Understanding ALDH2 deficiency is essential if you are someone who gets a flushed red face after you consume alcohol. This will not only help you drink more comfortably but also help you avoid serious health risks specific to people with this condition.
What is ALDH2 deficiency?
ALDH2 deficiency refers to a deficiency in a detoxifying enzyme that makes it harder for the liver to break down some toxins that enter the body.
The typical human liver contains two major aldehyde dehydrogenase enzymes, a cytosolic ALDH1 component, and a mitochondrial ALDH2 component. Many people, notably about 30% to 40% of East Asian Orientals, have only the ALDH1 enzyme and are deficient in the ALDH2 enzyme.
Being deficient in the ALDH2 enzyme means that your body is less able to safely deal with a particular set of toxins that can enter from the external environment.
One example is the toxin acetaldehyde that enters our body when we consume alcohol. The ALDH2 enzyme is responsible for detoxifying acetaldehyde, so if you're ALDH2 deficient your body will undergo acetaldehyde toxicity whenever you drink alcohol.
This is commonly referred to as alcohol flush reaction or Asian flush (because of the large proportion of Asian people affected).
What causes ALDH2 deficiency?
ALDH2 deficiency is a genetic condition thought to be originally caused by the emergence of rice cultivation in Asia between 7,000 to 10,000 years ago.
A mutation in the ALDH2 gene is thought to be the cause, in that it encodes a form of the aldehyde dehydrogenase 2 protein that is very bad at metabolising environmental toxins like acetaldehyde from alcohol.
A team of researchers headed by Bing Su, a geneticist at the Kunming Institute of Zoology, conducted a study to identify the source of this genetic ALDH2 deficiency.
The team searched for ALDH2 deficiency in 2,275 people across China representing 38 different ethnic groups. They reported that 99% of the people in the southeast region of China had ALDH2 deficiency, with less prevalence seen in western China and Tibet.
Notably, the team found a strong geographical correlation between regions with a high prevalence of ALDH2 deficiency and archaeological sites in China where rice had been domestically cultivated thousands of years ago. The geographical correlation suggests the potential of a culture-wide dietary catalyst for the gene mutation that causes ALDH2 deficiency.
What are the symptoms of ALDH2 deficiency?
The symptoms of ALDH2 deficiency can vary depending on the one's sensitivity to the environmental toxin not being broken down.
In the case of alcohol, the specific toxin not being broken down in ALDH2 deficient individuals is acetaldehyde.
When acetaldehyde enters the body it provokes a histamine release that can cause any of the following short-term symptoms:
- Erythema - redness of the skin caused by increased blood flow to superficial capillaries in the face, neck and upper body.
- Tachycardia - a heart rate that exceeds the normal resting rate.
- Nausea - uneasy feeling in the upper stomach with an urge to vomit.
- Headache - pain in the head often throbbing or pulsing.
This normally occurs 20 to 30 minutes after consuming a sufficient quantity of alcohol and can take up to 2 to 3 hours to subside depending on the individual.
Longer term effects of consistent acetaldehyde exposure include an increased risk of various types of cancers of the esophagus and upper digestive tract.
For more information about common long-term risks facing people with ALDH2 deficiency check out our article titled: Debunking The Asian Flush Cancer Risk.
Is it possible to test your DNA for ALDH2 deficiency?
The easiest way to test for ALDH2 deficiency is to check if you suffer from the symptoms mentioned above. After receiving a few emails from customers (and also for people who are not yet of drinking age or for those who don't drink alcohol at all but still want to know if they have a gene deficiency), we looked into more definitive methods of checking for mutations in peoples genes.
23andMe is a DNA analysis service providing information and tools for individuals to learn about and explore their DNA.
Quite simply, you send in a saliva sample and they run a full genome analysis on you, uploading the results online. The test results are (of course!) fascinating, as you will no-doubt found out new things about yourself, and your ancestry that you did not know before. For the purpose of testing for ALDH2 deficiency, however, we are mostly interested in the part of the report that addresses the ALDH2 gene and alcohol flush reactions.
View a sample of the ALDH2 gene report section here, or sign up via their website to get a full DNA check (we are not affiliated with 23andMe, and there are other gene testing services out there like those shown on genetests.org, but they seem more complex, expensive and hard to understand for us to fully recommend them).
Is there a treatment for ALDH2 deficiency?
Preliminary research into treating the enzyme issue is ongoing. To date, the most effective treatment for ALDH2 deficiency is detoxification assistance.
Researchers at Stanford University conducted a study that found that a small molecule called alda-89 could increase the ALDH2 enzyme function in ALDH2 deficient mice. It does this by causing other enzymes to mimic the function of the broken ALDH2 enzyme. Unfortunately, alda-89 is not safe for human consumption due to its toxicity, but researchers at Standford are hopeful of finding a safer molecule that performs the same function.
Another molecule that has garnered the attention of researchers is ALDA-1. ALDA-1 has been shown in studies to modulate the kinetic properties of the ALDH2 enzyme and increase its function dramatically. Although not thoroughly tested for safety in human subjects, research is ongoing to determine the therapeutic benefit of alda-1 in treating ALDH2 deficiency.
Saadeh Suleiman of the Bristol Heart Institute, comments that the research is initially exciting but also cautions that human ALDH2 might not be as easy to work with as it is in rats.
So what is the cure?
To date, the best way to treat ALDH2 deficiency has been to address the toxicity issue rather than the enzyme deficiency. This method will vary depending on the particular toxin not being broken down in ALDH2 deficient individuals.
As mentioned above, in the case of alcohol the toxin in question is acetaldehyde. Research has shown that precise supplementation of a combination of compounds can reduce acetaldehyde toxicity and aid the deficient ALDH2 enzyme in metabolizing alcohol — treating the symptoms immediately, rather than preventing them completely.
To find out more check out our article titled: The Science of an Alcohol Red Face and How to Cure it.