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Dr. Sears' Blog

Keep Up with the Latest Nutrition Science
Written By: Dr. Barry Sears Creator of the Zone Diet

Written by Dr. Barry Sears
on March 30, 2021

One of the critical factors for the success of the Zone diet is improved glycemic control. This concept simply means that blood sugar levels are more stabilized from one meal to the next. The benefits are lack of hunger, better mental cognition, and reduction of inflammation.

For decades, the diabetic research community has known that fructose has been the ideal simple sugar for better glycemic control. The reason is that fructose has a glycemic index that is five times lower than glucose. Consequently, this means less glucose enters the blood, and the result is better hormonal control. Part of the reason is that much of the dietary fructose never reaches the blood because bacteria metabolize it in the gut. That’s why I have always used fructose as a primary carbohydrate in Zone bars and shakes. It just makes scientific sense.

Unfortunately, like politics, science is also prone to social media. In 2004, a short letter was written observing a correlation in the rise of obesity with the increase of high-fructose corn syrup (1). Keep in mind that high-fructose corn syrup is about 50 percent fructose and 50 percent glucose which is virtual identical to the composition of table sugar. Then came several popular diet books such as Fat Chance claiming our obesity epidemic is caused by fructose (2). One problem with that theory is that fruits are rich in fructose, and no one has ever advocated the stopping of fruit consumption. Another problem with that theory is that high-fructose corn syrup consumption peaked in 1999 and has declined by 40 percent since that time (3). Today the consumption of high-fructose corn syrup is below the level it was in 1990, and our obesity epidemic continues to increase.

Rather than cursing the darkness of quasi-scientific misinformation, the best policy is to embrace new science. Now an alternative sweetener has come to market that might have even better glycemic properties than fructose. That’s why I am excited about allulose. Allulose is a natural sugar found in low quantities in various fruits. What is unique about allulose is that 90 percent never enters the blood and thus goes directly to the colon to improve gut health. Consequently, the FDA doesn’t consider allulose to be a sugar because it is not absorbed, but the FDA also doesn’t treat it as a fiber. It's like a “phantom” carbohydrate. However, what it does do in the gut is to increase AMPK levels (4). One of the consequences of activating AMPK is that you live longer (5). Thus, allulose can be considered an “anti-aging “sugar.

Now that allulose can be produced in large amounts by biotechnology, it has been recently granted Generally Regarded as Safe (GRAS) status meaning it can be incorporated into food products. This opens up an entirely new potential for our next generation of Zone shakes and bars for enhanced glycemic control.

For example, with the replacement of fructose by allulose in our ZoneRx shakes (currently available in Chocolate and Vanilla), the decrease in total carbohydrates now allows for the addition of extra berries to each shake to achieve a truly Zone balance. The amount of berries we recommend for better glycemic control is based on science not guessing. I recommend adding two blocks of berries (strawberries, blueberries, raspberries, or blackberries). That is also about 1 cup or about 6 oz of berries. This amount adds even more polyphenols and fermentable fiber to the final ZoneRx shake while maintaining the Zone macronutrient balance needed for optimal hormonal control. Of course, it also makes a complete meal that tastes likes a gourmet dessert in seconds. For maximum convenience, just purchase frozen berries (they have a higher nutrient quality than fresh berries) and keep enough already thawed in the refrigerator to make about two Zone shakes.

As the leader in nutrition for the last 30 years, we are the first company to have shakes using allulose. Our ZoneRx bars containing allulose are under development and will be available shortly. The more science we can bring to your kitchen, the easier it becomes to retake control of your health by being in the Zone.

ZoneRx Chocolate and Vanilla Shakes Now Contain Allulose



  1. Bray GA et al. “Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity.” Am J ClinNutr 79:537-43 (2004)
  2. Lustig RH. Fat Chance. Penguin Books. New York, NY (2012)
  3. USDA Economic Research Service. “Per capita sweetener deliveries show steady downturn largely due to reduced demand for high fructose corn syrup.” Sugar and Sweetners Data (2021)
  4. Shintani T et al. “d-Allulose, a stereoisomer of d-fructose, extends Caenorhabditis elegans lifespan through a dietary restriction mechanism: A new candidate dietary restriction mimetic.” Biochem Biophys Res Commun 493:1528-1533 (2017)
  1. Ingram DK and Roth GS. “Glycolytic inhibition: An effective strategy for developing calorie restriction mimetics.” Geroscience https://doi.org/10.1007/s11357-020-00298-7 (2020)            

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