Stage 4 CKD: When “Healthy” Foods, Medicines and Supplements Need a Second Look

A David at 91 reflection on food, drugs, turmeric, supplements and the wisdom of knowing what not to take

As I grow older, I realize that wellness is not always about adding something good to our lives. Sometimes it is about knowing what to leave out.

I have written many articles about wellness, healthy aging, medicines, vitamins, herbal remedies and dietary supplements. My philosophy has always been influenced by two worlds that have been important throughout my life.

One is the traditional wisdom I learned growing up in the Philippines, where herbal and plant remedies were part of everyday life.

The other is modern pharmaceutical science. I earned my PhD in Pharmaceutical Chemistry, spent years in the pharmaceutical industry, and eventually worked for many years at the FDA.

Those two experiences have taught me something important:

Natural does not automatically mean safe and a substance that is beneficial in one form or dose may not be appropriate in another.

My Stage 4 chronic kidney disease has made that lesson much more personal.

My Stage 4 CKD Food List

The photograph accompanying this article is a “CKD Stage 4 Food List.” It divides foods into three categories:

EAT — LIMIT — AVOID

It is a useful reminder that when kidney function becomes severely reduced, nutrition becomes more complicated.

Stage 4 CKD generally means an eGFR of 15–29 for three months or longer. At this stage, the kidneys have lost a substantial amount of their filtering ability, and some medicines and substances can remain in the body longer than they should. 

But there is an important qualification about any generic food chart:

There is no single Stage 4 CKD diet that is right for everybody.

Depending on laboratory results and other medical conditions, a person may need to pay particular attention to sodium, potassium, phosphorus, protein and other nutrients.

For example, bananas, oranges, potatoes, tomatoes, avocados and some leafy vegetables are nutritious foods for many people. But some contain substantial potassium, which can become a problem when the kidneys cannot regulate potassium properly.

Similarly, dairy products, nuts, seeds, beans and some whole grains may require attention because of phosphorus.

And processed foods such as bacon, sausage, pepperoni, canned soups, fast foods and many frozen meals can contain large amounts of sodium.

So I have learned that the question is no longer simply: “Is this a healthy food?”

The more appropriate question is: “Is this healthy for my kidneys, at this stage of my life, and according to my latest blood tests?”

That is why a renal dietitian can be so helpful. The National Kidney Foundation recommends individualized nutritional guidance for people with CKD. 

Then I Started Thinking About the Other Side of Wellness: Medicines

The food chart made me think about something that may be just as important as what we eat:  What medicines, vitamins and supplements should someone with Stage 4 CKD be careful about?

This is especially important because many people assume that an over-the-counter medicine must be safe. It isn't necessarily.

In Stage 4 CKD, some medicines can accumulate because the kidneys are responsible for removing them from the bloodstream. The National Kidney Foundation notes that approximately half of FDA-approved medications are removed from the blood by the kidneys. 

OTC Medicines That Deserve Special Attention

One of the biggest groups is the NSAIDs -nonsteroidal anti-inflammatory drugs.

Examples include:

• Ibuprofen — Advil, Motrin
• Naproxen — Aleve
• Indomethacin
• Diclofenac tablets or capsules
• Celecoxib — Celebrex
• Meloxicam — Mobic
• High-dose aspirin, generally more than 325 mg/day

NSAIDs can reduce blood flow through the kidneys and can cause acute kidney injury or worsen existing CKD, particularly with higher doses or prolonged use. The National Kidney Foundation recommends that people with CKD avoid self-treating with NSAIDs and consult their healthcare professional. 

This is a good example of why reading the label matters.

An NSAID can also be hidden inside combination cold, flu or pain products.

Acetaminophen, commonly known as Tylenol, is generally considered kidney-safe at recommended doses, but it is still important to check with one's healthcare professional and avoid accidentally taking it in several different combination products. 

And Then There Are Dietary Supplements

This is where my earlier wellness articles come back into the picture.

I have written about vitamins, supplements and traditional remedies because I believe they are legitimate subjects for discussion. But I have also become more cautious.

The word “natural” is one of the most powerful words in health advertising.

Yet nature contains some very powerful chemicals.

