just as blood pressure varies throughout the day, so does what you need of any given nutrient at any given time.
i.e. during times of increased stress, including exercise, etc.
this is why, in part, that the body can manufacture, and/or recycle and/or store certain nutrients for use during nutritionally lean times.
In addition, the body can, and does substitute when it needs to being short of one thing or another. It is not ideal in most cases, however it can do this ...
So in essence, it is more about harmony than balance.
That said, pollution in our environment, including genetic pollution has changed things over the last hundred years or so to affect all people - not just those who have had occupational exposures, along with those having poor diets and exposure to famines, since man has walked this planet; which is why we have found cancers, diabetes, plaque build up, etc. in ancient cultures.
Today, as a result of this pollution, some people cannot break down and absorb nutrients from food sources, and/or manufacture one or more nutrients on their own and must take a bio-available supplement as they would a pharmaceutical in order to realize better health.
Food cannot provide it all for people such as these... in addition, many people cannot convert plant nutrients into the forms required for animals and they must consume animal products... they cannot ever be healthy as a vegetarian, let alone vegan and are asking for health issues.
We see this all around us with one person or another and it is likely why Merck came out with and patented metafolin - there are other forms of bio-active supplements that pharmaceuticals have their mitts into.
Some available over the counter... and some not.
The thing that should make people angry is that it has come to this in the first place and that it is getting worse and worse with each generation - we did it to ourselves.