Latest / Common Sense Health / PRAL Explained: Are You Eating Too Much "Acid?"

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PRAL Explained: Are You Eating Too Much "Acid?" · Common Sense Health

• Stephen Thomas BSc. Hons: Hello Every so often nutrition throws another acronym at us and asks us to bow politely. This week's contestant is Prowl, which stands for potential renal acid load. Now it sounds impressive, I suppose, but Prowl, I mean it sounds like something that should arrive wearing a white coat, carrying a clipboard and quietly judging your lunch. And to be fair, there is some genuine physiology hiding in there and The kidneys do help regulate acid base balance. Diet can influence what the kidneys need to excrete. And in advanced kidney disease, acid base can genuinely matter. So I'm not saying we should just laugh at Prowl and laugh out of the room, but I do think we should make it sit down, have a cup of tea, and explain itself properly. Because Prowl leaves the narrow world of kidney physiology and wanders into the wider nutritional world and it starts developing some holes, some big ones. The sort of holes you could lose a dietitian in. Now the basic idea is that different foods create different amounts of acid load in inverted commas for the kidneys. Foods higher in protein and phosphorus tend to have a higher prowl score. Foods higher in potassium, magnesium, and calcium tend to have a lower, more alkali producing score. So meat, fish, eggs, and cheese usually come out as higher prowl foods. Fruits, vegetables, beans and some plant foods usually come out as a lower prowl food. And this is where the trouble starts, because nutrition has a terrible habit of taking one measurement, polishing it, giving it a lam laminated badge and letting its boss do everything around you. Because you know, that's what calories are like. You know, that does things. The glycemic index, that does everything. Cholesterol theory, that well, that does everything. And now Prowl seems to be standing at the front of the classroom saying, Don't worry everyone, I can explain human health with this spreadsheet. No, Prowl, no you cannot. One of the stranger ideas around Prowl and alkaline diet thinking is the suggestion that we can meaningful meaningfully alkalise the body by eating certain foods. Now that sounds lovely until you rem remember one fairly important detail. The body tightly regulates blood pH. Blood pH is normally maintained in a very narrow range, around 7.35 to 7.45. Water is neutral at seven, and blood is around, like I say, 7.4, because it has an alkaline base, a reservoir of alkaline. It works out already. But anyway, if your blood pH moves significantly outside that range, you don't need a green juice. You need urgent medical care. Your body regulates acid base balance through the lungs. Through the kidneys, bicarbonate buffering, respiration, electric handling, and multiple layers of biochemical control. It is not sitting there waiting for a broccoli to arrive and take over middle management. This is why the phrase alkalize your body is so often misleading. And urine pH can change, renal acid excretion can change by Carbonate levels can matter, especially in certain disease states, but blood pH is not casually drifting around because someone's had a salad. Your body is not like a paddling pool. You don't alkalyze it by throwing in a cucumber. And then we have the stomach acid problem. Your stomach acid is incredibly acidic. Stomach acid can sit around pH 1 to 2. Remember the pH scale is logarithmic, which means each whole number represents a tenfold difference. So something at pH two is not just a bit more acidic than something at pH seven, it's about a hundred thousand times more acidic. At pH one it is about a million times more acidic than neutral pH seven. So when someone implies that broccoli, quinoa, lemon water or fruit is going to have some dramatic alkalising effect on the body, We need to have a little pause, not because broccoli is bad necessarily, I'm I'm gonna say that broccoli is innocent, but because the human digestive system is not impressed by a prowl table taped to your fridge. A piece of broccoli lands in stomach acid that's powerful enough to dissolve many of the arguments made by vegans about broccoli. Now, to be fair, prowl is not exactly the same as testing the pH of food, and that distinction does matter. A lemon may taste acidic and have an acidic pH, but it may be considered alkali producing according to Prowl because of what happens after metabolism. Likewise, meat does not taste acidic, but it tends to have a higher prowl score because of its protein and phosphorus content. So yes, prowl is more sophisticated than simply saying lemons are acidic and spinach is alkaline. But more sophisticated does not automatically mean clinically useful for everyone. A chocolate teapot is also more sophisticated than a paper cup. I still wouldn't make it central to kidney care. And this brings us to one of the strangest parts of the alkaline diet world, the old acid ash hypothesis. In simple terms, foods were burned down, the remaining mineral ash was assessed, and from that