S3 Ep. 111: Jaclyn Downs | Breaking Down MTHFR, Histamine & Fertility

On this episode of The Mama Making Podcast, I sat down with Jaclyn Downs, a functional genomic nutritionist, birth worker turned biochemistry researcher, and the author of Enhancing Fertility Through Functional Medicine. Her mission is simple but powerful: to help individuals understand the genetic, nutritional, and environmental roots of fertility issues, inflammation, and chronic conditions.

We dove into everything from oxidative stress and histamine intolerance to the controversial MTHFR gene, unraveling how genetic variations can influence everything from fertility to mental health. Whether you’re trying to conceive or just trying to feel better in your body, Jaclyn’s approach is a reminder that you are not broken — you just might be missing some key information.

From Doula to Genetic Detective

Jaclyn’s career began in the birth world as a doula, prenatal yoga instructor, and home birth apprentice. But as she supported clients through pregnancy and loss, she realized how often fertility struggles went unexplained. That curiosity eventually led her to functional genomics: the intersection of how genes express themselves based on nutrition, environment, and lifestyle.

"Every single reaction in our body is powered by an enzyme, and every enzyme is made from a gene," Jaclyn explained. "Those enzymes require nutrients to function properly. If you’re deficient, it’s like your metabolic engine is running on empty."

Her work today focuses on identifying oxidative stress — or cellular damage — and removing roadblocks like toxins, inflammation, and nutrient deficiencies. Fertility, she says, is often the first system to suffer when the body senses stress. The body will prioritize survival over reproduction, and that makes fertility the canary in the coal mine for underlying health challenges.

What Is Oxidative Stress?

Oxidative stress is cellular damage caused by an imbalance between free radicals and antioxidants. It affects the health of every cell in your body, and as Jaclyn explained, cellular health is foundational. If your cells are inflamed, undernourished, or overloaded with toxins, it ripples out to every tissue, organ, and system — including reproductive health.

Jaclyn shared that symptoms like inflammation, period problems, low energy, skin flare-ups, or blood sugar swings are often your body’s "check engine light." They're signs something is off under the hood. You may experience frequent fatigue, poor sleep, brain fog, or digestive issues long before any diagnosis is made. The good news? We can do something about it.

Functional genomic testing can give us clarity. It tells us how well your body is detoxing, methylating, managing inflammation, and utilizing nutrients — all the root systems that support your hormonal and reproductive health.

The Role of Functional Genomic Testing

Unlike traditional lab work, Jaclyn’s approach layers genetic testing with a deep dive into symptoms, history, exposures, and functional labs. She looks at how your genes are functioning, not just what you inherited.

"Just because you have a genetic variant doesn't mean it's expressing. We need context," she explained. "That’s why we pair genes with symptoms and lab data."

By interpreting genes in a personalized, context-rich way, she can build targeted protocols using nutrition, lifestyle, and (when needed) supplements. Her work often complements fertility treatments or helps clients avoid them altogether. And the benefits go far beyond fertility: improved mental health, energy, detox capacity, sleep, and resilience.

Let’s Talk MTHFR

One of Jaclyn’s most-requested topics is the MTHFR gene. It’s a popular buzzword in wellness spaces, often linked to anxiety, mood disorders, and infertility. But Jaclyn says it’s misunderstood.

"MTHFR doesn’t convert folic acid into methylfolate like people think. That’s actually another gene called DHFR. MTHFR attaches a methyl group onto folate. And if you're not doing that well, it affects everything from DNA repair to neurotransmitter function."

Still, she warns against treating MTHFR in isolation. "It’s just one piece of the puzzle. High doses of methylfolate without support from other nutrients can backfire. We have to zoom out and see the whole picture."

It’s why she encourages comprehensive panels, not just a handful of gene variants. "Methylation is complex. It impacts hormones, detox, mental health, and even your ability to tolerate histamine."

Histamine Intolerance: The Hidden Factor

Many of Jaclyn’s clients come to her unaware that histamine could be playing a role in their symptoms. While most people associate histamine with allergies, Jaclyn explained it also plays a role in digestion, mood, body temperature, and reproductive health.

"Histamine and estrogen feed each other. If you're someone who feels worse around ovulation, gets migraines, or has PMS, histamine might be the missing piece."

Foods like kombucha, sauerkraut, aged cheeses, and bone broth may be nutrient-rich — but for someone with histamine intolerance, they can cause a flare. Jaclyn helps clients identify sensitivities and support their body’s ability to clear excess histamine naturally.

Histamine intolerance can look like insomnia, anxiety, itchy skin, food reactions, or irregular periods — and is often mistaken for hormone imbalance alone. Through a combination of testing and targeted support, Jaclyn helps calm inflammation at the source.

The Power of Personalized Nutrition

When it comes to nutrition, Jaclyn emphasized a nourishing diet over trendy notions of "healthy."

"What’s healthy for one person could be inflammatory for another. That’s why personalization is key."

She recommends a colorful, minimally processed diet focused on antioxidant-rich, organic foods — but also encourages people to explore how their body responds to common triggers like dairy, gluten, soy, corn, and eggs. Her goal isn’t perfection, but empowerment. She also shares how too much of even a good thing (like spinach or nuts) can be problematic for people with oxalate sensitivity, another hidden issue that often arises with chronic inflammation.

Real-Life Fertility Support

For those facing fertility challenges, Jaclyn’s advice is to work upstream. Before considering assisted reproductive technology (ART), she helps clients address inflammation, nutrient status, and environmental toxins.

"You can’t pour from an empty cup. Optimizing cellular health makes everything downstream more effective. Even if you do need fertility treatment, you’ll respond better when your body isn’t in survival mode."

She emphasizes that fertility is not just about reproduction — it’s about vitality. Clear skin, good energy, healthy digestion, and balanced cycles all point to a body in rhythm. When those things are off, fertility will be, too.

Start Here: Small Steps with Big Impact

If you’re feeling overwhelmed, Jaclyn offers a few places to begin:

• Prioritize clean air, water, and food

• Look into low-tox swaps for body and home products

• Get quality sleep and manage light exposure

• Explore apps like Detox Me for step-by-step toxin reduction

• Consider a functional intake with someone like Jaclyn to get a full picture

Most of all, she encourages curiosity over fear. Genetic data isn’t destiny — it’s a flashlight, not a life sentence.

"It’s not about being perfect," she said. "It’s about giving your body what it needs to function the way it was designed to."

Whether you’re in the thick of your fertility journey or just trying to solve a lingering health mystery, Jaclyn’s work offers a roadmap rooted in curiosity, compassion, and root-cause healing. Her work bridges the gap between science and intuition — and reminds us that true wellness starts at the cellular level.

TL;DR

Functional genomic nutritionist Jaclyn Downs explains how oxidative stress, histamine intolerance, and genetic expression influence fertility, hormone health, and inflammation. From decoding MTHFR myths to identifying root causes through gene testing, she shares a personalized, empowering roadmap for anyone on a wellness or fertility journey.

How to connect with the Jaclyn:

IG: @functionalgenomics

Website:  www.jaclyndowns.com

Extras: Buy Jaclyn’s Book: Enhancing Fertility through Functional Medicine

The Mama Making Podcast Mom podcast, Motherhood Podcast, Motherhood Journey, Postpartum Mental Health, Pregnancy, New Mom Support, functional genomics, reproductive health, histamine intolerance, MTHFR, nutrition, genetic testing, fertility, oxidative stress, health optimization, nutrient deficiencies