Bromeline “Diet Pills”

Stephen Barrett, M.D.
October 18, 1999

I have seen ads for diet pills whose special ingredient is said to be bromelain from pineapples? Do they work?


Bromelain (also spelled bromelin) is a mixture of protein-digesting and milk-clotting enzymes found in the juice and stem of the pineapple plant Ananas comosus (Linné) Merr (Fam Bromeliancaea). A leading textbook of pharmacognosy (plant medicine) states that bromelain is used to make protein hydrolysates, to tenderize meat, and in the leather industry [1]. I know of no scientific evidence that bromelain digests fats or is effective as part of a weight-reduction regimen.

In 1995, the Pennsylvania Attorney General obtained an injunction against Ananas, Inc., a Canadian company that was marketing bromeline products in Pennsylvania [2]. The company’s claims included:

  • Users would lose up to 20 pounds in two weeks and never be hungry.
  • No dietary changes or exercise would be necessary
  • Ananas Bromeline was an astonishing discovery of German researchers who found an enzyme that digests 900 times its own weight in fat.
  • Six to eight Bromeline capsules per day will force your organism to dissolve all of its excess fats.
  • In a controlled medical tests three people lost their excess weight while eating more than usual.
  • After breing absorbed into your bloodstream, Bromeline attacks surplus fat in your hips, thighs, stomach, buttocks, and calves, to uniformly reduce their size.
  • Bromeline will drain fatty accumulations out of your body.

The Attorney General charged that all of the above statements was fraudulent, false, or misleading. The Complaint noted that the company had received approximately 11,000 orders totaling $385,000. I served as a consultant in the case. My report pointed out:

  • No nonprescription product can produce weight reduction without reducing caloric intake. Nor can most people lose weight without increasing the amount of exercise they do.
  • Weight loss is a matter of arithmetic. There are about 3500 calories stored in a pound of fat. The solicitation claims that 98% of people using the product lost an average of 1.8 pounds a day. That would require an average deficit of 6,300 calories per day. This claim is absurd. Most people who lead a moderately active life need about 15 calories per pound to maintain their weight. Such a person with a steady weight of 200 pounds would consume about 3,000 calories per day. Even fasting (which would be very dangerous after a few days) would not result in loss of a pound of fat per day. (Starvation will trigger loss of body fluid, but that is unsafe and does not contribute to meaningful weight reduction.)
  • Literature for the product claims that a controlled experiment demonstrated weight loss among people in Brussels who took Bromeline capsules. But no reference for this alleged study is cited.
  • Bromelain is not absorbed into the bloodstream and transported throughout the body. Bromelain is a protein. When eaten by humans, it is broken down into its component amino acids and is not absorbed intact into the body. Even if it were absorbed and could “attack surplus fat,” the breakdown products would be reassembled into fat and not “efficiently eliminated by your body’s natural functions.”
1. Tyler VE, Brady LR, Robbers JE. Pharmacognosy, 9th edition. Philadelphia, Lea & Febiger, 1988.
2. Commonwealth of Pennsylvania vs. Ananas, Inc, and Margaret Agnes Lebovits. Civil action No. 95-165, Court of Common Please of Centre County. Judicial order, Jan 24, 1995.

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This Article was posted on October 18, 1999.