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 suggests that consuming acid-forming foods may prompt the body to compensate in order to maintain blood pH within the normal range of 7.25 to 7.45.
This may lead to the body drawing calcium from the bones to help maintain stable blood pH. According to this proposed mechanism, while blood pH remains balanced, it could potentially contribute to conditions like osteoporosis.
Foods to Avoid
Acid-forming foods are not as easy to guess as you would think.
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
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.
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.
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 aim to dive much deeper into the topic than I have here. However, the alkaline diet simply doesn’t have enough scientific basis to support a more in-depth discussion. It is largely built 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.
