There are many foods that heal the gut. Foods high in fiber, in particular, are often recommended for their ability to build a healthy microbiome.
Fiber acts as food for beneficial bacteria in the gut, which increases their presence. These beneficial critters ferment fiber in to beneficial metabolites called short chain fatty acids(SCFAs) that promote gut health.
But on the flipside, sometimes people with SIBO & IBS experience severe gas and bloating when eating these foods. Consequently, they adopt a lower fiber diet, such as the low FODMAP diet, in an effort to reduce these symptoms.
While this generally leads to a decrease in gas and bloating, it can have bad effects in the long term. It may lead to erosion of the mucus layer, dysbiosis, and intolerance to the foods they avoid.
Unfortunately, many of the foods they avoid have other components that promote gut health, and even healthy aging. So while a low fiber diet may help manage symptoms in the short term, in the long term it may impair gut health.
One nutrient found predominantly in foods restricted in essentially all low fiber diets is the polyamine spermidine. While we make spermidine, our ability to do so decreases with age. And tissues with high turnover generally require more spermidine.
A new paper indicates that consuming spermidine in our diet plays a role in preventing leaky gut and maintaining metabolic health. In today’s blog we’ll discuss what spermidine does in the gut and where we get it in our diet.
What is spermidine?
Spermidine is somewhat of a rock star in longevity research. Most people may have heard of it as an inducer of autophagy: The process through which we recycle unused or damaged proteins. But it has many more functions in the human body.
Spermidine belongs to a group of molecules known as polyamines, along with the related molecule spermine. We convert the diamine putrescine into spermidine. In turn, spermidine acts as a precursor to spermine.
In addition to the induction of autophagy, spermidine also suppresses inflammation and increases nitric oxide. Spermidine also plays a role in circadian rhythms, while circadian rhythms regulate spermidine production.
In mice, aging causes a decline in spermidine. This leads to a longer circadian period reversed with spermidine supplementation. This may drive age-related circadian disruption.
Spermidine production also declines with age in humans. Furthermore, increased intake of foods high in spermidine is associated with reduced risk for all cause mortality, cardiovascular disease and Cancer in particular.
For the most part, autophagy appears to be the primary way in which spermidine increases lifespan, though it may help in other ways. Interestingly, a new paper indicates this may be through strengthening the intestinal barrier.
Spermidine: Decreased in human obesity, reverses leaky gut in mice
Our gut becomes leakier with age, and spermidine has been shown to improve aging in animal models. So, researchers decided to see if there is a relationship in humans between obesity and insulin sensitivity with spermidine intake.
They found a relationship, and decided to dig a little deeper. They found that spermidine supplementation in mice reduced body fat and improved insulin sensitivity. It did this by altering the microbiome and reducing leaky gut.
Overall, spermidine accumulated in the gut with very little systemic absorption. It caused an increase in tight junction proteins, increased mucus production, and upregulated autophagy.
The result: A stronger gut barrier, thicker mucus layer, decreased gut inflammation, and altered microbiome that was essential for the effects of spermidine.
So, science is cool and all…But you’re probably wondering: Which foods are high in spermidine?
Foods that heal the gut=Foods that damage the gut???
Remember above where we discussed how restriction diets can lead to bigger problems down the road? And we kinda sorta focused on diets that restrict fibrous vegetables? Well, there is a method to that madness.
First off, meat has little to no spermidine, it actually has more spermine. Furthermore, most ways meat is cooked such as roasting and pan-frying, reduces spermidine by 40-60%.
Though not studied in many animal organs, sheep and lamb liver only contain ~15mg/kg, pre-cooking, with chicken liver having ~48mg/kg. The only foods of animal origin that contain a significant amount of spermidine are cheeses, particularly bleu cheese and aged cheddar with 199 mg/kg.
Plants are a different story: they’re loaded with spermidine. And the plants with the most spermidine are the ones that most people restrict.
Soy contains 207mg/kg while fermented soy products generally contain more since fermentation increases polyamine content. Wheat germ contains a whopping 353mg/kg of spermidine, the greatest source of spermidine by weight by far.
Mushrooms(89 mg/kg), rice bran(50mg/kg) and green peas(46mg/kg) are also moderately high in spermidine. Essentially, grains, legumes and dairy are the primary sources of spermidine in our diet.
So are they foods that heal the gut or foods that damage the gut?
So how can these foods be good for the gut and bad for the gut at the same time? Well, the truth is, foods have both good and bad components in them.
While a food may contain something that’s bad for you, it may have several things that are good for you at the same time. This is why it’s important not to vilify or elevate foods based on the presence of a single or small number of things they contain.
You want to look at the big picture. Rather than looking for things that may look bad mechanistically, you want to look at what happens when people consume these foods.
You also want to look at the dose response: What happens to people who eat a lot of said food vs people who eat none or little of it. This is the purpose of epidemiological research, to find global patterns in the consumption of foods.
This is why it’s hard to take the claims that plant foods are bad because they have toxic components such as oxalates or lectins in them seriously. Most epidemiological research shows decreased mortality with higher plant food consumption.
