Focus on color means white veggies dropped like a hot potato

May 14, 2013  


Connie Weaver

Connie Weaver 
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WEST LAFAYETTE, Ind. - Colorful vegetables are promoted as key to a healthy diet, but white vegetables, especially potatoes, shouldn't be forgotten, according to a Purdue University expert.

"Potatoes are a great source for potassium, and only 3 percent of American adults consume the recommended daily intake for this mineral that's essential to healthy blood pressure," says Connie Weaver, distinguished professor of nutrition science. "Potatoes are often discounted from being healthy because of how they are cooked, topped or the amount consumed, but, when prepared in a healthy way, potatoes are nutritious. People need to remember that white veggies have a place at the table, too."

In addition to potatoes, other white vegetables often neglected are cauliflower, turnips, onions, parsnips, mushrooms, corn and kohlrabi. These vegetables, and related topics such as ambiguity regarding classification of white vegetables and limitations of color as measure of nutritional content, are published this month in the Advances in Nutrition journal supplement, "White Vegetables: An Forgotten Source of Nutrients." The journal is published by the American Society for Nutrition and highlights research reviews in the field.

Weaver is editor of the journal supplement on white vegetables, and she served as chair for the June 2012 white vegetables roundtable. The roundtable was funded by the Alliance for Potato Research and Education.

"It's recommended that the variety of fruits and vegetables consumed daily should include dark green and orange vegetables, but no such recommendation exists for white vegetables, even though they are rich in fiber, potassium and magnesium," Weaver says. "Overall, Americans are not eating enough vegetables, and promoting white vegetables, some of which are common and affordable, may be a pathway to increasing vegetable consumption in general."

The daily recommendation is 4.5 cups of fruits and vegetables in a 2,000-calorie diet, but Americans consume less than half of that, or about 1.8 cups.

In 2004 the adequate intake for potassium was set at 4,700 milligrams a day, but the average adult intake is about half that amount. Potassium is one four nutrients identified by the Dietary Guidelines for Americans as lacking in daily diets.

"Western diets have led to a decrease in potassium with fewer fruits and vegetables, and at the same time, there's been an increase in sodium consumption because people eat more processed foods," says Weaver, who is an expert in mineral bioavailability, calcium metabolism and bone health.

While potatoes are one of the highest sources of dietary potassium, when processed, they are often higher in salt. While potassium improves blood flow, too much salt increases blood pressure, making the vascular system work harder.

"The relationship between potassium and sodium is interesting because how the two work together may influence risk of cardiovascular disease," Weaver says. "The human body needs both, but today's problem is sodium consumption is up and potassium is down. Because potassium-to-sodium intake ratios are more strongly related to cardiovascular disease risk than either nutrient alone, more research is needed to understand this relationship."

Potassium also shows signs of supporting bone health and reducing the risk of cardiovascular disease and stroke, as well as protecting against age-related bone loss and reducing kidney stones, but more research also is needed in these areas, Weaver says.

Weaver is a member of the Institute of Medicine, which is the health arm of the National Academy of Sciences, and she is deputy director of the National Institutes of Health-funded Indiana Clinical and Translational Science Institute. In 2011 she was appointed to the Institute of Medicine's Food and Nutrition Board, and in 2005 she was appointed to the U.S. Dietary Guidelines Advisory Committee, and she served on the National Academy of Sciences Food and Nutrition Board Panel to develop new requirement recommendations for calcium and related minerals.

The executive summary, by Weaver and Elizabeth T. Marr, a consultant to the Alliance for Potato Research and Education, for the "White Vegetables: An Forgotten Source of Nutrients" supplement is available at http://advances.nutrition.org/content/4/3#SupplementWhiteVegetablesAForgottenSourceofNutrients

Writer: Amy Patterson Neubert, 765-494-9723, apatterson@purdue.edu

Source: Connie Weaver, 765-494-8237, weavercm@purdue.edu 

Note to Journalists: A copy of Connie Weaver's Advances in Nutrition article is available at http://asn-cdn-remembers.s3.amazonaws.com/73b1b176eeedd16e40e4dec571785cc8.pdf


ABSTRACT

Potassium and Health

Connie Weaver

Potassium was identified as a shortfall nutrient by the Dietary Guidelines for Americans 2010 advisory committee. The committee concluded that there was a moderate body of evidence for the association between potassium intake and blood pressure reduction in adults, which, in turn, influences of risk of stroke and coronary heart disease. Evidence is also accumulating for the protective effect of adequate dietary potassium on age-related bone loss and on reduction of kidney stones. These benefits depend on organic anions associated with potassium as occurs in foods, such as vegetables, in contrast to similar blood pressure lowering benefits of potassium chloride. Benefits to blood pressure and bone health may occur at levels below current recommendations for potassium intake, especially from diet, but dose response trials are needed to conform to this. Nevertheless, intakes considerably above current levels are needed for optimal health, and studies evaluating small increases in fruit and vegetable intake on bone and heart outcomes for short periods have had disappointing results. In modern societies, Western diets have led to a decrease in potassium intake with reduced consumption of fruits and vegetables with a concomitant increase in sodium consumption through increased consumption of processed foods. Consumption of white vegetables is associated with decreased risk of stroke, possibly related to their high potassium content. Potatoes are the highest source of dietary potassium but addition of salt should be limited. Low potassium to sodium intake ratios are more strongly related to cardiovascular disease risk than either nutrient alone. This relationship deserves further attention for multiple target tissue end points. 

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