Most of the fruit and vegetable juices in the U.S. diet are consumed as commercially processed juices. Your orange, apple, grape, tomato, grapefruit, and pineapple juices are not made fresh and frequently contain added sugar, salt, stabilizers and preservatives. Typically, fiber, vitamins, minerals and certain phytochemicals are removed or destroyed during commercial processing. You’re left with these liquid concoctions which often maintain nutritional characteristics similar to sugared soda beverages, “liquid candy,” which increasingly are recognized to promote obesity, type 2 diabetes and diseases of insulin resistance. So, for most of you there is really nothing new here.
A recent report surfaced on the internet suggesting that fruit smoothies are also not much better than commercially processed juices and soft drinks. Fortunately, the best science available today indicates otherwise. While commercial pure fruit and vegetable juices have been available for decades, it has only been in recent years that fruit and vegetable smoothies or mixtures of both have appeared in supermarket and health food stores.
Most commercially available fruit smoothie servings typically contain at least 80 grams of whole, crushed fruit, plus one portion (150 ml) of juice, or often contain in excess of 80 grams of whole crushed fruit with the balance as juice.1 A 250 ml fruit smoothie serving contains 30 grams of total sugars, which is not significantly different than eating a comparable serving of the fruits themselves.1 Further, fruit smoothies make potentially important contributions to daily intakes of fiber, vitamin C and total antioxidant capacity (ORAC).1 Unlike pure juices, smoothies often contain a variety of fruit and vegetable mixtures with numerous phytochemicals and antioxidants in high concentrations that contribute to ORAC.12 A recent study demonstrated that the addition of a daily fruit smoothie containing 22.5 grams of blueberries improved insulin sensitivity in obese, insulin resistant participants.3 Meaning that even overweight or obese subjects, by including ample amounts of blueberries in the concoction of their smoothies, should enjoy a few smoothies during the week. Active, non-overweight people and athletes should enjoy these delicious treats whenever they like .
In The Paleo Diet Cookbook, my co-authors and I offer a variety of recipes for homemade fruit smoothies. In many of these recipes we recommend adding powdered egg white, a rich source of the branch chain amino acids (leucine, isoleucine and valine), which are indispensable to athletes and other active people because these nutrients promote rapid recovery from exercise via their anabolic muscle building effects. Further, the addition of a concentrated protein source like egg white powder to the natural sugars found in fruit smoothies, reduces the glycemic load of the smoothie and helps to minimize spike in blood glucose and insulin levels. Enjoy these delicious fruit and vegetable concoctions, they will help you obtain a healthy Paleo diet balanced by plenty of fresh fruit and veggies.
Loren Cordain, Ph.D., Professor
2. Ruxton CH, Gardner EJ, Walker D. Can pure fruit and vegetable juices protect against cancer and cardiovascular disease too? A review of the evidence. Int J Food Sci Nutr. 2006 May-Jun;57(3-4):249-72.
3. Stull AJ, Cash KC, Johnson WD, Champagne CM, Cefalu WT. Bioactives in blueberries improve insulin sensitivity in obese, insulin-resistant men and women. J Nutr. 2010 Oct;140(10):1764-8. Epub 2010 Aug 19