The Impact of Food Processing on Phosphorus in Plant-Based Foods
- Andrew Kowalski
- Sep 13
- 4 min read
Andrew Kowalski, MD, FASN
The current trend in providing healthy food options has been "lion in sheeps clothing." The plant-based trend has taken the Western food markets by storm creating a ridiculous amount of alternative choices. The fact that anyone can walk into a grocery and buy a plant based alternative to literally anything should, I hope, cause anyone to take pause and question their food choices. Unfortunately, much of the truth behind these "healthy" products appears to be baried in the advertising campaigns and helped by recycled internet posts and "professional opinions." The truth is that these products tend to be just as unhealthy, if not more, than the alternative classic protein options that have been lambasted across all information outlets.
I am not saying that the carnivor diet is the best option, I even encourage patients to develope a more plant centered diet. The crux of the issues is that processing plant proteins to look like their meat counterparts are what is going to continue to propagate current disease trends.
Anything that is processed is significantly altered from their original nutritious creation, whether it is a meat or plant product. With a focus on CKD patients the abscent information about these products will contribute to greater downstream issues.
I have a feeling I will be revisiting this topic again, so I'll keep this blog brief.
Through the lens of the CKD patient, food processing plays a major role in determining how much phosphorus from plant-based foods is absorbed by the body. In their natural state, legumes, whole grains, nuts, and seeds contain phosphorus primarily in the form of phytate (phytic acid). Because humans lack the digestive enzyme phytase, most of this phytate-bound phosphorus passes through the gastrointestinal tract unabsorbed, resulting in lower phosphorus bioavailability compared with animal proteins.

However, processing methods such as soaking, sprouting, fermenting, and milling can break down phytates, releasing phosphorus into forms that are more readily absorbed. For example, sprouted beans or sourdough bread have higher available phosphorus than their unsprouted or unfermented counterparts.
Modern food processing also introduces an additional challenge: the widespread use of phosphate additives. In many packaged plant-based foods such as meat substitutes, flavored soy products, fortified non-dairy milks, and processed grain products—phosphate salts are added to improve texture, shelf life, and flavor. Unlike natural phytate-bound phosphorus, these inorganic phosphate additives are absorbed almost completely (90–100%), making them a hidden but significant source of dietary phosphorus. This is particularly concerning for patients with CKD, since even small amounts of these additives can raise phosphorus levels more effectively than larger portions of natural plant-based foods.

Processing that involves refining grains such as turning whole wheat into white flour or brown rice into white rice tends to lower phosphorus content. While this reduces nutrient density by stripping away fiber and micronutrients, it also makes these refined foods a safer choice for phosphorus restriction in CKD. Similarly, plain tofu or seitan, when minimally processed and without additives, remain moderate in phosphorus load, whereas highly engineered plant-based meat analogues can be unexpectedly high due to enrichment with phosphate-containing binders.
In summary, the way a plant-based food is processed often matters more than the raw phosphorus numbers. Minimally processed plant foods generally provide protein with lower phosphorus bioavailability, while fortified and additive-rich plant-based alternatives pose a much higher phosphorus burden due to their easily absorbed inorganic content. For patients with CKD, choosing whole, unfortified, and additive-free plant foods allows the benefits of a plant-based diet without the risks of phosphorus overload.
Plant-Based Protein Alternatives (Meat Substitutes)
1. Soy Products:
Tofu, tempeh, soy milk, and soy protein powders vary in phosphorus.
Tofu (especially calcium-set) is moderate in phosphorus but has lower absorption than meat.
Highly processed soy protein isolates (e.g., veggie burgers, meat substitutes) may contain phosphate additives, raising bioavailability.
2. Seitan (wheat gluten):
Popular plant-based meat substitute, high in protein.
Naturally lower in phosphorus than beans/nuts, but processing may introduce additives.
3. Plant-Based Milks:
Rice milk, almond milk, and oat milk often contain phosphate additives if fortified.
Unenriched, additive-free versions are lower in phosphorus and better suited for CKD.

Impact of Food Processing
Processing can dramatically affect phosphorus content and absorption:
Natural, minimally processed foods (beans, whole grains, nuts, tofu) contain phosphorus mostly in phytate form → lower absorption.
Sprouting/fermenting increases phosphorus bioavailability by breaking phytates.
Fortified foods and processed protein products often have added phosphates for texture, shelf life, or flavor → these additives are almost fully absorbed and should be avoided.

Key Takeaway
Higher phosphorus plant-based foods: nuts, seeds, legumes, whole grains (though less absorbed due to phytates).
Lower phosphorus plant-based foods: refined grains, unenriched rice or almond milk, fresh fruits and vegetables, unprocessed seitan, plain tofu.
Greatest concern: processed plant-based protein alternatives and fortified beverages with phosphate additives, since these forms are nearly 100% absorbed.
For more information or to speak with a nephrologist close to you in the Midwest or New Jersey check out www.nephdocs.com