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Can a Plant Based Diet Suppress the Immune System?

platelet and white blood cell count on a plant based diet

How does adherence to a whole foods, plant based (“wfpb”) diet impact the immune system?

Could it be responsible for low white blood cell and platelet count?

If so, does the reduced immune system activity benefit us by putting out the fire of many autoimmune conditions, or conversely, does it cause problems by making the immune system too quiet, and therefore less effective?

A reader, and custom nutrition plan customer, recently sent us these questions, which were so interesting we wanted to address them with a blog devoted to the subject.

Can diet alone quiet the immune system?

The question, from Eric, was as follows:

Is there any correlation between a low platelet count and low white blood cell count with a wfpb diet? My latest counts are 170 platelets and 4.9 wbc. Still normal, but at the very low end of normal. Also, my MPV shot up to 13 recently from 9.1 six months prior. Last spring/summer the platelets were 290 and the wbc at 7.1 collectively when I was still eating meat and not adhering strictly to a wfpb diet. This seems like a considerable drop with just diet. Now, keep in mind I have not been supplementing with vitamin B12 or Vitamin d-3 and do not know my current folate/iron/b-12 levels. Will get tested accordingly for those.

Platelets, white blood cells and the immune system

Platelets and white blood cells are part of the blood system, the complex cast of cells that regulate the blood flowing through our veins and whose job it is to defend the body from invaders.

Before we dive into Eric’s question, a brief summary of the major players in the blood system.

Platelets – anti-clotting activity

When viewed under a microscope, platelets are indeed disc shaped cells. They are made in our bone marrow and their job is to form clots to stop bleeding, for example when we accidentally fall and draw blood. Platelets repair damage when a blood vessel is injured.

According to the University of Rochester Medical Center, a normal platelet count is between 150,000 to 450,000 platelets per microliter of blood.1

White blood cells – guardians of the immune system

White blood cells, or leukocytes, are the guardians of the immune system. It’s their job to find and destroy fungi and bacteria that makes their way into the body. We need white blood cells to have a properly functioning immune system. While too many white blood cells is a sign of inflammation, diseases like leukemia are marked by a dangerous drop in these essential protectors.

Red blood cells – oxygen transport

Also made in bone marrow, red blood cells are the cells responsible for carrying oxygen throughout the body. There is a protein inside red blood cells, which is called hemoglobin. Hemoglobin is the oxygen carrying protein, and foods rich in iron help the body make enough hemoglobin. Iron in the diet is found in foods like eggs, beef and chicken, but can also be ingested by cooking foods in cast iron skillets.2

Diet and white blood cell count

Now on to the meat (no pun intended) of Eric’s question.

Does diet play a role in platelet and white blood cell count, and therefore in the state of inflammation in the body?

We found a study that seems largely to be on point. A large study following populations in Italy found that those who adhered to a strict Mediterranean diet had the lowest levels of white blood cells and platelets, but not abnormally low levels.3 The study authors paint the lower white blood cell and platelet counts as a positive since elevated levels of both types of cells have been linked to chronic inflammation and disease.4 5 The Mediterranean diet is characterized by eating mostly minimally processed cereal grains, beans, fish, seasonal fruit, leafy greens, olive oil, and occasionally red wine. Small amounts of meat and goat or sheep dairy can also be included, however it is thought to be the high polyphenol count of the diet that is most protective.

The study scored participants based on the quantities consumed of the following foods:

  • vegetables,
  • legumes,
  • fruits and nuts,
  • dairy products,
  • cereals,
  • meat and meat products,
  • fish,
  • alcohol, and
  • monounsaturated to saturated fat ratio

Note that the population here was not vegan or vegetarian. The purpose of the study was to look at inflammatory markers in healthy Italians following a Mediterranean diet.

The aim of this study was to investigate the association of an MD with PLT or WBC count based on the hypothesis that a diet rich in healthy compounds could favorably influence these 2 cellular biomarkers of low-grade inflammation in subjects without any overt chronic or hematologic disease.

What did the authors consider to be normal ranges for platelets (PLT) and white blood cells (WBC)?