The National Kidney Foundation cautions that herbal supplements may worsen kidney disease, interact with prescription medications or increase the risk of CKD complications. 

The American Kidney Fund makes a similar point: herbal supplements are generally regulated as dietary supplements rather than as drugs, so their safety, effectiveness and purity can vary. 

That does not mean every herb is dangerous. It means:

A person with Stage 4 CKD should not assume that an herbal supplement is safe simply because it came from a plant.

Turmeric and Curcumin: A Good Example

This brings me to a supplement I recently thought about: Turmeric capsules containing curcumin.

Turmeric has a long history in cooking and traditional medicine. Curcumin is one of its principal active compounds and has been studied for its anti-inflammatory and antioxidant properties.

That sounds attractive. The advertisements often use phrases such as: “Reduces inflammation.” “Supports overall health and well-being.”

Those claims caught my attention because inflammation is an important subject in aging and chronic disease.

But my Stage 4 CKD makes me look at the same product differently.

Turmeric in Food Is Different From a Concentrated Capsule

The National Kidney Foundation says turmeric and other spices are safe when used in cooking, while advising caution when they are used as supplements or in large quantities. 

That distinction is important. Putting a little turmeric into a meal is not the same thing as taking a concentrated capsule containing a large amount of curcumin every day.

It is the difference between: Food and a concentrated biologically active supplement.

As someone trained in pharmaceutical chemistry, that distinction makes perfect sense to me.

Dose matters.

But Is Curcumin Actually Proven to Help CKD?

This is where I would be careful with advertising claims.

Curcumin has been studied for its effects on inflammation and oxidative stress, including in people with kidney disease. Some studies have reported improvements in inflammatory markers.

But that is different from proving that curcumin prevents CKD from progressing or improves kidney filtration. In other words:

Evidence that something changes an inflammatory marker is not the same as evidence that it improves kidney survival or kidney function.

That distinction is important whenever we read a supplement advertisement.

A Curious Kidney Case Involving Turmeric

There is another reason I would personally be cautious with concentrated turmeric supplements in Stage 4 CKD.

In 2024, researchers published a case report involving a 69-year-old man who developed oxalate nephropathy while taking approximately 2 grams of turmeric/curcumin daily for two years. He also had chronic diarrhea associated with previous antibiotic treatment, so the turmeric was not necessarily the only factor involved. The authors concluded that chronic turmeric supplementation was associated with the oxalate nephropathy. 

This is one case report, not proof that turmeric capsules commonly cause kidney failure.

I think that qualification is extremely important. But it does demonstrate why concentrated supplements deserve more scrutiny in someone whose kidneys are already functioning poorly.

What About Drug Interactions?

Another concern is that curcumin supplements can interact with medicines.

The National Kidney Foundation has specifically advised people with advanced CKD to discuss curcumin/turmeric supplements with their physician because of potential drug interactions and the limited safety information in CKD. 

Some turmeric products also contain piperine or black-pepper extract, which is intended to increase curcumin absorption.

That may make the supplement more biologically active, but it also makes it even more important to know what you are taking and whether it could interact with your medications.

My Turmeric Rule at 91

If someone with Stage 4 CKD asked me:

“David, should I take a turmeric/curcumin capsule for inflammation?”

I would not answer simply yes or no. I would say:

Show the bottle to your nephrologist or pharmacist first.

The exact product matters. I would want to know:

• How much turmeric does it contain?
• How much curcumin?
• Does it contain piperine/black pepper extract?
• What other ingredients are present?
• What medications is the person taking?
• What are the person's potassium, phosphorus and other relevant laboratory results?
• What is the person's current kidney function?

And most importantly: What evidence is there that this particular person actually needs it?

That last question applies to virtually every supplement.

My Stage 4 CKD “Think Before You Take It” List

If I were putting a small card beside my medicine cabinet, it might say:

BEFORE TAKING ANY NEW MEDICINE OR SUPPLEMENT

☐ Check whether it needs a dose adjustment for CKD.

☐ Avoid NSAIDs unless specifically directed by your healthcare professional.

☐ Check cold and flu products for hidden NSAIDs or duplicate ingredients.

☐ Be cautious with potassium, magnesium and phosphorus-containing supplements.

