It'll make your text sounding more professional if you apply the following adjustments to it:
tend to choose [...]in favor of leading a healthy lifestyle.
However [...], it now became quite challenging for people to succeed in this undertaking because there is still much uncertainty about the nutritional value of every particular kind of food.
the technique to [...]increase such value in foods.
They called GMO [...] In this respect, we can refer to the technology of growing genetically modified vegetables.
Some people consider [...] this technique [...] not altogether safe.
to deal with [...] consume...
Sometimes [...] people are able to figure what is good or not good for them by simply looking at a particular vegetable.
But [...] This approach, however, will not prove very useful when it comes to identifying harmful substances in vegetables. There are someone [...] this sentence doesn't make much sense.
Organically [...] grown fruits and vegetables are not supposed to have any pesticides in them.
I hope it helped. Regards.