Exhibit 5

K&L Gates LLP 3580 Carmel Mountain Road Suite 200 San Diego, CA 92130-6768 T  858.509.7400       www.klgates.com

May 13, 2014

Natural Alternatives International, Inc.

1185 Linda Vista Drive

San Marcos, California 92078

Ladies and Gentlemen:

We have acted as your counsel in connection with the Registration Statement on Form S-8 (the “Registration Statement”) to be filed with the United States Securities and Exchange Commission under the Securities Act of 1933, as amended (the “1933 Act”), for the registration of 200,000 shares (the “Shares”) of Common Stock, par value $0.01, of Natural Alternatives International, Inc., a Delaware corporation (the “Company”), issuable under the Company’s 2009 Omnibus Incentive Plan (the “Plan”).

You have requested our opinion as to the matters set forth below in connection with the Registration Statement. For purposes of rendering that opinion, we have examined the Registration Statement, the Company’s Certificate of Incorporation, as amended, and Bylaws, the Plan and the corporate action of the Company that provides for the issuance of the Shares, and we have made such other investigation as we have deemed appropriate. We have examined and relied upon certificates of public officials and, as to certain matters of fact that are material to our opinion, we have also relied on a certificate of an officer of the Company. In rendering our opinion, we also have made the assumptions that are customary in opinion letters of this kind. We have not verified any of those assumptions.

Our opinion set forth below is limited to the Delaware General Corporation Law, including the applicable provisions of the Delaware Constitution and reported judicial decisions interpreting those laws.

Based upon and subject to the foregoing, it is our opinion that the Shares are duly authorized for issuance by the Company and, when issued and sold in accordance with the terms set forth in the Plan will be validly issued, fully paid, and nonassessable.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement. In giving our consent we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the 1933 Act or the rules and regulations thereunder.

Yours truly,

/s/ K&L Gates LLP

K&L Gates LLP