What is an alkaline diet and how does it affect your health?

Many people still remember the terms base and acid from chemistry class, when they used yellow strips to determine the pH values of various substances. But what is alkaline nutrition all about? The acid-base balance is an important factor to consider for a healthy and balanced diet. We will explain why an alkaline diet can be beneficial and how to achieve it.

What is the body's pH value?

Generally, all substances with a pH value greater than 7 are alkaline, and all those below 7 are acidic. A value of 7 is considered pH-neutral. Our body has many different environments, each with a different pH value. For example, our skin has a pH value of 5.5-6.5, which is slightly acidic. This is because a weakly acidic environment makes it difficult for bacteria and microbes to survive and multiply on the skin. This is also known as the "acid mantle of the skin". Washing too frequently with highly alkaline detergents (e.g., soap) can increase this value and thus destroy the protective mantle. Therefore, for daily washing, you should use a mild, preferably soap-free product.

Our stomach acid, with a value of 1.5, is one of the most acidic substances of all, which promotes the dissolution and processing of food. Anyone who has ever experienced heartburn knows that stomach acid is a very irritating substance. If the stomach is confronted with particularly large amounts of food or very fatty food, it produces more stomach acid. This can lead to the stomach lining becoming acidic and excess stomach acid flowing into the esophagus, where it causes irritation. Neutralization and relief of symptoms can be achieved by taking alkaline remedies that restore the pH value to equilibrium.

Human blood normally has a pH value of 7.5. To prevent this from fluctuating too much, the lungs, kidneys, and liver have certain "buffering mechanisms" that can compensate for short-term fluctuations. For example, a higher CO2 content in the blood lowers the pH value and thus regulates it through breathing. A permanent change in the pH value may be an indication of a disease of the lungs, kidneys, or liver. Severe blood acidification occurs, among other things, with alcohol poisoning, severe diarrhea, or states of hunger.

What does "alkaline" mean in nutrition?

The pH value of urine is relatively unstable in the human body. Depending on what we eat and drink on a given day, how effective our digestion is, whether we exercise or not, our urine can be more acidic or alkaline. This is because an excess of acids is primarily regulated by the kidneys and excreted in the urine. Thus, the pH value of urine can indicate whether someone's diet is more acidic or alkaline.

The regulation of pH is achieved through the release of calcium phosphates and calcium carbonates, which neutralize excess acids and are then measurable in the urine. It is estimated that a person on a highly acidic diet will excrete approximately 480g of calcium over 20 years. This is a significant amount, considering that our entire skeleton contains about 1150g of calcium.³ This means that an acidic diet leads to a greatly increased calcium requirement, which the affected person may not even be aware of. Since calcium is primarily important for the building and maintenance of muscles, nerves, and bones, a chronic deficiency can lead to serious problems. Symptoms such as muscle cramps and twitching, and even osteoporosis as a long-term consequence, can be attributed to calcium deficiency.

How is the acid value of foods measured?

In this case, something being considered "acidic" doesn't refer to its taste or pH value. It's more about the processes that foods initiate and trigger in the body. That's why the term "acid-forming" is usually used. Acid-forming foods cause acids to be released in the body during their metabolism, and inflammation levels to rise. They often have a very low water content, so water is drawn from the body for their processing and excretion. They also contain few to no antioxidants or other beneficial plant compounds that protect the body against oxidative stress. In this way, acid-forming foods disrupt the body's natural acid-base balance. An acid excess or acidosis occurs. The diet most prevalent in Western industrialized nations is rich in salt, dairy products, and meat, as well as highly processed foods like grains and convenience foods, which have a low content of vitamins and minerals. All of these are foods considered acid-forming. An alkaline diet, therefore, aims to balance the acid-base balance to end or avoid the acidic state of acidosis and thus relieve the body.

All these factors impact the burden on the kidneys, which must excrete the resulting acids. Therefore, the PRAL value is used to classify foods as acid- or base-forming. PRAL stands for Potential Renal Acid Load.² The higher this value, the more acid-forming the food is. The PRAL value for base-forming foods, on the other hand, goes into the negative range. This illustrates that they can counteract the values of acid-forming foods. Below, we have listed some that are strongly acid- or base-forming.

These foods are acid-forming

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At first glance, it is clear that there are almost no vegetables among the acid-forming foods, but many meat and dairy products. Of course, this does not mean that these acid-formers should be completely avoided in an alkaline diet. Rather, it is about consuming these components of the diet more consciously so that the acid-base balance does not shift too much towards acids.

These foods are base-forming

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Again, it's quickly apparent that base-forming foods mainly include fruits and vegetables. This further emphasizes that the PRAL value has nothing to do with taste. Citrus fruits and berries, which often have a sour taste, all have a neutral or negative, i.e., slightly alkaline to alkaline, PRAL value.

However, the absolute frontrunner by far is the microalga spirulina. Not only is it highly alkaline-forming, but it is also rich in many important macro and micronutrients, as well as secondary plant compounds. For an alkaline-rich diet, it is excellent as an addition to bowls, smoothies, or shakes. However, this table should not be considered exclusive, as, for example, the nutrient content is not taken into account in the PRAL value. An alkaline-forming diet is not necessarily balanced just because it consists exclusively of base-forming foods.

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The positive effects of alkaline nutrition

An "alkaline-rich diet" generally refers to one where the proportion of base-forming foods in the diet is 70-80%, and acid-forming foods make up 20-30% accordingly. With a diet rich in base-forming components like fruits and vegetables, many positive effects on health have been observed. For example, researchers found that the incidence of hip fractures in older women is less frequent in countries where fruits and vegetables make up a significantly higher proportion of the diet than meat and dairy products. They therefore recommend an alkaline-rich diet for bone health and stability.⁵ Further studies suggest that a diet rich in base-forming fruits and vegetables protects the kidneys and can prevent long-term kidney damage.^{6, 8}

Alkaline-rich nutrition - how to achieve it

As mentioned, an alkaline-rich diet is about the ratio of acid-forming to base-forming foods to maintain acid-base balance. This means that you don't necessarily have to give up anything when switching to an alkaline diet. You achieve the right balance by planning your meals around base-forming foods as the main component. Any acid-forming foods you wish to eat should then only be added as a supplement.

However, this does not mean that you can only consume foods with a negative PRAL value when on an alkaline-rich diet. There are some so-called good acid-formers that, while acid-forming, also supply the body with important minerals or stimulate the formation of amino acids. These include, for example, legumes, nuts, fruits, or pseudo-grains like buckwheat and quinoa. These should ideally make up the 20-30% proportion of acid-formers in your diet.

Perhaps you already mostly eat a base-forming diet and would like to give your body an extra portion of alkaline foods from time to time. In this case, tablets or powders that you can take between meals or stir into your bowl or smoothie are particularly suitable. A good supplement to a balanced base-forming diet is the microalga spirulina. In addition to a strongly alkaline PRAL value, it offers a wide spectrum of vital nutrients, providing you with a daily alkaline nutrient boost. You can learn more about this in this article.

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6. Frassetto L, Remer T, Banerjee T. Dietary Contributions to Metabolic Acidosis. Adv Chronic Kidney Dis. 2022 Jul;29(4):373-380. doi: 10.1053/j.ackd.2022.03.008. PMID: 36175075. https://pubmed.ncbi.nlm.nih.gov/36175075/
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