You could have the healthiest diet, monitoring carbs, protein, fat, and fiber with precision that rivals the immortal wannabe, Bryan Johnson.
But the benefits of a nutritious diet might only be as useful as the nutrients your body can digest and absorb. And for many people (especially as we age!), it could be harder for our bodies to absorb the essentials—including B12, vitamin D, calcium, and iron—affecting our quality of life and long-term health.
Whether changes in stomach acid and digestion or new medications are to blame, many factors could be a play. Whatever the case may be, the bacteria in your gut are at the center of it all.
How would you describe your digestion?
The gut: The first pass for metabolism (before the official first pass)
Metabolism begins before food ever reaches the liver.
Grant Antoine, a naturopathic doctor and the Translational Science Clinical Lead at Viome Life Sciences, describes the microbiome as the “first metabolic pass” before the liver’s better-known first pass for metabolism.
Researchers at Cornell have even called the microbiome our “second liver,” when results from a study showed that mice without microbes have fewer signs of amino acid absorption (ie, they were not digesting protein well).
Like the liver, the gut helps break down complex food molecules into nutrients our body can use. A piece of salmon becomes amino acids that build muscle, or an apple provides fiber that our gut microbes can ferment, and antioxidants that can protect against cholesterol.
These microbes still have digestive functions beyond breaking things.
Beyond the breakdown
Your gut also creates molecules that support digestion, gut health, and nutrient absorption.
Certain beneficial microbes support bile acids that digest fats. Gut bugs can produce the mucus that strengthens the gut lining and make certain B vitamins, including B12, which we use for energy metabolism, cognition, and the nervous system.
And then there are short-chain fatty acids (SCFAs), compounds that are produced when gut bugs ferment fiber.
SCFAs have many functions for gut health. They nourish the gut lining—a biological “Great Wall of China,” as Antoine puts it—the barrier between the gut and the body that separates the gut from the rest of the body. It also supports better blood sugar metabolism, liver health, and nutrient absorption.
Unfortunately the effects of aging can also catch up to the microbiome. This can alter gut bug activity and reduce our ability to absorb essential nutrients.
Aging, nutrient absorption, and sponges
Nutrient absorption is like pouring water into a sponge, writes the Institute for Natural Medicine.
“A new sponge will readily soak up nutrients, while a used, porous sponge might let most of the good stuff run off.”
No, aging does not turn our guts into used sponges! But several things might make nutrient absorption harder:
Lower stomach acid can make it harder to release and absorb vitamin B12 from food, and it may also affect iron, calcium, and vitamin D absorption, which can affect hormones, bones, and energy.
Changes in digestive enzymes—more often a reduction—can make it harder to absorb fats, proteins, and other micronutrients.
Some medications can affect nutrient absorption. That includes long-term use of proton-pump inhibitors for reflux, diuretics, and even Metformin, which has been linked to lower B12 absorption.
Persistent nutritional imbalances may starve cells of resources they need to function properly, which could be linked to greater inflammation, worse immune health, metabolic dysfunction, and a compromised gut barrier.
Nutritional imbalances can also beget gut imbalances, which leave footprints across disease types.
In certain studies, heart disease have been linked to different gut microbiomes than healthy adults.
People with IBS and IBD often have altered gut microbiomes, which could be influenced by gut transit time.
As many as 80% of Parkinson’s patients show signs of constipation, often years before other symptoms appear.
Differences in digestion, health conditions, medications, genetic makeup, and the composition of your gut microbiome may also affect how well your body responds to certain foods and absorbs certain nutrients.
A blood test can help flag certain deficiencies that may be worth addressing. Antoine, who works for the consumer gut-testing company Viome (not affiliated), says gut tests can be a useful starting point. Some of them can analyze stool samples for microbial DNA or RNA, then use algorithms to offer recommendations around food, supplements, or lifestyle.
That said, direct-to-consumer microbiome tests have limited proven clinical value, so independent experts suggest treating them as wellness tools.
What can you do now?
Many aspects of aging are within our control. Fortunately, that includes supporting the gut and how the body digests and absorbs nutrients.
Consider these simple strategies:
Probiotics and fermented foods: Probiotics can support a healthy gut barrier and increase SCFAs. Yogurt, kefir, kimchi, and sauerkraut are quality options. Prebiotics found in oats, onions, garlic, beans, and bananas can also feed beneficial bacteria.
Pair vitamins and foods: Certain food combinations can improve vitamin and mineral absorption. Vitamin C can boost iron absorption from plants, while vitamin D helps the body absorb calcium. Adding healthy fats to vegetables also helps the body absorb fat-soluble vitamins A, D, E, and K.
Breathe before eating: It may seem too simple, but taking a few deep breaths before a meal (and between bites) may put the body into a “rest-and-digest” state that signal your body to release digestive enzymes.
Consider a gut test: It can’t diagnose nutrient absorption effectiveness, but it might offer insights around how your gut reacts to food, and make recommendations that support your gut and absorption. Basic labs can also highlight specific nutrient deficiencies.
Monitor medications: Some medicines can affect how well your body absorbs, uses, or processes certain nutrients. Check the bottle or talk to a doctor about supplementing with those nutrients.
Healthy food is how it’s absorbed
“Biology is always a delicate balance,” Antoine says. Healthy food is not only what you eat, but what your body can absorb.
The ability to absorb nutrients can decline with age or change from dysbiosis, stress, or your environment, but it’s reassuring to know that we can take steps to protect the gut. In doing so, we can protect its ability to help process nutrients.
The gut might just be second liver, but it’s one of the first for processing nutrients, and it’s key to getting more good from the good food you’re already eating.
Poll response
This question comes from last week’s issue, Your blood may be aging, too.
We asked: What aspect of aging deserves a proper title?
Add ‘Retir-aging’ to your ‘-aging’ vocabulary. Retirement can be an honest, well-deserved reward for a lifetime of hard work, but studies show it could impact lifespan if your responsibilities shrink from 100 → 0. A reflection from one of our readers, who frames retirement in an entirely new light.
“True retirement shouldn't be about slowing down into passive aging; it’s about reclaiming finite time to direct it toward work and endeavors that carry genuine purpose and value!”
Until next time!
Erin
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The information provided about wellness and health is for general informational and educational purposes only. We are not licensed medical professionals, and the content here should not be considered medical advice. Talk to a doctor before trying any of these suggestions.
