Blog Post

The Alkaline Diet: A Dietitian’s Review

The Alkaline Diet

The alkaline diet is based on the premise that the food we eat affects our blood’s balance.

A pH of 0 is highly acidic, 7 is neutral and 14 is very alkaline.

Typically, the pH of the blood is tightly regulated and stays between 7.25 and 7.45.

How is it Proposed to Work?

Eating too much acid-forming food is proposed to lead to a lot of health issues. This is suggested to increase the risk of cancer, bone loss, fatigue, and weight gain, among other things.

Not only is the mechanism based on directly affecting blood pH, but it is also about the chain reaction of events involved in regulating pH in that narrow range.

The acid-ash hypothesis is focuses on how if you have acid-forming food, it can cause the body to try and counteract this to keep blood pH within that 7.25-7.45 range.

This can then lead to other aspects such as taking calcium from the bone to keep the pH of the blood stable. Based on this proposed mechanism, blood pH stays stable, but it could contribute to osteoporosis, for example.

Foods to Avoid

Acid-forming foods are not as easy to guess as you would think.

pH Scale, foods to avoid

For example, because lemons are acidic, most people would assume they are “acid-forming.” But they are categorised as alkaline-forming.

More comprehensive lists can be found elsewhere, but a brief list of foods to minimise includes:

  • Refined Sugar
  • Alcohol
  • Meat
  • Processed foods
  • Coffee/tea/caffeine
  • Dairy
  • Fish
  • Eggs
  • Grains

Sometimes natural sugars, starches and fats are either included in this category, or a neutral category.

Foods to Include

Since there is a long list of foods to avoid, it makes sense to also have a brief list of foods to focus on:

  • Most fruits
  • Most vegetables
  • Water
  • Nuts
  • Legumes
  • Tofu

Flaws in the Logic

While a lot of the foods in the alkaline list are associated with positive health outcomes, it is worth unpacking a few aspects where this hypothesis falls apart.

Bone Health

Bone Health

The easiest aspect to unpack is the impact on bone health.

Proponents of the acid-ash hypothesis claim that eating acid-forming foods contributes to osteoporosis. They claim that excessive protein intake causes the body to balance things out by breaking down the contents of the bone.

Often this is in reference to the calcium content specifically. From a theoretical perspective, we can identify that calcium is not actually the largest aspect of bone. Collagen makes up ~90% of bone. It is also a form of protein too.

Instead of looking at theoretical explanations though, we can jump straight to outcomes. Based on this hypothesis, higher protein diets should lead to increased rates of osteoporosis.

When looking at the research on protein intake and bone mineral density though, that is not the case. On average bone mineral density is higher in those with higher protein intake. This also reflects higher meat intake, even though meat theoretically is acid-forming.

The current consensus is to not go out of your way to go beyond >2g/kg per day without reason. But there is no need to actively reduce it.  

This is an example of how looking at a single mechanism can make you miss the big picture.

Cancer

The alkaline diet is promoted to either help prevent or cure cancer.

This logic is based on the argument that cancer only grows in an acidic environment.

But as mentioned earlier, the pH of the blood and many other areas is tightly regulated. We do not actually change them much with our food.

Secondly, researchers have also demonstrated that cancer cells can be grown in an alkaline environment as well.

While they might grow faster in an acidic environment, the cancer cells themselves actually contribute to creating that type of environment.

A scientific review of the effectiveness of the alkaline diet concluded that:

“There is no scientific literature establishing the benefit of an alkaline diet for cancer prevention at this time.”

That pretty much summarises it. That paper is from 2012 but is still relevant now. There are some reasons people believe that it can help, but there is no evidence supporting it.

If you wanted to look at things from an anecdotal perspective, it is also worth reading some accounts about the founder of the diet and the experiences people have had. A lot of people point to success stories, but it is important to look at both the good and the bad.

Dr Robert Young Controversy

Weight Loss

From the weight loss perspective, there is no real reason to believe that the alkaline vs acidic aspect plays a major role.

We have a wealth of evidence showing that different dietary approaches lead to similar amounts of fat loss when total calories and protein are equated for.

Energy Balance

People on the alkaline diet often reduce their calorie intake significantly, which leads to fat loss.

If you significantly decrease your intake of the following, do you think your calorie intake would likely increase or decrease?

  • Refined Sugar
  • Alcohol
  • Processed foods
  • High-fat meat
  • Grains
  • Dairy

Almost everybody would have their calorie intake decrease.

Practical Summary

Often when reviewing a dietary approach like this I will try and go far deeper on the topic than I have done here. But the alkaline diet just does not have enough of a basis behind it to support a deeper discussion. It is largely based on false premises.  

Increasing your intake of fruits, vegetables, water, and other alkaline foods is typically good. Not because they are alkaline, but for a whole bunch of other health-related reasons.

There are foods on the “avoid” list that you probably do want to minimise. But there are also other foods in there that can fit perfectly into a well-balanced diet.

I would mostly disregard the acid vs alkaline aspect, and instead, just focus on the overall nutrition principles outside of that.

By Aidan Muir

Aidan is a Brisbane based dietitian who prides himself on staying up-to-date with evidence-based approaches to dietetic intervention. He has long been interested in all things nutrition, particularly the effects of different dietary approaches on body composition and sports performance. Due to this passion, he has built up an extensive knowledge base and experience in multiple areas of nutrition and is able to help clients with a variety of conditions. One of Aidan’s main strengths is his ability to adapt plans based on the client's desires. By having such a thorough understanding of optimal nutrition for different situations he is able to develop detailed meal plans and guidance for clients that can contribute to improving the clients overall quality of life and performance. He offers services both in-person and online.