Digestive health is a hot topic these days. Problems in the gut not only play a large part in digestive issues like irritable bowel syndrome or reflux, but the gut has an effect on practically every part of our body.
Imbalances in the gut can create rashes, exacerbate joint pain and even cause depression – it’s no wonder we all want to learn how to keep the gut healthy!
One of the most pressing concerns regarding the gut is something called intestinal permeability, often referred to as “leaky gut”. The barrier of the gut plays an important role in maintaining our health by protecting us from the many things we’re exposed to from the outside world. If you think about it, our digestive tract is technically not “in” our body, it’s outside.
Think about your body as a donut and the digestive tract is the donut hole – technically, not “in” the donut. It’s easy to see now that our gut lining is exposed to everything we swallow – food particles, bacteria, dust, etc – and has to decide what to do with all that material! Think of the gut barrier as the decision-maker: some particles are allowed to pass through, while others are told to move on through.
When functioning normally, the gut barrier keeps us healthy by keeping out potentially hazardous materials and letting nutrients and water in. But when it starts to become more permeable (or “leaky”) than normal, we run into problems.
Of course one of the most important things for preventing excessive intestinal permeability is to eat a Paleo diet that works for you (a la Your Personal Paleo Code; The Paleo Cure in paperback). However, there are definitely other nutritional components that can help, quercetin being one of them!
Mast Cells = Leaky Gut?
Researchers have discovered that mast cells play a part in developing leaky gut. While it’s been known for a long time that severe physical stress (i.e. trauma or surgery) causes intestinal permeability, newer research has shown that chronic stress also has this effect. (1) Interestingly, researchers determined that it is the mast cells in the intestine that are responsible for the increase intestinal permeability in these stressful situations. (2)
You may have heard of mast cells before as the cells responsible for allergy symptoms like congestion, runny nose, etc. This is because when mast cells “degranulate” or become “unstabilized”, they release histamine, the chemical that causes allergy symptoms. But you have mast cells in your gut, too and when they “degranulate” or become “unstabilized” there, they cause leaky gut.
Quercetin for Leaky Gut
Quercetin is one of the most abundant flavonoids present in our food supply, found in high amounts in onions, kale and apples. (3) It is well-known for many things, including its anti-allergy properties, anti-cancer effects, and as an antioxidant. But did you know that it can heal leaky gut, too?
Given that intestinal permeability is caused (at least in part) by unstabilized mast cells in the gut, it makes sense that quercetin would have this effect. This is because quercetin stabilizes mast cells and prevents the release of histamine and other chemicals from these cells. (4) When researchers breed rats to have no mast cells in the gut (thus they are unable to have unstabilized mast cells that release histamine), they no longer develop intestinal permeability. (5)
Quercetin has also been shown to enhance gut barrier function by having a “sealing” effect due to its role in the assembly and expression of tight junction proteins. (6) Tight junctions regulate our intestinal permeability by connecting intestinal cells, thus only allowing the nutrients that we need in and keeping everything else out.
In rats given DSS (a substance that causes colon damage), treatment with quercetin restores barrier integrity and partially heals colitis. (7) Rats given another substance to cause colitis and treated with quercetin preserved normal fluid absorption (which is altered by colitis), counteracted glutathione (our “master antioxidant”) depletion and ameliorated colonic damage at two days. (8)
I’d say that’s some pretty good news for those suffering from leaky gut!
Quercetin in the Diet
Now that we know quercetin is healing substance for a leaky gut, how do we get enough?
Well, the good news is that on a Paleo diet, you should be getting quercetin by eating your fruits and vegetables. Remember that a Paleo diet can, and for most people, should be a diet high in fruits and vegetables, which naturally contain quercetin. But if you’d like to add some extra quercetin to your diet (or you can’t tolerate many fruits and vegetables), a quercetin supplement is also an option.
There is limited data regarding the amount of quercetin in our food, but below are the estimates available. (9) Your best bet is to just eat a wide variety and a lot of plant matter for optimal intake and consider supplementation if needed.
- Fruits: 2 – 250 mg/kg
- Vegetables: 0 – 100 mg/kg (onions are especially high at 200 – 600 mg/kg)
- Tea: 10 – 25 mg/L
- Fruit juice: 2 – 23 mg/L
- Red wine: 4 – 16 mg/L
It’s also important to note that other flavonoids such as naringinen seem to have similar healing effects on leaky gut, so including a wide variety of plant matter to increase your intake of many different polyphenols is a great idea. (10) Not to mention that polyphenols improve your gut bacteria, too!
Here’s the take-home message: eat your fruits and veggies for your daily dose of quercetin, or consider a supplement if you can’t tolerate much plant matter or if you’ve got a severely leaky gut. If you’d like to go the supplement route, aim for 800 mg twice a day or 400 mg three times a day for a total of 1,200 – 1600 mg per day. It’s very difficult to get these levels from food, so a supplement is a good choice.
Now I’d like to hear from you. What do you think about quercetin as a gut-healing nutrient? How do you make sure to get enough fruits and vegetables in your diet? Share your thoughts in the comments!
This is a guest post written by Kelsey Marksteiner, RD. Kelsey is a Registered Dietitian with a Bachelors degree in Nutrition from NYU and a Master’s in Human Nutrition and Functional Medicine. She works in private practice and recommends individualized dietary therapy focusing on biologically appropriate diet principles to aid her clients in losing weight, gaining energy, and pursuing continued health. She is a firm believer that everyone is different, and she tailors her plan for each and every individual. Through her work, she aims to meld the dietary wisdom of traditional cultures with the latest science in integrative and functional medicine to create plans for her clients that work in the modern world. You can learn more about Kelsey on her staff bio page, or by visiting her private practice website. Join her newsletter here!