Here's why:

* Digestion: When you eat food containing nucleic acids, your digestive system breaks them down into their building blocks: nucleotides. These individual nucleotides are then absorbed and used for various functions in the body, but they don't reassemble into the original DNA or RNA molecules.

* Cellular Processes: Your body already has the machinery to build its own DNA and RNA using the nucleotides it receives from your diet.

However, you can still obtain the building blocks for nucleic acids (nucleotides) through your diet:

1. Foods rich in protein: Protein contains all the essential amino acids, including those that are used to synthesize purines and pyrimidines, the building blocks of nucleotides. Examples include:

* Lean meats

* Eggs

* Dairy products

* Legumes

* Nuts and seeds

2. Foods containing certain vitamins and minerals: Specific vitamins and minerals are crucial for the biosynthesis of nucleic acids. Examples include:

* Vitamin B12: Essential for the synthesis of thymine, one of the bases in DNA.

* Folic acid: Required for the synthesis of purines and pyrimidines.

* Iron: Necessary for the proper function of enzymes involved in DNA synthesis.

While directly "getting nucleic acids" into your body might not be the best way to think about it, consuming these nutrient-rich foods provides the necessary building blocks for your cells to create their own DNA and RNA.