The Benefits of Wakame Seaweed Salad on Blood Pressure

I used to think of seaweed as just a beneficial whole-food source of minerals like iodine, for which it is the most concentrated dietary source. Indeed, just a daily half-teaspoon of mild seaweeds, like arame or dulse, or two sheets of nori should net you all the iodine you need for the day. But, the intake of seaweeds is advised not only as a whole-food source of iodine, but also, evidently, “for the prevention of lifestyle-related diseases, including cancer, cardiovascular and cerebrovascular disease….” Based on what?

As I discuss in my video Wakame Seaweed Salad May Lower Blood Pressure, the reasoning is that the Japanese live long and eat seaweed, so there is speculation that seaweed might have “influence on life expectancy,” based on suggestive reports. But when we see long lists of the supposed benefits a particular food is purported to have, such as “compounds found in [seaweed] have various biological activities including anticoagulant, anti-viral, antioxidant, anti-allergic, anti-cancer, anti-inflammatory, anti-obesity, and neuroprotective properties,” we need to know if they are based on clinical data, meaning studies with actual people, or so-called preclinical data, that is, from test tubes and lab animals. I mean, what are we supposed to do with a study talking about the effects of “seaweed-restructured pork diets” on rats? Those researchers tried to use seaweed, as well as other ingredients, to “improv[e] the ‘image’ of meat product.” Researchers also tried to add grape seeds to meat, they tried flaxseeds, they tried walnuts, they tried purple rice, and they even tried “thong-weed.”

When you look at epidemiological studies, where you compare the diets and disease rates within a population, you see that Japanese pre-schoolers who eat seaweed tend to have lower blood pressures, suggesting “seaweed might have beneficial effects on blood pressure among children.” That could make sense given all the minerals and fiber in seaweed, but cause and effect can’t be proven with this kind of study. Perhaps other components of the diet that went along with seaweed eating that made the difference.

It’s even harder to do these kinds of studies on adults, since so many people are on high blood pressure medications. University of Tokyo researchers took an innovative approach by comparing the diets of people on different intensities of medication: low-dose of a single blood pressure drug, high-dose of a single drug, and multiple drugs. And, although they all had artificially normalized blood pressure “as a result of effective medication,” those who ate the most fruits and sea vegetables tended to be the ones on the lower dose of a single drug, supporting a dietary role for seaweed. An interesting finding, but why not just put it to the test?

A double-blind, crossover trial found that seaweed fiber lowered blood pressure, apparently by pulling sodium out of the system. Real seaweed couldn’t be used in the study, because the subjects wouldn’t be able to be fooled with a placebo, but why not just put whole powdered seaweed into pills? That was finally attempted ten years later. Compared to doing nothing, subjects receiving a daily dose of dried wakame powder in capsules had beautiful drops in blood pressure. The researchers, however, desalinized the seaweed, taking out about two-thirds of the sodium naturally found in it. So, we still don’t know if eating seaweed salad is actually going to help with blood pressure. What we need is a randomized, controlled trial with plain, straight seaweed. No one had ever done that research, until…they did!

Six grams of wakame, with all of its natural sodium, led to a significant drop in blood pressure, especially in those who started out with high pressure. The subjects experienced only minor side effects and ones that could be expected with increasing fiber intake. A nice thing about whole-food, plant-based interventions is that we sometimes get good side effects, such as the resolution of gastritis (stomach inflammation) some subject had been having, as well as the disappearance of chronic headaches. 

What other foods might help with high blood pressure? See:

For more on preventing and treating hypertension, one of our leading killers, see:

Want more on seaweed and iodine? Check out:

My video Salt of the Earth: Sodium and Plant-Based Diets further addresses the sodium question.

In health,
Michael Greger, M.D.


How to Increase Gut Bacterial Richness

We live in an “obesogenic environment,” with cheap junk food everywhere, thanks in part to subsidies going to the “‘food industrial complex,’ which manufactures obesogenic foods that foster addiction…The root causes…[may] make obesity difficult to escape,” but a lot of people do. If it were simply the external environment, why isn’t everyone obese?

