I keep talking about food quality but haven’t yet mentioned what that might actually mean, let’s start that discussion now. There are a number of qualitative factors that can be applied to food, but one that’s familiar to most people is the nutritional value. Fruits and vegetables are good sources of many important vitamins and minerals, aren’t they?
In a 2004 study (1) of common garden vegetables there was found to be a significantly reliable decline from 1950 to 1999 according to USDA data. It’s actually quite easy to look up the information yourself, and I did just that for three vegetables: broccoli, carrots and corn. The chart to the right shows the numbers from 1950 (2) and the latest information from 2001 and 2008 (3). I added an extra column showing the percent difference.
Broccoli is frequently touted as a high calcium food but as you can see here it contains 2/3 less calcium than it did only 50 years earlier. To get the same nutrition as your grandparents you would need to consume up to three times more! Nearly all of the vitamins and minerals for these foods has declined, and there’s nothing unusual about these three either, as the data shows similar declines for every vegetable, fruit and grain.
USDA data only goes to 1950, but the British have information that goes back to 1936, and a similar 50 year study from the United Kingdom (4) demonstrated the exact same thing, consistent dilution of nutritive value of all foods.
There were significant reductions in the levels of Ca, Mg, Cu and Na, in vegetables and Mg, Fe, Cu and K in fruits. The greatest change was the reduction of copper levels in vegetables to less than one-fifth of the old level.
If any cause for this decline is ever given, I believe it to be poorly conceived. In the Davis study the author boldly says “any real declines are generally most easily explained by changes in cultivated varieties.” I am not questioning that plant genetics can make an impact, but that soil quality makes a far greater one. This fact is occasionally mentioned but never discussed in detail.
There are also a number of documents showing how differing soil across the US can significantly change food nutrition. The study Variation in Mineral Composition of Vegetables (5) illustrates this quite clearly. Tomatoes grown in Indiana contained 250% more calcium (15 mg) than those grown in Georgia ( 6 mg). Today the USDA says tomatoes contain 10 mg of calcium.
A huge variation also exists between two otherwise identically looking products. In the same study the best tomato had 23 mg of calcium, while the worst had only 4.5. Spinach is even more amusing as it’s known for being high in iron. I found this website that ranked spinach at #8 in the top 10 sources for iron, and the number given isn’t even accurate, it’s 1/3 higher than the USDA says it is. In the study the best spinach contained 1,584 ppm of iron, while the worst had but 1.
Please don’t think that I’m saying 50 years ago food quality was high, it was better for sure, but was it great? Unfortunately, it was already well known long before 1950 that the nutritional value of our food had been in decline, already beyond the point of giving good human and animal health. The most glaring example comes from the 1936 US Senate Document 264, an article written about the problem:
The alarming fact is that foods — fruits and vegetables and grains — now being raised on million acres of land that no longer contains enough of certain needed minerals, are starving us, no matter how much of them we eat.
And what about your own garden? I was shocked when I realized just how poor much of my garden produce was, but I also had a few successes and that encouraged me. As a gardener you are in the best possible position, for you have an opportunity to take charge of your food, your environment and your health by growing exceptionally nutritious food.
~Sean
1 Changes in USDA Food Composition Data for 43 Garden Crops 1950 to 1999. Journal of the american College of Nutrition, Vol. 23, No. 6, 669-683 (2004) 2.Composition of foods: raw, processed, prepared USDA Agriculture handbooks, 1950, http://naldc.nal.usda.gov/naldcPUB/search.xhtml 3. USDA National Nutrient Database, USDA National Agricultural Library search engine, http://ndb.nal.usda.gov/ndb/search/list 4. Historical changes in the mineral content of fruits and vegetables, Anne-Marie Mayer, British Food Journal 99/6, 1997, 207-211. 5. Variation in Mineral Composition of Vegetables Firmane E. Bear, Stephen J Toth, and Arthur L Pice, Soil Science Society of America Proceedings 1948, Volume 13. pp. 380-4, The Soil Science Society of America, Madison, Wisconsin, 1949
Blaming Nature 
Would dissolving river sand, egg shells and other mineral rich items in vinegar or other acid to create a ph neutral mineral rich plant food soup be beneficial?
Hi Matt, that’s very hard to say and I don’t think i would recommend anything that is too harsh. The first thing I would do is get a good soil test to understand what the situation looks like and remineralize to bring some balance back. Once balance is restored your pH begin to balance itself out too. At the same time provide your soil organisms with nourishment so that they can unlock the riches for your plants. In general though, the best plant foods are those that are diverse in nutrients and beneficial to the soil organisms such as kelp meal. Egg shells do work well for calcium, some other nice options are crab meal and oyster shells. The soil test results will provide you with additional options, some of which are very cost effective.
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Most likely due to the lack of accuracy in equipment used in 1950 more than anything else. I’d be interested in seeing differentials between 2018 and 2001 instead.