The number one food that causes most canker sores and how simple avoidance is all that is needed for most people to banish them for good! 
Chances are, you’ve suffered from a canker sore or two in your life. These painful, open ulcers on the inside of your lips, cheeks, or even your tongue seem to take forever to heal and can really cause some grief!
One young man I know in our community suffers excessively from canker sores. His frequent outbreaks are so bad that ulcers often occur not only in his mouth but also down into his throat. This causes severe pain even when swallowing sips of water.
Canker sores should not be confused with cold sores on your lips or nose that are caused by a virus and are contagious. This cold sore remedy works great for that type of skin issue.
Unlike cold sores, canker sores are not contagious. In most cases, they are the direct result of what you eat.
Even if a canker sore seems to be triggered by something else, like a scrape from a dental appliance like braces or accidentally biting your tongue, the underlying cause is still diet. In other words, the mouth inflammation was already present such that the wound that occurred in the mouth resulted in a canker sore!
That’s right! What you eat GREATLY affects whether or not you suffer from mouth ulcers on a regular or infrequent basis.
The Number One Food That Causes Canker Sores
Guess what frankenfood is the primary cause of canker sores in the Western diet?
That culprit would be high fructose corn syrup or HFCS. Manufacturers sometimes list it as corn sugar on some food labels.
High fructose corn syrup promotes inflammation in the body, which in turn impairs the immune system. An impaired immune system is thought to be the underlying cause of canker sores.
A person on a typical diet of supermarket foods is a prime candidate for frequent mouth ulcers. This is because this stuff is in everything. Plain corn syrup is problematic as well.
This is why eating too much fruit or fruit juice can cause canker sores as well. The sugar in fruit is primarily fructose. Surprisingly, it isn’t the acid in most cases that is causing the problem. Although, acidity may be a contributing factor.
If acid were the primary problem, drinking kombucha tea would also cause canker sores. Most people I know prone to mouth ulcers can drink kombucha regularly without issue.
TOO MUCH FRUCTOSE = CANKER SORES
Even agave nectar, which many consider a health food, contributes to canker sores. The truth is that agave nectar is best avoided. It is highly processed in a manner very similar to HFCS. It is neither healthy nor helpful in any way to the person consuming it. Stay away from it if you want to avoid canker sores!
I used to suffer from canker sores all the time to the point where I had at least one bothering me much of the time.
I haven’t had a canker sore now in over 25 years. Simply cutting out all HFCS from my diet easily accomplished this huge improvement in quality of life! In addition, I watch my intake of regular fructose from other sources like fruit.
If you start checking food labels, you will be shocked. Even commercial peanut butter and ketchup contain it. Simply switching to health food store brands will quickly rid it from your life in most cases.
How Much Fructose is Too Much?
A good idea is to limit your intake of fructose from all sources to no more than 15 grams per day. This is about half the amount of total sugar intake per day that can be tolerated without ill effects.
Dr. Richard Johnson MD in The Sugar Fix describes how important it is to limit your fructose intake for health and weight control.
To give you some idea, in a big, ripe banana, you’d get maybe 10 grams of fructose.
So, if you eliminate HFCS in your diet completely and eat no more than 1-2 pieces of fruit a day, that would be a good way to go.
Be aware also that going over the fructose limit of 15 g per day (25 g at the absolute most) can cause a canker sore very quickly. Sometimes, within a few hours, one or more can appear.
When my kids were younger and attended birthday parties, if they had even ONE Capri Sun juice or a half a can of soda they would invariably have a canker sore within a day or two. I trained them very early to only drink water.
Bottom line is that even if you control your fructose intake 99% of the time, consuming a single food loaded with HFCS can cause one of these baddies very fast.
Imagine what incredible damage a high fructose diet is doing to a person’s insides if it can cause an ulcer in the mouth so quickly!
A
I get canker sores when I eat raw walnuts…
I think you’re onto something, Elaine. I love walnuts, eat them raw as a snack. My diet doesn’t reflect the ingredients mentioned here. But when I bite my cheek, I’m going to get a canker sore. Last time I got one, I had slowed down on the walnuts and the bit lip was sore for a day then never developed into an ulcer.