If they were toxic, increasing doses would increase mortality, but we actually see the opposite in the population. Even if you assume the healthy user bias, that healthy people eat those foods because they’re recommended, you still shouldn’t see better outcomes if these foods are toxic.
And what percentage of the population do you think is healthy? It’s certainly not most, given that less than 12% of Americans have optimal metabolic health.
Keep in mind, just because a food is fine for the general population doesn’t necessarily mean it’s right for you. We are all different, and some of us may not do well with certain foods.
And there may be circumstances where you need to restrict otherwise healthy foods to manage symptoms, as people who deal with SIBO do with lower fiber diets.Furthermore, if restricting certain foods leads you to optimal metabolic health, that may be the best option for you.
But this doesn’t mean these foods are “bad” per se. Just because a food is bad for you doesn’t mean it’s bad for everyone. It simply means they may not be right for you right now.
And there may be repercussions to avoiding them down the road if you do so unnecessarily.
My experience with the Paleo diet
Truth be told, I do have some experience with restrictive dieting. I’ve done a couple of different types of Keto and followed the Paleo diet for a couple of years.
I started low carb Paleo because I was having some digestive issues, primarily GERD, and was prediabetic despite more than a dozen hours of exercise per week. It worked great, I lost close to 40 lbs, and was no longer prediabetic.
But after a couple of years things started to go South. I started getting different digestive issues(teetering between loose stools and constipation), adrenal issues, and disturbing heart issues along with insomnia.
I noticed a trend where other people actually had issues as well, and they tended to move toward greater restriction. This was not a direction I wanted to go, so I decided to expand my diet rather than restrict it further.
I enjoy things like craft beer and sandwiches, and maybe the odd slice of pizza here or there. But this would not be a regular occurrence if I went stricter, so I expanded my diet.
I wanted nutritional freedom, and the flexibility to enjoy whatever I wanted. It certainly took some time to adjust: Greens and beans were tough in particular.
But now I eat basically anything I want, weigh 5lbs less than I did on Paleo, and my HgA1c floats between 4.7%-4.9%. To be clear, I did a lot of other things:
- Prioritized sleep
- Optimized circadian rhythms
- Stick to 3 meals/day
- Do less exercise, get more physical activity
- Eat foods I never really ate before(Fermented soy, kefir, and beans)
Overall, I’m extremely happy with the direction I decided to go and feel as though I’m flourishing as a result.
Foods that heal the gut for you!
So what should you do to build rock-solid gut health? Should you eat a high fiber diet? Or perhaps Keto or Carnivore? Or maybe you should go Paleo like I did.
To be clear, there are a lot of things to consider for gut health that aren’t diet-related. For a strong gut, you need to address all the things I addressed above, particularly circadian rhythms as they regulate gut function.
When choosing a diet, one of the most important factors to determine if it’s right for you is if it allows you to maintain a healthy weight. If eating a standard omnivorous diet causes you to be overweight, but you lose weight on Keto or Carnivore, I’d go with the latter.
You also have to consider social factors. Diets low in fiber, as Keto and Carnivore are, may decrease the thickness of the mucus layer in the colon. Note: Recent evidence indicates that there may be long term adaptations to these diets that may prevent this effect. There is certainly a bias in the microbiome research towards higher fiber diets that future studies should address.
By decreasing the amount of fiber available to microbes in the colon, they direct our microbes to consume our mucus layer. It also decreases mucus production due to lower SCFA production.
If you plan on regularly drinking alcohol, I don’t believe this is a good thing. The mucus layer separates bacteria from the cells lining our gut, and alcohol increases pathogenic bacteria in the gut. But this is manageable if you go Keto and include fiber.
Any diet can be good or bad for your gut depending on the specific contents of the diet. For me, Paleo didn’t work because I relied too heavily on things made with nut flours and nut butters.
I also consumed alcohol, but feel my diet was too fat and protein heavy to allow for occasional alcohol intake. My current diet is essentially Mediterranean, but I don’t restrict anything. It’s high carb(>300g/day), high fiber, moderate protein, and moderate fat.
At 44 years of age, I do try to consume foods higher in spermidine to maintain a healthy circadian rhythm and promote healthy aging. All the biomarkers I assess(Stool color/quality, A1c, sleep, HRV, and CMP data) are as good as they’ve ever been. Plus, subjectively, I feel excellent.
Foods that heal the gut differ from person to person. The diet that’s best for you ultimately depends on your specific needs and goals.
People generally look for simple concepts when developing a diet, and many people pushing specific diets don’t take this into consideration. Any dietary paradigm can be used improperly and lead to a diet that is bad for the gut.
In my experience, the low carb Paleo diet didn’t work for me. But, truthfully, I developed a bad Paleo diet. It served me early on and helped normalize by weight and blood sugar, but down the road it caught up to me.
So I moved on, realizing it didn’t serve my specific needs. I like carbs, and I like beer in moderation. My primary motivation with Paleo was to improve my blood sugar and get rid of GERD.
I accomplished these goals and was able to transition to a diet without restriction. As a general recommendation, a more diverse diet is best for the gut long term.
It builds stability and resilience, but may not be suitable to people in the healing stage. Thus, the foods that heal the gut for you depend on where you are, and where you want to go.