Health organizations have been warning us about the dangers of salt for a long time.
That's because high salt intake has been claimed to cause a number of health problems, including high blood pressure and heart disease.
Photo credit: Shutterstock
However, decades of research have failed to provide convincing evidence to support this (1).
What's more, many studies actually show that eating too little salt can be harmful.
This article takes a detailed look at salt and its health effects.
What is Salt?
Salt is by far the biggest dietary source of sodium and the words “salt" and “sodium" are often used interchangeably.
The essential minerals in salt act as important electrolytes in the body. They help with fluid balance, nerve transmission and muscle function.
Some amount of salt is naturally found in most foods. It's also frequently added to foods in order to improve flavor.
Historically, salt was used to preserve food. High amounts can prevent growth of the bacteria that cause food to go bad.
Salt is harvested in two main ways: from salt mines and by evaporating sea water or other mineral-rich water.
There are actually many types of salt available. Common varieties include plain table salt, Himalayan pink salt and sea salt.
This is What Salt Looks Like:
Photo credit: Shutterstock
The different types of salt may vary in taste, texture and color. In the picture above, the salt on the left is more coarsely ground. The salt on the right is finely ground table salt.
In case you're wondering which type is the healthiest, the truth is that they are all quite similar.
Bottom Line: Salt is mainly composed of two minerals, sodium and chloride, which have various functions in the body. It is found naturally in most foods and is widely used to improve flavor.
How Does Salt Affect Heart Health?
This amounts to about one teaspoon or 6 grams of salt (salt is 40 percent sodium, so multiply sodium grams by 2.5).
However, about 90 percent of U.S. adults consume a lot more than that (7).
Eating too much salt is claimed to raise blood pressure, thereby increasing the risk of heart disease and stroke.
However, there are some serious doubts about the true benefits of sodium restriction.
It is true that reducing salt intake can lower blood pressure, especially in people with a medical condition called salt-sensitive hypertension (8).
But, for healthy individuals, the average reduction is very subtle.
One study from 2013 found that for individuals with normal blood pressure, restricting salt intake reduced systolic blood pressure by only 2.42 mmHg and diastolic blood pressure by only 1.00 mmHg (9).
That is like going from 130/75 mmHg to 128/74 mmHg. These are not exactly the impressive results you would hope to get from enduring a tasteless diet.
Bottom Line: Limiting salt intake does result in a slight reduction in blood pressure. However, there is no strong evidence linking reduced salt intake to a lower risk of heart attacks, strokes or death.
Low Salt Intake can be Harmful
There is some evidence suggesting that a low-salt diet can be downright harmful.
The negative health effects include:
- Elevated LDL cholesterol and triglycerides: Salt restriction has been linked to elevated LDL (the “bad") cholesterol and triglycerides (12).
- Heart disease: Several studies report that less than 3,000 mg of sodium per day is linked to an increased risk of dying from heart disease (13, 14, 15, 16).
- Heart failure: One analysis found that restricting salt intake increased the risk of dying for people with heart failure. The effect was staggering, with a 160 percent higher risk of death in individuals who reduced their salt intake (17).
- Insulin resistance: Some studies have reported that a low-salt diet may increase insulin resistance (18, 19, 20, 21).
- Type 2 diabetes: One study found that in type 2 diabetes patients, less sodium was associated with an increased risk of death (22).
Bottom Line: A low-salt diet has been linked to higher LDL and triglyceride levels and increased insulin resistance. It may increase the risk of death from heart disease, heart failure and type 2 diabetes.
High Salt Intake is Linked to Stomach Cancer
Stomach cancer, also known as gastric cancer, is the fifth most common cancer.
It is the third leading cause of cancer death worldwide and is responsible for more than 700,000 deaths each year (23).
A massive review article from 2012 looked at data from seven prospective studies, including a total of 268,718 participants (28).
It found that people with high salt intake have a 68 percent higher risk of stomach cancer, compared to those who have a low salt intake.
