Comedy writer Robert Orben wrote in 1978:
 
“My rather elderly neighbor is complaining: ‘I’m at that age when I’ll have nothing to do with natural foods. I need all the preservatives I can get.’”
 
Comedian George Burns (1896-1996) also used the line in the 1980s. A slightly different version (with “natural foods” replaced with “health foods”) is: “Old people shouldn’t eat health foods. They need all the preservatives they can get.”
   
 
Wikipedia: Robert Orben
Robert Orben (born March 4, 1927) is best known as an American professional comedy writer, though he also worked as a speechwriter for Gerald R. Ford and as a magician. He has written multiple books on comedy, mostly collections of gags and “one-liners” originally written for his newsletter, Orben’s Current Comedy, and he has also written books for magicians.
 
13 August 1978, Trenton (NJ) Evening Times, “Quips & Quotes,” Family Weekly magazine, pg. 21, col. 3:
My rather elderly neighbor is complaining: “I’m at that age when I’ll have nothing to do with natural foods. I need all the preservatives I can get.”
—Robert Orben
 
3 September 1978, Sunday World-Herald (Omaha, NE),  “Coffee Break” by Susan M. Stein, Magazine, pg. 10, col. 4:
When a friend got on the same bandwagon, her husband insisted that at his age he needed all the preservatives he can get.
 
20 November 1980, Boston (MA) Herald American, Paul Sullivan column, pg. B12, col. 2:
SO, GEORGE BURNS, what do you think of natural foods?
“I am at an age when I have nothing to do with natural foods. I need all the preservatives I can get.”
 
3 May 1982, Winnipeg (Manitoba) Free Press, “Le Grand Chef Piere” comic strip, pg. 8B col. 2:
(The character is reading a box of “ALL NATURAL CEREAL”—ed.)
GEE, EVERYTHING IS NATURAL THESE DAYS!
NO PRESERVATIVES.
WELL, AS FAR AS I’M CONCERNED…
I’LL TAKE ALL THE PRESERVATIVES I CAN GET! (SIGH!)
   
Google Books
Dear George:
Advice & answers from America’s leading expert on everything from A to B
By George Burns
New York, NY: Putnam
1985
Pg. 17:
What do you think about all those natural food and high-fiber diets I’m always hear ing about? Aging Gracefully
Dear Aging — I personally stay away from natural foods. At my age I need all the preservatives I can get. On the other hand, what could be wrong with a high-fiber diet? When was the last time you saw a fat moth?
 
Google News Archive
4 October 1986, Modesto (CA) Bee, pg. A-2:
Today’s chuckle
At a certain age, you don’t want to eat natural foods anymore. You need all the preservatives you can get.
 
Google Books
The 2,548 Best Things Anybody Ever Said
By Robert Byrne
New York, NY: Fireside (Simon & Schuster)
2002
314
Old people shouldn’t eat health foods. They need all the preservatives they can get. —Robert Orben
 
Google Books
The Greatest Quotations of All-Time
By Anthony St Peter
Xlibris Corporation (Xlibris.com)
2010
Pg. 42:
I stay away from natural foods. At my age need all the preservatives I can get.
George Burns