Beef

Beef from cattle reared outdoors on grass is less fatty and contains more omega-3 fatty acids than cattle reared indoors and fed mainly grain. However, consumers preferred the taste of latter, according to a 2014 study.

Pasta

Today’s pasta might be less nutritious thanks to modern, fast-growing wheat varieties introduced in the 1960s. Levels of zinc, iron and magnesium remained constant in wheat grain from 1865 to the mid-1960s, then decreased significantly as yields shot up.

Carrots

Carrots from the 1940s contained less than half the vitamin A levels of carrots grown in the US 50 years later. The reason? A preference for more orangey carrots. The colour comes mainly from the pigment beta-carotene, which the body can use to make vitamin A.

Milk

Milk from cows reared the old-fashioned way – mainly feeding on grass outdoors – has a better nutritional profile of proteins, fatty acids and antioxidants than milk from cows reared indoors and fed intensively.

Spinach

Spinach is a good source of iron, but its iron content was once thought to be 10 times higher. That was the result of a historical error that may have been perpetuated by the spinach-derived superpowers of the cartoon character Popeye. There is no clear data about whether the iron content of spinach is changing due to modern agriculture.

However, fluorescent lighting in supermarkets can be beneficial to spinach . A 2010 study found that spinach leaves stored in simulated retail conditions had higher levels of vitamins C, E, K and folic acid. After nine days of continuous light exposure, folic acid increased between 84 and 100 per cent. In spinach stored in darkness, nutrient levels stayed the same or fell.

Eggs

Eggs have been the subject of health scares over cholesterol, but now they are promoted as a health food. A 2012 study found that UK eggs are getting more nutritious, with lower fat and cholesterol compared to eggs from 1989 – probably because of smaller yolk sizes. They also contained more selenium and vitamin D than in the past, thanks to improved hen feed.

Tomatoes

Supermarket tomatoes are often labelled as “vine-ripened”, but that doesn’t always mean what you hope. It may be ripened on the vine but the vine may not have been attached to the plant. However,  the downsides of early picking are small and an unavoidable consequence of consumer demand. If you pick a tomato grown at home it tastes fabulous because it’s absolutely ready to eat. “But there’s no way you could do that at a commercial level because of the bruising that would occur if ripe fruits were transported through a typical supply chain. There has to be a compromise somewhere.

Frozen fruit and veg

They may not be fashionable, but frozen fruit and vegetables are often nutritionally better than fresh, experts say. Frozen veg is extremely good in terms of nutritional value because it really has been in suspended animation from the point of harvest. You can leave it on the plant longer, so it’s at a better ripening stage when it’s picked.

Peas

Can lose half of their vitamin C in the first 48 hours after harvesting, but if frozen within 2 hours of picking they retain it. Frozen peas are much more nutritious than peas you buy ready to shell. Furthermore,  frozen foods often have fewer additive, freezing being a preservative.

Bread

Humans have been making bread for 10,000 years, but the way we do it has changed dramatically in the last half-century. In 1961, a new method of mass-producing bread was devised at the Chorleywood laboratories, just north of London. It used extra yeasts, additives called processing aids and machinery to slash fermentation times, so a loaf could be made in just a few hours. Around 80 per cent of bread consumed in the UK is now made this way, and the Chorleywood process is used to some extent in many other countries.

But there are concerns that such methods have altered the digestibility of bread, and this may explain why many people with irritable bowel syndrome name bread as a trigger. For a significant subset of those with IBS, the condition is thought to be linked to gut bacteria reacting to fermentable foods, causing bloating.

Last year, Jeremy Sanderson at King’s College London and colleagues compared the effects of fast and slow-fermented breads on gut microbiota from donors with IBS and those free from it. They found that sourdough bread – which is left to rise for several hours using its natural yeasts – produced “significantly lower cumulative gas” in the IBS donors’ microbiota than fast-fermented bread. The theory is that if bread is left to ferment for longer, its carbohydrates will reach the gut in a predigested state and gut bacteria won’t react so much. “If you under-ferment bread and add a lot of yeast, it’s hardly surprising this will set up problems for people who have a problem with fermentation in their gut,” says Sanderson.

Slow-fermented breads may benefit other groups too: sourdough produces a lower glucose response in the body than other breads. What’s not yet clear is whether eating slow-fermented breads would lead to a general improvement in the gut flora of healthy people. “That’s difficult, but it’s a reasonable hypothesis,” says Sanderson. “After all, bread-making probably evolved to match what the gut could cope with.”  (Excerpted from an article the New Scientist by Chloe Lambert)