☐ Don't assume an herbal product is kidney-safe.

☐ Don't assume “natural” means harmless.

☐ Be particularly cautious with concentrated herbal extracts.

☐ Ask about possible drug interactions.

☐ Bring all vitamins and supplements to medical appointments.

☐ When in doubt, ask the pharmacist.

The National Kidney Foundation specifically recommends that people with Stage 4 CKD bring an updated list of medications, vitamins, supplements and herbal medicines to medical appointments and check with their healthcare professional before starting supplements or OTC products. 

Prescription Medicines Are Different

I also want to make an important distinction. It would be misleading to publish a list saying:

“These prescription drugs are bad for Stage 4 CKD.”

Many prescription medicines are actually important treatments for people with CKD.

Some simply require dose adjustments or monitoring.

Others may need to be avoided under particular circumstances.

For example, NSAIDs can be prescription drugs as well as OTC drugs. Other medications may require dosage changes because the kidneys remove them from the body.

At the same time, the National Kidney Foundation notes that physicians may prescribe medications such as ACE inhibitors/ARBs, SGLT2 inhibitors, GLP-1 receptor agonists or other therapies to reduce health risks or slow CKD progression in appropriate patients. 

So my rule is: Never stop a prescription medicine simply because you read something about it on the Internet.

Talk to the doctor who prescribed it.

What My FDA Years Taught Me

Perhaps my scientific background makes this subject especially interesting to me.

I spent years working with pharmaceuticals and eventually at the FDA.

One lesson that stayed with me is: Dose matters.

The difference between a food, a supplement and a drug isn't always as simple as we might think. A plant may contain a biologically active compound.

A manufacturer can concentrate that compound.

A capsule can deliver much more of it than we would ordinarily consume as food.

And once we concentrate something, we also concentrate the possibility of both benefit and harm.

That is why I have become increasingly skeptical of advertisements that use phrases such as:

“Natural cure.” “Detox.” “Supports kidney health.” “Reduces inflammation.”

Those phrases may sound reassuring, but they don't tell us whether the product has been adequately studied in a person with Stage 4 CKD.

Wellness at 91: Sometimes Less Is More

This brings me back to my earlier wellness articles. I have written about vitamins.

I have written about herbal medicine. I have written about healthy aging.

I have written about medicines. I have written about exercise, walking, human touch and many other ways of trying to live longer and live better.

But my kidney journey has added another dimension to my understanding of wellness.

Wellness is not always about adding something. Sometimes wellness means:

Less salt. Less processed food. Less unnecessary medication.

Less unnecessary supplementation. Less faith in miracle cures.

Less assumption that something is safe because it is sold over the counter.

And sometimes it means simply asking one more question before swallowing a pill.

My Final Thought: The Wisdom of Knowing What Not to Take

At 91, I am still curious. That may be one of the reasons I continue to write.

I remain interested in new medicines, new scientific discoveries, traditional remedies and the many ways people try to improve their health.

But I have learned that curiosity should be accompanied by caution.

Especially with Stage 4 CKD.

A banana may be healthy for one person but need to be restricted by another.

A medicine that is safe for one person may need a different dose for someone with reduced kidney function.

And turmeric may be a wonderful spice in our food while a concentrated curcumin capsule deserves a much closer look.

That is not a contradiction. It is pharmacology.

And perhaps this is one of the lessons I can pass along from my years as a chemist, pharmaceutical scientist, FDA retiree and now a 91-year-old student of aging:

The wisdom of aging is not always knowing what to take. Sometimes it is knowing what not to take.

My kidneys may be aging, but my curiosity has not retired. And neither has my desire to keep learning.

A Note to My Readers

This article is for education and personal reflection, not individual medical advice. Stage 4 CKD nutrition and medication decisions depend on kidney function, laboratory results, other medical conditions and the complete list of medicines and supplements a person takes. The safest approach is to discuss any new supplement, including turmeric/curcumin with a nephrologist, physician or pharmacist before starting it. 

Related theme for my earlier wellness articles: What I have learned about medicines, herbal remedies, vitamins and dietary supplements from traditional Filipino wisdom to my years in pharmaceutical science and the FDA.