07.07.2026

Testosterone – What's True and What's Not

By Dr. Rahel Sahli, Endocrinologist, Ärztezentrum Ittigen

Testosterone is one of the most talked-about hormones—and at the same time, one of the most misunderstood. Promises of miracle supplements are circulating on social media, influencers on YouTube explain how to “naturally boost” your levels, and people whisper tips to each other at the gym. What’s the truth? I was recently a guest on the national SRF Puls chat and answered the most common questions from the Swiss public.

In this article, we debunk the most common myths surrounding testosterone and show what is scientifically proven—and what isn’t.

Myth 1: Herbs and supplements can treat low testosterone

During my office hours, I regularly encounter patients who show me products they’ve bought online—often with the promise of melting away belly fat, building muscle, and normalizing testosterone levels. All “natural,” of course.
My clear message on this: There is no scientific evidence for such effects. This applies to both common herbal supplements and combination products that are aggressively marketed in advertisements. On top of that, there are real risks: Many of these products are not officially approved, their composition is unclear, and there is a risk of liver toxicity and dangerous interactions with other medications.
My advice: Do not take anything that is not an officially approved medication—and always consult a doctor first.

Myth 2: Soy products “feminize” men

This myth persists—especially in certain fitness communities. The fear is that phytoestrogens in soy lower testosterone levels and “feminize” men.

What the current data shows: Moderate consumption of soy products does not lead to a significant reduction in testosterone levels in men. Only with extreme intake levels—far above normal—would hormonal effects be theoretically conceivable—but such levels play virtually no role in real-world diets. On the contrary: There is even evidence that regular soy consumption may be associated with a lower risk of prostate cancer.

Myth 3: A low testosterone level automatically means treatment is needed

A single lab result in the lower range does not constitute a diagnosis. Testosterone deficiency is only diagnosed when two criteria are met: a consistently low level (measured in the morning on an empty stomach) and corresponding clinical symptoms. The overall picture is what matters—not the lab result alone.

Myth 4: Testosterone is an anti-aging agent

Testosterone is not a lifestyle supplement. Treatment is medically justified only if there is a genuine deficiency. Taking testosterone when levels are normal offers no proven benefits—but it does carry real risks, such as acne, hair loss, and an increase in red blood cells.

What Really Helps

Before considering hormone therapy, it’s almost always worth taking a look at your lifestyle first. Good sleep, regular strength training, reducing visceral belly fat, and a balanced diet can naturally and positively influence testosterone levels—and there is proven evidence to support this.

If you have any questions, Dr. Rahel Sahli will be happy to assist you.

Board-Certified Specialist in Endocrinology

Ärztezentrum Ittigen

Dr. Sahli studied medicine at the University of Zurich and graduated in 1994. After completing her residency at various renowned hospitals in Switzerland, including Inselspital Bern, she earned her board certification in Endocrinology and Diabetology in 2005 and in Internal Medicine in 2007. From 2008 to 2011, she served as a senior physician at the University Clinic for Endocrinology, Diabetology, and Clinical Nutrition at Inselspital Bern. She then worked at the STEPS Metabolic Center in Biel and, starting in 2014, at the Sanacare Group Practice in Bern. In addition to her clinical work, she is active in various professional committees and has many years of expertise in the fields of diabetes, metabolic disorders, and endocrinology. She joined the team at the Ittigen Medical Center in 2026 and brings her extensive experience to the care of her patients.

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