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Eating Seaweed Salad May Boost Immune Function

Eating seaweed salad may boost the efficacy of vaccinations and help treat cold sores, herpes, Epstein-Barr virus, and shingles.

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 experience fewer seasonal allergy symptoms. There’s a problem with these cross-sectional, correlational studies, however, in that they can’t prove cause and effect. Maybe seaweed consumption is just an indicator that people generally are following “traditional Japanese dietary customs,” which have lots of different aspects that could protect against disease. To know for certain whether seaweed can modulate immune function, you have to put it to the test.

As I discuss in my video How to Boost Your Immune System with Wakame Seaweed, typically, researchers start out with in vitro studies, meaning in a test tube or a petri dish, which make for quicker, cheaper, and easier experiments. One study, for example, took eight different types of seaweed and essentially made seaweed teas to drip onto human immune system cells in a petri dish. Studies like these showed that the seaweed wakame, which is the kind 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.

No one actually gave seaweed to people with herpes until a study published in 2002. Researchers 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. “All fifteen patients with active Herpetic viral infections”—including herpes virus 1, the cause of oral herpes, which causes cold sores; herpes virus 2, which causes genital herpes; herpes virus 3, which causes shingles and chicken pox; and herpes virus 4, also known as Epstein-Barr virus, which causes mono—“experienced significant lessening or disappearance of symptoms,” as you can see at 2:06 in my video. There was no control group in the study, but with no downsides to eating seaweed, why not give it a try?

Researchers also found that wakame boosted antibody production, so could it be useful to boost the efficacy of vaccines? The elderly are particularly vulnerable to suffering and dying from influenza. While the flu vaccine can help, ironically, the elderly are less likely to benefit from it because immune function tends to decline as we get older. So, researchers took 70 volunteers over the age 60. As you can see at 2:50 in my video, their baseline level of antibodies against a flu virus was about 10 GMT. What you’re looking for in a vaccination is to get a two-and-a-half-fold response, so we’d like to see that antibody level get up to at least 25 GMT to consider it an effective response. The vaccine only boosted levels to 15 to 20 GMT, though. What happened after the subjects were given some wakame extract every day for a month before the vaccination? Their levels jumped up to 30 to 35 GMT. The researchers used an extract in a pill rather than the real thing, though, so they could perform this randomized placebo-controlled study. After all, it’s kind of hard to make a convincing placebo seaweed salad.

“It is hoped that the popular seaweeds eaten daily in Japan, though almost unknown around the world outside of Japanese restaurants, will be consumed…for possible immunopotentiation”—that is, immune-boosting potential—“and for attenuating the burden of infectious diseases in the elderly.”

What else can seaweed salad do (other than taste delicious)? See my video Wakame Seaweed Salad May Lower Blood Pressure.

In general, sea vegetables are good sources of iodine, as I discuss in Iodine Supplements Before, During, and After Pregnancy, and may also be one reason Japanese women have historically had such low rates of breast cancer, which I cover in Which Seaweed Is Most Protective Against Breast Cancer?.

What else can we do to boost our immunity? Check out my videos:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

30 responses to “Eating Seaweed Salad May Boost Immune Function

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    1. RichardW, check out the other videos listed for more ideas on improving immune function. Exercise, sleep, fruits and veggies all work.
      Dr. Greger lists some especially good choices, tomato juice, cruciferous veggies, apples, kiwi, green tea etc.
      The seaweed most likely works because of the iodine content.

      1. Btw, remember reading that tomatoes and cruciferous veggies are synergistic. Like 1+1=3 for benefits. Can’t find the article now.
        My personal favorite, tomato or Knudson’s Very Veggie juice plus sticks of daikon radish with a cup of green tea. Great snack!

        1. Synergistic. I loved that video.

          I love when my nutritional benefits take wings.

          You mentioned daikon radish and, lately, I have been looking at microgreens and I ended up finding beets and daikon radish microgreens. Arugula, Broccoli, and a few others were always there, but I saw the color of those two and smiled.

          I don’t like the messiness of beets and don’t necessarily like food prep in general, but microgreens are magically delicious and no prep, unless you grow your own, which I have broccoli microgreens to grow at home.

          It sometimes takes me time to figure out systems for that, but the beet microgreens and daikon microgreens made me smile so much.

