Sugar, or sucrose if you want to get fancy, is comprised of both glucose and fructose at the molecular level.
While glucose can be used by every cell in the body for energy, fructose, is only metabolized in the liver.
Those gummy bears you love to binge eat might look cute, but they pack quite the punch when all that sugar makes its way to the liver, arguably the body’s most important organ after the heart.
In fact, the more sugar we eat, the harder it is on the liver, which is why cases of non-alcoholic fatty liver disease (“NAFLD”) in children eating high sugar diets are on the rise.
Of course, fructose isn’t all bad.
Sugar rich sports drinks like Gatorade can replenish glycogen in the liver after extreme athletic events. 1 For example, when you run a marathon, the body relies on all of its stored “carbohydrate fuel,” known as glycogen, to power your muscles. When you’re truly depleted after the race, sending sugar into the liver can be a positive thing. However, for most of us most of the time, sugar is like a torpedo to the liver which causes the storage of fat rather than the glycogen we need for a big day of activity.
One way to estimate liver health is to measure for an enzyme produced by the liver when it’s under stress known as alanine aminotransferase or “ALT.”
When the liver is damaged, it releases more ALT as a cry for help.
Alongside uric acid, ALT is often viewed as a sign of fructose toxicity in the liver.
What are healthy ALT levels?
According to the lab I used to measure my ALT levels, Boston Heart Diagnostics, healthy ALT levels are <40 U/L and the borderline range extends all the way to 120 U/L.
However, in light of new studies associating ALT of over 31 U/L for men and 23 U/L for women with insulin resistance and metabolic syndrome, it seems the targets for ALT should move lower. 2
How I lowered my ALT levels
My normal ALT levels have historically been on the upper end of the healthy range, with an average number sitting around 26 U/L.
However, I have also seen elevated ALT.
Reviewing past labs, I had an outlier number of 48 U/L in September of 2018 (racking my brain as I write this to remember what was going on in September of 2018 which gave me such high ALT levels). One explanation could be strenuous exercise and a subsequent poorly timed blood test, which has been shown to transiently elevate ALT in some healthy people. 3
Unfortunately, I haven’t had ALT measured as frequently as my lipid panels, but I do have some historical data to share below.
Previous lab results:
- 9/30/15 – 16 U/L
- 7/29/16 – 33 U/L
- 2/23/17 – 29 U/L
- 11/1/17 – 26 U/L
- 9/9/18 – 48 U/L
- 4/5/19 – 41 U/L
- 3/17/20 – 20 U/L
The ALT lab value of 41 U/L you see in April of last year came after I did my infamous pizza and mezcal blood draw, so that higher number is easily explained.
The latest value of 20 U/L is interesting to me for two reasons:
- It came after I gave up sugar for 40 days during Lent;
- I also gave up coffee for Lent and;
- I didn’t go low carb
Why is this interesting?
Giving up sugar lowered my ALT
Although there are a number of things that can cause ALT to spike, including liver disease and alcohol abuse, many physicians believe ALT is a marker of fructose induced damage to the liver.
As such, it wasn’t a huge shock that my ALT levels fell to a 5 year low by simply removing sugar from my diet. My insulin resistance lab results have always been excellent, but during the period that this blood draw reported on, specifically Lent, I focused on staying as insulin sensitive as possible. Not only did I exclude all sugar, I exercised with strenuous skiing at high altitude in Jackson Hole, and when I got back to my home gym, made sure to lift heavy weights to move glycogen out of my muscles.
Insulin resistance is associated with high ALT, and studies show low sugar diets reliably bring ALT levels down. 4
Coffee wasn’t keeping my ALT levels low
Regular readers of this blog will know that I have a complicated relationship with coffee. And while we can debate the pros and cons of a morning cup of Joe, one of the commonly cited coffee benefits is promoting liver health.
Every single listacle on the internet discussing ALT will tell you – drink coffee to lower ALT!
Perhaps had I added my usual cup of coffee to my sugar free diet my ALT would have gone even lower, but I was able to achieve some of my best ALT levels without any coffee at all.
Low carb diets and ALT
Studies are mixed on this issue, but a recent meta-analysis showed reduced liver fat content in patients with NAFLD, but no significant reduction in ALT and other liver enzymes when following a low carbohydrate diet (defined by the American Diabetes Association as between 26-45% of total calories from carbohydrate).
In my case, fruit in the form of apples and bananas, as well as potatoes, rice, beans and other complex carbohydrates remained on my menu for the duration of this experiment. I was still able to achieve a healthy ALT level even with the fructose in fruit.
Ketogenic diets and ALT
Is is important to note that some people following a ketogenic diet will see elevated liver enzymes as well, so the Gene Food message of personalized nutrition applies to this conversation as usual. 7 Consider this case study in which a woman saw ALT go from 18 U/L to 119 U/L after going keto. The ALT values returned to 25 U/L eight months after ending keto. The lesson here is that a lower carb diet is not a zero carb diet and going zero carb, say carnivore for example, could have a deleterious effect on ALT levels.
- Elevated ALT levels can be a sign of too much sugar
- Coffee could lower ALT, but in many people the results will be modest
- Sugar free diets may help improve liver health
- Low carbohydrate diets can lower fat in the liver in some people, but taking it too far and going full ketogenic may actually contribute to NAFLD and elevated ALT