Is the Alkaline Diet Good for Your Health?

The pro­po­nents of the Alka­line Diet are urg­ing you to eat the right foods, but for the wrong rea­sons. The Alka­line Diet is based on the idea that you should eat foods that have an alka­lin­iz­ing (pH-rais­ing) effect on the body, while avoid­ing foods that have an acid­i­fy­ing (pH-low­er­ing) effect on the body. The pro­po­nents of the Alka­line Diet often make claims that are clear­ly non­sense. For exam­ple, some of them claim that the diet will cause your blood pH to rise to 8.5, thus killing can­cer cells while allow­ing ordi­nary cells to sur­vive. That is clear­ly false. On the oth­er hand, some detrac­tors of the Alka­line Diet also say some things that are false. Some of them are sim­ply against veg­an diets, for ide­o­log­i­cal rea­sons. Oth­ers fail to grasp how an acidic food, such as lemon juice, could end up hav­ing a net alka­lin­iz­ing effect on the body, as I’ll explain below.

If you eat the kind of diet that the pro­mot­ers of the Alka­line Diet rec­om­mend, your health will almost cer­tain­ly improve. The foods that have the strongest acid­i­fy­ing effect on the body come from ani­mals: dairy foods, meats, fish, and eggs. Grains and beans have only a small acid­i­fy­ing effect. In con­trast, near­ly all fruits and veg­eta­bles have a net alka­lin­iz­ing effect. For this rea­son, peo­ple who avoid the most acid­i­fy­ing foods will end up eat­ing a veg­an diet, includ­ing lots of fruit and veg­eta­bles.

A veg­an diet is great for your health, as long as you don’t eat too much fat (from oils, nuts, or avo­ca­does) or too much refined sug­ar (emp­ty calo­ries) and as long as you take a vit­a­min B12 sup­ple­ment. A low-fat veg­an diet pro­vides plen­ty of fiber and car­bo­hy­drate. It pro­vides no cho­les­terol or ani­mal pro­tein. As a result, a low-fat veg­an diet will sta­bi­lize your blood sug­ar, help you lose weight, and reduce your risk of heart attack, stroke, and many can­cers and autoim­mune dis­eases. Yet even if you are eat­ing a lot of alka­lin­iz­ing fruits and veg­eta­bles, your blood pH will not change. It will stay at almost exact­ly 7.4, unless you get real­ly sick. Nev­er­the­less, the alka­lin­iz­ing effect of a veg­an diet does pro­vide a few ben­e­fits: a decrease in the risk of gout, kid­ney stones, and osteo­poro­sis.

The Alka­line Diet has come under fire from skep­tics who point out (cor­rect­ly) that this diet does not real­ly alter the pH of your blood. Unfor­tu­nate­ly, many of these skep­tics are unaware of (or in denial about) the health ben­e­fits of a low-fat veg­an diet. Some of them even fail to under­stand how an acidic food like lemon juice (pH of 2.0 to 3.0) could have a net alka­lin­iz­ing effect on the body.

All foods are mix­tures of organ­ic and inor­gan­ic com­pounds. If you burn a piece of food in a lab­o­ra­to­ry, most of the organ­ic com­pounds will be oxi­dized to form car­bon diox­ide and water. After the food is com­plete­ly burned, you will be left with an ash that con­tains inor­gan­ic com­pounds. The ash will con­tain some impor­tant cations (pro­nounced cat-eye-ons), includ­ing the alka­line met­als (sodi­um and potas­si­um) and alka­line earth met­als (cal­ci­um and mag­ne­sium), and some impor­tant anions, includ­ing sul­fates and phos­phates. If you dis­solve that ash in water, the pH of the water could go up or down. If the ash is rich­er in the alka­line met­als and alka­line earth met­als than in sul­fates and phos­phates, the pH of the water will go up (alka­lin­iz­ing effect). If the ash is rich­er in sul­fates and phos­phates than in the alka­line and alka­line earth met­als, the pH of the water will go down (acid­i­fy­ing effect).

When you metab­o­lize your food, you burn up most of the organ­ic com­pounds, includ­ing many (but not all) of the organ­ic acids. You will be left with an alka­line or acidic ash, plus the organ­ic acids that your body can­not metab­o­lize. These acidic and alka­line byprod­ucts of metab­o­lism will cir­cu­late in your blood­stream until they are lost in your urine. In the mean­time, they will seem to have lit­tle or no effect on the pH of your blood. Instead, they will main­ly affect the pH of your urine. You can make a rea­son­ably accu­rate pre­dic­tion of how much of an effect a serv­ing of any food will have on the pH of urine by mea­sur­ing the amounts of pro­tein (a source of sul­fur), phos­pho­rus, cal­ci­um, potas­si­um, and mag­ne­sium that are in the food and plug­ging the results into an equa­tion.