Exactly how or why this happens is not well understood, but several theories exist:
- Growth of bacteria: High salt intake may increase the growth of Helicobacter pylori, a bacteria that can lead to inflammation and gastric ulcers. This may increase the risk of stomach cancer (29, 30, 31).
- Damage to stomach lining: A diet high in salt may damage and inflame the stomach lining, thus exposing it to carcinogens (25, 31).
However, keep in mind that these are observational studies. They can not prove that high salt intake causes stomach cancer, only that the two are strongly associated.
Bottom Line: Several observational studies have linked high salt intake with an increased risk of stomach cancer. This may be caused by several factors.
Which Foods are High in Salt/Sodium?
In fact, it is estimated that about 75 percent of the salt in the U.S. diet comes from processed food. Only 25 percent of the intake occurs naturally in foods or is added during cooking or at the table (32).
There are also some seemingly un-salty foods that actually contain surprisingly high amounts of salt, including bread, cottage cheese and some breakfast cereals.
If you are trying to cut back, then food labels almost always list the sodium content.
Bottom Line: Foods that are high in salt include processed foods, such as salted snacks and instant soups. Less obvious foods, such as bread and cottage cheese, may also contain a lot of salt.
Should You Eat Less Salt?
However, if you are a healthy person who eats mostly whole, single ingredient foods, then there is probably no need for you to worry about your salt intake.
In this case, you can feel free to add salt during cooking or at the table in order to improve flavor.
Eating extremely high amounts of salt can be harmful, but eating too little may be just as bad for your health (16).
As is so often the case in nutrition, the optimal intake is somewhere between the two extremes.
This article was reposted from our media associate Authority Nutrition.
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The last Ice Age eliminated some giant mammals, like the woolly rhino. Conventional thinking initially attributed their extinction to hunting. While overhunting may have contributed, a new study pinpointed a different reason for the woolly rhinos' extinction: climate change.
The last of the woolly rhinos went extinct in Siberia nearly 14,000 years ago, just when the Earth's climate began changing from its frozen conditions to something warmer, wetter and less favorable to the large land mammal. DNA tests conducted by scientists on 14 well-preserved rhinos point to rapid warming as the culprit, CNN reported.
"Humans are well known to alter their environment and so the assumption is that if it was a large animal it would have been useful to people as food and that must have caused its demise," says Edana Lord, a graduate student at the Center for Paleogenetics in Stockholm, Sweden, and co-first author of the paper, Smithsonian Magazine reported. "But our findings highlight the role of rapid climate change in the woolly rhino's extinction."
The study, published in Current Biology, notes that the rhino population stayed fairly consistent for tens of thousands of years until 18,500 years ago. That means that people and rhinos lived together in Northern Siberia for roughly 13,000 years before rhinos went extinct, Science News reported.
The findings are an ominous harbinger for large species during the current climate crisis. As EcoWatch reported, nearly 1,000 species are expected to go extinct within the next 100 years due to their inability to adapt to a rapidly changing climate. Tigers, eagles and rhinos are especially vulnerable.
The difference between now and the phenomenon 14,000 years ago is that human activity is directly responsible for the current climate crisis.
To figure out the cause of the woolly rhinos' extinction, scientists examined DNA from different rhinos across Siberia. The tissue, bone and hair samples allowed them to deduce the population size and diversity for tens of thousands of years prior to extinction, CNN reported.
Researchers spent years exploring the Siberian permafrost to find enough samples. Then they had to look for pristine genetic material, Smithsonian Magazine reported.
It turns out the wooly rhinos actually thrived as they lived alongside humans.
"It was initially thought that humans appeared in northeastern Siberia fourteen or fifteen thousand years ago, around when the woolly rhinoceros went extinct. But recently, there have been several discoveries of much older human occupation sites, the most famous of which is around thirty thousand years old," senior author Love Dalén, a professor of evolutionary genetics at the Center for Paleogenetics, said in a press release.