I’ve quoted their ranges below.

Low PLT count (thrombocytopenia) was defined as PLT <156 × 109/L or <140 × 109/L for women aged <64 years or >64 years, respectively; for men, low PLT count was defined as PLT <141 × 109/L or <122 × 109/L for men aged <64 years or >64 years, respectively.

Cutoffs for high PLT count (thrombocytosis) were set when PLT >405 × 109/L or >379 × 109/L for women aged <64 years or >64 years, respectively; high PLT count was defined as PLT >362 × 109/L or >350 × 109/L for men aged <64 or >64 years, respectively.

High (leukocytosis) or low (leukopenia) WBC categories were defined as WBC <4 × 109/L or WBC >10 × 109/L, respectively.

What about the plant based diet?

Based on Eric’s N=1 data, it seems that a whole foods, plant based diet can lower levels of both white blood cells and platelets in similar fashion to the Mediterranean diet. When I dug around, I found a study that was in line with Eric’s experience. This study, which appeared in the Journal Epidemiology, looked at immune system markers in both vegetarians and non-vegetarians. They found that white blood cell and inflammatory immune activity was much lower in the vegetarian group.

Very interesting, especially in light of the commonly held belief that grains are a major cause of inflammation in some people, presumably because they are often difficult for many people to digest. For more on that topic, see: What Vegans Don’t Understand About the Paleo Diet.

But, if you take it as gospel that elevated white blood cells and platelets are inflammatory, there does seem to be some evidence that a plant based diet would quell inflammation as well.

Vegetarian diets to treat autoimmune conditions

Reading Eric’s question, and some of the relevant research, made me realize why a plant based diet is often prescribed for autoimmune conditions like Rhuematoid arthritis, it appears to quiet down the immune system.6

The question for the folks out there, like Eric, who are on a strict plant based diet is what does the total absence of B12 and iron do over time? Are some vegans and vegetarians at risk for white blood cell count that is too low?

The Italian study I cite above tends to indicate that inflammation can be kept in check with a Mediterranean diet that includes some fish and small amounts of dairy and meat.

From a health perspective, are most of us better off getting least some fish and maybe some sheep or goat dairy into our diet every so often?

The answer will depend on the individual.

In Eric’s case, his concerns about his white blood cell numbers getting too low are one factor to consider, but other factors, like lipid metabolism must enter in to the equation as well.

Eric was categorized into a mixed fat diet group based on our fat scoring algorithm. As such, it’s likely he has the ability to add some saturated fat into his diet without putting his LDL numbers out of range.

When white blood cells get too low

The second part of Eric’s question centered around whether he should be eating slightly more in the way of meat and fish to get his white blood cell count a little higher.

His father passed away from leukemia and he was concerned with numbers that were trending ever lower.

I’ve included the second part of his question below:

My cholesterol panel that I received today is as follows: Total = 114; HDL = 49 LDL= 56 Trig= 30
Based on me being in the balanced nutrition plan I am thinking I may see a benefit to raising some of my blood markers up above if I introduced beef sparingly back into the diet?

It’s an interesting question.

What is the Goldilocks zone for immune function? The dietary protocols of even the most stringent plant based advocates, such as Caldwell B. Esselstyn, shoot for a total cholesterol below 150. 7 Eric is at 114, which is very low, and according to some experts, too low.

As far as the LDL numbers are concerned, ideally we’d want to see the LDL-P number, as that is the biggest predictor of cardiovascular risk. But in light of the fact that Eric’s Triglycerides and LDL-C are so low, it’s reasonably likely that his LDL-P will track with his LDL-C number. It probably hovers below 750 which means he’s at very low risk for heart disease.

Would he be better off with an LDL-C of 75 and a more robust white blood cell count?

That’s a question for his doctor, but its does demonstrate an important principle: there is no one size fits all when it comes to nutrition. In this case, the wrong diet is the diet that puts the white blood cell count too high, but also the diet that brings it too low.

John O'Connor

John O'Connor is the founder of Gene Food. Read his full bio here.

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