The pH of your blood must stay at almost exact­ly 7.4 (slight­ly alka­line) all the time, or you will die. To keep the blood pH at 7.4, the body has an elab­o­rate sys­tem of buffers. The main buffer is derived from car­bon diox­ide. The body uses an enzyme called car­bon­ic anhy­drase to speed up the con­ver­sion of car­bon diox­ide and water to car­bon­ic acid (H2CO3) and vice ver­sa. Car­bon­ic acid is a weak acid, which means that when it is dis­solved in water, only a small per­cent­age of its mol­e­cules get pulled apart into hydro­gen ions (H+) and the acid’s con­ju­gate base (bicar­bon­ate, HCO3). An even small­er per­cent­age of the bicar­bon­ate ions get pulled apart into H+ and car­bon­ate ions (CO3–2).

The pH of an aque­ous solu­tion is a mea­sure of the con­cen­tra­tion of H+ ions. In pure water, the H+ con­cen­tra­tion is about 1 ten mil­lionth of a mole per liter, or 1 × 10–7 M, which is a pH of 7 (the neg­a­tive of the base-10 log­a­rithm of the H+ con­cen­tra­tion). If you added enough acid to make the H+ con­cen­tra­tion go up to one mil­lionth of a mole per liter (1 × 10–6 M), the pH would go down to 6. In oth­er words, more H+ means low­er pH. (That explains why sea water is becom­ing more acidic as the amount of car­bon diox­ide in the atmos­phere ris­es!) In con­trast, when the con­cen­tra­tion of H+ in an aque­ous solu­tion goes down, the pH of the solu­tion goes up.

The con­ju­gate bases of a weak acid (e.g., bicar­bon­ate and car­bon­ate ions) are unsta­ble. When they meet up with a hydro­gen ion in solu­tion, they are like­ly to react with it. Thus, a car­bon­ate ion is like­ly to bond with an H+, to become a bicar­bon­ate ion. A bicar­bon­ate ion is like­ly to bond with an H+, to become car­bon­ic acid. If the car­bon­ic acid con­tent of the solu­tion ris­es, more of the car­bon­ic acid gets con­vert­ed back to car­bon diox­ide and water. The car­bon diox­ide can then be lost to the atmos­phere.

When you mix a weak acid with its con­ju­gate base, such as mix­ing car­bon­ic acid with sodi­um bicar­bon­ate, you get a pH buffer. If you add a lit­tle bit of acid to blood, the bicar­bon­ate and car­bon­ate ions will imme­di­ate­ly bind most of the incom­ing hydro­gen ions. Thus, the num­ber of hydro­gen ions in the solu­tion will go up very lit­tle (i.e., the pH will not drop by much). The abil­i­ty of a solu­tion to take in acids or alka­lis with­out chang­ing its pH is called the buffer capac­i­ty.

The car­bon­ic acid/bicarbonate buffer sys­tem plays an impor­tant role in sta­bi­liz­ing the pH of your blood. If you hold your breath, car­bon diox­ide will start to build up in your blood. As a result, the pH of your blood will drop (res­pi­ra­to­ry aci­do­sis). Your brain will notice this drop in pH and tell your res­pi­ra­to­ry sys­tem to breathe faster. As you blow off that extra car­bon diox­ide, your blood pH will rise back to a nor­mal lev­el. If you hyper­ven­ti­late, you will cause the car­bon diox­ide lev­els in your blood to drop to abnor­mal­ly low lev­els. As a result, your blood pH will go up. This effect is called res­pi­ra­to­ry alka­lo­sis. If some process in your body is gen­er­at­ing excess acid or alka­li, your res­pi­ra­to­ry sys­tem will try to com­pen­sate by adjust­ing your res­pi­ra­to­ry rate, to adjust the amount of car­bon diox­ide in your blood. As a result, your blood pH may still stay close to 7.4, even if you have a seri­ous prob­lem with acid-base bal­ance.

The kid­neys also play a role in con­trol­ling the pH of the blood. If your blood pH drops too low, you will pass more H+ and less bicar­bon­ate in your urine. As a result, your urine will become more acidic. If the pH of the blood ris­es too high, you will pass less H+ and more bicar­bon­ate in your urine. As a result, your urine will become more alka­line. Because of these and oth­er reg­u­la­to­ry sys­tems, the pH of your blood will stay remark­ably steady at about 7.4 (slight­ly alka­line), as long as you are in rea­son­ably good health. Mean­while, the pH of your urine will change dra­mat­i­cal­ly, depend­ing on what you have been eat­ing.

