First popularized in Hollywood in the 1930s and again in the 1980s, the grapefruit diet is back, reincarnated in pill form. Grapefruit diet pills contain a grapefruit extract (often the insoluble fiber pectin) along with other herbs, fibers, or vitamins. The ingredients vary from product to product. (There is a supplement called grapefruit seed extract. It's not intended for fat loss, though, but is supposed to be a good anti-fungal remedy.)
Grapefruit diet pills have been promoted to burn off fat or cellulite, either by following a very-low-calorie diet (roughly 800 calories) or by eating as much as you want depending upon the dietary recommendations that accompany the pills. There is no valid scientific evidence supporting these claims. Eating lots of grapefruit daily or popping several grapefruit pills a day will not help you lose weight. The small amount of pectin you ingest from these pills is better obtained by eating real grapefruits, oranges, and other citrus fruits.
By itself, the grapefruit pectin in these pills is not harmful. However, some of these products are formulated with undesirable ingredients such as phenylpropanoline. You must check labels.
The supplement vanadyl sulfate is a commercial derivative of vanadium, a trace mineral found in vegetables and fish. The body needs very little vanadium, and more than 90 percent of what is taken in is excreted in the urine. To the knowledge of the medical community, no one has ever been diagnosed with a vanadium deficiency disease.
As a supplement, vanadyl sulfate is supposed to have a tissue-building effect by moving glucose and amino acids into the muscles faster and elevating insulin to promote growth. But the evidence for this has been found only in rats. Still, vanadyl sulfate is being aggressively marketed as a tissue-building supplement for strength trainers and athletes. It is also an ingredient in many natural weight-loss supplements, usually in tiny amounts.
But does it work the magic its promoters say it does? A group of researchers in New Zealand asked the same question. In a 12-week study, forty strength-trainers (thirty men and ten women) took either a placebo or a daily dose of vanadyl sulfate in amounts matched to their weight. So that strength could be assessed, the strength-trainers performed bench presses and leg extensions in one- and ten-repetition sets during the course of the experiment.
The study found that vanadyl sulfate did not increase lean body mass. There were some modest improvements in strength-training performance, but these improvements were short-lived, tapering off after the first month of the study. About 20 percent of the strength-trainers felt extremely tired during and after training.
Experts at the USDA Human Nutrition Research Center in Grand Forks, North Dakota, where the most authoritative work on vanadium has been conducted, say there's no reason for anyone to supplement with this mineral, even if you have trouble metabolizing glucose. At high doses, vanadium is extremely toxic and may cause excessive fatigue. But it's probably not harmful in the small amounts you find in some natural diet products.