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Gut Health Beyond Yogurt – A Fishy Story
Probiotics are in the health spotlight, but yogurt isn't the only star

10/12/2017 By Michelle Lee with Craig Weatherby

It’s time for a gut-health check … and this is not about yogurt or pickled veggies.

More and more research points to the critical of a healthy gut to a healthy body and mind.

And exciting new evidence indicates that omega-3s play a much bigger role than we thought.

Let's scan some recent findings — including a large clinical study — that bring omega-3s to the fore.

The role your GI biome plays in good health
More than 100 trillion bacteria and other microbes dwell in your gut — some good, some bad.

Together, these microbes constitute what’s called the gut biome or microbiota, which encompasses about 1,000 unique “tribes,” or species of bacteria.

Your gut biome helps extract energy from foods, produce micronutrients, battle unfriendly bacteria, and help keep your immune system on an even keel.

Conversely, an unbalanced biome can promote everything from obesity, diabetes, and allergies, to irritable bowel syndrome (IBS), colitis, and inflammatory bowel disease (IBD).

Myriad factors influence each person’s unique microbial mix — especially your diet, age, environment, and genetic profile.

We know that certain things can throw your gut bacteria badly out of balance:

  • Antibiotics
  • Excess dietary sugar and starch
  • Diets low in "probiotics" such as the friendly bugs in fermented foods.
  • Diets low in "prebiotics" such as fiber, and the "resistant" starch in beans, which feed and foster the growth of friendly bacteria.

And recent findings suggest that we should add "diets low in omega-3s" — especially diets low in seafood-source DHA — to that list of negative factors.

UK study shows gut benefits from omega-3s
British researchers recently published the intriguing results of a large study in women.

They wanted to compare the women’s blood levels of omega-3 fatty acids — and estimated intakes of omega-3s — to the diversity and health of their microbiomes (Menni C et al. 2017).

The UK group analyzed data collected from 876 middle-aged and elderly female twins (average age 65) who’d previously been studied to look for links between their genetic profiles and gut microbiomes as they relate to weight gain and disease.

And the results of the new analysis linked higher blood levels of omega-3s — especially DHA — and higher dietary intakes of omega-3s to healthier, more diverse microbiomes.

The healthier microbiomes seen in the women with higher omega-3 blood levels and dietary intakes were in part signaled by higher levels of a friendly bacteria called Lachnospiraceaes.

Although previous research suggested that omega-3s might benefit the microbiome, this is the biggest human study on the subject — which makes the results more meaningful than findings from animal studies or small human studies.

The authors acknowledged that it’s impossible to be completely certain whether the women’s omega-3 intakes improved their microbiome diversity/health or vice versa.

However, the analysis linked the women’s estimated omega-3 intakes to the diversity/health of their microbiomes — a link almost as strong as to omega-3 blood levels.

That finding suggests that the higher blood levels of omega-3s seen in women with healthier microbiomes was more likely the cause of better gut health, rather than its effect.

As the researchers wrote, the somewhat weaker link between estimated omega-3 intakes and microbiome health, “… is likely to simply reflect the [relative unreliability] of accurate estimates of [omega-3] intake from food questionnaire data, compared to the accuracy of serum [blood] level measurements.”

Finally, the British team linked high omega-3 blood levels to high fecal levels of NCG (N-carbamylglutamate) — a compound that exerts antioxidant effects in the gut, and is likely to reduce inflammation.

According to co-author Dr. Cristina Menni, “We believe that some of the good effects of omega-3 in the gut may be due to the fact that omega-3 induces bacteria to produce this substance.”

Earlier studies shed additional light on omega-3s and the gut
Two animal studies published in 2014 examined the effects of dietary omega-3 and omega-6 fatty acids impact gut health.

It’s been shown that the relative intakes and blood levels of these two families of fatty acids can affect the risks and severity of inflammatory bowel disease, colitis, and Crohn’s disease.

Study #1
A University of British Columbia team led by Dr. Deanna Gibson, Ph.D., examined how omega-3 and omega-6 fatty acids affected mice whose guts were deliberately infected with a microbe known to promote colitis.

The mice with diets high in omega-6 (from corn oil) experienced more intestinal damage, immune-cell damage, and growth of harmful bacteria.

In contrast, the mice fed diets high in seafood-source omega-3 EPA and DHA had higher levels of anti-inflammatory microbes known to reduce the damage caused by colitis.

However, mice on the omega-3-rich diet suffered sepsis, because their immune responses to the artificially introduced colitis-causing bacteria were impaired.

As Dr. Gibson said, “… excess omega-6 intakes may be harmful to gut health. Conversely, while omega-3 supplementation promotes beneficial microbes in the gut, thereby decreasing inflammation, this advantage under normal conditions may be problematic in the presence of [excessive amounts of] harmful bacteria.”

Interestingly, when mice were fed a diet rich in saturated fats plus fish oil, they did not suffer from sepsis from the artificially introduced pathogen.

This finding supports the idea that diets dominated by saturated fats and omega-3s are generally healthier than diets — such as the standard American diet — that feature an overload of omega-6 fats .

Study #2
This mouse study came from scientists at Harvard Medical School and Massachusetts General Hospital.

They found that diets providing a lower ratio of omega-6 to omega-3s lowered the amounts of harmful bacteria while boosting the amounts of beneficial bacteria, and thereby improved the animals' gut biomes.

This healthy balance in the animals’ gut biomes also led to lower levels of inflammation.

Lead researcher Jing X. Kang, M.D., Ph.D., said this about their findings:

  • “Chronic low-grade inflammation contributes to the development of many chronic diseases and can be induced by harmful gut microbiota.”
  • “Therefore, dietary strategies that lower the omega-6/omega-3 PUFA ratio to optimize gut microbiota — such as reducing intake of vegetable oils high in omega-6 fat, processed foods and grain-raised livestock and increasing intake of fish and green vegetables — could prove effective for managing such diseases.”
  • “For management of certain health conditions, a high quality, concentrated omega-3 supplement is also practical.”

So, to maximize your gut health, it makes sense to ensure you’re getting plenty of fish — or fish oil — as well as ample amounts of fiber and fermented dairy foods or vegetables.


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