people started making assumptions about whether a food was acid forming or alkaline forming in the body. Which is quite a leap. Well because and forgive me for getting technical here, you're not a Bunsen burner. When food is eaten, it is not incinerated into a little pile of ash while the kidneys sit there interpreting the smoke signals. You chew it, digest it, the body absorbs it, then it metabolizes it. Some is stored, some is converted, some byproducts are breathed out, others are excreted. Hormones respond, the liver responds, and the gut. gets involved as well. The pancreas has an opinion. The kidneys and the lungs help regulate the whole system and the nervous system is never that far away. In other words, you're alive, which is metabolically inconvenient for these overly tidy theories. Burning a piece of fruit in a lab destroys the sugar. It destroys the structure and it destroys the yeast, the fibre matrix, the organic compounds, and much of the context that matters in a real human body. But when a person actually eats fruit, for instance, the sugar has to be metabolized. And fructose is a perfect example of why the ash idea can be misleading. Burn fruit in a lab and the sugar's gone. Eat it and the fructose enters metabolism. In the liver, fructose can drive ATP depletion, activate AMP degradation pathways, and increase uric acid production. Now that is not theoretical ash chemistry, that is human biochemistry. Just as an aside, uric acid gets oversimplified as well very often. High uric acid is often treated as if it is automatically predicting gout. When in real life it's usually far messier than that. That's from decades of private blood testing. But the point still stands. A food's ash value tells us very little about the metabolic consequences of actually eating it. The same applies to carbohydrate metabolism more broadly. I mean when carbohydrate is metabolized, Carbon dioxide is produced. Carbon dioxide combine combines with water to form carbonic acid. Thankfully the body has a very clever system for this. Much of that CO2 is just simply breathed out. The lungs and kidneys are constantly involved in acid base regulation. So when someone says fruit is alkalising, the obvious question is compared with what? Compared with what's burnt and the remains in a dish? Compared with its mineral content on a spreadsheet, or compared with what actually happens in a person with carbohydrate intolerance or type 2 diabetes, fatty liver, high triglycerides, insulin problems, and kidney disease. Because those are very different conversations. And this is where prowl can become nutritional origami. Fold the food enough times and you can make it look like anything. A fruit may look wonderful on a prowl table because of potassium and mininum. and mineral content. But if that same fruit worsens blood glucose, increases glycemic variability, raises insulin demand, contributes to fatty liver, or drives fructose metabolism in someone already metabolically unwell, then waiving a negative prowl score is a is a is a it's really not about joint up thinking. It is just a spreadsheet of nutrition. And spreadsheet nutrition is what happens when someone studies the map so intensely They forget to look out of the window and notice the car is in a ditch. The body is not interested in whether a food behaved itself after being cremated in a lab. It is interested in what happens after it is eaten. Glucose, insulin, liver metabolism, uric acid, bicarbonate, kidney function, respiratory compensation, electrolytes, blood pressure, inflammation satiety, nutritional density, and the person's actual health history all matter. So saying fruit is alkalising while ignoring fructose metabolism is like saying this petrol is very hydrating because it contains hydrogen. Technically interesting, but practically that is insane. Anyway, another important point is this urine pH is not blood pH. Prowl may influence urine pH. That does not mean it is meaningfully changing blood pH. If urine Becomes more acidic after eating certain foods, that does not mean the whole body has become dangerously acidic. It means the kidneys are excreting acid. That's not a failure. That is what the kidneys are doing. They're doing their job. Looking at urine pH and concluding that the whole body is too acidic is like looking in your kitchen bin and concluding your entire house is made of banana skins. The bin is where waste goes. Urine is one way the body gets rid of what it needs to get rid of. That is not the same as your bloodstream turning into vinegar. Now, let's be sensible. Metabolic acidosis is real in people with significant kidney dysfunction. The kidneys may struggle to excrete acid properly and maintain their bicarbonate levels. Low serum bicarbonate can be clinically important. So I'm not saying acid-based physiology is irrelevant. I'm saying it is frequently oversimplified. And there is a world of difference between saying advanced kidney disease can impair acid excretion and contribute to metabolic acidosis and saying meat is acidic, fruit is alkalising, therefore eat more plants. The first statement is physiology. The second is like a little