6 food combinations you should avoid – and what to eat instead
From beans on toast to bran cereal, some “healthy” food pairings might not be as good for you as you think.
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From beans on toast to bran cereal, some “healthy” food pairings might not be as good for you as you think.
Some healthy-sounding foods make surprisingly bad company. Combine them in the same meal and your body may absorb less of some vitamins and minerals than you expect. That’s because some compounds in one food can inhibit the absorption of certain nutrients from another, while certain combinations can help the body absorb nutrients more effectively, says nutritional therapist Julie Gough.
“These interactions matter more when nutrient intake or absorption is already compromised,” she explains. In later life, lower appetite, medications and illness can all play a part.
Plant-based meals often crop up in these combinations because non-haem iron, the form supplied by plant foods, is harder to absorb than haem iron in meat and more easily affected by other foods.
In a 2021 study by researchers in Morocco and at ETH Zurich, green tea reduced absorption of the added iron by more than 85% compared to water, both in women with iron-deficiency anaemia and those without it. The study used fortified wheat flour rather than porridge, but tea polyphenols inhibit absorption of non-haem iron from a range of foods, so the same interaction is relevant to the iron in oats.
Both black and green tea contain polyphenols that can bind to non-haem iron, making it less available for absorption, says Julie.
“The effect could be quite significant when tea is drunk with the meal,” says Sophie Nielsen, a nutritional therapist at Urban Wellness. This is particularly relevant for people with low iron stores or who rely heavily on plant-based iron.
A 2021 review by the Scientific Advisory Committee on Nutrition found 12% of women aged 75 and over had iron intakes below recommended levels.
Wait at least an hour after your porridge before having tea, suggests Sophie: “Eating the porridge first and drinking tea immediately afterwards would probably not provide much benefit, as they would still overlap during digestion.”
A kiwi or a handful of berries can also boost iron absorption, says Julie. If you want a hot drink with breakfast, rooibos may interfere less: a small 1979 study found that ordinary tea significantly inhibited iron absorption, while rooibos did not have a significant effect.
“Rooibos appears to be less of a concern than black tea, although the human evidence is limited,” says Julie.
Beans and wholegrains both contain phytates, natural plant compounds that can interfere with mineral absorption. A 2024 review of more than 40 studies led by researchers at the University of Thessaly in Greece found that phytate-rich foods can reduce iron and zinc absorption.
“Both beans and wholegrain bread contain phytate, so the meal may have a relatively high phytate to mineral ratio,” says Julie. “Phytate binds iron and zinc within the gut, reducing their bioavailability.” She adds that zinc is particularly affected.
Baked beans already contain some vitamin C from the tomato sauce, but adding half a red pepper or a kiwi can help your body absorb more iron, says Julie.
However, vitamin C doesn’t overcome phytate’s effect on zinc. “Vitamin C has a well-established enhancing effect on non-haem iron, but it does not appear to meaningfully counteract phytate’s effect on zinc absorption,” says Julie.
However, beans are still a useful source of fibre and plant protein, she notes.
A 2022 review of 12 trails by researchers at the National University of Singapore found that eating fat with carotenoid-rich foods helped the body absorb more carotenoids, particularly when the fat was unsaturated.
Carotenoids are natural pigments in colourful fruit and vegetables that may act as antioxidants. Some, such as beta-carotene, can also be converted into vitamin A.
Vitamins E and K are also fat-soluble, so we need some dietary fat to absorb them efficiently, says Julie.
Add olive oil, avocado, nuts or seeds to your salad, suggests Sophie: “Even a small amount can improve absorption.” Cheese or chicken thighs can also provide enough fat to help.
Low-fat dressing is also likely to be better than fat-free, says Julie, although how much fat is in the rest of the meal counts, too.
Lentils contain non-haem iron, which is more sensitive to other components of a meal than the haem iron found in red meat, says dietitian Nichola Ludlam-Raine, author of How Not to Eat Ultra-Processed. “Red wine is rich in polyphenols, which can bind to iron in the digestive tract and make some of it less available for absorption,” she explains.
If you have low iron stores, try to drink red wine away from your main iron-rich meal, Nichola suggests. Vitamin C can also help: put peppers or tomatoes in the filling or serve broccoli with your meal.
For most people, there’s no need to avoid the pairing altogether. The researchers concluded that the effect of red wine polyphenols was unlikely to make a significant difference to overall iron balance, says Nichola.
A 2024 study led by a researcher at San Diego State University identified phytate and oxalate – natural substances found in plant foods – as the two main factors reducing calcium absorption.
“Wheat bran is particularly rich in phytate, which can bind minerals including calcium and reduce their bioavailability,” says Nichola. Other components of the bran may also physically bind or trap some calcium.
The effect may be more relevant after menopause. “Maintaining an adequate calcium intake becomes particularly important as we get older and for post-menopausal women, when declining oestrogen accelerates bone loss,” she says.
If bran cereal is a staple, vary your breakfasts and get calcium elsewhere in the day, suggests Nichola. Yogurt, kefir, milk, cheese or calcium-fortified alternatives are all useful sources.
“There’s no need to give up bran cereal and milk,” she adds. The effect appears to be particularly relevant to concentrated wheat bran rather than wholegrain foods generally.
Like beans on toast, this pairing can be high in phytates. Chickpeas and wholegrains both contain them, which can reduce absorption of iron and zinc, says Julie.
Add peppers, tomatoes or lemon to help boost iron absorption, suggests Julie. Fermented or sourdough flatbread may also help because fermentation can reduce phytate.
An international 2026 review led by a researcher at Democritus University of Thrace in Greece found some evidence that lower-phytate breads improved short-term non-haem iron bioavailability, although the evidence for sourdough and bread fermentation overall was inconclusive.
A 2025 review by researchers at the University of Osijek in Croatia and Oslo University Hospital in Norway found that calcium can inhibit absorption of both haem and non-haem iron but noted that findings from human studies have produced mixed results.
“The evidence isn’t completely consistent,” Nichola says. Other research found that adding a modest amount of cheese to a meal containing beef didn’t significantly affect absorption of either type of iron.
If you have low iron stores and have been advised to maximise iron absorption, having calcium-rich foods at another meal may be sensible.
For most people eating a varied diet, these interactions are unlikely to cause a deficiency, says Julie.
“Nutrition is much more about what we eat consistently across the day and week than achieving ‘perfect’ nutrient absorption from every meal,” agrees Nichola. The effects can be more relevant if you are deficient in a particular nutrient or have increased requirements.
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