Pitfalls and Problems with Food Nutrient Rankings
There are many issues and problems with trying to rank foods based on their nutrient content. Here are a few to consider:
- There tends to be tremendous variation in vitamin content, even in the same foods. One orange may have 200% DV for vitamin C while another one may have 30%. Thus the rankings should be seen as describing the average for any particular food.
- Not all vitamins are created equal. Synthetic or added vitamins are just that: Synthetic! And they come packaged in foods your body has not evolved to absorb. As a result your bodies response will be different. Should foods with added vitamins be included in the rankings? Wherever possible, only natural sources are listed. Are added vitamins better or worse? That is an issue of contention because it depends on too many variables to know for sure. Current research suggests that natural is best when possible.
- Levels of consumption of foods differ from people to people. Not everyone eats the foods in the rankings in the quantities they are shown. Should the rankings be based on weight? On calories? Or on how much is typically consumed? All this can cause wide variation in how you rank foods. When it comes down to it, you still have to check nutrient labels on everything you eat and match it to serving size.
- The amount of any vitamin your body absorbs depends on your body and what you eat with the food. For example, drinking milk will reduce the amount of copper you absorb. Also, certain enzymes in your body will control the amount of any nutrient you absorb. This is different for everyone. The food which provides me with the most copper might work well for me, but might not work as well for you. More than this, the amount of any nutrient a food is willing to give up in your body can be quite different from the amount it contains, a characteristic known as bio-availability.
- Different foods contain different natural vitamins and hold them in different ways and thus may be finicky about how willing they are to give those vitamins to your body. When scientists measure nutrients they take an orange and then see how much vitamin C is in it. Just because the orange has that amount of vitamin C, doesn't mean your body is going to get it. It might get more from eating an apple. How could we know this? How could we measure it? And if we are already taking averages (problem 1) how likely is it that measuring the food then measuring the absorbency is going to be true for everyone?
So where to go from here? The best is to eat natural foods that are mostly plants, since research has shown that most nutrients are more easily absorbed from plants. When creating the top ten nutrient rankings this has been taken into consideration. Herbs have also always ranked high because they are likely to contain vitamins that have yet to be discovered. Take even a short look at the history of nutrition timeline and you see that most vitamin discoveries are quite recent (1920s-1940s). How could it be possible that we know all of the vitamins yet? We simply don't, but till we do, the nutrient lists here provide a good rule of thumb.