fridge magnet wearing a stethoscope. And this is where Prowl recommendations start to wobble pretty badly. I mean, a lot of people with kidney disease are not there because they ate too much steak. One of the biggest drivers of chronic kidney disease is type 2 diabetes. And type 2 diabetes is common sense. When you look at it, it's chronically elevated blood glucose and carbohydrate intolerance. I know this from hundreds of people reversing type 2 diabetes by removing carbohydrates. Real world experience. So if someone has kidney disease driven by years of poor blood glucose control or as people call it insulin resistance or hypertension and metabolic dysfunction, then recommending more fruit, beans and carbohydrate rich plant foods as a blanket kidney friendly strategy, well that's that's pretty glib. It may look good on a prowl chart, but does it make sense in the person in front of you? If someone's kidneys have been damaged by long term glucose dysregulation, improving glucose control should be central, not an afterthought. Telling a person with carbohydrate intolerance to eat more sugar containing foods because they are alkalizing is a little bit like telling someone with sunburn to stand closer to the sun because vitamin D is important. There may be a sil a sort of sliver of truth in there somewhere, but it is ridiculous. But the application here is that we need to look at the whole person. You you could start with the HBA1C of your patient, although HBA1C is useful. Because it gives an idea of an average blood glucose over two to three months in a in a person eating the standard diet. But it can be affected by red blood cell turnover or anemia or kidney disease and other fac factors. So the fructosamine assay can be especially useful because it reflects roughly the previous three weeks of lifestyle. And that shorter window can be incredibly helpful when someone has recently changed their diet, for instance, reducing carbohydrates, or they've gone ketogenic or moved towards carnival. If someone has made big dietary changes, fructosamine may actually give you a quicker sense of what is happening metabolically than waiting months for an HBA one C to fully catch up. And this matters because kidney health should not be discussed in isolation from glucose control, especially when diabetes is such a major root cause. The same problem appears with the claim that fruit is automatically kidney friendly. Fruits are often presented as kidney friendly because many have a low or negative prowl value. But fruit is not just potassium and water wearing a nice colour. Many fruits contain sugar, some contain a meaningful amount of fructose. And fructose metabolism has specific effects in the liver, including ATP depletion and uric acid production pathways. That does not mean all fruit is evil, by the way. It means a blanket eat more fruit for kidney health message is too simplistic. The first thing that matters is the person eating it. Their blood glucose response matters, their carbohydrate tolerance matters, fatty liver, triglycerides, insulin, sensual obesity, hypertension, kidney function, medication use, and type 2 diabetes, they all change the conversation in some way. Then we need to look at those markers, like I say, HBA1C gives us part of the picture, fruct fructosamine can show what has happened over the last few weeks. But what about waste circumference, blood pressure, liver enzymes? Again, triglycerides and kidney markers help fill in the rest. In other words, look at the person, look at their markers. Not just the fruit bowl. The body does not care if a food won the Prowl Beauty contest, it cares what happens after it is eaten. Another common trick is to compare a high acid diet with a plant-based diet and then imply that meat is the problem. But what is often called a meat-rich or high-acid Western diet is usually not just meat. It is often burgers in buns, chips, seed oils, fizzy drinks, sweet sauces, biscuits, pizza, breakfast cereals, crisps, refined grains, alcohol, desserts, ultra-processed snacks and and a lifestyle held together by caffeine and a lot of regret. That's not carnivore, that is not even properly meat based. That is a processed food diet with occasional animal products at the crime scene. Now blaming meat for the health effects of the standard American diet is like blaming the lifeboat because the ship hit an iceberg. A steak with eggs and salt is metabolically very different from a burger in a bun with fries cooked in industrial oils with ketchup and coda and it is large enough to require planning permission. So the context matters and And this is where interpreting bloods in the context of a carnivore or ketogenic way of eating is crucial. Without that context, perfectly explainable patterns can be misread. A person eating low carb or carnivore may have very different glucose, insulin levels, triglyceride, HDL, uric acid, thyroid, and kidney marker patterns compared with someone eating a standard processed diet. You cannot interpret physiology properly if you ignore the diet producing it. Meat tends to score higher on the prowl because it contains protein and phosphorus. But that