Massive variation in vegetable minerals

Variation is a fact of life, think about how many shades of green there are in nature. Trace element variation in food is made worse as they only contain the trace elements that are found in the soil. So if the soil is depleted of these elements then the food produced on that soil is also depleted. As trace elements are not deemed "essential" to cropping they are often depleted in our soils, either by the soil already having a low level, or after decades of cropping the minerals have been removed from the soil. The following graphs show the maximum and minimum levels found in common veges for boron, manganese and iron. As you can see the variation is massive, from the vegetables virtually having no trace elements to a much higher level. The bottom of the line is the lowest mineral content, with the highest being the top of the line.

 

You can see how much iron spinach does have (and tomatoes for that matter!) however the spinach you eat to get some iron may have almost no iron in it! For the technical people the change is over two orders of magnitude (which to the rest of us means its big). Again for your technical people you will be asking how many standard deviations this is, regrettably my source does not give means or standard deviations.

Once again we cannot trust our fresh fruit and vegetables to have the minerals in them that we need. You have two options to get these minerals. (1) Start growing your own fruits and vegetables and make sure you use a high quality trace element mix (one that has iodine and selenium which is not included in the cheaper brands of trace element mixes) or (2) supplement 

Reference: Thorsons complete guide to Vitamins and Minerals. All you need to know about vitamins and mineral for your health by Leonard Mervyn.pg 220