With New Years’ weight loss resolutions freshly made, let’s take a science-based look at another of the latest diet books being promoted by various public relations agencies. In my last post we explored the claims made by the hysterical Eat To Save Your Life authors in their book featuring a demonic cheeseburger on its cover jacket. Today I will review, Shred: The Revolutionary Diet ‚ 6 Weeks, 4 Inches, 2 Sizes, by Ian K. Smith, M.D.

I’m not sure what images the word “shred” conjures up for you, but if they have anything to do with muscle-bound, uber-lean bodybuilders on steroids you will be pleased to note that this book has nothing to do with them. In fact, what you’ll find in this book is a rather practical and healthy eating and exercise prescription with recipes and careful calorie counting. You’ll also find one fairly harmless chapter of liver detox pseudoscience, and an odd command to stare at yourself in the mirror at the beginning of week six.

Quietly stand in front of the mirror, and look deeply into your eyes as if you’re trying to see all the way into the depths of your soul… [p. 167]

The purpose of this visual exercise is never explained.

Since our purpose here at Science Based Medicine is (in large part) to evaluate medical claims, I will spend the remaining paragraphs focusing on the “cleanse” phase of the diet since that is the major area of scientific controversy. Shred’s week five is devoted to “eating particular foods and drinking certain beverages that naturally activate enzymes in the liver to enhance the detoxification process.” As detox regimens go, I was pleased to find nothing of harm here (I had braced myself for an exploration of coffee enemas, high dose vitamins, and extreme laxatives). Dr. Smith’s detox plan includes one daily cup of each: lemon water with flaxseed oil, cranberry juice, and hibiscus tea.

The claims? Doing this will “cause your gastrointestinal tract to move better, your energy levels will increase, and your skin will even appear healthier (some have said that it takes on a certain glow).”p. 126. So what we have here is an exceedingly mild “detox” regimen with very soft clinical endpoints that are difficult to measure objectively. 

But just for fun, let’s take a look at the potential liver enzyme influence that these 4 detox ingredients might have: hibiscus flower, lemon juice, cranberry juice, and flaxseed oil.

1. Hibiscus sabdariffa

The hibiscus plant (hibiscus sabdariffa is used to make tea) contains over 88 different chemicals, according to Dr. Duke’s Phytochemical and Ethnobotanical Databases. There is nothing particularly noteworthy about the plant’s chemical makeup, other than that it contains a significant amount of vitamin C. A review of the PubMed database revealed a smattering of small, animal and in vitro studies linking hibiscus to inducement of rat testicular atrophy and decreased hematocrit when exposed to very large doses. Hibiscus extract was found to be somewhat bacteriostatic in vitro, possibly because of its acidity.  One human study of the effects of drinking hibiscus tea was presented at a medical conference. The study, sponsored by a tea company, found that hibiscus tea consumption could reduce systolic blood pressure by an average of 8mmHg in mildly hypertensive adults. The study included 65 participants in a 6 week placebo controlled trial. 

So as far as hibiscus tea is concerned, there is almost no evidence to date of its usefulness as a liver enzyme stimulator. In large doses it has some possible toxicity in rats, and in humans it may have a blood pressure lowering effect – which is interesting, but unrelated to Dr. Smith’s claims.

2. Lemon juice

In terms of the potential therapeutic effects of lemon juice, kidney stone prevention is probably the most well studied. Lemon juice is an excellent source of vitamin C, which is important for general nutritional needs.

Grapefruit is known to be an inhibitor of certain liver and intestinal enzymes that help to break down medications. Luckily, this is not a citrus “class effect” but is related to a compound unique to grapefruit.  As for lemons, they seem to have no major effect on the liver.

3. Cranberry juice

Although there was some initial enthusiasm years ago about the potential for cranberry juice to reduce urinary tract infections in women, follow up studies have not found cranberry juice to be more effective than placebo. At least one small study suggests that overweight women experience an improvement in lipid oxidation (a risk factor for heart disease) with consumption of two cups of cranberry juice per day. Cranberries, like lemons and hibiscus, contain vitamin C and therefore have anti-oxidant and pro-collagen synthesis properties. As far as direct liver enzyme influence is concerned, I found nothing in the medical literature to support that claim.

