God does not have a "Thus saith the Lord" for each and every little situation that may come up with in a firstfruit's Christian life. When we do not have a specific law or scripture to cover the specific instance, we then look to specific or overriding biblical principles. Side-by-side with this is something we read about in Romans 14.
...for whatsoever is not of faith
is sin. -Rom 14:23
Paul is writing to Romans about members weak in the faith and one or
more who could not bring themselves to eat meat which had been offered
to idols. Paul writes:
Hast thou faith? have it to thyself before God. Happy is he that
condemneth not himself in that thing which he alloweth. And he that
doubteth is damned if he eat, because he eateth not of faith: for
whatsoever is not of faith is sin. -Rom 14:22-23
Notice the commentary
22-23. Hast thou faith? have it to thyself before God. Faith here means a firm conviction before God that what you believe is right. Paul remarks that it is proper to have and cherish a conviction, but we must not force our convictions upon others. We do not have the prerogative to do so. We must hold that conviction before God. And he that doubteth is damned if he eat. For the translators of the AV the word damned did not have the force it does today. It did not mean that if someone violates his conscience by eating that which he feels is wrong he will be damned to (the lake of fire). Rather the meaning is that he is condemned in his conscience for doing that which it will not allow. If he does not eat in faith believing that it is acceptable to God, he eats in sin for whatsoever is not of faith is sin. If our actions do not arise from our convictions then they are sinful actions and unacceptable to God. -KJV Bible Commentary ( red emphasis mine)
Understand that you probably have a number of
PEBs regarding health. These beliefs could be about food,
diet, water treatment or sources, equipment [water
and air filters], vitamins, supplements, minerals, herbs,
folk cures, diets, fasting, exercise, exercise equipment, medical
plans, medical insurance, doctors, nurses, health care providers,
clinics, hospitals, hospices, nursing homes, in-home care, medic
alerts, ambulance services, surgeons, operations, treatments,
procedures and hundreds of related subjects.
We are directed by this doctrine and therefore, the Word of God not
to attempt to force these PEBs on others or to believe that our PEBs
are more spiritual or more correct than any others (Romans
14:22-23).
Further reading:
Faith Cannot Be Legislated
Good Systematic Theology
Personal Elements of Belief - Questions and Answers