If you start eat­ing the Alka­line Diet, your blood pH will not change much. How­ev­er, your body’s abil­i­ty to buffer an acid load will increase. This increase in buffer­ing capac­i­ty explains why veg­an diets are use­ful in the man­age­ment of gout. Gout results when the blood becomes over­sat­u­rat­ed with uric acid. Uric acid is pro­duced when your body breaks down purines, which come from the break­down of DNA and RNA. Tis­sue that is high­ly active meta­bol­i­cal­ly (e.g., organ meats) is rich in purines. So is beer, because yeast is high­ly active meta­bol­i­cal­ly. When the blood becomes over­sat­u­rat­ed with uric acid from the diges­tion of purines, the uric acid starts to pre­cip­i­tate out as crys­tals in the joints (espe­cial­ly of the big toe) and the kid­neys. The result is gouty arthri­tis and kid­ney stones.

Although many veg­eta­bles are also fair­ly rich sources of purines, veg­etable foods do not seem to increase the risk of gout, prob­a­bly because they raise the blood’s acid-buffer­ing capac­i­ty. When the blood’s acid-buffer­ing capac­i­ty is high, more of the uric acid can remain dis­solved in the blood and urine. As a result, few­er urate crys­tals will form in the joints or in the uri­nary tract.

Not all kid­ney stones are made of urate crys­tals. Many kid­ney stones are made of cal­ci­um oxalate. Cal­ci­um oxalate kid­ney stones are also a com­mon result of an acid-form­ing diet. When the ordi­nary buffer­ing sys­tems are not enough to keep the blood pH at 7.4, the body may bor­row some cal­ci­um from the bones, to use as an antacid. How­ev­er, the body must also keep the cal­ci­um lev­els in the blood with­in a nar­row range, or the heart will stop. For this rea­son, the excess cal­ci­um is quick­ly lost in the urine. In the short run, this prob­lem can lead to the for­ma­tion of cal­ci­um oxalate kid­ney stones. In the long run, it can con­tribute to osteo­poro­sis.

Osteo­poro­sis is com­mon only where peo­ple eat a high­ly acid­i­fy­ing high-pro­tein diet. Tak­ing cal­ci­um sup­ple­ments may help to cor­rect the meta­bol­ic aci­do­sis in the short run, because of the calcium’s alka­lin­iz­ing effect. But in the long run, the com­bi­na­tion of an acid over­load and a cal­ci­um over­load (either from dairy foods or fish bones or from sup­ple­ments) can under­mine the body’s abil­i­ty to reg­u­late its cal­ci­um con­tent. If the blood cal­ci­um lev­els are chron­i­cal­ly high, the body may even­tu­al­ly lose the abil­i­ty to con­serve cal­ci­um. As a result, the cal­ci­um that has been bor­rowed from the bones is not effec­tive­ly replaced. So instead of rec­om­mend­ing cal­ci­um sup­ple­ments, doc­tors should be urg­ing patients to avoid eat­ing ani­mal foods and to eat more veg­eta­bles and fruit. Doc­tors should also urge patients to go out­side and play: to get exer­cise and rea­son­able expo­sure to sun­shine.

You can mea­sure the effects of diet on urine pH with­in a mat­ter of hours. But to see the effects of diet on health, you often must study a large num­ber of peo­ple over a long peri­od of time. For this rea­son, much of what we know about the effects of diet has been learned from epi­demi­o­log­ic stud­ies. Some of these stud­ies com­pare dif­fer­ent pop­u­la­tions at one point in time. Oth­ers focus on peo­ple who have migrat­ed from one coun­try to anoth­er. Still oth­ers track the same pop­u­la­tion over time. Each of these kinds of stud­ies has its own strengths and weak­ness­es. For exam­ple, dif­fer­ences between coun­tries could be due to con­found­ing vari­ables, such as genet­ic dif­fer­ences. Unfor­tu­nate­ly, many “skep­tics” dis­miss all of these stud­ies as “pseu­do­science” because these epi­demi­o­log­ic stud­ies do not fol­low the same meth­ods as phar­ma­ceu­ti­cal research. Up until recent­ly, “skep­tics” who worked for the tobac­co indus­try used the same kind of argu­ments to make peo­ple doubt that cig­a­rette smok­ing caus­es lung can­cer.

In oth­er words, the pro­po­nents of the Alka­line Diet are urg­ing you to eat a good diet, but for bad rea­sons. Mean­while, the skep­tics who debunk the Alka­line Diet are often try­ing to scare you away from eat­ing a good diet, for equal­ly bad rea­sons.

Pho­to by blu­men­bi­ene

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