does not mean meat is harmful. It means meat contains nutrients that influence renal acid handling. But meat also provides highly bioavailable protein and B vitamins and hemine and zinc, selenium, creatine, carnitine, taurine, glycine, the amino acids that make collagen. And depending on the cut, That can be in quite big quantities and many other nutrients. Don't forget fish. That may so may also provide DHA, which is an essential fatty acid. It's critically important for brain health as well. A prowl score captures none of that richness. It cannot show whether someone is preserving muscle, eating enough protein, reversing type two diabetes, improving blood pressure, losing visceral fat, lowering triglycerides. Reducing cravings or finally escaping the snack cupboard. It also cannot separate a person from eating ribeye and eggs from someone eating ultra processed nonsense with a slice of ham hiding inside it. Prowl gives you just one narrow number, which is it useful in context? Well possibly. A complete nutritional f philosophy? No, absolutely not. Another implied message in some Prowl discussions is that Proud. Protein, especially animal protein, is automatically hard on the kidneys. Now this needs nuance too. In people with established kidney disease, protein intake may need to be personalized. And that is a proper clinical discussion based on kidney function, stage of the disease, overall health, medications, muscle mass, nutritional status, and goals. But in people with normal kidney function, protein is not a kidney destroying villain hiding inside a chicken breast. The kidneys filter. That is what kidneys do, amongst other things. Say saying protein makes the kidneys work harder can be like saying working your legs harder comes from walking. You know, technically true, but walking is good for you. Not automatically a problem, obviously. And if someone is older, under muscled, have problems with insulin or trying to lose weight, adequate protein may be the one thing that is most important as a part of their diet. A low prowl diet that leads to poor protein intake, muscle loss, and worsening metabolic health is not a triumph. It's a spreadsheet winning an argument against a bicep. I mean kidney function is often assessed using EGFR, commonly calculated from creatinine. Now creatinine based EGFR can be useful, but it can also be misleading. Creatinine is influenced by muscle mass and meat intake, creatinine, creatine, sorry, supplementation, hydration, and other factors. So someone eating a meat heavy diet, some muscular or someone using creatin may have a creatinine problem that actually needs careful interpretation. This is why cystatin C tends to be a more accurate test in many situations when assessing kidney function, because it is less influenced by these things, muscle mass, ethnic. origin and meat intake. That does not mean creatinine is useless, it just means, again, context matters. It's annoying, isn't it? Almost as if humans are more complicated than a colour coded diet chart. You will also often see claims that high prowl diets are associated with. Kidney disease or hypertension or osteoporosis or insulin resistance, cardiovascular disease, and other problems, but associated with is doing a lot of heavy lifting. A high prowl diet in population studies may also be a diet higher in ultra processed foods, or refined grains, or sugar, or industrial oils, alcohol, and poor lifestyle patterns. So when poorer outcomes are observed, we have to slow down. Was it really the acid load? Or was it the background noise doing most of the damage? Was it the sugar? Was it obesity? Insulin? hypertension, poor sleep, alcohol, smoking, inactivity, ultra processed food, and low nutritional density. I mean all of those things often travel together. They do not politely stand apart in a study and wait for the researchers to blame one of them at a time. If someone eats burgers, chips, biscuits, cereal, pizza and cola, is the real reason an issue the prowl score? Or is the issue that they are eating like a raccoon at a motorway service station? And then this is why better questions matter. Instead of obsessing over whether a food is acid forming or alkalising, the more useful question is what actually happens in the person eating it? After a meal, does the blood glucose does it rise gently or does it spike dramatically or barely move at all depending on the person and the food? Over the next few weeks, it's Fruitosamine could show whether lifestyle is genuinely improving and the reaction to glucose. Over a few months, you could use the HBO1C because that does not add another layer of information. And then there is the much bigger picture which is which is appetite and cravings, your blood pressure, triglycerides, waste circumference, liver enzymes, muscle mass, energy, sleep, inflammation, and medication use, because they all matter. A food that looks perfect on a prowl chart. But drives hunger and glucose swings and fat gain that's not helping. And a food that scores badly on prowl but improves satiety, supports muscle, stabilizes blood glucose, reduces cravings and helps reverse type 2 diabetes should not be