All About Dietary Acids and Bases

By Ryan Andrews

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What are dietary acids and bases?

An acid, as it relates to acid-base regulation, may be defined as a substance capable of releasing hydrogen ions in solution. A base (alkaline) is any substance that tends to accept hydrogen ions in solution.

That may sound complicated, but you’re probably familiar with some common acids and bases. Lemon juice and vinegar are household acids, and baking soda and drain cleaners are bases.

But here, we’re talking about acids and bases in the body, not around the house.

The metabolism of many major nutrients continuously generates acids, which must be neutralized. Acids can also be formed in the body through normal metabolic processes, such as respiration.

To guard against acid loads from food consumption and tissue metabolism, we have 3 main regulatory systems:

  1. Buffer systems that work in cellular fluid and the bloodstream to keep pH constant
  2. The respiratory center (aka the lungs and oxygen or carbon-dioxide carrying structures)
  3. Kidney regulation

We’re going to look mostly at the third system in this article.

When a food is ingested, digested, and absorbed, each part of that food will present itself to the kidneys as either an acid-forming compound or an alkaline-forming one.

It’s the kidneys’ job to adjust the pH to a constant level by changing either what they secrete, and/or how they filter things.

Foods are thus often measured with a potential renal acid load — or PRAL — score that describes the level of acid loads they present to the kidneys.

acid-base-balancing-by-kidneys
How the kidneys regulate acid-base loads by adjusting hydrogen ion (H+) secretion and bicarbonate (HCO3) filtration in response to elevated carbon dioxide (CO2) or HCO3

Why are dietary acids and bases so important?

Keeping things balanced

The acid-base balance in body fluids is one of the most vital aspects of homeostasis. The balance needs to be controlled within a narrow range.

Values outside of this range are not compatible with life; our cells only function at a certain acid-base balance.

No matter what you decide to eat for lunch, the body will maintain a narrow acid-base range by any means necessary.

A disturbance of the acid-base balance occurs when acid-base changes surpass the body’s ability to regulate it, or when normal regulatory mechanisms become ineffective. This can happen with chronic consumption of an acidic diet.

Health problems

If pH levels aren’t balanced, this can mean negative health outcomes that include:

  • Decreased growth factors
  • Growth hormone resistance
  • Mild hypothyroidism
  • Higher levels of blood cortisol
  • Loss of muscle mass
  • Enzymatic changes in cells
  • Altered regulation of metabolites and minerals
  • Decreased uptake and release of oxygen

“Borrowing” buffers

Why do these health problems occur?

One reason is that in order to counteract high acid loads in the diet, the body looks for buffering substances, such as minerals and proteins. It often has to “borrow” these from elsewhere.

For example, the body can use calcium and phosphorus to buffer acid loads. Where’s the biggest stockpile of these minerals in the body? Your bones.

One of the primary causes of osteoporosis is the loss of calcium from bones to buffer acid loads in the body, not lack of dietary calcium. The United States, Finland, England, Israel and Sweden have the highest intake of calcium from dairy, yet they also have the highest rates of osteoporosis.

Not only does leaching minerals turn your bones into Swiss cheese, chances of kidney stone formation are increased with heavy mineral losses eliminated in the urine.

Glutamine is another buffer used to counteract the high dietary acid loads. Most glutamine is found in skeletal muscle. Thus, to neutralize the excess of dietary acids, glutamine is leached from muscle, which can contribute to muscle loss.

Acid build up from physical exercise can also lead to muscular stiffness, fatigue and joint soreness.

What you should know

You’re the pH master

You can affect the acid/base status of your body with the foods you eat, and thus your overall health and recovery from exercise.

If you consistently eat a diet high in acid-forming foods, you may suffer low grade acidosis.

What are acidic and basic foods?

You can’t judge the acid-forming and basic/alkaline-forming properties of a food by the actual acidity of the food itself. For example, citrus fruits and vinegars are acidic, but when we consume them, they are alkaline-forming.

What determines a food’s acidity or alkalinity is how it breaks down when digested.

