Why We Should Cut Down on Salt Independently of Blood Pressure

If you put people on a low-salt diet, meaning only getting twice as much sodium as they need, as opposed to a usual salt diet where they’re getting five times more, you get a significant improvement in artery function. Lower salt begets better arterial function, suggesting heart-protective effects beyond just blood pressure reduction. Now, this was after dropping people’s salt intake by about a teaspoon a day for two weeks. What if you only dropped salt intake by a half teaspoon or so a day? You still get a significant improvement in artery function, and it happens within just two days of reducing one’s salt intake—or, even after a single meal. A high-salt meal, which is to say just a “typical amount of salt consumed in a commonly eaten meal, can significantly suppress [artery function] within 30 [minutes].” In my video Sodium and Arterial Function: A-Salting Our Endothelium, I show what happens 30, 60, 90, and 120 minutes after consuming a meal with just a pinch of salt in it versus eating the same meal, but made with a quarter teaspoon of salt rather than a pinch: a significant suppression of arterial function. Now, is this in addition to the spike in blood pressure from salt or because of the spike in blood pressure?

If you take people with normal blood pressure and give them a bowl of soup containing the amount of salt a regular meal might contain, their blood pressure goes up over the next three hours compared to the same soup with no added salt. Now, this doesn’t happen to everyone; this is just the average response. Some people are resistant to the effects of salt on their blood pressure. So what if you repeated the artery function experiment on them? You get a paper entitled (*spoiler alert*): “High dietary sodium intake impairs endothelium-dependent dilation in healthy salt-resistant humans.” Indeed, even in people whose blood pressure is unresponsive to salt intake, they still suffer significant suppression of their artery function. So, independent of any effects on blood pressure, salt hurts our arteries, and that harm begins within minutes of consumption for our major arteries and even our tiny blood vessels.

Using something called laser Doppler flowmetry, you can measure blood flow in the tiny vessels in our skin. In the video, you can see the measurement of blood flow at baseline. Now, to get the blood vessels to open up, they warmed the skin. The reason we may turn pink when we get into a hot bath is that the blood vessels in our skin are opening up, and that’s what happened: a big increase in blood flow with the warming. That was on the low-salt diet, however. A high-salt diet starts out the same, but after the same warming, there’s significantly less blood flow. The arteries just don’t seem to open up as well on a high-salt diet, unless you inject vitamin C into the skin. That seems to reverse the salt-induced suppression of blood vessel function. So if an antioxidant reverses the salt effect, then the way salt may be damaging our artery function is through oxidative stress, the formation of free radicals in our blood stream. But, how?

There’s an enzyme in our body that can detoxify a million free radicals per second (!), 24 hours a day, 7 days a week. But, compared to a low-salt diet, if we consume a normal-salt diet, we suppress the activity of this detoxifying powerhouse of an enzyme. That may help explain why our artery function is much lower on salt. With our antioxidant enzymes crippled by the salt, all the excess free radicals may be crippling our arteries. Mop up those extra free radicals by infusing vitamin C into the bloodstream, however, and artery function returns to normal. In contrast, on a low-salt diet, if you drip vitamin C into people’s veins, nothing happens because our antioxidant enzymes are already taking care of business and haven’t been shackled by the sodium of a normal-salt diet.

Whereas potassium, concentrated in fruits and vegetables, softens the cells that line our arteries and increases the release of nitric oxide that allows our arteries to relax, sodium in our blood stiffens the artery lining within minutes and reduces nitric oxide release. The more salt, the less nitric oxide is produced. Consume one salty meal, and not only does our blood pressure go up, but our arteries literally stiffen. That’s why we could figure out four thousand years ago that too much salt was bad for us. Maybe we don’t need a double-blind trial. Maybe we don’t need to follow people around for a decade. We may just have to feed someone a bag of potato chips and take their pulse.


