Not All Veggies Are Equal: Why Legumes and Cruciferous Greens Stand Out for Young Adults

The Raine Study is one of the most-followed birth cohorts in the world, tracking participants from before birth into adulthood in Western Australia. At the 22-year follow-up, researchers asked a deceptively simple question: when young adults eat vegetables, does it matter which ones?

Using food frequency questionnaires, the team sorted vegetables into five buckets — allium (think onions, garlic, leeks), cruciferous (broccoli, cabbage, Brussels sprouts, cauliflower, kale), green leafy, legumes (beans, lentils, chickpeas, peas), and the yellow-orange-red group (carrots, capsicum, tomatoes, pumpkin). Participants were then classified as 'high' cardiometabolic risk if they met two or more of the International Diabetes Federation's metabolic syndrome criteria, and 'low' risk otherwise.

When the analysts compared the two groups, two patterns jumped out: men in the lower-risk group ate more legumes, and women in the lower-risk group ate more cruciferous and green leafy vegetables. The other categories — allium and yellow-orange-red — did not show the same separation.

After the researchers adjusted for sociodemographic factors, lifestyle behaviours and the rest of the diet, the legume finding in men held up: each additional 75-gram serve per day was associated with substantially lower odds of being in the high cardiometabolic risk group (odds ratio 0.278). That is a striking effect size for a single food category — and one of the reasons the paper is getting attention.

Mechanistically, the result is plausible. Legumes deliver a dense package of soluble fibre, plant protein, polyphenols, magnesium and potassium — nutrients linked in broader literature to better blood pressure, lipid profiles and insulin sensitivity. They are also one of the few foods that reliably displaces less helpful staples (refined grains, processed meats) when people eat more of them.

Why the legume signal was clearer in men is a genuinely open question. The authors note that males in the cohort started from a higher baseline cardiometabolic risk, which can make protective associations easier to detect statistically. Differences in portion sizes, body composition and hormonal physiology may also play a role. It is not evidence that women don't benefit from legumes — only that, in this dataset, the cleanest signal landed on one side of the cohort.

For young women in the cohort, the unadjusted differences pointed to cruciferous and green leafy vegetables. Broccoli, cabbage, kale, Brussels sprouts and cauliflower share a family of sulfur-containing compounds called glucosinolates, which the body converts into bioactive molecules like sulforaphane. These have been studied for effects on inflammation and oxidative stress — both relevant to early cardiometabolic trajectories — though the human evidence in young adults specifically is still thin.

It's worth being precise about what the study can and can't tell us. A cross-sectional analysis captures a single snapshot: it cannot prove that eating more broccoli caused lower risk, only that the two travelled together. Reverse causation (healthier young adults eating more vegetables for other reasons) and residual confounding are always possibilities. That is exactly why the editorial evidence rating for this piece is moderate, not strong.

The most defensible read of the data is also the least dramatic: among young adults, vegetable category appears to matter, and the categories that showed up best are inexpensive, widely available and easy to add. A daily serve of legumes — a half-cup of lentils in a salad, chickpeas in a curry, black beans in a burrito bowl — is a low-effort change with strong supporting biology. A few weekly meals built around cruciferous vegetables follow the same logic.

What this study does not justify is swapping out other vegetables, buying expensive supplements marketed around 'sulforaphane' or 'legume polyphenols,' or treating any single food as a hedge against the rest of the diet. The cohort that did well wasn't eating beans in isolation; they were eating beans as part of broader dietary patterns the researchers adjusted for.

If you are in your twenties and thinking about long-term metabolic health, the honest message is the unglamorous one: the evidence here is moderate, the direction is encouraging, and the specific upgrades — more lentils, more broccoli — are some of the safest bets in nutrition. Anyone with existing cardiometabolic concerns should bring questions about their own diet to a clinician or dietitian who can see the full picture.