Cramer noted that GNC's downturn was much more severe than Vitamin Shoppe. In 2016 GNC began reporting worrisome sales and earnings shortfalls. It began aggressively marking down vitamins to deal with excess inventory and franchisees started having trouble.
In April of 2016, guidance from GNC was so weak the stock lost 29 percent of its value in a single day. Cramer was most worried about its balance sheet, with has over a billion dollars in long-term debt, most of which comes due in the next few years, versus just $834 million in cash and current assets.
If anything, GNC seemed to Cramer like one more company that has been gobbled up by Amazon.
The decline in Vitamin Shoppe also illustrated that this may not be specific to GNC, but is an industry-wide problem. While the weakness in Vitamin Shoppe has been less dramatic and it has a cleaner balance sheet, it still has been plagued by the same issues: declining same-store sales, a weakening outlook and many analysts downgrading the stock.
"Vitamin Shoppe is getting beat on pricing, convenience, product, promotions and innovation — just like GNC — as online retailers and just ordinary supermarkets and pharmacies take more and more share from specialist vitamin retailers," Cramer said.
When Cramer looked at GNC and Vitamin Shoppe, he saw an industry in secular decline. While both companies have put forth initiatives to turn things around, he wasn't sure there is anything they can do at this point.
"To me, they are having an existential crisis as in, why would these vitamin retailers even exist? Do they have a reason for being in this world where you can order all of this stuff online?" Cramer asked.
Cramer warned to stay away from the stocks of GNC and Vitamin Shoppe due to lack of purpose, aside from being market-share donors to Amazon.
CNCB has reached out to GNC and Vitamin Shoppe for comment but did not immediately receive a response.
Questions for Cramer?
Call Cramer: 1-800-743-CNBC
Want to take a deep dive into Cramer's world? Hit him up!
Mad Money Twitter - Jim Cramer Twitter - Facebook - Instagram - Vine
Questions, comments, suggestions for the "Mad Money" website? email@example.com