dismissed because it it's upset the calculator. Kidney health also needs a root cause conversation. Is the problem long-term diabetes or hypertension? Is it medication related? Or is it an autoimmune condition? Is it infection related? Is it structural? Is it something else entirely? And once that is clearer, the bloods need interpreting properly. Not just creatinine-based EGFR in isolation, but the wider pattern with cystatin C where appropriate. And most importantly, we need to watch what happens over time, because that is real life. That is joined up thinking, not broccoli good beef bad thinking. From a ketogenic or carnivore perspective, PREL has to be interpreted very carefully. A carnivore diet may score as acid producing on paper, but in the real world, many people eating this way see improvements in body weight, in blood glucose, in insulin management, triglycerides, blood pressure, fatty liver markers, appetite control, inflammation, and overall metabolic health. That matters. So, if someone improves the very metabolic factors that damage the kidneys, should we panic because a formula says the diet has a positive prowl score? That seems like staring at the dashboard while driving into a wall. A positive prowl score does not automatically mean harm, and a negative prowl score does not automatically mean health. If a person eating a high carbohydrate alkalizing diet has worsening glucose control, A rising HBA1C, poor fructosamine, increasing waste circumference, high triglycerides and declining kidney function, I am not reassured because the kidney beans scored well on a chart. Equally, if someone eating meat, eggs and fish improves metabolic health, normalizes glucose, lowers blood pressure, improves their body composition and has stable kidney markers, I'm not panicking because their lunch offended a prowl calculator. So where does that leave us? Prow is not completely useless. It may provide some insight into estimated renal acid load, particularly in specific kidney disease contexts where acid base handling does genuinely matter. But the way Prow is often presented has obvious holes. The body tightly regulates blood pH, and urine pH is not blood pH. Stomach acid is vastly more acidic than the foods people worry about. The old acid ash idea came from burning food. This is where prowl got their origins from. Burning food and judging the residual, which is not the same as human metabolism. Like I say, fruit may look alkalising on the prowl chart, but fructose still has to be metabolized in the body and can contribute to acid uric acid production. Carbohydrate metabolism produces carbon dioxide, which feeds into acid bate food. Based physiology and is largely handled through respiration. A prowl score does not define whether a food is healthy, and association does not prove causation. The standard American diet is not the same as a ketogenic or carnivore diet. Most kidney disease discussions start with root cause, especially type 2 diabetes, then hypertension and metabolic dysfunction. Creatinin based EGFR can be misleading. And cystatin C often gives a better picture. HBA1C is useful, but fructosamine can be especially helpful because it reflects the previous three weeks of lifestyle. And above all, interpreting blood in the context of carnival or a ketogenic way of eating is crucial. So, Prowl might be an interesting tool, but if your entire nutritional worldview depends on the idea that broccoli is bravely defending your bloodstream from a pork chop. It may be time to step away from the calculator and just return completely to physiology. You know, the kidneys are clever, the lungs know what they're doing, the liver knows what it's doing. The human body is very clever. Nutrition should try to keep up. And before blaming the steak, perhaps check whether the person has spent the last 20 years bathing their metabolism in toast, cereal, orange juice, pasta, muffins, and healthy fruit smoothies. The broccoli may be innocent. But it probably isn't the hero of this film. So that's it in a nutshell. Hope you enjoyed that. If you did, please consider liking, sharing, and subscribing. Hitting the notification bell if you want to be reminded of new videos that are coming up. I sort of try and do one or two a week if I can. Drop a comment and any thoughts if you've got any real experience. I'm a great believer actually in looking what's happened to real people. So recently I did a great success story, Ben who got his EGFR from four to forty-nine and he was eating carnivore. And when he went plant plant-based before that his kidney function actually started go towards four. So, you know, I see this all the time. I've got more than one success story on here regarding returning kidney function. So yeah, I'm quite passionate about it. And I do think we need to look at the broader aspects of human physiology before we start using check boxes and and just talking about what you've seen when you've got some fruit and you've burnt it and you've looked at the ash and thought, yes, this is very alkalising based on what's left in the ash. Anyway, thanks very much for watching. See you on the next one. I'll be back.