Exhibit 99.(a)(1)(D)

Offer to Purchase for Cash

All Outstanding Shares of Common Stock

of

USANA HEALTH SCIENCES, INC.

at

$26.00 PER SHARE

by

UNITY ACQUISITION CORP.

a wholly-owned subsidiary of

GULL-UNITY HOLDING CORP.

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON FRIDAY, JUNE 27, 2008, UNLESS THE OFFER IS EXTENDED.

June 2, 2008

To Brokers, Dealers, Banks, Trust Companies and other Nominees:

Unity Acquisition Corp., a Utah corporation (“Purchaser”), is offering to purchase all of the outstanding shares of common stock, $0.001 par value per share (the “Shares”), of USANA Health Sciences, Inc. (“USANA”) not currently owned by certain shareholders of USANA, at a price of $26.00 per share, net to the seller in cash, without interest thereon, upon the terms and subject to the conditions set forth in the Offer to Purchase dated June 2, 2008, and in the related Letter of Transmittal (which, together with any amendments or supplements thereto, collectively constitute the “Offer”).

Please furnish copies of the enclosed materials to those of your clients for whom you hold Shares registered in your name or in the name of your nominee.

Enclosed herewith are copies of the following documents:

1. Offer to Purchase dated June 2, 2008;

2. Letter of Transmittal to be used by shareholders of USANA in accepting the Offer (manually signed facsimile copies of the Letter of Transmittal may be used to tender the Shares);

3. A printed form of letter that may be sent to your clients for whose account you hold Shares in your name or in the name of a nominee, with space provided for obtaining such clients’ instructions with regard to the Offer;

4. Notice of Guaranteed Delivery with respect to Shares;

5. Guidelines for Certification of Taxpayer Identification Number on Substitute Form W-9; and

6. Return envelope addressed to American Stock Transfer & Trust Co., the Depositary for the Offer.

WE URGE YOU TO CONTACT YOUR CLIENTS PROMPTLY. PLEASE NOTE THAT THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON FRIDAY, JUNE 27, 2008, UNLESS THE OFFER IS EXTENDED.

In all cases, payment for Shares accepted for payment pursuant to the Offer will be made only after timely receipt by the Depositary of (a) Share certificates (or a timely Book-Entry Confirmation, as defined in the Offer to Purchase), (b) a properly completed and duly executed Letter of Transmittal (or facsimile thereof), with any required signature guarantees (or, in the case of a book-entry transfer effected pursuant to the procedures set forth

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in the Offer to Purchase, an Agent’s Message (as defined in the Offer to Purchase) in lieu of a Letter of Transmittal) and (c) any other documents required by the Letter of Transmittal. Accordingly, tendering shareholders may be paid at different times depending upon when Share certificates or Book-Entry Confirmations with respect to Shares are actually received by the Depositary. Under no circumstances will interest be paid on the purchase price to be paid by Purchaser for the Shares, regardless of any extension of the Offer or any delay in making such payment.

Purchaser will not pay any fees or commissions to any broker or dealer or other person (other than as described in the Offer to Purchase) in connection with the solicitation of tenders of Shares pursuant to the Offer. You will be reimbursed by Purchaser upon request for customary mailing and handling expenses incurred by you in forwarding the enclosed materials to your customers.

Questions and requests for assistance or additional copies of the enclosed materials may be directed to the Information Agent at the address and telephone number set forth on the back cover of the Offer to Purchase.

Very truly yours,

UNITY ACQUISITION CORP.

NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL RENDER YOU OR ANY OTHER PERSON THE AGENT OF PURCHASER, THE DEPOSITARY OR THE INFORMATION AGENT OR AUTHORIZE YOU OR ANY OTHER PERSON TO GIVE ANY INFORMATION OR MAKE ANY REPRESENTATION ON BEHALF OF ANY OF THEM WITH RESPECT TO THE OFFER NOT CONTAINED IN THE OFFER TO PURCHASE OR THE LETTER OF TRANSMITTAL.

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