Could what's on your dinner plate tonight be quietly shaping the future of your family? That question sounds dramatic — but after reading what a new study from Rotterdam found, it doesn't feel so far-fetched.
Welcome, dear reader. Here at FreeAstroScience.com, we believe that science is for everyone — not just those in white coats. Every week, we take complex research and break it down into plain, honest language, so you can make sense of the world around you. Today, we're doing exactly that with a groundbreaking study just published on March 24, 2026, in the prestigious journal Human Reproduction.
This study is the first of its kind to look at how both parents' diets — specifically their consumption of ultra-processed foods — affect their ability to conceive and how well the embryo develops in those critical first weeks of life. The results are eye-opening, even a little uncomfortable. And we think you deserve to know them. Stick with us to the end — there's a lot more to this story than headlines tell you.
When Junk Food Affects Not Just You — But the Life You're Trying to Create
What Are Ultra-Processed Foods, Exactly?
Before we get into the science, let's get clear on what we're talking about. Ultra-processed foods (UPFs) are products that go far beyond simple cooking. They're manufactured with industrial ingredients — artificial colors, emulsifiers, preservatives, stabilizers, and flavor enhancers — that you'd never find in a home kitchen.
Think: packaged chips, instant noodles, sugary breakfast cereals, pre-made frozen meals, fizzy soft drinks, fast food burgers, and mass-produced pastries. Scientists classify them using the NOVA food classification system, which groups foods into four categories based on how much processing they undergo. NOVA Group 4 — the ultra-processed tier — is what this study focuses on.
UPFs now make up a frightening share of daily calories in many countries. In this study's Dutch cohort, women got 22% of their total food intake from UPFs, while men consumed even more — about 25%. Those aren't extreme numbers. That's pretty normal for modern life. And that's exactly what makes these findings so relevant to you.
What Did This New Study Actually Find?
Researchers at Erasmus University Medical Center in Rotterdam, the Netherlands, led by Dr. Romy Gaillard — a paediatrician and associate professor of developmental epidemiology — conducted what is now the first study to examine the combined dietary impact of both parents on conception and early embryonic development.
The team analyzed data from 831 women and their 651 male partners, all enrolled in the Generation R Study Next Programme, a long-term Dutch cohort study that has followed families from before conception into their children's early years. Couples joined between 2017 and 2021. Diet was assessed around the 12-week mark of pregnancy using a detailed food questionnaire.
The study also used transvaginal ultrasound scans to measure embryo size and yolk sac volume at weeks 7, 9, and 11 of pregnancy. That level of detail is rare. Most fertility research looks at just one factor — sperm count, say, or birth outcomes. This one connected the dots from the dinner table to the womb, in real time.
Why Are Men's Fertility Numbers So Alarming?
A 63% Higher Risk — Is That Number Real?
Yes, it is. Men who ate higher amounts of UPFs were 63% more likely to experience subfertility — defined as taking 12 months or longer to conceive, or needing assisted reproductive technology like IVF. They also took longer, on average, to achieve pregnancy with their partner.
First author Celine Lin, a PhD student at Erasmus University Medical Center, explained it clearly: "In men, we observed that higher UPF consumption was related to a higher risk of subfertility and a longer duration until pregnancy was achieved." Sperm, it turns out, is remarkably sensitive to what a man eats.
This tracks with earlier research, too. A 2024 study in Human Reproduction Open — involving 200 healthy men of reproductive age — found that higher UPF consumption was directly linked to reduced total sperm count, lower sperm concentration, and decreased sperm motility (the sperm's ability to swim). Swap those UPFs for minimally processed foods? Semen quality improved. The pattern is consistent.
And another 2025 study confirmed that the Mediterranean diet — rich in vegetables, fish, whole grains, and olive oil — was associated with better sperm quality parameters, including viability and typical morphology. The contrast with UPF-heavy diets is stark.
How Does a Mother's Diet Shape Early Embryo Growth?
For women, the story is different — but equally striking. Higher maternal UPF consumption didn't consistently affect whether a woman could conceive. What it did affect was what happened once she did.
