Are fruits and vegetables getting less nutritious?

Dirt is dead.

And because dirt is dead you are going to be sick and get acne.

Confused? Allow me to explain.

One of the most persistent scare stories of the natural health movement is the story of soil depletion. The evil and greedy agricultural practices have killed the soil. The use of industrial agriculture and synthetic fertilizers has left the soil barren of minerals and nutrients. Dead soil grows dead plants, so the food grown in the soil lacks the essential nutrients we require.

Apparently we even have scientific studies to ‘prove’ this. And those studies paint a scary picture. The average mineral content of fruits and vegetables has declined by 15 to 50% in the last 50 years. Some nutrients have suffered even greater losses. Vitamin A has completely disappeared from potatoes and copper levels have dropped by 80%.

At this point you should be sufficiently scared so that they can pitch you the supplement that will save the day. The supplement contains everything you need and is grown with love, care and daily prayers in lush and fertile soil. By the way, why is it that these supplements, cleanses and other non-sense has to be sold using fear?

Let’s see if there’s any truth to this.

What’s the evidence?

A couple of studies attempted to compare nutritional value of vegetables grown in the 50s and 60s with vegetables grown today. The studies did find differences and for the most part the produce grown in the 50s and 60s was more nutritious that the produce grown today. The average declines ranged from 5 to 40% on many minerals. Some nutrients showed more dramatic drops. For example copper levels plummeted staggering 80%.

These studies have been widely, but very selectively, highlighted in books and websites promoting nutritional supplements. Many authors have taken the liberty of translating this to mean that fruits and vegetables have lost 80% of their nutritional value.

However these numbers tell only a part of the story. For example, nobody bothers to mention that the levels of some nutrients have actually increased during the last 50 years. That wouldn’t scare you into buying supplements – would it?

But the fact remains that the studies show decline in most nutrients. Why our fruits and vegetables are less nutritious today than they were 50 years ago?

First I have to mention that making such comparison studies is very difficult. There are too many unknown and random factors. The study authors offer the following reasons to explain the differences in nutrient levels. Funny that the studies never mention soil depletion, but that’s the only thing the articles referring to these studies mention.

Changes in geography

50 years ago a higher proportion of the fruits and vegetables were grown in home gardens. Today most are grown industrially and often come from overseas. Naturally tomatoes grown in different parts of the world have different nutritional values.

Changes in sampling and measuring techniques

This accounts for most of the big changes in nutrient levels. For example, the dramatic drop in chromium levels has a simple explanation.

Anderson and colleagues found only about 15 years ago [12,13] that earlier measurements of chromium in foods were often several-fold too high, because of contamination from stainless steel laboratory equipment (personal communication, R.A. Anderson).

Changes in USDA Food Composition Data for 43 Garden Crops, 1950 to 1999

Many articles refer to a similar drop in iron levels. The soil contains 10’000 times more iron than plants. So tiny amounts of unremoved soil can raise the values for iron.

Random variation between samples

Take two tomatoes that are grown at slightly different locations or different time of year and you’ll find differences in nutrient levels. These differences are more than most people realize and can be up to 40% for many nutrients.

Genetic variations and trade-offs

Genetic variation is perhaps the most important reason behind the decline in nutrient levels. For decades farmers have selected cultivars (A variety of a plant developed from a natural species and maintained under cultivation) for higher yield.

In many cases there are trade-offs between yield and nutrient content. Higher yielding cultivars often contain fewer nutrients. It makes sense that if one cultivar yields 2 kg of tomatoes and another one yields 1 kg from the same soil at the same time that the cultivar that yields 2 kg would have fewer nutrients.

Farmers are compensated by weight and volume of their produce – not nutritional content. This compensation system naturally leads to produce with lower nutritional value.

On the positive side, this trend can be reversed, and it’s already happening. As people become more aware of the nutritional quality and taste of the produce (nutritionally dense produce often tastes better), farmers shift to breeding fruits and vegetables with higher nutritional content.

What about soil depletion?

It’s possible that soil depletion plays a role in the decline in nutritional value. However the authors of these studies don’t see it as an important factor. Also keep in mind that demineralization of the soil can be corrected fairly easily by applying rock dust on the soil.

Take away

Fruits and vegetables are still healthy. They are still densely packed with minerals, vitamins and other micro-nutrients. The fact remains that almost all studies show measurable health improvements when fruit and vegetable consumption goes up.

If you don’t get all the nutrients you require it’s mainly because you are not eating enough fresh, whole foods – not because food today contains fewer nutrients.

If anything these studies highlight the importance of knowing where your food comes from. Local farmers often take better care of their soil and crops than large industrial farms do. As a result they produce food that not only tastes better but is also more nutritious and healthier.

If at all possible, shop at local farmers’ market. Something magical happens when you shake the hand of the person that grows your food. You re-establish the connection to the soil (at least metaphorically) and when the farmer looks you into eyes he/she has more of an incentive to produce high quality food for you.

Sources:

Changes in USDA Food Composition Data for 43 Garden Crops, 1950 to 1999

Declining Fruit and Vegetable Nutrient Composition: What Is the Evidence? (PDF)

Tagged as: nutrition, soil depletion

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