The Alkaline Diet: Foods, pH Claims and Evidence

The alkaline diet is an eating pattern that favors foods said to be "alkaline-forming", mainly vegetables and fruits, and limits "acid-forming" foods such as meat, cheese and many grain products. What you eat does change the acidity of your urine, but your body keeps blood pH within a very narrow range regardless of diet, so the central promise of "alkalizing your body" is not supported. The parts that help are the ordinary ones: more vegetables and fruit and fewer highly processed foods.

Key Takeaways

The diet ranks foods by their estimated acid load after digestion (potential renal acid load, or PRAL), not by how acidic they taste [3].
Blood pH is tightly regulated at about 7.35-7.45; diet shifts urine pH instead [1, 2, 4].
Systematic reviews found no support for the popular bone-protection claim and almost no research at all behind the larger health claims [5, 6].
Its genuine upside is eating more vegetables and fruit and less highly processed food, which matches federal dietary guidance [7].
Strict versions can cut protein foods and dairy too far; people with reduced kidney function should check potassium intake with a clinician [7, 8].

Evidence grade: Emerging. Diet reliably changes urine pH in human studies, but there are almost no controlled trials of the alkaline diet itself, and systematic reviews of its main claims found either no supporting evidence or no eligible trials [4, 5, 6].

What the Alkaline Diet Is

The alkaline diet (also sold as the "acid-alkaline" or "alkaline ash" diet) rests on one idea: some foods leave an acid residue in the body after they are metabolized and others leave an alkaline one, so eating mostly "alkaline" foods should shift the body toward a healthier pH. Supporters usually say the ideal is "slightly alkaline, around 7.4". That number is real, but it describes blood, and it is already where your body holds it [1].

Researchers do have a way to estimate a food's acid effect. The potential renal acid load (PRAL), developed by Remer and Manz, uses a food's protein, phosphorus, potassium, magnesium and calcium content to predict how much acid the kidneys will need to excrete. In their 1995 calculations, values ranged from about +23.6 mEq per 100 g for some hard cheeses, through 0 for fats and oils, to about -3 for fruits, fruit juices and vegetables (negative means alkaline-forming) [3]. Taste is not the measure: orange juice tastes acidic but has a negative (alkaline-forming) PRAL [1].

Basket of fresh apples and walnuts on a wooden bench

Foods the Alkaline Diet Emphasizes and Limits

Popular alkaline-diet lists vary, and some of them do not match the PRAL data. A 2012 review reproduced published PRAL values for common foods; a selection is below (per 100 g; negative = alkaline-forming, positive = acid-forming) [1].

Food group	Example PRAL values (mEq/100 g)	Alkaline-diet view
Vegetables	Spinach -14.0; celery -5.2; tomato -3.1; broccoli -1.2; green beans -3.1	Emphasized
Fruits and juices	Raisins -21.0; banana -5.5; apricots -4.8; orange juice -2.9; apples -2.2	Emphasized
Fats and oils	Olive oil 0.0; butter 0.6	Neutral
Grains	Brown rice 12.5; rolled oats 10.7; whole-wheat bread 1.8	Often limited, though whole grains are frequently listed as "allowed"
Nuts and legumes	Peanuts 8.3; walnuts 6.8; lentils 3.5	Often listed as alkaline, but these values are positive
Meat, fish and eggs	Turkey 9.9; lean beef 7.8; cod 7.1; whole egg 8.2	Limited
Dairy	Parmesan 34.2; hard cheese (average) 19.2; whole milk 0.7	Limited, especially cheese

Two things stand out. First, the foods with the most negative values are vegetables and fruit, which is the part of the diet worth keeping. Second, many nuts, legumes and whole grains that alkaline-diet blogs promote are mildly acid-forming by PRAL, which shows how loosely the label is used. A food's PRAL is also not a measure of its nutritional value: lentils, oats and fish are nutritious foods with positive scores.

Can Food Change Your Blood pH?

Not in a healthy person. Human blood is held at about pH 7.4, within a range of roughly 7.35 to 7.45 [1]; the MedlinePlus reference range for arterial blood is 7.38 to 7.42 [2]. The lungs and kidneys keep it there whatever you eat. A value outside that range is a medical problem that needs care, not something a meal plan creates or fixes.

What diet does change is urine. Remer and Manz found that estimated net acid excretion from diet correlated strongly with urine pH (r = 0.83) [3]. In the EPIC-Norfolk study of 22,034 adults, a lower dietary acid load, more fruit and vegetables and less meat were each associated with more alkaline urine [4]. Urine pH changes because the kidneys are doing their job of removing excess acid or base, which is why the body's blood pH stays stable.

That is also why home urine strips are a poor guide. They can tell you your recent diet contained more produce, but they are not a reading of your blood or of your "body pH".

What the Research Says About the Bigger Claims

Bones and calcium

The best-known theory, the "acid-ash hypothesis", says acid-forming diets draw calcium out of bone to buffer acid. A 2009 meta-analysis limited to high-quality calcium balance studies in healthy adults (5 of 16 studies qualified) found that higher acid excretion did raise urine calcium, but it did not change overall calcium balance or a blood marker of bone breakdown. The authors concluded that promoting the alkaline diet to prevent calcium loss is not justified [5].

Larger health claims

Some promoters claim the diet protects against serious illness, including cancer. A 2016 systematic review in BMJ Open screened 8,278 citations on dietary acid load, alkaline water and cancer and found only one study that met its criteria, a cohort study that showed no association. It found no randomized trials, and the authors wrote that there is almost no research to support or disprove these ideas and that promoting the diet or alkaline water to the public for that purpose is not justified [6].

