Optimally fueling your midlife gut microbiome [Part 3 of the 21-day challenge]
With fiber of course
I discovered the world of nutrition after graduating high school. There was a neighborhood restaurant called Skinny Haven (I know, terrible name) where I’d visit the salad bar and pile it high with vegetables.
Boy, did I feel great from adding fruits, vegetables, and beans to my diet. My mood, sleep, and bowel movements were pretty impressive. I was 18, too, which no doubt helped.
I didn’t realize it, but I was feeding my microbiome what it needed to thrive: dietary fiber and plant compounds. As we reach midlife, this need intensifies because of changes due to Aging Pause.
In this 21-day challenge, we started with the oral-intestinal connection and the importance of nitrate-rich veggies. We discussed probiotics in fermented foods that can increase the diversity of the microbiome.
Now it’s time for us to feed gut bacteria so that the good guys can grow, strengthen the gut, and keep inflammation low. And we can do this while considering the unique needs of midlife women.
Why plant foods?
Plant foods do wonders for the gut microbiome because of their fiber content, which survives the acidic environment of the stomach. This means they are food for bacteria in the gut.
As gut microbes ferment fiber, they produce metabolites that not only act on the gut but systematically in the body.
In the last post I talked about how the important metabolite short-chain fatty acids (SCFAs) declines at midlife. Research tells us that those who eat plant foods have more of the most beneficial SCFA, butyrate. That’s because butyrate is a byproduct of fermentable fiber.
SCFA butyrate is like a magic wand for your gut. It’s an energy source for colonocytes (cells in the colon), enhances the gut-brain axis and strengthens tight junctions, thus decreasing permeability (leaky gut). It serves as a protector for your gut, preventing toxins from entering the intestines and reducing inflammation associated with Aging Pause.
“Butyrate could be the vitamin D of the next decade: the sunshine from within molecule,” said Chris Damman MD, and creator of GutBites.org in a press release about a new study. “Only 5% percent of us are eating enough fiber, and in effect, getting enough butyrate from our microbiomes. I think that contributes to some of these chronic diseases we’ve been seeing in high-income countries, and that are now on the rise in lower- and middle-income countries.”
High meat, low fiber
Our diet has the power to produce beneficial metabolites like SCFA or not-so-good ones like trimethylamine-N-oxide (TMAO). TMAO comes from the consumption of high amounts of animal foods, especially red meat. Research shows the risk of cardiovascular disease is elevated by TMAO.
Yet studies on meat intake and TMAO are inconsistent, and we’re learning why. Using a pig model, researchers discovered a potential explanation: background diet matters.
When the pigs ate meat but also consumed a high-fiber vegetable-rich diet, they had a lower urinary TMAO. Yet the pigs put on a high-fat, low-vegetable diet showed the opposite.
The present study revealed that urinary TMAO concentration following red and processed meat intake is affected by the type of background diet consumed in combination with the red and processed meat-based diet.
This was also evident in a randomized control trial where some of the subjects on a plant-rich diet incorporated meat. There were no short-term differences in the microbiome between the groups.
This is good news because it means the benefits come more from what you add to your diet, not takeaway.
From gut health to heart health
Many women in midlife experience an increase in cholesterol, prediabetes, and high triglycerides that blindside them. It’s important to add that plant-based foods rich in fiber benefit heart health.
Most of the studies on midlife women focus on the type of fat, which shows mixed results. Yet the Diet and Androgens Randomized Trial (DIANA), an 18-week intervention with 99 healthy postmenopausal women, showed that those on a plant-based diet decreased cholesterol (14%) more than the control group (4%).
A study with premenopausal women found that those who consumed more than 22g of fiber per day had lower cholesterol than those with lower fiber consumption, and the effect was independent of estrogen levels.
Fiber, particularly soluble fiber, lowers the amount of cholesterol absorbed in the bloodstream. And SCFAs work to decrease cholesterol synthesis in the liver. Studies show high-fiber diets lower cholesterol on average by 5-10%.
Diversify fiber for gut health
Jenna came to me because her cholesterol was inching up despite a healthy diet. She upped her protein, decreased carbs, and ate plenty of vegetables and some fruit. I told her fiber intake was unbalanced.
I explained that plant foods have different kinds of fiber, including soluble, insoluble, and resistant starch. Fermentable soluble fiber forms a viscous gel that slows digestion and helps lower cholesterol.
Most of her fiber sources were non-fermentable insoluble fiber, the “bulking fiber” that helps promote regular bowel movements but does not lower cholesterol or increase SCFA.
And her low carb eating meant no resistance starch, an insoluble but fermentable fiber that passes to the large intestine undigested. Two of the best sources of fermentable fiber – helping to promote SCFA butyrate - are resistant starch and soluble fiber beta glucan (b-glucan).
Resistant starch is especially beneficial to lowering blood sugar after insulin after eating. Food sources include legumes, grains, green bananas, and cooked and cooled potatoes and rice.
That’s right, the amount of resistant starch increases after it’s cooked and then cooled in the refrigerator! B-glucan is a soluble fiber found in a variety of plants but is particularly high in oats, barley, and rye.
It didn’t take Jenna long to get back on track and eat in a way that was more satisfying for her.
Quick note: Some people have trouble tolerating fermentable, oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPS) foods which also increase SFCAs. If this is you, I recommend you see a dietitian to manage these foods while still getting the fiber you need.
Getting a boost from polyphenols
Besides fiber, plant foods contain polyphenols, potent antioxidants that help prevent atherosclerosis and chronic conditions associated with aging. Emerging research shows polyphenols also play a key role in gut health.
Ninety percent of polyphenols in plants reach the large intestine intact where they are metabolized by microbes to polyphenolic compounds such as phenolic acids.
These compounds promote the growth of beneficial bacteria, such as Lactobacillus and Bifidobacterium, while inhibiting the growth of potentially harmful microbes like Escherichia coli, and Staphylococcus aureus.
Fruits, vegetables, cereals, tea, coffee, and wine contain polyphenols. There are different classes of polyphenols - phenolic acids, flavonoids, lignans, and stilbenes - but they all have the phenolic ring in common.
Of particular importance to women in perimenopause and beyond is phytoestrogens, which are polyphenols that can act (weakly) on estrogen receptors. Food sources that have the greatest impact are lignans (flaxseed) and isoflavones (soy).
Last post we discussed how estrogens are deconjugated in the gut, with the ability to re-enter circulation.
Well, the same thing occurs with phytoestrogens. And they not only help the gut, they may decrease menopausal symptoms like hot flashes. A 2021 study in Menopause showed that women on a vegan diet with ½ cup of soybeans experienced an 79% reduction in hot flashes.
I plan to do an extensive post on this subject but just know these plant compounds make a great addition to a midlife women’s diet.
Now onto the challenge!