At 7 weeks of gestation, women with higher UPF diets had embryos that were measurably smaller than those of women eating fewer ultra-processed foods. Their yolk sacs were also smaller. These differences faded somewhat by weeks 9 and 11, but the early window clearly matters.
As Celine Lin put it: "Maternal UPF consumption may directly influence the environment in the womb in which the embryo develops from the start of life onwards." Think of it like soil quality. The embryo can only grow as well as the environment around it allows. A nutrient-poor, additive-laden environment in those first weeks may leave early marks — even if they're difficult to see clearly yet.
What Is the Yolk Sac and Why Does It Matter So Much?
Most people have heard of the yolk of an egg. In human embryology, the yolk sac plays a similar role — it's the embryo's first source of nourishment before the placenta takes over. It forms in the very first weeks of pregnancy, typically visible by ultrasound around week 5 or 6.
A healthy, properly-sized yolk sac is linked to better early development outcomes. A smaller or irregularly formed yolk sac, on the other hand, is associated with a higher risk of miscarriage and developmental complications. Impaired yolk sac development in the first trimester has also been connected to adverse birth outcomes — including premature birth, low birth weight, and even cardiovascular issues in childhood.
We're talking about differences measured in fractions of a standard deviation (–0.14 SDS per unit increase in UPF intake, to be precise). Small? Yes. Irrelevant? Far from it. At a population level, small shifts in embryo development can translate into large public health implications.
Key Study Numbers at a Glance
We've pulled the most important numbers together in one place.
| Factor | Group | Finding |
|---|---|---|
| Study cohort size | Both parents | 831 women, 651 male partners |
| Avg. UPF share of diet | Men / Women | ~25% / ~22% of total food intake |
| Subfertility risk | Men (high UPF) | 63% higher likelihood of subfertility |
| Embryo size at 7 weeks | Women (high UPF) | Measurably smaller crown-rump length |
| Yolk sac volume | Women (high UPF) | –0.14 SDS per unit UPF increase (95% CI: –0.26, –0.02) |
| Associations at 9–11 weeks | Women | Effects attenuated (reduced) at later weeks |
| Study enrollment period | Both | 2017 – 2021, Rotterdam, Netherlands |
| Published journal | — | Human Reproduction, Oxford University Press |
Why Might UPFs Cause This Kind of Damage?
Is It the Empty Calories, or Something More Sinister?
Honestly? We don't know yet. And the researchers are the first to admit that. There are two leading theories, and they're not mutually exclusive.
The first is simple: UPFs tend to crowd out nutritious foods. When 25% of a man's diet is chips and packaged snacks, that's 25% not spent on zinc-rich legumes, antioxidant-packed vegetables, or omega-3 fatty acids from fish — all nutrients known to support sperm quality and reproductive hormone levels. Poor nutritional density alone could explain a lot.
The second theory is more unsettling. UPFs contain a cocktail of food additives — emulsifiers, artificial sweeteners, colorings, and preservatives — whose long-term reproductive effects are largely unknown. Some researchers also point to microplastics, which contaminate packaging and have been found in human sperm, blood, and placental tissue. Whether these microplastics actively disrupt sperm production or embryonic signaling is still an open question.
Sperm cells are particularly vulnerable. They take roughly 74 days to fully mature — and during that entire window, they're being shaped by diet, toxins, and environment. Every chip bag, every soda, every microwave meal a man consumes during those three months could theoretically nudge his sperm quality in one direction or another. That's a sobering thought.
Should We Trust These Results? Limitations and Nuances
Good science always names its limits. This study is no exception, and we'd be doing you a disservice if we glossed over them.
First: this is an observational study. That means it can identify associations between UPF intake and fertility outcomes — but it cannot prove direct causation. People who eat more UPFs may also sleep less, exercise less, smoke more, or live in more stressful environments. Disentangling all those variables is genuinely hard.
Second: diet was assessed at 12 weeks of pregnancy, not at the time of conception. It's reasonable to assume eating habits hadn't changed dramatically, but we can't be certain. Also, the study cohort consisted entirely of couples who did eventually conceive — so the impact on couples who never got pregnant at all may be even larger than these numbers suggest.
