Bio-Individuality: There's no one-size-fits-all diet that works for everyone

Bio-individuality is one of the most important concepts at the Institute for Integrative Nutrition (IIN). In short, we know that one type of diet can work for a certain person and not for another. The same phenomenon can happen with supplements, and one of the main reasons is that our bodies are different and the way they process food or supplements is equally different.

Two patients. Same diagnosis. Same age. Same gender. Identical treatment. Results may differ.

Bio-individuality must be seriously considered by all healthcare professionals, because this could be the reason why many treatments fail.

What is bio-individuality?

Bio-individuality is the concept that each person has unique needs. What works excellently for one person may not work for another — or, in certain cases, may even be harmful.

One person's ideal diet can lead another to gain weight. The morning run that energizes one individual can leave another's body exhausted. The intermittent fasting that transformed one person's life can disrupt another's hormonal balance.

“One man’s food is another man’s poison.” — Institute for Integrative Nutrition (IIN)

Why are we biologically different?

Each person's genetics, gut microbiome, metabolism, medical history, stress level, sleep quality, and environment are unique.

Individual needs also change over time; what worked at 25 may no longer be suitable at 45.

Factors defining each person's bio-individuality include:

• Genetics and epigenetics — genes and how the environment activates or silences them

• Gut microbiome — the microorganisms inhabiting the gut

• Metabolism — the speed and efficiency with which the body processes nutrients

• Life stage — needs change with age, pregnancy, and other transitions

• Stress level and sleep quality — directly affect digestion and metabolism.

• Culture, traditions, and geographical environment — profoundly influence the body's needs.

What science tells us

Bio-individuality is not just a concept launched by IIN. In the scientific world, it is known as personalized nutrition, one of the fastest-growing areas in modern nutrition research.

A clinical trial published in Nature Medicine in 2024 demonstrated that the same food produces distinct biological responses in different people regarding glucose, triglycerides, and microbiome, and that personalized nutrition yielded superior improvements compared to standard dietary recommendations.

A systematic review from 2026 that analyzed 24 clinical trials published between 2000 and 2025 concluded that personalized nutrition approaches consistently improve metabolic markers such as HbA1c, triglycerides, and insulin sensitivity.

The PREVENTOMICS study (2025) confirmed that individual genetic and phenotypic characterization is fundamental for determining each person's specific nutritional requirements.

What this means in practice

Next time a friend’s diet doesn’t work for you, the answer isn't a lack of willpower or some other excuse; the explanation may lie here: in bio-individuality.

Four practical principles:

• Stop comparing your body to your friend’s or neighbor’s; every health journey is unique, and what works for someone else may not work for you.

• Experiment and observe — your body provides clear signals of what works and what doesn't. Be your body's own scientist, and pay attention, as it will give you valuable information.

• Re-evaluate periodically — what was suitable five years ago may no longer be so, therefore, changes are needed from time to time.

• Seek personalized guidance — laboratory analyses are the map of your bio-individuality. Seek a healthcare professional who can help you in this continuous learning process.

Pharmacist's advice: Before starting any diet or supplementation protocol, consult a healthcare professional and get a complete blood test; it’s the best way to get to know yourself internally. There are other exams you can do if you want to delve deeper into yourself, but the starting point is here.

Want to explore this topic further?

This article is based on the free guide "A Saúde Começa Aqui" (Health Starts Here), available here. In the guide, I delve deeper into this and two other concepts that transformed my understanding of health: Primary Food and Food is Medicine.

> Download the free guide here

Author:

Luis Coutinho

Pharmacist | IIN Health Coach.

Founder of Balance by LC — balancebylc.com

This article is for informational and educational purposes only. It does not replace professional pharmaceutical or medical advice.