"This paper shows that woolly rhino coexisted with people for millennia without any significant impact on their population," Grant Zazula, a paleontologist for Canada's Yukon territory and Simon Fraser University who was not involved in the research, told Smithsonian Magazine. "Then all of a sudden the climate changed and they went extinct."
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Transitioning to renewable energy can help reduce global warming, and Jennie Stephens of Northeastern University says it can also drive social change.
For example, she says that locally owned businesses can lead the local clean energy economy and create new jobs in underserved communities.
"We really need to think about … connecting climate and energy with other issues that people wake up every day really worried about," she says, "whether it be jobs, housing, transportation, health and well-being."
To maximize that potential, she says the energy sector must have more women and people of color in positions of influence. Research shows that leadership in the solar industry, for example, is currently dominated by white men.
"I think that a more inclusive, diverse leadership is essential to be able to effectively make these connections," Stephens says. "Diversity is not just about who people are and their identity, but the ideas and the priorities and the approaches and the lens that they bring to the world."
So she says by elevating diverse voices, organizations can better connect the climate benefits of clean energy with social and economic transformation.
Reposted with permission from Yale Climate Connections.
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If weather is your mood, climate is your personality. That's an analogy some scientists use to help explain the difference between two words people often get mixed up.
Size Matters<p>Climates are a bit like woven tapestries. The big picture is important, no question. But so are all the seemingly minor details found inside the larger whole.</p><p><a href="https://research-information.bris.ac.uk/en/persons/tommaso-jucker" target="_blank">Tommaso Jucker</a> is an environmental scientist at the University of Bristol. In an email, Jucker says he'd define the term microclimate as "the suite of climatic conditions (temperature, rainfall, humidity, solar radiation) measured in localized areas, typically near the ground and at spatial scales that are directly relevant to ecological processes."</p><p>We'll talk about that last bit in a minute. But first, there's another criteria to discuss. According to some researchers, a microclimate — by definition — must differ from the larger area that surrounds it.</p><p><a href="https://www.cfc.umt.edu/research/paleoecologylab/publications/Davis_et_al_2019_Ecography.pdf" target="_blank">Forests</a> provide us with some great examples. "The climate near the ground in a tropical rainforest is dramatically different from the climate in the canopy 50 meters [164 feet] above," says University of Montana ecologist <a href="https://www.cfc.umt.edu/personnel/details.php?ID=1110" target="_blank">Solomon Dobrowski</a> in an email. "This vertical gradient among other factors allows for the staggering biodiversity we see in the tropics."</p><p>Likewise, scientists observed that a 2015 partial <a href="https://animals.howstuffworks.com/insects/bees-stopped-buzzing-during-2017-solar-eclipse.htm" target="_blank">solar eclipse</a> caused the air temperature of an Eastern European meadow to <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/wea.2802" target="_blank">change more dramatically</a> than it did in a nearby forest. That's because trees provide not only shade, but their leaves also reflect solar radiation. At the same time, forests tend to reduce wind speeds.</p><p>All those factors add up. A 2019 review of 98 wooded places — spread out across five continents — found that forests are 7.2 degrees Fahrenheit (4 degrees Celsius) <a href="https://natureecoevocommunity.nature.com/posts/47363-forests-protect-animals-and-plants-against-warming" target="_blank">cooler on average</a> than the areas outside them.</p><p>Now if you hate the cold, don't worry; there's a cozy exception to the rule. According to that same study, forests are usually 1.8 degrees Fahrenheit (1 degree Celsius) warmer than the external environment during the wintertime. Pretty cool.</p>
