OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
                                       OF
                              REXALL SUNDOWN, INC.
                                       AT
                              $24.00 NET PER SHARE
                                       BY
                           NUTRICIA INVESTMENT CORP.
                     AN INDIRECT WHOLLY OWNED SUBSIDIARY OF

                            KONINKLIJKE NUMICO N.V.
                                 (ROYAL NUMICO)

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         THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
   NEW YORK CITY TIME, ON FRIDAY, JUNE 2, 2000, UNLESS THE OFFER IS EXTENDED.

- --------------------------------------------------------------------------------

                                                                     May 5, 2000

To Brokers, Dealers, Commercial Banks,
Trust Companies and Other Nominees:

    We have been engaged by Nutricia Investment Corp., a Florida corporation
(the "Purchaser") and an indirect wholly owned subsidiary of Koninklijke Numico
N.V., a company incorporated under the laws of the Netherlands ("Numico"), to
act as Dealer Manager in connection with the Purchaser's offer to purchase all
outstanding shares of common stock, par value $0.01 per share (the "Shares"), of
Rexall Sundown, Inc., a Florida corporation (the "Company"), at $24.00 per
Share, net to the seller in cash, without interest thereon, on the terms and
subject to the conditions set forth in the Offer to Purchase dated May 5, 2000
(as amended or supplemented from time to time, the "Offer to Purchase"), and in
the related Letter of Transmittal (the "Letter of Transmittal," which, together
with the Offer to Purchase, as each may be amended or supplemented from time to
time, 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 the following documents:

    1.  The Offer to Purchase dated May 5, 2000;

    2.  The letter to shareholders of the Company from the President and Chief
       Executive Officer of the Company accompanied by the Company's
       Solicitation/Recommendation Statement on Schedule 14D-9;

    3.  The Letter of Transmittal to be used by shareholders of the Company in
       accepting the Offer;

    4.  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 your nominee, with
       space provided for obtaining such clients' instructions with regard to
       the Offer;

    5.  The Notice of Guaranteed Delivery with respect to Shares;

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

    7.  A return envelope addressed to Wilmington Trust Company, the Depositary.

    THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, (i) THERE BEING VALIDLY
TENDERED AND NOT WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER A NUMBER OF
SHARES EQUIVALENT TO A MAJORITY OF THE TOTAL ISSUED AND OUTSTANDING SHARES ON A
FULLY DILUTED BASIS AS OF THE DATE SUCH SHARES ARE PURCHASED PURSUANT TO THE
OFFER AND (ii) THE EXPIRATION OR TERMINATION OF ANY APPLICABLE WAITING PERIOD
UNDER THE HART-SCOTT-RODINO ANTITRUST IMPROVEMENTS ACT OF 1976, AS AMENDED. THE
OFFER IS ALSO SUBJECT TO CERTAIN OTHER CONDITIONS DESCRIBED IN SECTION 12 OF THE
OFFER TO PURCHASE.

    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 2, 2000, UNLESS THE OFFER IS EXTENDED.

    The Offer is being made pursuant to an Agreement and Plan of Merger (the
"Merger Agreement"), dated as of April 30, 2000, by and among the Company,
Numico and the Purchaser. The Merger Agreement provides that, among other
things, following the consummation of the Offer and the satisfaction or waiver
of the other conditions set forth in the Merger Agreement, the Purchaser will be
merged with and into the Company (the "Merger"). Pursuant to the Merger
Agreement, each issued and outstanding Share (other than Shares owned by the
Company, Numico or the Purchaser or Shares that are held by shareholders
exercising dissenters' rights under Florida law) shall, by virtue of the Merger
and without any action on the part of the holder thereof, be converted into and
represent the right to receive an amount in cash, without interest thereon,
equal to the price paid for each Share pursuant to the Offer.

    The Board of Directors of the Company has unanimously approved the Merger
Agreement, the Offer and the Merger, determined that the Offer and the Merger
are fair to, and in the best interests of, the shareholders of the Company, and
recommends that shareholders tender their Shares pursuant to the Offer.

    In all cases, payment for Shares accepted for payment pursuant to the Offer
will be made only after timely receipt by Wilmington Trust Company (the
"Depositary") of (i) certificates for such Shares or timely confirmation of the
book-entry transfer of such Shares into the Depositary's account at the Book-
Entry Transfer Facility (as defined in the Offer to Purchase) pursuant to the
procedures set forth in Section 3 of the Offer to Purchase, (ii) the Letter of
Transmittal (or a manually signed facsimile thereof), properly completed and
duly executed, with any required signature guarantees (or, in the case of a
book-entry transfer, an Agent's Message (as defined in the Offer to Purchase))
and (iii) any other documents required by such Letter of Transmittal. UNDER NO
CIRCUMSTANCES WILL INTEREST BE PAID ON THE PURCHASE PRICE FOR SHARES, REGARDLESS
OF ANY EXTENSION OF THE OFFER OR ANY DELAY IN MAKING SUCH PAYMENT PURSUANT TO
THE OFFER.

    Neither Numico nor the Purchaser will pay any fees or commissions to any
broker or dealer or other person (other than the Depositary, the Information
Agent and the Dealer Manager, as disclosed in the Offer to Purchase) in
connection with the solicitation of tenders of Shares pursuant to the Offer. You
will be reimbursed upon request for customary mailing and handling expenses
incurred by you in forwarding the enclosed offering materials to your clients.
The Purchaser will pay all stock transfer taxes applicable to its purchase of
Shares pursuant to the Offer, subject to Instruction 6 of the Letter of
Transmittal.

                                       2

    Questions and requests for assistance may be directed to the Information
Agent or the Dealer Manager at their respective addresses and telephone numbers
set forth on the back cover of the enclosed Offer to Purchase. Requests for
additional copies of the enclosed materials may be directed to the Information
Agent or to brokers, dealers, commercial banks or trust companies.

                                        Very truly yours,

                                          SALOMON SMITH BARNEY INC.

    NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL RENDER YOU OR
ANY OTHER PERSON AS AN AGENT OF NUMICO, THE PURCHASER, THE DEALER MANAGER, THE
DEPOSITARY OR THE INFORMATION AGENT, OR ANY AFFILIATE OF ANY OF THEM, OR
AUTHORIZE YOU OR ANY OTHER PERSON TO GIVE ANY INFORMATION OR USE ANY DOCUMENT 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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