My video Sodium and Arterial Function: A-Salting Our Endothelium is part of an extended video series on sodium, trying to set the record straight on the “controversy” manufactured by the processed food industries. Check out the other installments:

Other salt-related videos of interest include:

I touched on potassium in Preventing Strokes with Diet and Lowering our Sodium-to-Potassium Ratio to Reduce Stroke Risk, but I’m looking forward to doing a deep dive into the mineral when I get a chance.

In health,
Michael Greger, M.D.

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

The Best Source of Vitamin D

If one is going to make an evolutionary argument for what a “natural” vitamin D level may be, how about getting vitamin D in the way nature intended—that is, from the sun instead of supplements? I run through the pros and cons in my video The Best Way to Get Vitamin D: Sun, Supplements, or Salons?. Though supplements may only cost about 10 dollars a year, sunlight is free. We never have to worry about getting too much vitamin D from sunlight, since our body has a way to regulate production in the skin, so if we get our D from the sun, we don’t have to trust poorly regulated supplement companies not to mislabel their products. Indeed, only about half the supplement brands that researchers tested came within 10 percent of their labeled amount.

Sunlight may also have benefits beyond vitamin D, such as how our body may use the sun’s near-infra-red rays that penetrate our skin to activate chlorophyll by-products in our bloodstream to make Co-Q10. (See my video How to Regenerate Coenzyme Q10 (CoQ10) Naturally for more on this.) There’s another way our body appears to use the sun’s rays to maximize the effects of the greens we eat: Within 30 minutes of exposure to the ultraviolet (UV) rays in sunlight, we can get a significant drop in blood pressure and improvement in artery function, thanks to a burst of nitric oxide-releasing compounds that flow into our bloodstream. We can even measure the nitric oxide gas coming straight off our skin. Of course, we have to eat greens or beets in the first place, but that combo of greens and sunlight may help explain some of the protection that plant-based eaters experience.

Morning sun exposure may help those with seasonal affective disorder, as well as improve the mood of wheelchair-bound nursing home residents. Previously, I’ve talked about the benefits of avoiding light at night—see my video Melatonin and Breast Cancer if you’d like to know more—but underexposure to daytime sunlight may also affect our melatonin levels, which don’t only regulate our circadian rhythms but may also be helpful in the prevention of cancer and other diseases. Older men and women getting two hours of outside light during the day appear to secrete 13 percent more melatonin at night, though we’re not sure what, if any, clinical significance this has.

The downsides of sun exposure include increased risk of cataracts, a leading cause of vision loss, though this risk can be minimized by wearing a brimmed hat and sunglasses. Sunlight also ages our skin. In my The Best Way to Get Vitamin D: Sun, Supplements, or Salons? video, you can see a dramatic photo of a truck driver who spent decades getting more sun on the left side of his face—though his driver’s side window. “The effects of sunlight on the skin are profound, and are estimated to account for up to 90% of visible skin aging”—that is, wrinkles, thickening, and loss of elasticity. Things like sun exposure and smoking can make us look 11 years older. Cosmetic surgery can make us look up to eight years younger, but a healthy lifestyle may work even better. Doctors don’t preach about sun protection for youthful facial looks, though, but because of skin cancer. Medical authorities from the World Health Organization, the American Cancer Society, to the Surgeon General warn about excess sun exposure and for good reason, given the millions of skin cancers and thousands of deaths diagnosed every year in the United States alone.

The UV rays in sunlight are considered a complete carcinogen, meaning they can not only initiate cancer, but promote its progression and spread. Melanoma is the scariest, which “makes the rising incidence of melanoma in young women particularly alarming.” This increase has been blamed on the increased usage of tanning salons. Tanning beds and UV rays in general are considered class 1 carcinogens, like processed meat, accounting for as many as three quarters of melanoma cases among young people and six times the risk of melanoma for those who visited tanning salons ten or more times before the age of 30.

The tanning industry is big business, bringing in billions of dollars. There may be more tanning salons than there are Starbucks, and they use those dollars like the tobacco industry: to downplay the risks of their products. Laws are being passed to regulate tanning salons, from complete prohibitions, like in the country of Brazil, to age restrictions for minors. But, unlike tobacco, tanning isn’t addictive. Or is it?