A Bug's Life<p>When does a microclimate stop being, well, micro? In other words, is there a maximum size we should be aware of when discussing them?</p><p>Depends on who you ask. "In terms of horizontal scale, some have defined 'microclimate' as anything that is less than 100 meters [328 feet] in range," Jucker says. "I'm personally less prescriptive about this."</p><p>Instead, he says the "scale at which we want to measure [a particular] microclimate" ought to be "dictated" by the questions we're trying to answer.</p><p>"If I want to know how temperature affects the photosynthesis of a leaf, I should be measuring temperature at centimeter scale," Jucker explains. "If I want to know if and how temperature affects the habitat preference of a large, mobile mammal, it's probably more relevant to capture temperature variation across [tens to hundreds] of meters."</p><p>For instance, solitary plants have the power to generate itty-bitty microclimates. Just ask <a href="https://www.colorado.edu/geography/peter-blanken-0" target="_blank">Peter Blanken</a>, a geography professor at the University of Colorado, Boulder and the co-author of the 2016 book, "<a href="https://amzn.to/2XN6FT8" target="_blank">Microclimate and Local Climate</a>."</p>
The urban heat island effect is a good example of how microclimates work. NOAA
Microclimates on a Grand Scale<p>It's no secret that our planet is going through some rough times at the macro level. The global temperature is <a href="https://climate.nasa.gov/vital-signs/global-temperature/" target="_blank">climbing</a>; nine out of the <a href="https://www.noaa.gov/news/2019-was-2nd-hottest-year-on-record-for-earth-say-noaa-nasa" target="_blank">10 hottest years on record</a> have occurred since 2005. And by one recent estimate, roughly 1 million species around the world are <a href="https://ipbes.net/sites/default/files/2020-02/ipbes_global_assessment_report_summary_for_policymakers_en.pdf" target="_blank">facing extinction</a> due to human activities.</p><p>"One of the big questions that ecologists and environmental scientists are trying to answer right now is how will individual species and whole ecosystems respond to rapid climate change and habitat loss," says Jucker. "...To me, [microclimates are] a key component of this research — if we don't measure and understand climate at the appropriate scale, then predicting how things will change in the future becomes a lot harder."</p><p>Developers have long understood the impact small-scale climates have on our daily lives. <a href="https://science.howstuffworks.com/environmental/green-science/urban-heat-island.htm#pt0" target="_blank">Urban heat islands</a> are cities that have higher temperatures than neighboring rural areas.</p><p>Plants release vapors that can moderate local climates. But in cities, natural greenery is often scarce. To make matters worse, plenty of our roads and buildings have a bad habit of absorbing or re-emitting heat from the sun. <a href="https://www.google.com/books/edition/Microclimate_and_Local_Climate/LHUZDAAAQBAJ?hl=en&gbpv=1&bsq=urban%20heat%20island" target="_blank">Vehicle emissions</a> don't exactly help the situation.</p><p>Still, it's not like Boston or Beijing are thermal monoliths. Sometimes, the documented temperatures <a href="https://e360.yale.edu/features/can-we-turn-down-the-temperature-on-urban-heat-islands" target="_blank">within a single city</a> vary by 15 to 20 degrees Fahrenheit (8.3 to 11.1 degrees Celsius).</p><p>That's where metro parks and city trees come in. They have nice cooling effects on nearby neighborhoods. "Several cities around the world have developed programs to increase urban green spaces," says Blanken. "Tree planting programs and green roof programs, have been shown to lower surface temperatures, decrease air pollution and decrease surface water runoff (urban flash-flooding) in urban areas."</p>
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Note: This story was originally published on August 6, 2020
If asked to recall a hurricane, odds are you'd immediately invoke memorable names like Sandy, Katrina or Harvey. You'd probably even remember something specific about the impact of the storm. But if asked to recall a heat wave, a vague recollection that it was hot during your last summer vacation may be about as specific as you can get.
<div id="ecf36" class="rm-shortcode" data-rm-shortcode-id="c2dcc9d48a6cd61f247df1544539a783"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1290959314132361216" data-partner="rebelmouse"><div style="margin:1em 0">Naming heatwaves is a good idea—making the abstract concrete, the invisible visible. Why should hurricanes and wild… https://t.co/hDWgYb79Ob</div> — Ed Maibach (@Ed Maibach)<a href="https://twitter.com/MaibachEd/statuses/1290959314132361216">1596623660.0</a></blockquote></div>
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