October 19, 2015
We know more than ever about what food
does to the body and the importance of
and a low
Were the people who foraged for these wild foods healthier than we are today?
They did not live nearly as long as we
do, but growing evidence suggests that they were much less likely to
die from degenerative diseases, even the minority who lived 70 years
and more. The primary cause of death for most adults, according to
anthropologists, was injury and infections.
Some of the most eye-catching work in this area has come from Donald Davis, a now-retired biochemist at the University of Texas.
In 2011, he compared the nutrients in US crops from 1950 and 2009, and found notable declines in five nutrients in various fruits, including tomatoes, eggplants and squash. For example, there was a 43 per cent drop in iron and a 12 per cent decline in calcium.
This was in line with his 1999 study - mainly of vegetables - which found a 15 per cent drop in vitamin C and a 38 per cent fall in vitamin B2.
Fruit and vegetables grown have shown similar depletions.
A 1997 comparison of
data from the 1930s and 1980s found
that calcium in fresh vegetables appeared to drop by 19 per cent,
and iron by 22 per cent. A
reanalysis of the data in 2005 concluded that 1980s
vegetables had less copper,
magnesium and sodium, and fruit less copper, iron and potassium.
For example, tomatoes grown by organic methods contain more phenolic compounds than those grown using commercial standards.
study - published in the Journal of Agricultural and Food Chemistry
- analyzed the phenolic profiles of Daniela tomatoes grown either
using 'conventional' or organic methods, finding that those grown
under organic conditions contained significantly higher levels of
phenolic compounds than those grown conventionally.
Davis and others blame agricultural practices that emphasize quantity over quality.
High-yielding crops produce more food, more rapidly, but they can't make or absorb nutrients at the same pace, so the nutrition is diluted.
But the idea that modern agriculture produces crops that are less nourishing remains controversial, and "then and now" nutritional comparisons have been much criticized.
The differences found may be down to
older, less accurate methods of assessing nutrition, and nutrient
levels can vary widely according to the variety of plant, the year
of harvest and the time of harvest.
They found no clear relationship between mineral levels and the year that a particular cultivar was released, but there was evidence of a dilution effect:
But, as the study also noted, Waltham 29 is less tough than modern cultivars and so would be unlikely to succeed if grown in the same way.
And there lies the rub.
Even if the arrival of intensive agriculture has meant that our vegetables contain slightly less nutrients than those our grandparents ate, it has also led to a huge increase in food supply, which has undoubtedly had a positive effect on our diet and health.
Other crops are also getting subtly less nutritious.
The introduction of semi-dwarf,
higher-yielding varieties of wheat in the green revolution of the
1960s means that modern crops contain lower levels of iron and zinc
than old-fashioned varieties.
Throughout the ages, our farming ancestors have chosen the least bitter plants to grow in their gardens. It is now known that many of the most beneficial phytonutrients have a bitter, sour or astringent taste. Second, early farmers favored plants that were relatively low in fiber and high in sugar, starch and oil.
These energy-dense plants were pleasurable to eat and provided the calories needed to fuel a strenuous lifestyle. The more palatable our fruits and vegetables became, however, the less advantageous they were for our health.
And as farmers strain to feed ever more mouths in the face of environmental change, the problem may become worse.
Last year, researchers at Harvard University warned that crops grown in the future will have significantly less zinc and iron, due to rising levels of carbon dioxide from fossil fuel use.
The team grew 41 different types of grains and legumes, including wheat, rice, maize, soybeans and field peas, under CO2 levels crops are likely to experience 40 to 60 years from now. They found that under these conditions, wheat had 9 per cent less zinc, 5 per cent less iron and 6 per cent less protein than a crop grown at today's CO2 levels.
Zinc and iron - but not protein - were also lower in legumes grown under elevated CO2.
A 2003 study evaluated the nutritional content of broccoli kept in conditions that simulated commercial transport and distribution:
By the end, the broccoli had lost between 71 and 80 per cent of its glucosinolates - sulphur-containing compounds shown to have cancer-fighting properties - and around 60 per cent of its flavonoid antioxidants.
Many kinds of mass-produced fruit and veg - most famously tomatoes - are picked unripe so that they bruise less easily during transit. They are then sprayed with ethylene to ripen them.
Some studies suggest that tomatoes harvested early have lower antioxidant activity and less flavor.
Supermarket tomatoes are often labeled as "vine-ripened", but that doesn't always mean what you hope, she says.
However, Wagstaff stresses that the downsides of early picking are small and an unavoidable consequence of consumer demand.
Another complication is that each method of shipping and storing foods has different effects on the compounds they contain.
Vitamin C, for example, breaks down in the dark, whereas glucosinolates - found in vegetables like broccoli and cabbage - deplete in the light.
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.
What's more, frozen foods often have fewer additives.
Similarly, processing has become a maligned word in the context of food, but there are some cases where it enhances a food's health benefits. In fact, you arguably get more benefits from processed tomatoes, such as in purees, sauces or ready chopped in cans, than fresh.
Although salad leaves that have been picked and stored for several days before being eaten are a bit less nutritious than a freshly harvested lettuce, chilling and using packaging to reduce oxygen exposure may slow the nutrient loss.
And any loss of nutrients must be weighed against the fact that these products may encourage people to eat better overall.
The bottom line is that although aspects of today's food production, processing and storage might make what we eat a bit less nutritious, they are also making foods more available - and this is far more important.
The majority of us consume far less fruit and vegetables than we ought to.
We eat too much fat, sugar and salt and not enough oily fish.
What's really on your plate
How have modern farming methods affected the nutrients in common foods?
If modern, high-intensity farming is causing food to lose some of its goodness, could organic food offer an alternative?
For many consumers the answer is yes...