4. Flaxseed oil

In theory, flaxseed oil could have anti-inflammatory effects in vivo. A recent study found no change in inflammatory markers or clotting pathways with 8 weeks of regular intake of low dose flaxseed oil. Some studies have noted a decrease in serum LDL cholesterol levels with daily consumption of flaxseed oil. Most experts agree that the desirable anti-inflammatory properties of omega-3 fatty acids are experienced in vivo via consumption of marine sources of omega-3’s only. This is because the chemical properties of fish oil and flax seeds are not biologically equivalent. While flaxseed oil may reduce LDL cholesterol, fish oil is a much more potent source of healthy omega-3 fatty acids. As far as liver “detoxification” is concerned, that does not seem to be a primary benefit of flaxseed oil.

As for the claims of “improved gastrointestinal movement” – small amounts of vitamin C, water, and plant oil are probably not going to make a noticeable difference – at least, not taken by mouth as prescribed by Shred. A “healthier, glowing skin” might be a real benefit of increased vitamin C intake in dieters with true deficiency (think scurvy) – but for those of us who are currently meeting our vitamin C needs, the excess will be excreted (as are all water-soluble vitamins) in our urine. As for the “increased energy levels” I can’t see any reason why citrus or flaxseed would provoke that response, unless you count the increased effort it will take to make a few extra bathroom breaks to relieve oneself of all the tea and juice.

And so, without further belaboring the point, I think we can safely say that Dr. Smith’s liver detox week is little more than hand waving and some increased fluid intake. 

That being said, the recipes, diet plan, and exercise prescriptions in Shred are quite sensible. Eating is organized into four, calorie-controlled meals and three snacks at regularly scheduled intervals throughout the day. Alcohol and soda are limited. The diet is rich in fruits, vegetables, whole grains, lean proteins, and healthy fats. Sugar and refined carbohydrates are avoided. Cardiovascular exercise is recommended for at least forty-five minutes per day, five days a week. The plan is presented in such detail that one can follow instructions for each meal, snack, and exercise every day for six weeks. You simply repeat the six week “course” (perhaps skipping the detox section and the part about staring into your eyes in a mirror) as many times as you like to achieve your total weight loss goal.

In my view, the Shred diet, is a reiteration of sound nutritional and exercise principles in an easy-to-follow menu format that requires little thought processing. If it didn’t wander off into the liver detox fantasy world in chapter five, it would be a sensible book indeed. 

Shred: The Revolutionary Diet – 6 Weeks, 4 Inches, 2 Sizes is now in hardcover and Kindle editions from



Posted by Val Jones

Val Jones , M.D., is the President and CEO of Better Health, PLLC, a health education company devoted to providing scientifically accurate health information to consumers. Most recently she was the Senior Medical Director of Revolution Health, a consumer health portal with over 120 million page views per month in its network. Prior to her work with Revolution Health, Dr. Jones served as the founding editor of Clinical Nutrition & Obesity, a peer-reviewed e-section of the online Medscape medical journal. Dr. Jones is also a consultant for Elsevier Science, ensuring the medical accuracy of First Consult, a decision support tool for physicians. Dr. Jones was the principal investigator of several clinical trials relating to sleep, diabetes and metabolism, and she won first place in the Peter Cyrus Rizzo III research competition. Dr. Jones is the author of the popular blog, “Dr. Val and the Voice of Reason,” which won The Best New Medical Blog award in 2007. Her cartoons have been featured at Medscape, the P&S Journal, and the Placebo Journal. She was inducted as a member of the National Press Club in Washington , DC in July, 2008. Dr. Jones has been quoted by various major media outlets, including USA Today, The Wall Street Journal, and the LA Times. She has been a guest on over 20 different radio shows, and was featured on CBS News.