Have you ever wondered if there’s a natural way to lower your high blood pressure, guard against Alzheimer's, lose weight, and feel better? Well as it turns out there is. Michael Greger, M.D. FACLM, founder of NutritionFacts.org, and author of the instant New York Times bestseller “How Not to Die” celebrates evidence-based nutrition to add years to our life and life to our years.

Boosting Immune Function

Don’t like getting sick?  Here are some ways to avoid it through our diets

This episode features audio from Preventing the Common Cold with Probiotics?How to Boost Your Immune System with Wakame Seaweed, and Are Happier People Actually Healthier?. Visit the video pages for all sources and doctor’s notes related to this podcast.


Here’s a question for you. What’s the best way to live a longer, healthier life? Diet? Exercise? Both—eating healthy while doing jumping jacks? Welcome to the Nutrition Facts Podcast. I’m your host Dr. Michael Greger and I’m here to help you answer that question. We have tremendous power over our health destiny and longevity. The vast majority of premature death and disability is preventable with a healthy enough diet and lifestyle. And, I’m here to bring you the latest peer-reviewed research to give you the tools to put it into practice.

On today’s show –we look at some of the ways to potentially boost our immune function –starting with probiotics.

Babies delivered via Caesarean section appear to be at increased increase for various allergic diseases. The thought is that “vaginal delivery leads to the first colonization of the gut with maternal vaginal bacteria, while c-section babies are deprived of this natural exposure, and exhibit a different gut flora.” This is supported by research noting that a disturbance in maternal vaginal flora during pregnancy may be associated with early asthma in their children. This all suggests our natural gut flora can affect the development of our immune system for better, or for worse.

In adulthood, two studies published back in 2001 suggested that probiotics could have “systemic immunity-enhancing effects.” Subjects were given a probiotic regimen between weeks three to six, and saw a significant boost in the ability of their white blood cells to chomp down on potential invaders. And, what’s interesting is that even after the probiotics were stopped, there was still enhanced immune function a few weeks later, compared to baseline. The same boost was found in the ability of their natural killer cells to kill cancer cells. And, similar results were also found using a different probiotic strain.

Now, improving immune cell function in a petri dish is nice, but does this actually translate into people having fewer infections? For that, we had to wait another ten years. But, now we have randomized, double-blind, placebo-controlled studies showing that those taking probiotics may have significantly fewer colds, fewer sick days, and fewer symptoms.

The latest review of the best studies to date found that probiotics, such as those in yogurt, soy yogurt, or supplements, may indeed reduce one’s risk of upper respiratory tract infection. But, the totality of evidence is still considered weak, so it’s probably too early to make a blanket recommendation.

Unless one has suffered a major disruption of gut flora by antibiotics, or an intestinal infection—unless one is symptomatic—with, like, diarrhea, or bloating, I would suggest focusing on feeding the good bacteria we already have—by eating so-called prebiotics, such as fiber.

After all, as we saw before, who knows what you’re getting when you buy probiotics? They may not even be alive by the time you buy them. They also have to survive the journey down to the large intestine. Altogether, these points suggest that the advantages of prebiotics—found in plant foods—outweigh those of probiotics.

And, by eating raw fruits and vegetables, we may be getting both. Fruits and vegetables are covered with millions of lactic acid bacteria, some of which are the same type used as probiotics. So, when studies show eating more fruits and vegetables boosts immunity, prebiotics and probiotics may both be playing a role.

In our next story, we discover the effect of eating seaweed salad on the efficacy of vaccinations and the treatment of viral infections—cold sores, herpes, Epstein-Barr virus, and shingles. Here’s the research.

Billions of pounds of seaweed are harvested each year, the “consumption of which has been linked to a lower incidence of chronic diseases,” both physical and mental. For example, women who eat more seaweed during pregnancy appear to be less depressed, and have less seasonal allergy symptoms.

But, the problem with these cross-sectional, correlational studies is that you can’t prove cause and effect. Maybe seaweed consumption is just an indicator that they’re following “traditional Japanese dietary customs” in general, which have lots of different aspects that could protect against disease. To know for sure if seaweed could modulate immune function, you have to put it to the test.

So, typically, researchers start out like this: in vitro (meaning, like, in a test tube), which makes for quicker, cheaper, easier experiments. Take eight different types of seaweed, and basically make some seaweed tea you can drip on human immune system cells in a petri dish.

It was studies like these that showed that the seaweed wakame, which is what you find in seaweed salad, can quadruple the replication potential of T cells, which are an important part of our immune defense against viruses like herpes simplex virus. Yeah, but no one actually tried giving seaweed to people with herpes, until this study.

They gave people suffering from various herpes infections about two grams a day of pure powdered wakame, which is equivalent to about a quarter-cup of seaweed salad. And, “all fifteen patients with active Herpetic viral infections experienced significant lessening or disappearance of symptoms.” This included herpes virus 1, the cause of oral herpes, which causes cold sores; herpes virus 2, which causes genital herpes; herpes virus 4, also known as Epstein-Barr virus, which causes mono; and herpes 3, which causes shingles and chicken pox. There was no control group, though—but with no downsides, why not give it a try? Anyway, if you’re on a date, and they order seaweed salad, you might want to ask them about their history.

