Health literature is full of recommendations to alkalize your body and protect it from the harmful effects of acid forming foods. Claims for the health benefits of alkalizing diets include protection from osteoporosis, cancer and vague claims for optimized health. However, the data supporting these claims is controversial at best and the recommendations by most authors demonstrate bias generally based on their opinions around animal protein. Below is a review of concepts around acid base balance in the body and a critical discussion of the literature both for and against the idea of alkalizing your diet for your health and your bones.
The concept of acid base balance is based on the effect food has on the body “pH.” PH is a logarithmic scale created to describe the number of available hydrogen ions in a fluid. While this scale doesn’t directly describe the “acidity” of foods it does apply to our body fluids in a critical way.
The human body maintains VERY tightly controlled systems around acid base balance particularly in our blood. As measured by pH our arterial blood stays between 7.35 and 7.45. Certain areas of our body are more acidic than others with the stomach being the most acidic boasting a pH of around 1.0.
In order to understand the metabolic effect of foods they are frequently divided into acidic or alkaline categories based on their ability to produce acid during metabolism:
It’s easy to appreciate the potential bias to this discussion when you view these lists. The hotly debated topic of animal protein is broadly exposed here as these lists nearly divide the food groups of carnivore and vegan followers with the notable exception of alcohol and grains joining the acid category.
Body pH is relatively difficult to test. An arterial blood draw would be required to accurately diagnose an acidic body balance. This type of test is not practical to do at home so the recommendation is to use urine pH as a surrogate marker. Unfortunately, this method of testing does not reflect the acidic changes over a 24 hour period of time. The body is much more complex than this testing method allows.
While the foods in each list do create acidic or alkaline environments in an isolated space the body is complex and has several mechanisms in place to handle inputs that alter the blood pH. Additionally, metabolism itself creates acidic and alkaline byproducts which the body has to quickly balance to maintain optimal health. The most common tissue buffers in the body discussed include the kidneys, red blood cells, skeletal muscle and bones.
The kidneys do an amazing job of creating the necessary byproducts to buffer the blood and excrete what they need to in order to keep the system in balance. Only when kidney function begins to decline either with age or disease should they need any help with this process.
The red blood cells and skeletal muscle act as remarkable reservoirs for the substrate needed to buffer acidic or alkaline inputs to the system. Your red blood cell volume is relatively fixed but skeletal muscle mass varies dramatically from person to person. Preventing loss of muscle mass as we age is a critical factor in health span. Muscle participation in acid base balance is part of its contribution to healthy aging.
Bones do contain calcium salts which can buffer acid. Whether they do buffer acid is a controversial topic which we will explore in depth.
The acidic food list includes ALL animal products, grains and alcohol. Advocates for plant-based diets would love the opportunity to prove that these acid producing foods are toxic to our bodies to help support their belief. It is not uncommon for claims made regarding acid base balance to come from such vocal groups. However, in the world of nutrition science we must rely on the best evidence to make an informed decision. This is critical when deciding to eliminate such a potent source of protein which is generally under consumed and often misunderstood.
Bones have many roles in the body but one of them is to act as storage for calcium and other minerals. Calcium can be released from the bone in response to an acidic environment to help buffer the acid and in chronically acidic scenarios this would happen, but this is not the most efficient way to buffer acid from food.
Advocates for alkaline diets point to animal research that shows that an acid producing diet does indeed demonstrate bone loss. Additionally alkaline water given consistently may improve bone density and does reduce bone resorption markers. Supplementation of alkaline potassium salt supplements can reduce excretion of calcium, improve bone density on DEXA and reduce fracture risk scores. This sounds convincing but note that some conclusions recommend eliminating potential nutrient sources while others are discussion adding healthy ones!
Bones make the perfect tool to identify the risk associated with acid producing diets because of the unique nature of the cells involved. The cells that break bone down, osteoclasts, are activated by acidic environments with a pH of 7.0 and demonstrate reduced activity as pH reaches 7.4. Not coincidentally right in the middle of the physiologic neutral for body acid balance. The cells that build bone, osteoblasts, are most active at this neutral pH of 7.4 and cease to function at the acidic pH of 7.0. This contrasting function and easy testability of calcium and bone turnover make bones the target of discussion around the effects from acid forming diets.
As pointed out above some advocates for alkali diets point to the increased or decreased excretion of calcium as a sign of bone loss with changes in diet. However, when you calculate the bone loss that would occur from an acid forming diet if bone was the primary source of buffer, an animal protein consuming human would dissolve its entire skeleton in about 4 years. Additional animal studies providing adequate dietary calcium and using an acid forming diet also show that calcium excretion in urine goes up but without negative impact on bone density or strength. Using calcium excretion alone cannot paint a clear picture of what’s happening to bone.
While animal studies and physiology can help us to create theories and hypotheses they should always be taken in context with human studies when available. When urine pH in humans was reviewed as a tool for bone loss and fracture risk NO ASSOCIATION was found. When alkalizing supplements and an alkaline diet were compared with placebo there was no difference in bone turnover markers at all.
There are two ways to view this controversy from a nutrition perspective. One view is flaunted by those opposed to society eating meat at all. They try to use this data to convince you to stop eating animal products. The second way to view this controversy is neither malevolent or restrictive. If adding alkaline foods MAY have benefit and they are good for you. Simply add them. Eating fruits and vegetables within the boundaries of your other dietary goals is great for you and MAY prevent bone loss from excessive exposure to acid forming foods. We should focus on adding the positive rather than eliminating the best protein source for strong bones.
Several studies show potential benefit of alkalizing your body with alkaline water. While these studies are valid, we must consider any potential negatives of using this approach. The studies using alkaline water showed benefit when the water was consumed constantly. If we do that in real life, we will negatively impact our stomach environment.
It is critical for our stomach to remain an acidic environment to support proper digestions. When this is altered from chronic exposure to alkaline water or to acid suppressing medications gut function decreases and nutrient absorption is negatively impacted.
Having strong bones is part of preventing fracture but it’s not the only factor. Maintaining muscle mass as we age can prevent falls from occurring and prevent fractures when they do. The best way to maintain muscle mass is to stay active and consume adequate high-quality protein! Don’t eliminate animal products in your diet because you are worried about the acid forming nature of them damaging your body!
If you’ve made it this far, congratulations! This is a tough topic to understand but an important one to grasp. The big picture is this.
Create your optimal life by arming yourself with the knowledge to avoid harmful recommendations. A logical approach can resolve this controversy without restriction of nutrient rich foods.