Most fertility nutrition advice falls into one of two buckets: vague ("eat well") or alarmist ("cut these eleven foods immediately"). The honest picture sits somewhere quieter. There's a small set of dietary patterns with consistent, repeated evidence behind them, and a much larger set of individual foods and supplements where the evidence is thin, conflicting, or comes from studies that weren't designed to answer the question being asked.
Knowing the difference is the work.
The strongest dietary signal in the fertility literature is the Mediterranean pattern, high in vegetables, legumes, whole grains, fish, olive oil, and nuts, with red and processed meat kept to the edges. The evidence isn't from one study; it's from multiple cohorts, in multiple countries, looking at both natural conception and IVF outcomes.
The reason it shows up so consistently is that it does several useful things at once, it lowers inflammatory markers, stabilises blood sugar, and provides the micronutrient backdrop (folate, B12, omega-3, antioxidants) that egg and sperm development draw on.
Blood sugar regulation matters more than most people realise, and not in the way social media frames it. You don't need to eliminate carbohydrates. What the evidence supports is reducing the *swings*, large spikes followed by sharp drops, repeated several times a day.
Sustained insulin resistance is associated with ovulatory dysfunction, particularly in PMOS (previously called PCOS), but also more broadly. The practical version of this is boring: protein and fibre with most meals, fewer ultra-processed snacks between them. That's it.
Caffeine and alcohol both have real dose-response data, but the doses are higher than the internet suggests. Up to about 200mg of caffeine a day, roughly two small coffees, has not been shown to harm fertility or early pregnancy outcomes. Alcohol is messier: light intake (under about three to four units a week) doesn't show a clear signal in most studies, but heavy intake clearly does, and the evidence is stronger in men than people expect.
Sperm production is a 74-day cycle, so changes today take ten to twelve weeks to show up.
What nutrition cannot do is reverse age-related egg quality, fix structural issues, or compensate for moderate-to-severe sperm problems. It is one input, and an important one, but it is not the input. People who frame food as the thing that will or won't get them pregnant tend to end up exhausted and no further forward.
The honest framing is: nutrition is the foundation under everything else, it makes the rest of what you do work better, but it doesn't replace it.
What to try this week
If you're going to change one thing, change breakfast. Most people skip protein at the start of the day and then chase blood sugar for the next eight hours. Add 20–30g of protein to whatever you already eat in the morning, eggs, Greek yoghurt, tinned fish on toast, leftover dinner.
Hold that for two weeks and notice whether your afternoon energy and cravings shift. That single change does more for blood sugar stability than cutting anything out, and it's a foundation you can build the rest of the pattern on top of.