Worried about coffee's potential effects on your health? There is a simple solution.
Is it true that drinking coffee removes vitamins and minerals from the body? How much would I have to drink for this to have a significant effect?
Coffee does affect absorption of essential nutrients, so we should remember this when quenching our thirst for flat whites. But the good news is, with a few minor tweaks to your caffeine habit, you can have your coffee and your nutrients, too, according to recent research.
New Zealanders love their coffee, with nearly a quarter of us having three a day, according to the Wild Bean Café Kiwi Coffee Consensus survey, and 70 per cent of us at least one a day. As in previous surveys, the flat white topped the popularity stakes nationwide. However, Wellingtonians were more likely than residents of other cities to order a latte.
Although we talk about coffee in a singular sense, it's worth remembering that roasted coffee is a diverse affair. Different types of beans, roasting and grinding processes and preparation methods are used to create our brew, whether it's an espresso, drip coffee, French press, percolator or some other style. These factors dramatically influence the intricate mixture of more than 1000 bioactive compounds that end up in our morning cup.
Coffee's active compounds include some that are potentially good for us, and there's plausible evidence of antioxidant, anti-inflammatory and anti-cancer effects.
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Of course, no discussion would be complete without noting the effect of our genes and gut microbiome in determining how we respond to coffee and its metabolites. Which is a roundabout way of saying, "It's complicated."
Nonetheless, it's clear that coffee consumption affects our nutrient status in specific ways.
Clinical trials from the 1980s showed that a cup of coffee reduced iron absorption from a hamburger meal by 39 per cent. Sounds drastic, but remember that a cup of tea resulted in a 64 per cent decrease in iron absorption. Another study, from the 1990s, found that a cup of coffee, tea or certain herbal teas reduced iron absorption from a bread meal by 69-90 per cent. Observational studies also found that older adults who were regular coffee drinkers were more likely to have lower levels of stored iron.
It may sound like doom and gloom, but there's a simple solution. If coffee is drunk an hour or more before a meal, iron absorption is unaffected. So, drinking the coffee and clearing it out of the gut before the food arrives resolves this problem. Conversely, if the coffee is consumed an hour after a meal, the effect on iron absorption is as bad as if it had been drunk with the meal. The solution, then, is to drink coffee at least one hour before a meal rather than with a meal or soon after.
There have also been concerns about caffeine affecting bone health through inhibiting vitamin D absorption and increasing calcium excretion. It is true caffeine increases excretion of calcium – an essential component of bone.
However, a recent review in the British Medical Journal concluded "a caffeine intake of 400mg/day [about four cups of coffee] was not associated with adverse effects on the risk of fracture, falls, bone mineral density or calcium metabolism". Some studies have found that caffeine consumption is associated with a risk of lower bone density, but only among women with inadequate calcium intake.
To look after your bone health, ensure you're consuming the recommended two or more servings of low-fat milk products (milk, yogurt, cheese) or milk alternatives a day. For example, one glass of milk (250ml), one small pottle of yogurt (125-150g), two slices of cheese (40g) or one glass of calcium-added (fortified) soy milk (250 ml). And remember to enjoy those coffees at least one hour before main meals.