Researchers also found that wakame boosted antibody production. So, might it be useful to boost the efficacy of vaccines? The elderly are particularly vulnerable to suffering and dying from influenza. Now, the flu vaccine can help, but ironically, the elderly are less likely to benefit, because immune function tends to decline as we get older.

So, they took 70 volunteers over the age 60.  And, what you’re looking for in a vaccination is to get a two-and-a-half fold response. So, we’d like to see this get up to at least 25 to consider it an effective response. Give them some wakame extract every day, though, for a month before the vaccination, and they jumped up. They used an extract rather than the real thing, because they needed to put it into a pill, so they could perform this randomized, placebo-controlled study—it’s kinda hard to make a convincing placebo seaweed salad.

“It is hoped that the popular seaweeds eaten daily in Japan, though almost unknown” everywhere else outside of Japanese restaurants, will start to be more widely “consumed for possible immunopotentiation boosting immunity and for attenuating the burden of infectious diseases in the elderly.”

In our final story, we look at how happier people may actually be healthier.  Here’s the research.

More than 60 years ago, the World Health Organization defined health as a “state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.” Just because you’re not depressed doesn’t necessarily mean you’re happy. But if you look in the medical literature, there are 20 times more studies published on health and depression than there are on health and happiness.

In recent years, though, research on positive psychology has emerged: what we can do to increase our success, functioning, and happiness; all inherently good in themselves, but are happier people, healthier people?

There is growing evidence that positive psychological well-being is associated with reduced risk of physical illness. But it’s not surprising that healthier people are happier than sick people. The intriguing issue is whether psychological well-being protects against future illness or inhibits the progression of chronic disease. To figure out which came first, you’d have to get more than just a snapshot in time; you’d need prospective studies, meaning studies that go forward in time, to see if people that start out happier live longer.  And yes, a review of such studies suggests that positive psychological well-being has a favorable effect on survival in both healthy and diseased populations.

But not so fast. Yes, positive states may be associated with less stress, and inflammation, and more resilience to infection, but positive well-being may also be accompanied by a healthy lifestyle that itself reduces the risk of disease. Happy people tend to smoke less, exercise more, drink less, and sleep better. So, maybe happiness leads to health only indirectly. However, the apparent protective effect of positive psychological well-being persisted even after controlling for all these healthy behaviors. Meaning effectively, even at the same level of smoking, drinking, exercise, and sleep, happier people seem to live longer.

Ideally, to definitively establish cause-and-effect, we’d do an interventional trial, in which participants are assigned at random to different mood levels and tracked for health outcomes. It’s rarely feasible or ethical to randomly make some people’s lives miserable to see what happens, but if you pay people enough you can do experiments like this.

It’s been thought that people who typically report experiencing negative emotions are at greater risk for disease, and those who typically report positive emotions are at less risk; so, they decided to test this using the common cold virus. Three hundred thirty-four healthy volunteers were assessed for how happy, pleased, and relaxed they were, or how anxious, hostile, and depressed. Subsequently, they were given nasal drops containing cold rhinoviruses to see who would be more likely to come down with the cold. Who would let someone drip viruses in their nose? Someone paid $800, that’s who.

Now, just because we get exposed to a virus doesn’t mean you automatically get sick, because you have an immune system that can fight it off, even if it’s dripped right into your nose. The question is whose immune system fights better?

In a third of the bummed out folks, their immune systems failed to fight off the virus and they came down with a cold, but only about one in five got a cold in the happy group. Maybe it’s because those with positive emotions slept better, got more exercise, had lower stress? No, it appears even after controlling for the healthy practices and levels of stress hormones, happier people still appear to have healthier immune systems, a greater resistance to developing the common cold.

Works with the flu too—they repeated the study with the flu virus, and like in their earlier study, increased positive emotions was associated with decreased verified illness rates. These results indicate that feeling vigorous, calm, and happy may play a more important role in health than previously thought.

We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. Go to NutritionFacts.org/testimonials. We may be able to share it on our social media to help inspire others. To see any graphs charts, graphics, images or studies mentioned here, please go to the Nutrition Facts Podcast landing page. There you’ll find all the detailed information you need plus links to all of the sources we cite for each of these topics.

NutritionFacts.org is a nonprofit, science-based public service, where you can sign up for free daily updates on the latest in nutrition research via bite-sized videos and articles. Everything on the website is free. There’s no ads, no corporate sponsorship. It’s strictly non-commercial. I’m not selling anything. I just put it up as a public service, as a labor of love, as a tribute to my grandmother –whose own life was saved with evidence-based nutrition. Thanks for listening to Nutrition Facts. I’m your host, Dr. Michael Greger.

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