In Romans chapter 14 Paul is talking about food; and in particular those who weigh and measure...so to speak...what others eat. The Jews were/are very careful about what they did/do not eat to the point of being compulsive and overlooking weightier matters. They and we still do that.
There are good reasons for the dietary guidelines that God gave the children of Israel that most practice for religious reasons but actually were instituted for reasons of health and well being. Biblical dietary guidelines are best viewed as part of our spiritual health. Paul tells us that our bodies are the temple of God. [1st Corinthians 6:10, 20]. He dwells in us when we invite Him into our life.
If one reads through the dietary guidelines in the OT and takes a careful look at the creatures God says, "Don't eat these," one will see that many are scavengers that feed on things dead and decaying. This includes shrimp, crab, etc., but also filter feeders that filter many things out of the water that ought not to be there. (And the list is growing along with pollution of all waters; fresh and salt.) So, if we eat the bottom dwelling scavengers and filter feeders, we are, in essence, eating what they ate. Simple enough, and not at all just Jewish, because if they fed on contaminates from leaking septic systems...so do we.
Now that foundation is laid we go back to Romans.
"Yet if your brother is grieved because of your food, you are no longer walking in love. Do not destroy with your food the one for whom Christ died. Therefore do not let your good be spoken of as evil; for the kingdom of God is not eating and drinking, but righteousness and peace and joy in the Holy Spirit. For he/she who serves Christ in these things is acceptable to God and approved by men." [Romans 14:15-18]
Christ was criticised because He ate with sinners and did not follow all the ceremonial washings. HaMashiach (The Messiah) was rejected because He did not fulfill the expectations of the Jews. Our witness is not be be one of personal expectations of others; it is to be of Jesus Christ sacrificed for our sins and sharing the good news of salvation. [See Matthew 23:23].
Healthy food is essential for a healthy life...short as it is. Balanced spiritual nutrition is essential for eternal life. Both sources are essential to the health of our mind, body, spirit. Put first things first.