Have you heard of “tanorexia”? Some people tan compulsively and report a so-called tanner’s high. Describing tanning behavior like a substance abuse disorder might seem a little silly—that is, until you stick people in a brain scanner and can show the same kind of reward pathways light up in the brain, thanks to endorphins that are released by our skin when we’re exposed to UV rays. In fact, we can even induce withdrawal-like symptoms by giving tanners opiate-blocking drugs. So, tanning is potentially addictive and dangerous. Harvard researchers suggest that we should “view recreational tanning and opioid drug abuse as engaging in the same biological pathway.” But there’s a reason sun exposure feels good. Sunlight is the primary natural source of vitamin D, and, evolutionarily, it’s more important, in terms of passing along our genes, not to die of rickets in childhood. Unlike natural sunlight, tanning bed lights emit mostly UVA, which is the worst of both worlds: cancer risk with no vitamin D production. The small amount of UVB many tanning beds do emit, however, may be enough to raise vitamin D levels. Is there a way to raise D levels without risking cancer? Yes: vitamin D supplements.


Indeed, we can get some of the benefits of sun exposure without the risks by taking vitamin D supplements. But, for the sake of argument, what if such supplements didn’t exist? Would the benefits of sun exposure outweigh the risks? That’s the subject of my video The Risks and Benefits of Sensible Sun Exposure.

For other videos in this vitamin D series, see:

I also explore Vitamin D as it relates to specific diseases:

Here’s the video about that amazing chlorophyll activation: How to Regenerate Coenzyme Q10 (CoQ10) Naturally.

What do greens and beets have to do with artery function? Check out some of my latest videos on the wonders of nitrate-rich vegetables:

In health,
Michael Greger, M.D.

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

The Best Foods to Slow Your Metabolism

The largest component of our daily energy budget is resting metabolic rate. As I discuss in my video Slowing Our Metabolism with Nitrate-Rich Vegetables, the direct effects of physical activity are relatively small compared to how many calories we expend just living and breathing. Now, during something like training for the US Army’s Special Ops or climbing a four-mile-high mountain, we may burn 4,000 calories a day. For most people, however, the calories we burn just lying around existing exceeds normal physical activities. Thus, our resting metabolic rate can have implications for controlling our weight.

Researchers have shown that dietary nitrate found in beets and green leafy vegetables improves the efficiency of the little power plants within our cells, boosting athletic performance by extracting more energy from every breath. So, if we eat a lot of vegetables, might it slow our metabolism since our body can function so much more efficiently with the calories we give it?

Indeed, researchers found that after giving people a dose of nitrate equivalent to a few servings of spinach or beets, their resting metabolic rates slowed on average about 4 percent. That’s nearly a hundred calories a day. If our bodies burned that many fewer calories each yet we didn’t eat any less, couldn’t we could put on a few pounds? Of course, green leafy vegetables may be the healthiest food on the planet, so we shouldn’t decrease our greens intake to try to control our weight. What’s going on? Researchers think perhaps it was a way our body evolved to use vegetables to help preserve energy during lean times in our ancient past. That is, slowing our metabolism may have benefits for our longevity.

What else similarly slows our metabolism? Caloric restriction, such as eating every other day. This may be one reason why caloric restriction is associated with a longer lifespan in many animals. Maybe like a candle, burning with a smaller flame allows us to last longer. It’s hard to walk around starving all the time, but it’s easy to replicate that same metabolic benefit by eating a big salad every day.

This may be why eating leafy green vegetables is among the six most powerful things we can do to live longer, along with not smoking, not drinking heavily, walking at least an hour a day, getting seven hours of sleep a day, and achieving an ideal weight. Doing even just one of these six may cut our risk of premature death by around 20 to 25 percent.


What’s that about boosting athletic performance? See:

Don’t want to carry beets out onto the track with you? Try fennel seeds: Fennel Seeds to Improve Athletic Performance.

What else can greens do? Check out How to Regenerate Coenzyme Q10 Naturally.

In health,
Michael Greger, M.D.

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