The more favorable review

A 2012 narrative review by Schwalfenberg is often quoted by supporters. It agreed that alkaline diets make urine more alkaline, said there was no substantial evidence that this improves bone health, and suggested that the extra fruits and vegetables could have other benefits, while noting that there were limited scientific studies and that many more were needed [1]. A narrative review is not a trial, so these are hypotheses rather than findings.

What Is Genuinely Good About It

More vegetables and fruit. The 2025-2030 Dietary Guidelines for Americans recommend eating a variety of colorful vegetables and fruits, about 3 servings of vegetables and 2 of fruit a day at 2,000 calories [7]. Most alkaline-diet plans push past that.
Less highly processed food. The Guidelines advise limiting highly processed foods, added sugars and excess sodium [7], which most alkaline plans also discourage.
A better potassium-to-sodium balance. Schwalfenberg points out that modern diets have flipped from a high potassium-to-sodium ratio to a low one, and that more fruit and vegetables shifts it back [1]. Our guide to potassium benefits and food sources covers the mineral itself.

None of these depend on changing your pH. They are the same reasons almost every well-studied eating pattern, such as the Mediterranean diet, centers on plant foods.

What Is Not Supported

That food can make your blood more alkaline, or that you need to "alkalize" it [1, 2].
That urine pH readings show your body's pH [3, 4].
That acid-forming foods leach calcium from bone in healthy people [5].
That the diet or alkaline water prevents or treats serious disease [6].
That it boosts energy or "detoxes" the body. We found no controlled trials of these outcomes; for the detox idea in general, see debunking detox diets.

The Alkaline Diet and Weight

Weight loss is often presented as a built-in result of the diet. We could not find controlled trials of the alkaline diet itself with weight as the outcome, so there is no measured effect to report. Any weight change people notice is most plausibly explained by eating fewer calories than they burn, which NHLBI describes as the basis of weight loss on any plan [9]. Swapping processed snacks, cheese and refined grains for vegetables and fruit can make that easier, but the pH theory adds nothing. Celebrity endorsements, a theme of the older posts, are covered in our look at celebrity fad diets.

How to Try a Sensible Version

Build most meals around vegetables and fruit, aiming at or above the Dietary Guidelines servings [7].
Keep protein foods at every meal, as the Dietary Guidelines advise, choosing fish, poultry, eggs, beans and lentils as you prefer [7]. Do not drop them because of a positive PRAL.
Keep dairy or another calcium source; the Guidelines suggest about 3 dairy servings a day at 2,000 calories [7].
Cut highly processed foods, sugary drinks and salty snacks, which is where much of the benefit really comes from [7].
Skip pH test strips, alkaline water and "alkalizing" powders; they measure or target the wrong thing [1, 6].

Safety and Interactions

A produce-heavy diet is safe for most people, but strict alkaline plans raise a few issues:

Too little protein or calcium. Plans that cut meat, fish, eggs, dairy and grains together can leave gaps. The Dietary Guidelines recommend protein foods at every meal and regular dairy [7].
Potassium and kidney function. Fruits and vegetables are the main sources of dietary potassium. The NIH Office of Dietary Supplements notes that people with impaired potassium excretion, such as those with chronic kidney disease, can develop high blood potassium even from food [8]. If you have kidney problems, talk to your doctor or a registered dietitian before sharply increasing produce.
Medications. Talk to your doctor or pharmacist if you take an ACE inhibitor or a potassium-sparing diuretic, since ODS lists both as reducing potassium excretion [8].
Salt substitutes. Many contain potassium chloride, roughly 440 mg to 2,800 mg of potassium per teaspoon, so the same cautions apply [8].
Do not delay care. If you have a diagnosed condition, the alkaline diet is not a substitute for treatment from your clinician.

Frequently Asked Questions

Does the alkaline diet change your blood pH?

No. Blood pH stays at about 7.35-7.45 in healthy people whatever they eat; diet changes urine pH instead [1, 4].

Which foods are considered alkaline?

By PRAL, mainly vegetables and fruits, such as spinach, celery, tomatoes, bananas, apricots and raisins. Meat, fish, eggs, cheese and most grains are acid-forming, and so are peanuts, walnuts and lentils, even though many lists call them alkaline [1, 3].

Do urine pH strips show whether the diet is working?

They show that your urine became more alkaline, which mostly reflects eating more produce and less meat [4]. They do not measure blood or "body" pH.

Can the alkaline diet help with weight loss?

We found no controlled trials measuring weight on the alkaline diet itself. Weight change on any diet comes down to energy balance [9]; replacing processed foods with produce may help with that, independent of pH.

Is lemon water alkaline?

Lemons taste acidic, but PRAL tables put fruits and fruit juices on the alkaline-forming side [3]. That affects urine, not blood, so lemon water does not "alkalize" the body.

Is the alkaline diet safe?

A version built on plenty of vegetables and fruit with enough protein and calcium is reasonable for most people. Very strict versions can fall short on protein and calcium, and people with reduced kidney function or on certain medications should check their potassium intake with a clinician [7, 8].

Sources

Disclosure: OPA Nutrition sells supplements, including products mentioned in this article. This content is for education only and is not medical advice. Statements about dietary supplements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your healthcare provider before using any supplement, especially if you take medication or have a medical condition.

Written and reviewed by Michael Gonzales, Founder, OPA Nutrition · Last reviewed: October 17, 2026 · How OPA researches and writes

The Alkaline Diet: What It Is and What the Evidence Shows

Key Takeaways

What the Alkaline Diet Is

Foods the Alkaline Diet Emphasizes and Limits

Can Food Change Your Blood pH?