“Some individuals seem to be more susceptible to the obesogenic environment…than others,” which suggests a genetic component, supported by studies of twins and adopted kids, but the genes that have been identified so far account for only 6 to 11 percent of the genetic variation in body mass index between individuals. Perhaps variation in our “other genome”—that is, all the different microbes that inhabit our body, known as the microbiome—may be playing a role. We have a hundred times more bacterial genes inside us than human genes.

As I discuss in my video Gut Microbiome: Strike It Rich with Whole Grains, a study found that people tend to fall into one of two groups: those who have lots of different types of bacteria in their gut (high “gut bacterial richness”) and those with relatively few types. Those with low bacterial richness had more overall body fat, insulin resistance, which is the cause of type 2 diabetes, high triglycerides, and higher levels of inflammatory markers, like C-reactive protein, compared to those with high bacterial richness. Not only did people with lower bacterial richness start out heavier, but the obese individuals with lower bacterial richness also gained more weight over time.

The question then becomes: Can a dietary intervention have any impact “A number of studies have associated increased microbial richness…with diets higher in fruits, vegetables, and fiber.”

Just giving fiber-type supplements doesn’t seem to boost richness, however, but the “compositional complexity” of a whole food, like whole grains, “could potentially support a wider scope of bacterial taxa,” types of bacteria, “thereby leading to an increase in diversity.” Human studies to investigate the effects of whole grains had been neglected, though…until now.

Subjects were given whole-grain barley, brown rice, or a mixture of both for a month, and all three caused an increase in bacterial community diversity. Therefore, it may take a broad range of substrates to increase bacterial diversity, and this can be achieved by eating whole plant foods.

Moreover, the alterations of gut bacteria in the study coincided with a drop in systemic inflammation in the body. We used to think that the way fiber in whole grains helped us was by gelling in our small intestine right off of our stomach, slowing the rate at which sugars were absorbed and blunting the spike in blood sugars one might get from refined carbs. We now know, however, that fiber is broken down in our colon by our friendly flora, which release all sorts of beneficial substances into our bloodstream that can have anti-inflammatory effects, as well. So, perhaps what’s happening in our large intestine helps explain the protective effects of whole grain foods against type 2 diabetes.

Interestingly, the combination of both barley and brown rice worked better than either grain alone, suggesting a synergistic effect. This may help explain “the discrepancy of the health effects of whole grains obtained in epidemiological [population-based] and interventional studies.”

Observational studies “strongly suggest” that those who consume three or more servings of whole grains a day tend to have a lower body mass index, less belly fat, and less tendency to gain weight, but recent clinical trials, where researchers randomized subjects to eat white bread rolls versus whole-wheat rolls, failed to provide evidence of a beneficial effect on body weight. Of course, whole grains are so superior nutritionally that they should continue to be encouraged. However, the “[i]nterventional trials might have failed to show [weight] benefits because they focused on a limited selection of whole grains, while in epidemiological trials [or the population studies], subjects are likely to consume a diverse set of whole grains which might have synergistic activities.”

Until recently, we knew very little about how powerfully our gut bacteria can affect our health. Catch up on the latest science with these related videos:

When it comes to rice, even white rice can be better than many choices, but brown rice is better and pigmented rice is probably the best. See my videos Kempner Rice Diet: Whipping Us Into Shape and Is It Worth Switching from White Rice to Brown? for more.

But what about the arsenic in rice? Learn more:

In health,
Michael Greger, M.D.


What’s the Secret to Latino Longevity?

Latinos living in the United States tend to have “less education, a higher poverty rate, and worse access to health care” and “represent the ultimate paradigm of healthcare disparities,” with the highest rate of uninsured, lowest rates of health screening and counseling, and poorest levels of blood pressure and blood sugar control, as well as “other measures of deficient quality of care.” So they must have dismal public health statistics, right? According to the latest national data, the life expectancy of white men and women is 76 and 81 years, respectively, and that of black men and women is shorter by a handful of years. And Latinos? Amazingly, they beat out everyone.

Latinos live the longest.