          The beet microgreens really were delicious and not messy at all.

          I think arugula might be better for NO but I am going for synergy.

          Mostly, I have wanted to eat beets this whole time, but I buy beets and don’t eat them. I buy beet microgreens and eat them every day.

  1. Hi, RichardW! Some seaweeds are polluted. More on that here: There are two issues here. First of all, some seaweeds absorb pollutants more than others. For example, as mentioned in the video I linked, hiziki or hijiki seems to absorb more arsenic than other seaweeds. Second of all, fish and shellfish accumulate pollutants as they eat algae and other fish over time, so they tend to be much more polluted than seaweeds, generally. I hope that helps!

      1. Toxins and pollutants tend to become more concentrated the higher we go up the food chain.

        Seaweed is more or less at the bottom of the food chain and would be expected to have relatively less of those things compared to shellfish and other fish – all other things being equal that is.

  2. I would appreciate brand names of seaweed that are readily available. Thanks. The salad bar (before virus) had seaweed on it and when I asked to see the source, they pulled out a frozen bag and when I read the many different ingredients that included salt, sugar, food dye, and about 6 more—now I understood why it tasted so good but not for me. On its own, they would sell the frozen bag but it’s prohibitive in its cost. I just have not been able to get a credible source and the tiny dried packs would not be okay either.

  3. I am eager to try eating seaweed, but I too am worried about eating salad grown in what now is essentially a toilet bowl.

    How are microplastic particles kept from clinging to and getting inside kelp and seaweed?

    Could it be that ocean pollution is important only when discouraging ingestion of fish and promoting veganism, but not to be worried about when eating seaweed?

    1. Sydney,

      Just fyi: there are microplastic particles in our rivers, lakes, and soils. And evidence that they are present in plants. We eat and drink them every day, from beer to teas.

      Another issue with microplastics is that many chemicals tend to be adsorbed to them, and because they are so small, they can carry a lot of pollutants (large surface area to volume; chemicals are adsorbed to the surface of particles).

      So, pollution is not limited to the ocean, and neither are microplastic particles.

    2. Sure Sydney. It’s all a giant plot to stop you eating dead animals.

      As I understand it though, the issue is that toxins (and microplastics) tend to accumulate higher up in the food chain. That’s why for example most health authorities caution against eating sharks and other top marine predators. They are the ones that are likely to be carrying the biggest toxin load.

      You can rinse surface microplastics from seaweed but fish and marine animals actively eat microplastics. They are inside the fish and can’t be washed off.

      That said, I am not keen on eating seaweed. It necessarily comes from coastal areas and coastal waters tend to be polluted and certainly more heavily polluted than deepwater ocean areas.

  4. After reading this article I added some dried shredded nori seaweed to the eggless tofu salad I made. It was delicious. It blended well, did not clump up. I am able to buy the dried seaweed, with no additives, at a near by Japanese market.

  5. Dr Greger makes eating Wakame sound so great, I immediately went on Amazon to buy some. But I like to read the reviews first, and what did I find? In California it can only be sold with a label that warns that it causes cancer; in Canada the label points out that it contains cadmium and lead, and that death may result from consuming it; a reviewer in Germany points out that the advertising says that it comes from Japan, but the package itself names China as its country of origin; and a British reviewer notes that the Welpac Fueru brand of Wakame was tested by Natural News Labs, and found to contain high levels of heavy metals.

  6. This may be answered in the video but the article doesn’t mention what precisely makes the Wakame seaweed so effective. Is it just the iodine or something else?

  7. In the case of Hashimoto’s Thyroiditis, there is a downside to eating sea vegetables: you can overdo it and worsen your symptoms. About a year ago my thyroid antibodies skyrocketed to 1444. They’d been dropping steadily for several months and the only change I’d made was to increase my sea vegetable intake. It isn’t the heavy metal content – it’s the amount of iodine. I’d been eating dulse daily and the recommended intake is once weekly.

  8. Melinda,

    Your absolutely correct. Good catch !

    This is another reason to adhere to a personalized approach, ie. what does your body need.
    Remember relative to the immune boosting you have other options, including but not limited to nutritional yeast and lots of other foods/herbs that do not contain iodine.

    Dr. Alan Kadish moderator for Dr. Greger

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