Can You Please Tell Me More About the Acidity Alkalinity of Foods

8/11/2019 Can You Please Tell Me More About the Acidity Alkalinity of Foods

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Can you please tell me more about the

acidity/alkalinity of foods?

The issue of acid and alkaline foods is a confusing one,because there are several different ways of using these

words with respect to food.

The pH of foods

In food chemistry textbooks that take a Western science

approach to foods, every food has a value that is calledits "pH value." pH is a special scale created to measure

how acidic or alkaline a fluid or substance is. It ranges

from 0 (most acidic) to 14 (most alkaline) with 7.0 being

neutral. One way of thinking about it is that as you get

closer to 7.0 from either end, the food becomes less

acidic (6.0 vs 5.0, for example) or less alkaline (8.0 vs 9.0,for example).

Limes, for example, have a very low pH of 2.0 and are

highly acidic according to the pH scale. Lemons are

slightly less acidic at a pH of 2.2. Egg whites are not

acidic at all, and have a pH of 8.0. Meats are also non-

acidic, with a pH of about 7.0.

Many vegetables lie somewhere in the middle of the pH

range. The pH of asparagus, for example, is 5.6; of sweet

potatoes, 5.4; of cucumbers, 5.1; of carrots, 5.0; of green

peas, 6.2; of corn, 6.3. Tomatoes fit on the pH scale

toward the more acidic end in comparison to other



vegetables. Their pH ranges from 4.0 to 4.6. However,

this range is still higher (less acidic) than fruits like pears

(with a pH of 3.9) or peaches (with a pH of 3.5) or

strawberries (3.4) or plums (2.9).

Acid-forming foods

Another way to talk about food acidity is not to measure

the acidity of the food itself, but the to measure changes

in the acidity of body fluids once the food has been

eaten. In other words, from this second perspective, a

food is not labeled as "acidic," but instead as "acid-

forming."

Although the idea of acid-forming foods goes back

almost 100 years in the research, there's been very little

research published in this area until fairly recently. Inearlier publications, acid-forming foods were often

talked about as key components of an "acid-ash diet."

The term "ash" was used much more commonly in those

days to refer to the inorganic components of a diet

(mineral elements or molecules not containing carbon)

that remained after the digestion and metabolism offood had occurred. This ash was also commonly referred

to as a "residue" of the diet. Diets largely devoid of meat,

fish, eggs, cheese, and grains were described as

"alkaline-ash diets." These diets focused on consumption

of fruits and vegetables and also included cow's milk. By

contrast, diets containing large amounts of meat, fish,



eggs, cheese and grains were described as "acid-ash

diets."

Although the term "ash" is seldom used in currentresearch studies on diet, the idea of acid-forming foods

has remained a topic of research interest. A new term

has been created in the research world to refer to the

potential impact of certain foods on the kidneys and

urine acid levels. This term is "potential renal acid load"

or PRAL. For meats, a PRAL value of 9.5 has beenreported by researchers. Alongside of meats in terms of

high PRAL value are cheeses (8.0), fish (7.9), flour (7.0),

and noodles (6.7). In contrast with these high PRAL

values are the values for fruits (-3.1), vegetables (-2.8),

fruits, and cow's milk (1.0).

Researchers have been concerned about one particular

aspect of high-PRAL food intake, and that concern

involves bone health. It's always important for our

bloodstream to keep acidity under control. Our kidneys,

lungs, and other organ systems work hard to keep our

blood pH very close to 7.4. However, if presented with

too many acids from the digestion and metabolism offood, our body will try to neutralize those acids using a

process called buffering. To buffer an acid, our body

needs to link the acid with another chemical called a

"base." Sodium, potassium, calcium, and magnesium are

minerals that readily form bases for our body to use as

acid buffers. One readily available source for calcium is



bone, and researchers have wondered whether a diet

that is overly acid-forming will place too heavy demands

on our bone for calcium buffers. There's some research

that suggests this process may take place over the short

run (60 days or less), but the long-term impact of excess

acid-forming foods in the diet on bone calcium is not

clear from studies to date.

One of the factors that high-PRAL foods have in

common (with the exception of grains) is their highprotein content. Meat, fish, and cheese are all high-

protein foods. Because protein is composed of amino

acids, and because amino acids can be easily converted

in the body to organic acids, it makes sense for high-

protein foods to be treated as foods that can increase

potential renal acid load. When present-day researcherstry to model the potential acid-forming nature of a diet

(meaning the potential for a diet to increase the acidity

of our urine and acid load upon our kidneys), they

always factor in the protein density of the diet.

Potassium content, calcium content, and magnesium

content are also typically factored in because these

minerals readily form bases that can be used to help

buffer acids. Sometimes researchers also look at the ratio

of a potentially acid-forming component like protein to

an available buffering mineral like potassium.

The table below summaries primary higher PRAL and

lower PRAL food groups



Food Group PRALHigher or Lower

PRAL

Meats 9.5 HigherCheeses 8.0 Higher

Fish 7.9 Higher

Flour 7.0 Higher

Noodles 6.7 Higher

Fruits -3.1 Lower

Vegetables - 2.8 Lower

Cow's Milk 1.0 Lower

Source: Barzel US and Massey LK. (1998). Excess dietary

protein can adversely affect bone. J Nutr 128: 1051-1053.

Acid-alkaline and the World's Healthiest Foods

Although the impact of foods on our kidneys and urine

acidity is definitely an important topic from the

standpoint of diet and health, it is still one very narrow

component of our body's acid-base balance. All of our

bodily fluids have their own characteristic degree of

acidity, and our metabolism works in thousands of waysto protect acid-base levels in all of our tissue. So we

would not want to draw any hard and fast conclusions

about how to eat from studies on urine acidity and the

PRAL value of foods. However, I do believe that research

in this area supports our basic approach to healthy

eating at the World's Healthiest Foods. We place ourgreatest emphasis on daily intake of vegetables and



fruits, and in this urine acidity research, we discover that

vegetables and fruits have lower PRAL values than any

other food groups. We also encourage moderation

throughout our website with respect to consumption of

meats and believe this recommendation is in keeping

with urine acidity research that places meats at the top

of the PRAL list with a value of 9.5. While the PRAL

research was not a factor in our initial construction of the

World's Healthiest Foods list, we are reassured to see

that our Healthiest Way of Eating is one that shouldresult in little risk with respect to potential renal acid

load.

Other approaches to acid-alkaline and diet

On other websites, especially websites interested in

macrobiotic eating, Asian medicine, and energy

medicine, you'll find detailed discussion of acid-forming

and alkaline-forming foods that do not follow this

Western science research involving urine acidity and

PRAL values. Instead, these approaches typically look at

whole body acid-base balance (rather than acidity of one

body fluid like the urine) and they talk about "toxic acidicconditions" or the need for a slightly alkaline condition

in the body as whole. To find out more about these

alternative ways of approach acid-base balance in the

body and dietary choices, you may want to visit one or

more of the following websites:



http://www.gomf.macrobiotic.net/Info_Macrobiotics.htm

(The George Osawa Macrobiotic Foundation)

http://www.kushiinstitute.org/html/articles.html#Food%20&%20Healing (The Kushi Institute)

http://www.ppnf.org/catalog/ppnf/Articles/articles_list.ht

m (Price-Pottenger Nutrition Foundation)

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Can You Please Tell Me More About the Acidity Alkalinity of Foods