If you live in Boulder, Colorado, you probably know someone who follows a vegan or ketogenic (keto) diet. Maybe you are one of them. But do you know how these diets affect your immune system and your health? We all worry that vegan diets are protein-deficient and keto diets can clog arteries, but is this true? A recent study by the National Institutes of Health (NIH)^1,2 reveals some surprising insights into how switching to a vegan or a keto diet rapidly impacts your immune system, metabolism, and gut microbiome in just 2 weeks.

Study Design

The study involved 20 healthy volunteers who were randomly assigned to eat as much as they wanted of either a vegan or a keto diet for two weeks, followed by the other diet for another two weeks.

• The vegan diet was high in fiber, 75% carbohydrates, 10% fat, and eliminated animal products (e.g., no meat, eggs, or dairy).
• The keto diet was 76% fat, 10% carbohydrates, and included animal products like meat, eggs, and dairy.

Blood, urine, and stool samples were collected from each participant and used to measure immune responses, metabolic responses, and changes in the gut microbiome.

Immune Health

Vegan Diet Boosted Innate Immunity (The Immune System’s “General Security // Firewall // Shield”)

The vegan diet boosted the innate immune system, which is the body’s non-specific first line of defense against pathogens that it hasn’t encountered before.

Specifically, the vegan diet increased the activity of Type 1 Interferons (IFNs) that regulate inflammation and autoimmune responses, tumor recognition, and t-cell activation. The vegan diet also increased the activity of neutrophil white blood cells, antiviral responses, and anti-cancer pathways.

Together, this suggests that switching to a vegan diet can help fight:

• Cancer (together with a cancer treatment plan).
• Viral infections, including COVID-19, common colds, flu viruses, herpes, shingles, and chicken pox.

These findings suggest a vegan diet may be worth considering – even if just for a short time – for folks with high exposure to new germs and pathogens, including:

• Frequent travelers.
• Healthcare and education workers.
• Individuals with autoimmune disorders.

Keto Diet Boosted Adaptive Immunity (The Immune System’s “Special Forces / Antivirus // Sword”)

The keto diet enhanced the adaptive immune system, which is the body’s pathogen-specific immunity that keeps us safe from pathogens we’ve already been exposed to through real-life encounters and vaccinations.

Specifically, the keto diet increased immune components that recognize and eliminate foreign invaders, including:

• T and B lymphocyte red blood cells.
• Plasma cells.
• Natural Killer (NK) Cells.

These findings suggest a keto diet may be worth considering – even if just for a short time – for:

• Folks struggling with a cold they can’t kick.
• Families where the same flu gets passed around to everyone.

Metabolism

Vegan Diet Had Lower Calorie Consumption, More Iron, & Better Oxygen Delivery

The vegan diet was associated with:

• Lower calorie consumption (naturally).
• Higher:
  • Iron consumption.
  • Red blood cell production.
  • Heme synthesis (heme is the part of a blood cell that enables blood to carry energy-giving oxygen to tissues).

These findings may explain why some vegan endurance athletes, like Boulder’s own Scott Jurek, Sage Cannady, and Sandi Nypaver, perform and recover so well in ultra-endurance events. The increased iron and blood oxygen transport enables greater energy usage.

Keto Diet Had Higher Protein Abundance, Reduced Insulin Signaling, and Increased “Bad Fat” in the Blood

The keto diet had:

• Increased protein abundance in the plasma.
• Broader impact on the body, affecting proteins in the:
  • Blood.
  • Brain.
  • Bone Marrow.
• Increased production and degradation of branch chain amino acids (BCAAs).
• Reduced insulin signaling pathways from baseline.
• Increased intake of unsaturated (“good”) and saturated (“bad”) fatty acids.
• Increased unsaturated (“bad”) fatty acids in the blood.

These findings may explain why some keto bodybuilders and weightlifters perform and recover so well. They benefit from having an abundance of protein in the plasma.

These findings also suggest that a keto diet – even if tried just for a week or two – could improve:

• PreDiabetes.
• Diabetes.
• Insulin Resistance.

However, the increase of “bad” unsaturated fatty acids in the blood warrants long-term considerations.

All readers should follow up with a doctor, dietician, nutritionist, or health coach before making any major dietary changes.

The Bottom Line

Overall, the study suggests that different diets have distinct effects on the immune system, metabolism, and microbiome, and that these effects can occur quickly when diets change – in as soon as 2 weeks.

Folks looking to increase their overall immunity and energy levels – including those who love to travel and/or those who love to spend all day out on the trails may want to consider switching to a plant-based diet to boost innate immunity, iron consumption, and oxygen transport.

Folks looking to make extra gains in the weight room, increase their climbing game, kick that repeat cold or virus, or manage diabetes may want to consider a more keto-leaning diet with the help of clinical support.

Important Caveats to Consider

Importantly, the study was:

• Small (20 participants).
• Short-term (2 weeks per diet).
• Dietary guidelines were provided.

More research is needed to determine:

• If the observed effects are beneficial or harmful:
  • Over longer periods.
  • In larger populations.
  • Regarding overall health outcomes.
• What implications they have for the prevention and treatment of diseases such as cancer, autoimmune and inflammatory conditions, diabetes, and insulin resistance.

The bottom line is that your diet matters for your immune system and your health. Whether you choose to go vegan, keto, or something in between, you should be aware of the pros and cons of each diet and consult your doctor before making any drastic changes. And remember, moderation and variety are key to a balanced and healthy diet.

Hungry for Seconds?

If you are interested in learning more about the study, you can read the full article here and an NIH press release here. If you are considering changing your diet, you should consult with your doctor, dietitian, or health coach who can help you make informed and safe choices.

Remember that a healthy diet is only one part of a healthy lifestyle and that you should also exercise regularly, manage stress, and get enough sleep.

Stay healthy, Boulder!

Brenna Bray

Dr. Brenna Bray, a local health and wellness coach, stress researcher, associate professor, and avid ultra-marathon mountain runner, holds PhDs in Biomedical Science, Neuroscience, and Complementary and Integrative Health. Her journey through an eating disorder fuels her dedication to coaching, merging personal experiences with scientific expertise. Through her practice, Bray empowers clients to access and harness their innate healing abilities and achieve remarkable health and wellness transformations. Committed to community engagement and holistic well-being, Dr. Bray shapes a brighter, healthier future for all. Learn more about Dr. Bray at www.brennabray.com.