your article, and if this is typical content quality, as a very long-term T1, I wish to read more of your helpful articles., thanks very much.