This has been called the Hispanic Paradox (now also known as the Latino Paradox), which I explore in my video, The Hispanic Paradox: Why Do Latinos Live Longer?. Latinos have a 24 percent lower risk of premature death and “lower risks of nine of the leading 15 causes of death,” with notably less cancer and heart disease. This was first noticed 30 years ago but was understandably was met with great criticism. Maybe the data were unreliable? No, that didn’t seem to be it. Maybe only the healthiest people migrate? Turns out the opposite may be true. What about the “salmon bias” theory, which “proposes that Latinos return to their home country…to ‘die in their home’” so they aren’t counted in U.S. death statistics? That theory didn’t pan out either.

Systematic reviews “confirm the existence of a Hispanic Paradox.” Given the strong evidence, it may be time to accept it and move on to figuring out the cause. The very existence of the “Hispanic Paradox” could represent “a major opportunity to identify a protective factor for CVD [cardiovascular disease] applicable to the rest of the population.” After all, whatever is going on “is strong enough to overcome the disadvantageous effect” of poverty, language barriers, and low levels of education, health literacy, quality of healthcare, and insurance coverage. Before we get our hopes up too much, though, could it just be genetic? No. As foreign-born Latinos acculturate to the United States, as they embrace the American way of life, their mortality rates go up. So, what positive health behaviors may account for Latino longevity?

Perhaps they exercise more? No, Latinos appear to be even more sedentary. They do smoke less, however the paradox persists even after taking that into account. Could it be their diet? As they acculturate, they start eating more processed and animal-based foods, and consume fewer plant foods—and perhaps one plant food in particular: beans. Maybe a reason Latinos live longer is because they eat more beans. Although Latinos only represent about 10 percent of the population, they eat a third of the beans in the United States, individually eating four to five times more beans per capita, a few pounds a month as opposed to a few pounds per year. That may help explain the “Hispanic Paradox,” because legumes (beans, split peas, chickpeas, and lentils) cool down systemic inflammation.

In my video, you can see the mechanism researchers propose in terms of lung health. While cigarette smoking and air pollution cause lung inflammation, which increases the risk for emphysema and lung cancer, when we eat beans, the good bacteria in our gut take the fiber and resistant starch, and form small chain fatty acids that are absorbed back into our system and decrease systemic inflammation, which not only may inhibit lung cancer development, but also other cancers throughout the body. Latinos have the lowest rates of chronic obstructive pulmonary disease (COPD) and lung cancer, and also tend to have lower rates of bladder cancer, throat cancer, and colorectal cancer for both men and women.

This “systemic inflammation” concept is also supported by the fact that when Latinos do get cardiovascular disease or lung, colon, or breast cancer, they have improved survival rates. Decreasing whole body inflammation may be important for both prevention and survival.

Asian Americans also appear to have some protection, which may be because they eat more beans, too, particularly in the form of tofu and other soy foods, as soy intake is associated with both preventing lung cancer and surviving it.

Hispanics also eat more corn, tomatoes, and chili peppers. A quarter of the diet in Mexico is made up of corn tortillas, and Mexican-Americans, whether born in Mexico or the United States, continue to eat more than the general population. Looking at cancer rates around the world, not only was bean consumption associated with less colon, breast, and prostate cancer, but consumption of rice and corn appeared protectively correlated, too.

Since NAFTA, though, the North American Free Trade Agreement, the Mexican diet has changed to incorporate more soda and processed and animal foods, and their obesity rates are fast catching up to those in the United States.

In the United States, Latinos eat more fruits and vegetables than other groups, about six or seven servings a day, but still don’t even make the recommended minimum of nine daily servings, so their diet could stand some improvement. Yes, Hispanics may only have half the odds of dying from heart disease, but it’s “still the number one cause of death among Hispanics. Therefore, the current results should not be misinterpreted to mean that CVD is rare among Hispanics.” Ideally they’d be eating even more whole plant foods, but one thing everyone can learn from the Latino experience is that a shift toward a more plant-based diet in general can be a potent tool in the treatment and prevention of chronic disease.

Data like this support my Daily Dozen recommendation for eating legumes ideally at every meal, and we have free apps for both iPhone and Android that can help you meet these dietary goals.

For more on the wonders of beans, split peas, chickpeas, and lentils, see my videos and love your legumes!:

What’s the best way to eat them? See Canned Beans or Cooked Beans? and Cooked Beans or Sprouted Beans?.

In health,
Michael Greger, M.D.
