PrintStudy – Most Popular Diets Lack Vitamins and Minerals

Many popular diets do not provide sufficient micronutrients for long-term health.

When losing weight, people should be careful to not lose essential micronutrients.

Losing weight is an admirable goal, but not if proper nutrition is lost in the process. Most popular diets do not provide adequate intake of vitamins and minerals and these could put dieters at higher risk of  nutrient deficiencies, a new study reports.

Christopher Gardner and his colleagues from Stanford Prevention Research Center and the Department of Medicine, Stanford University Medical School evaluated micronutrient quality of four diets—Atkins, Zone, LEARN (Lifestyle, Exercise, Attitudes, Relationships), and Ornish—and found each failed to provide adequate amounts of certain vitamins and minerals.

The researchers, who published their findings June 23 in American Journal of Clinical Nutrition, wrote, “We found that among a free-living population trying to follow alternative weight-loss diets, the intakes of several micronutrients were potentially inadequate, which differed by diet group. Given that successful weight loss and its maintenance require adopting new dietary habits and sustaining them on an ongoing basis, the long-term implications of these potentially inadequate intakes could result in clinically relevant nutritional deficiencies.”

Study Details

In the study, participants included 311 premenopausal overweight or obese women ages 25 to 50 who were recruited from Stanford’s A TO Z trial (a large randomized trial comparing weight-loss diets). They were randomly assigned to read one of four diet books: Dr. Atkins New Diet Revolution (2002) (5); Enter the Zone, A Dietary Roadmap (1995) (6); The LEARN Program for Weight Management 2000 (9th edition, 2000) (20); or Eat More Weigh Less (2001) by Dean Ornish.

Each of the diet groups also attended one-hour evening classes each week for eight weeks. The participants were told to master their assigned diet during the eight weeks, and then follow it for the next 10 months. The researchers collected data on dietary intake from the participants by making unannounced 24-hour dietary recall assessments by telephone.

Of the four different diets, the Zone fared best for micronutrient adequacy, which the authors attribute to its balanced 40:30:30 distribution of calories from carbohydrate, fat and protein. The nutrients lacking in those following the Ornish diet were vitamin E, B12 and zinc; for Atkins: thiamin, folic acid, vitamin C and iron; and for LEARN: vitamin E, thiamin  and magnesium.

Data from the study were based on food intake alone and did not include  dietary supplements. However, the authors note that the participants who didn’t take supplements prior to dieting continued to avoid  multivitamin or multimineral supplement while dieting.  

Low Calories Without Sacrificing Micronutrients

When reducing caloric intake, it’s important to be aware that doing so may also lead to decreased micronutrient intake, the authors concluded. Additionally, the higher-protein, moderately low-carbohydrate Zone diet was the best in also providing nutrient-dense foods.    

Choosing foods that are nutrient dense or regular supplementation with essential vitamins and minerals is critical for long-term health. 

Similarly,  findings from another study (May issue of Journal of the International Society of Sports Nutrition), reported other popular diets such as Atkins for Life, The South Beach Diet, DASH, and The Best Life Diet also resulted in micronutrient deficiencies.

Study Reference: Gardner CD, Kim S, Bersamin A et al. Micronutrient quality of weight-loss diets that focus on macronutrients: results from the A TO Z study. Am J Clin Nutr 2010.