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Losing vitamins – along with weight – on a diet

If you're looking to shed a few pounds, you're probably focused on the amounts of fats, carbs or protein you can eat under the various diet plans available. But a new Stanford study suggests that you should also pay attention to how a diet will affect your consumption of key vitamins and minerals.

The study involving four popular diets - Atkins, Zone, Ornish and the LEARN diet based on the U.S. Department of Agriculture's food pyramid - showed that only those assigned to follow the Zone diet were able to avoid increasing their risks for inadequate intake of essential vitamins and minerals.

Christopher Gardner, PhD, associate professor of medicine at the Stanford Prevention Research Center and the lead author of the study, urged people to consider the overall nutritional quality of any diet plan they select, rather than focusing solely on the "macronutrients" such as carbohydrates and fats.

The study, which will be published in the August issue of the American Journal of Clinical Nutrition, is a follow-up to a 2007 paper in which Gardner and his colleagues did a head-to-head comparison of the four diet plans.

In the new study, Gardner looked at the vitamin and mineral levels of participants at the time they enrolled in the study and compared them to the levels eight weeks into their diets - when the women were the best at sticking to the new food plans. They found that in three of the diet groups, significant portions of the women increased their risk for inadequate intake of several micronutrients, such as vitamin C, vitamin E, thiamine, folic acid, iron, calcium and zinc.

That wasn't the case for the women assigned to the Zone diet, who actually increased their intake of some nutrients. Gardner noted that the Zone plan is a "moderately low-carbohydrate" diet, and speculated that this approach to reducing carbs may help dieters maintain a healthier balance. "You can cut a lot of calories out of your diet by eliminating refined grains and added sugars - the least nutritious carbs - without sacrificing nutrient adequacy," Gardner said.

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