Illustration: Kieran Blakey
The Nuance
There?s not much evidence that playing chemist with your body?s pH levels will do you any good
Markham Heid
Jan 306 min read
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pH and the skin
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pH and the body
In the 1999 film Fight Club, Brad Pitt?s character dumps a skin-searing powder onto the hand of the character played by Edward Norton. ?This is a chemical burn,? Pitt?s character explains. ?You can run water over your hand and make it worse? or you can use vinegar to neutralize the burn.?
While the scene is dramatized, to put it mildly, experts say that the chemical science it depicts is more or less accurate. ?The basic material he puts on his hand is lye, and he neutralizes it with vinegar, which is acidic,? says Adam Friedman, MD, a professor and interim chair of dermatology at the George Washington University School of Medicine and Health Sciences. ?And it?s true that when you get extreme shifts in the skin?s pH, that can disrupt every function of its biology.?
Chemists use the pH scale, which generally ranges from zero to 14, to measure acidity. Something that has a pH below seven is termed acidic, while something with a pH above seven is basic or alkaline. A pH of exactly seven is neutral. (The ?H? in pH refers to hydrogen ions, which the scale measures. But the origins of the ?p? are murky.)
Throughout the human body, pH is tightly regulated. In the stomach, digestive enzymes produce a highly acidic environment, which facilitates the breakdown of food. Meanwhile, the top layer of the skin functions best in a mildly acidic state. In these places and just about everywhere else, even small disruptions to the body?s pH can lead to major trouble. But while adjusting the skin?s pH may be beneficial in some cases, experts say attempts to balance or regulate the body?s internal pH is likely fruitless.
pH and the skin
?The skin, in its purest and most normalized form, is acidic,? Friedman says. This acidity encourages the healthy turnover, repair, and maintenance of the skin?s cells. But in someone who has eczema, for example, the skin tips toward a base pH. This interferes with the normal function of the skin?s cells, which contributes to the development of dry, flaky, and red patches of skin, he says.
?Acidity also affects the health of the skin?s microbiota,? Friedman says, referring to the billions of microscopic organisms that live on the surface of the skin and help form its protective barrier. When the skin?s pH levels are out of whack, this can encourage the growth of some bacteria over others, which can leave the skin vulnerable to breaches or infections, he explains.
A lot of skin care products tout the ability to regulate pH?and these claims are true, Friedman says. For example, many eczema creams utilize acidic ingredients like lactate and urea or ?buffering? agents like colloidal oatmeal to restore the pH required for proper repair and new cell formation.
But in some cases, products can also interfere with the skin?s pH levels. Friedman says that a lot of traditional soaps are ?very basic? and contain charged particles that break apart fats in the skin. While these attributes can help these soaps clean away dirt and grime, they can shift the skin?s acid balance in ways that dry it out and cause damage. For this reason, he recommends using a soap labeled as ?gentle? or for ?sensitive skin? or one made specifically for babies or people with eczema. ?These are either acidic or they contain buffering agents so they don?t mess with the skin?s pH,? Friedman says. ?I have patients who come in itching all over, and just changing soap cures them.? Even for those who don?t have dry or sensitive skin, he says there?s no downside to switching to one of these soaps.
?The body has very powerful mechanisms to adjust pH regardless of what you eat or drink. What you see online about pH seems like a distraction.?
pH and the body
Moving inside the body, the pH story becomes much more complicated. ?As a medical student, you?re taught to monitor blood pH in patients in the ICU, because this can alert you to a number of problems,? says Emeran Mayer, MD, a gastroenterologist and co-director of the CURE: Digestive Diseases Research Center at UCLA. That?s mainly because complications arising from diabetes, infection, and other serious medical issues can cause dangerous shifts in the body?s pH levels.
And while doctors have various methods of addressing these imbalances, there?s not much evidence that eating or drinking something will have a predictable effect on any element of a person?s health, according to Mayer. ?I?ve heard about the alkaline water stuff, but it?s almost never something you see in the scientific literature,? he says.
Some researchers, including the authors of a 2015 study in PLOS One, have speculated that acid-promoting or acid-reducing diets may affect the gut?s microbiome. And online, there?s no shortage of people making claims that low-acid or high-acid diets are able to induce health benefits ? in part by influencing the diversity or well-being of the microbiome. But Mayer, who studies the microbiome and gut health, says he?s aware of no evidence to back up these claims. ?The body has very powerful mechanisms to adjust pH regardless of what you eat or drink,? he says. ?What you see online about pH seems like a distraction.?
Others agree. ?If you read widely on the internet, you can find people that say that alkalinizing the diet will cure every disease known to man, but the research suggests no effects whatsoever,? says Tanis Fenton, a registered dietician and adjunct professor at the University of Calgary.
Fenton has published eight research papers on dietary acid load. Based on her findings, she says that focusing on a food or diet?s effect on urine pH is unhelpful ? at best. ?The alkaline water promotions are simply marketing,? she says. ?There?s no good evidence it does anything.?
When it comes to food, Fenton says, ?We know that eating fiber is very good for the microbiome and that plant foods have more fiber.? Compared to protein-heavy foods like meat, plant foods are also thought to produce less acid during digestion. But Fenton says a plant food?s fiber and other beneficial nutrients, not its effects on dietary acid, better explain its health benefits. ?Focusing on diet acid load just confuses matters,? she adds.
Not all researchers are ready to write off acid load as a potential factor in dietary health. Some studies, including a 2015 paper in the Journal of Bone and Mineral Research, have found that supplementing older adults? diets with alkaline salts of potassium seems to ?neutralize? dietary acid load in ways that may safeguard bones and muscles from age-related breakdown. ?We saw lower biochemical markers of bone resorption, which is suggestive of a lower rate of bone loss,? says Bess Dawson-Hughes, MD, first author on that study and director of the Bone Metabolism Laboratory at the USDA Nutrition Research Center on Aging at Tufts University. ?There were also indications that we may have reduced the rate of muscle wasting,? Dawson-Hughes says.
But these effects were observed primarily among those who had a big dietary acid disparity to begin with ? that is, people who tended to eat a lot of meat and grains and not enough fruits or vegetables. ?People didn?t benefit more and more beyond the point at which they reached a neutral pH,? Dawson-Hughes says. ?This was interesting because it suggests you don?t want to go too far and become alkaline.?
Dawson-Hughes says her findings need to be validated by longer-term studies. Even if they are, the resulting advice would more or less echo the guidelines nutrition authorities are already promoting. ?Protein and grain intakes are at record levels, while fruit and vegetable intake is far too low,? she says. ?We need to bring these into balance.?
To sum all this up, pH is important ? both inside and outside the body. And using harsh pH-disrupting soaps or solutions may contribute to skin-related problems. But to date, there?s little evidence to support claims that pH-centered diets or drinks can predictably improve any element of a person?s health.
?We know which ingredients make foods healthy,? Mayer says. ?I have not seen any data that suggests focusing on pH leads to any beneficial effects.?