A parallel study, published in the journal Nutrition and Health around the same time, analyzed data from over 2,500 American women in the US National Health and Nutrition Examination Survey. That study included women who were unable to conceive — and found the same direction of effect: lower UPF consumption was linked to a higher likelihood of pregnancy. That consistency across two independent datasets, using different methodologies, is meaningful.
What Can We Realistically Do About This?
We're not here to shame anyone's eating habits. Modern life is busy. Food is expensive. And whole foods take time to prepare. But if you're trying to conceive — or even just thinking about it — these findings give you a real, evidence-based reason to look at what's in your shopping trolley.
Here's what the science points to, without being preachy about it:
- Both partners should think about diet in the pre-conception window — not just the woman.
- A diet closer to the Mediterranean model (vegetables, fish, olive oil, legumes, whole grains) is consistently linked to better reproductive health in both sexes.
- Swapping UPFs for minimally processed alternatives — even gradually — appears to improve sperm quality parameters in men.
- The pre-conception period and first trimester are especially sensitive windows. Early exposure matters enormously.
- If you're concerned about fertility, speak to a doctor. Diet is one piece of a complex picture.
Dr. Romy Gaillard put it well when she said: "Our research shows that we should think more broadly about fertility and early pregnancy. Our results highlight the need to pay more attention to male health in the preconception period, which has traditionally been overlooked." We at FreeAstroScience couldn't agree more.
Final Thoughts from FreeAstroScience
What this research really tells us is that the body is not a sealed machine. It's a living system, constantly in conversation with its environment — including the food we feed it. A man's sperm, a woman's embryonic womb, the yolk sac quietly nourishing a new life: all of it responds to the world outside. That's both humbling and empowering.
We know there are people reading this who are in the middle of difficult fertility journeys. You are not alone. Science is beginning to look at factors that for too long were invisible — including male diet — and that matters. These findings aren't a verdict; they're a direction. A reason to ask better questions.
At FreeAstroScience.com, we write for you — the person on the train, the parent-to-be scrolling late at night, the curious mind who refuses to accept easy answers. We believe knowledge protects you. It shields you from misinformation, from fear-mongering, and from the kind of half-truths that circulate on social media masquerading as science.
We live by one principle here: never turn off your mind. Keep it active, keep it questioning, keep it open — because, as Goya warned us more than two centuries ago, the sleep of reason breeds monsters.
Come back to FreeAstroScience.com — where complex science is explained simply, every single day. Your knowledge is your superpower. Don't waste it.
📚 References & Sources
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Lin C. et al. (2026). Periconceptional ultra-processed food consumption in women and men associated with fertility, embryonic growth, and yolk sac development.
Human Reproduction, Oxford University Press. Published March 24, 2026.
https://academic.oup.com/humrep/advance-article/doi/10.1093/humrep/deag023/8537945 -
PubMed abstract — Lin et al. 2026. PMID: 41871947.
https://pubmed.ncbi.nlm.nih.gov/41871947/ -
US News & World Report Health (March 26, 2026). Ultra-Processed Foods Harm Fertility In Both Men And Women.
https://www.usnews.com/news/health-news/articles/2026-03-26/ultra-processed-foods-harm-fertility-in-both-men-and-women-studies-r -
News Medical Life Sciences (March 24, 2026). Study connects ultra-processed diets to fertility and embryo development.
https://www.news-medical.net/news/20260324/Study-connects-ultra-processed-diets-to-fertility-and-embryo-development.aspx -
Salas-Huetos A. et al. (2024). Ultra-processed food consumption and semen quality parameters in healthy men.
Human Reproduction Open.
https://academic.oup.com/hropen/article/2024/1/hoae001/7574732 -
Role of Mediterranean Diet and Ultra-Processed Foods on Sperm Parameters (2025). PMC.
https://pmc.ncbi.nlm.nih.gov/articles/PMC12250936/ -
ESHRE Focus on Reproduction (March 23, 2026). Ultra-processed foods are linked to reduced fertility and embryonic development.
https://www.focusonreproduction.eu/press-releases/ultra-processed-foods-are-linked-to-reduced-fertility-and-embryonic-development
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