Most of the foods that contain exclusively protein tend to be high in sulfur-containing amino acids. These amino acids are metabolized toward sulfuric acid.

Most of the plant foods don’t contain high levels of sulfur-containing amino acids and are generally alkaline-forming. The alkaline forming plant foods help to neutralize the acid-forming protein foods.

Foods that contain primarily fat are typically more neutral.

Due to food processing and an increase in wealth (among other reasons), most diets tend to be acidic. This is due to the high intake of dairy foods, grains and meats. Generally, the intake of these acid-forming foods isn’t balanced with adequate vegetable and fruit intake (alkaline-forming foods).

acidic-tipping-scales
Overly acidic diet: too much protein, processed foods, grains, dairy

balanced-diet-scales
Balanced diet: ensures adequate intake of alkaline-forming fruits and vegetables

We may benefit from having an even distribution of acid-forming and alkaline-forming foods in the diet. Even consuming slightly more alkaline-forming foods (vs. acid-forming foods) may be beneficial for long-term health outcomes.

Alkaline-forming foods Acid-forming foods Neutral/varied foods
Vegetables
Fruits
Green tea
Dairy
Meat
Fish
Artificial sweeteners
Legumes
Most whole grains
Isolated proteins (e.g., soy and whey)
Soft drinks
Vegetable oils
Butter
Margarine
Nuts
Seeds

To get an idea about how specific foods influence acid/base balance:

Table of acid-base loads of specific foods (PDF)
Acid-base calculator

For extra credit

Eskimo and Inuit in Arctic regions consume nearly 2,200 mg of calcium per day, yet have some of the highest levels of osteoporosis in the world. This is most likely due to their high-acid (and low alkaline) dietary intake.

Acidic anions in food include chloride, phosphorous, sulfates, and other organic acids.

Basic/alkaline cations in food include sodium, potassium, calcium, and magnesium.

Low grade acidosis can get worse with age due to a decrease in kidney function.

The net acid or base load from the diet is the potential renal acid load (PRAL). mEq is a unit of measure used to quantify this load.

  • A score of 0 would represent a neutral load.
  • A positive score is more acidic.
  • A negative score is more alkaline.

Pre-industrialized diets were around -88 mEq/L (thus more alkaline-forming). Modern diets are around +47 mEq/L (thus more acid-forming).

acid-base-modern-pre-industrial

Calculating your PRAL score

If you like a little math with your meals, it can be interesting to calculate the PRAL score for your diet. To figure out the PRAL for each meal, simply do the following:

  1. Record the amount (in grams) of each food you eat in a meal.
  2. Multiply the PRAL score for a food type by your food amount (be sure to convert grams to 100 grams by dividing by 100).

Sample:
¾ cup (170 g) cabbage
¾ cup (180 g) lentils
Small piece (100 g) of fruit

PRAL:
Broccoli: 1.7 x -2.8 mEq/100 g = -4.76 mEq (-2.8 is the PRAL for 100 g of vegetables)
Kidney beans: 1.8 x 2.6 mEq/100 g = 4.68 mEq (2.6 is the PRAL for 100 g of legumes)
Fruit: 1 x -3.1 mEq/100 g = -3.1 mEq (-3.1 is the PRAL for 100 g of fruit)
Net PRAL: -4.76 + 4.68 + -3.1 = -3.18 mEq (net alkalinity)

If you don’t feel like doing all this math, just remember one simple rule for helping to balance your diet: Eat your fruits and veggies!

Summary and recommendations

  • Eat vegetables and/or fruits with each feeding
  • Consider a glutamine supplement if you can’t consume adequate vegetables and fruits
  • Consider a sodium bicarbonate supplement if you can’t consume adequate vegetables and fruits
  • Avoid adding salt to foods
  • Avoid foods that already have a lot of added salt

More reading

Acid-Base: How do you stack up?
Covering Your Nutritional Bases: The Importance of Acid-Base Balance

References

Click here to view the information sources referenced in this article.

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