Before setting out to improve the nutrient density of my veg I figured it's probably worth establishing if the vegitables I currently grow truly are deficient. I was surprised to find this article that looks into the research claiming that essentially, reduction in nutritional value of veg over the years is a myth! Of course, it's possible to find studies and articles that say the opposite, but this side of the story doesn't get the same hype:
Here's a quote from the summary:
"As with many widespread beliefs, there is a grain of truth to the notion that the mineral nutrient content of certain crops has declined but the story of what has been seen and the importance of these changes are quite different from the popular narrative. Separating the wheat from the chaff when it comes to causes for apparent historical declines in nutrient content can be challenging.
Comparing government food composition table data from different publication years is not a valid approach and the results obtained from these comparisons are misleading as to the nature and degree of changes in the mineral nutrient content of foods over time.
Contemporaneous analysis of different varieties of the same crop grown side-by-side or of archived samples of grain have confirmed that some modern varieties of vegetables and grains are lower in some nutrients than older varieties due to a dilution effect of increased yield by accumulation of carbohydrate (starch, sugar and/or fibre) without a proportional increase in certain other nutrients. However, well-conducted comparisons have shown that consistent trends of decrease in content of certain nutrients are mostly seen only when crops are lumped into broad groups of vegetables, fruits, and grains. Statistical significance is lost when trying to see historical changes by comparing varieties of a single crop due to a high degree of variability. Some modern cultivars have higher concentrations of selected nutrients than older cultivars while other cultivars may have lower concentrations of selected nutrients. The ranges of values for mineral nutrient content may extend over two orders of magnitude or more.
Fruits, vegetables and grains are important dietary sources of mineral nutrients, so if apparent historical declines in their concentrations were real and substantial across a significant proportion of our foods that could have significant implications for the adequacy of our mineral nutrient dietary intake. However, the scientific evidence has shown that while percentage changes in nutrient content may appear to be very dramatic, such as an apparent decline in vegetables’ content of Cu by as much as 81%, in fact these large percentage changes represent small absolute changes that are all well within the range of natural variation in mineral nutrient content both within a single food and within the groups of foods reviewed in the literature. "
Here's a quote from the summary:
"As with many widespread beliefs, there is a grain of truth to the notion that the mineral nutrient content of certain crops has declined but the story of what has been seen and the importance of these changes are quite different from the popular narrative. Separating the wheat from the chaff when it comes to causes for apparent historical declines in nutrient content can be challenging.
Comparing government food composition table data from different publication years is not a valid approach and the results obtained from these comparisons are misleading as to the nature and degree of changes in the mineral nutrient content of foods over time.
Contemporaneous analysis of different varieties of the same crop grown side-by-side or of archived samples of grain have confirmed that some modern varieties of vegetables and grains are lower in some nutrients than older varieties due to a dilution effect of increased yield by accumulation of carbohydrate (starch, sugar and/or fibre) without a proportional increase in certain other nutrients. However, well-conducted comparisons have shown that consistent trends of decrease in content of certain nutrients are mostly seen only when crops are lumped into broad groups of vegetables, fruits, and grains. Statistical significance is lost when trying to see historical changes by comparing varieties of a single crop due to a high degree of variability. Some modern cultivars have higher concentrations of selected nutrients than older cultivars while other cultivars may have lower concentrations of selected nutrients. The ranges of values for mineral nutrient content may extend over two orders of magnitude or more.
Fruits, vegetables and grains are important dietary sources of mineral nutrients, so if apparent historical declines in their concentrations were real and substantial across a significant proportion of our foods that could have significant implications for the adequacy of our mineral nutrient dietary intake. However, the scientific evidence has shown that while percentage changes in nutrient content may appear to be very dramatic, such as an apparent decline in vegetables’ content of Cu by as much as 81%, in fact these large percentage changes represent small absolute changes that are all well within the range of natural variation in mineral nutrient content both within a single food and within the groups of foods reviewed in the literature. "