My daughter and I stayed with a friend for just one week . I didnt want to be rude to her so we ate what she had for us. Lucky charms, soda, cookies and much more by the end of the week my little girl was crying so bad from this pain in her mouth. I took her to the denist and he told me it was an ulcer in her gum. I could not believe it, just one week of eating like my friends do all the time and we eat so healthy? I thought we would be okay eating like that for the week. I learned my lesson and from now on I will go shopping even when staying as a guest. 🙂
Hi Sarah – canker sores are something that I’ve never had a problem with – even when my diet was poor. I have had a few throughout my life, but they have normally been few and far between. But, I totally agree with you that diet causes this problem. My husband used to get them regularly, and he relayed to my son (who also used to get them all the time) that when he ate sugar or grains, they would appear. Of course, in our house we eat very healthy. I have tried to stick to a campaign of not eating grains, and if we do, they are soaked, soured, or fermented. The only bread we keep in our house is normally long-fermented sourdough, and it’s in the freezer because we don’t go through it that fast. We rarely eat cereal, and it’s always soaked overnight or is grainless (a sprouted nut mixture). But I have noticed that each time my son gets a canker sore, it’s been just after he’s had grains or sugar or both (usually somewhere else like with my parents or at a friend’s house). I believe all types of processed foods are probably the cause of this problem and many others, but people need to know this! Thanks for sharing! 🙂
My husband and i suffered from cankers fairly regularly until switching to natural Toms of Maine toothpaste- now its a very rare occurance to get them.
I noticed that canker sores in my case are caused by a lack of probiotics in my system. I will get back on track with yogurt and probiotics and the canker sores go away. Usually it's triggered by stress.
Also, to keep cold sores away you should take L-Lysine. it's a harmless amino acid that you can take in pill form and it is the miracle cure for cold sores. You can also modify your diet to increase lysine in your foods. a web search will reveal foods high in lysine. i'm still trying to personally discover the relationship between lysine, zinc and a few other key items in my diet.
If I so much as look sideways at molasses or sorghum, I get a canker sore instantaneously. I have to check labels for this ingredient. If I begin to develop a canker sore, I buy those "canker covers" $11 for 6 patches from the health food store. Also, I've noticed they heal faster if I eat green vegetables like kale, collards.
Another great post! We have had no canker sores at all since we cut out all sweeteners except for raw honey and real maple syrup, and we eat those in small amounts. We eat organic fruit, but only as a dessert,and in small quantities.
Hi Jane, thanks so much for commenting! Sugar is bad in all forms when consumed to excess. In my experience, however, fructose really enhances inflammation in the form of canker sores much more quickly than plain sugar. For example, if I were to consume a HFCS soda – I would very very likely have a canker sore the next day. Consuming a soda made with plain sugar, however, as in the ones from the healthfood store, would not. Consuming sugar to excess will also give a person a propensity for canker sores, but fructose in excess of 25g a day max does this more quickly due to the differences in how it is metabolized and how it can raise uric levels and inflammation in the body so very rapidly. Hope that makes things more clear.
Are you aware that sugar (whether it’s white sugar, brown sugar, honey or maple syrup) is 50% fructose and 50% glucose.
Ok, so I have been really struggling with recurrent canker sores for quite a while. I have been able to link 2 specific things that have triggered these “outbreaks” 1)Sucralose- I do consume energy drinks regularly, and I’ve recently come to notice that most energy drinks with the exception of regular Red Bull has Sucralose in them, in addition to sugar and/or HFCS and glucose. So I’ve been staying away from Sucralose/Splenda at all costs. 2) I tried Organic Energy drinks (HiBall) that are processed 100% organic with organic Sugar and caffeine, and I was still having outbreaks. I’ve also tried coffee, and I’ve had outbreaks with that when using only sugar and half and half or even just black. So I’ve come to the conclusion that maybe the organic form of caffeine that is used in hiball, which is extracted from coffee beans, could be too acidic for me. If anyone else has any info in regards to this, that would be lovely! Thanks in advance! BTW, I know caffeine is not safe in large amounts, and I fully believe that I use it in fairly moderate amounts considering 1 “Bang” energy drink has more caffeine content than my full daily intake. The caffeine is not something I would willingly eliminate from my diet lest some one pry it from my cold, sleeping, not a morning person hands, and they might be fraught with much opposition?. Thanks!!
Hi Sarah,
So just to be clear, what you are really saying is that consuming too much sugar of any form is not good and that fructose is not necessarily any worse than the double sugars if you eat the same quantity. 15 grams of fructose is equally bad to 15 grams of sucrose? I realize many people eat lots of fruit thinking that they are not eating so much sugar when in reality they are consuming as much or more than if they ate candy instead. Thanks so much for the clarification