White Potatoes, Human Health, and Dietary Guidance^,

Abstract

The white potato is a concentrated source of carbohydrate, dietary fiber, and resistant starch and continues to be the staple food of choice for many cultures. The white potato is also a concentrated source of vitamin C and potassium. Two of the nutrients in white potatoes, dietary fiber and potassium, have been designated as nutrients of concern in the 2010 Dietary Guidelines for Americans. Potatoes are often maligned in nutrition circles because of their suspected link to obesity, and popular potato foods often contain more fat calories than carbohydrate calories. Some food guides do not include potatoes in the vegetable group because of their association with high-fat diets. However, potatoes should be included in the vegetable group because they contribute critical nutrients. All white vegetables, including white potatoes, provide nutrients needed in the diet and deserve a prominent position in food guides.

Introduction

White potatoes are consumed worldwide and follow only rice, wheat, and maize (corn) as a food crop for human consumption (1). Cultivated potatoes originated in South America >10,000 y ago (2). In the past 5 centuries, cultivation of this adaptable tuber has expanded to Europe, Africa, and Asia. Potatoes are now grown in >160 countries (2), and the mean per capita global consumption of potatoes is 33 kg/y (1). In 2010, China was the top potato producer with >74 million metric tons, followed by India, Russia, and Ukraine. The United States is fifth in potato production with 18.3 million metric tons. The potato is currently the predominant vegetable in the United States in terms of sales, production, and consumption (3). The demand for potatoes continues to increase in conjunction with expanding diet diversity, requests for prepared food items, and a need for inexpensive foods (1). The ability to grow potatoes in a wide range of climates and their adoption by a broad range of cultures have increased potato consumption worldwide.

US consumption of the white potato declined during the past century despite its continued prominence and increased global consumption (4). At the beginning of the 20th century, Americans primarily consumed fresh potatoes as a dietary staple. Over the past 50 y, however, fresh potato consumption has declined by approximately one half, whereas processed potato consumption has increased by approximately two thirds due to the increased availability of processed potato products and French fries. Since 2000, US per capita consumption of frozen potatoes has averaged 55 lb/y (25 kg/y) compared with 42 lb/y (19 kg/y) for fresh potatoes, 17 lb/y (7.7 kg/y) for potato chips, and 14 lb/y (6.4 kg/y) for dehydrated potatoes (5). From 2000 to 2020, the USDA Economic Research Service predicts an overall decrease in US potato consumption, with consumption of fried potatoes decreasing by nearly 9% and consumption of all other potatoes decreasing by 3% (6). This decrease is attributed to the aging of the US population, an increase in people favoring fruits and other vegetables over potatoes, increasing incomes, and better education. Although US potato consumption is projected to decrease, the intake of fruits, tomatoes, lettuce, and other vegetables may increase by ∼3–8%.

The potato contributes significant amounts of vitamins and minerals to the diet, but has been maligned as a contributor to the increasing rates of obesity, diabetes, and cardiovascular disease in the United States. Nutritionists, scientists, and various health and consumer agencies advise Americans to limit their consumption of potatoes, especially fried potatoes and potato snacks (2). In 2010, the Dietary Guidelines Advisory Committee recommended reducing the intake of fried white potatoes, which contribute only 5.5% of total solid fat intake, in order to significantly reduce the solid fat intake of Americans (7). In the same report, the Dietary Guidelines Advisory Committee recommended increasing the intake of vegetables, particularly those that provide substantial amounts of the 4 shortfall nutrients (dietary fiber, potassium, vitamin D, and calcium). White potatoes contain more potassium per standard serving than any other vegetable. These conflicting recommendations illustrate the confusion concerning the role of potatoes in the American diet. Although some nutritionists consider potatoes to be a major source of dietary fat and a contributor to the high prevalence of obesity in the United States, others consider them to be a nutrient-dense vegetable and inexpensive source of energy and protein. In this paper, we review the nutritional content of potatoes, the role of potatoes in human health and disease, past and present recommendations for potatoes in the American diet, and how to properly position this popular food in an overall healthy diet.

Nutritional value of white potatoes

Energy and macronutrients

White potatoes are considered a high-calorie food compared with other staple foods, such as rice and pasta. However, potatoes actually have less energy (94 kcal/100 g) than most other staple foods when compared on a gram-weight basis while providing substantial amounts of critical nutrients (Table 1) (8).

Table 1.

Nutritional composition of white potato and other staple foods¹

Food	Energy	Protein	Fat	CHO	Dietary fiber	Potassium	Magnesium	Phosphorus	Iron	Zinc	Vitamin C	Vitamin B-6
100 g	kcal	g				mg
Potato, white, flesh and skin, baked	94	2.10	0.15	21.08	2.1	544	27	75	0.64	0.35	12.6	0.211
Other staple foods
Pasta, enriched, cooked	158	5.80	0.93	30.86	1.8	44	18	58	1.28	0.51	0.0	0.049
Pasta, whole wheat, cooked	124	5.33	0.54	26.54	4.5	44	30	89	1.06	0.81	0.0	0.079
Cereal, whole wheat, cooked	62	2.00	0.40	13.70	1.6	71	22	69	0.62	0.48	0.0	0.073
Rice, white, cooked	130	2.38	0.21	28.59	0.3	29	13	37	1.49	0.42	0.0	0.050
Rice, brown, cooked	112	2.32	0.83	23.51	1.8	79	44	77	0.53	0.62	0.0	0.149
Grits, corn, cooked	71	1.71	0.46	14.76	0.8	27	7	20	0.57	0.18	0.0	0.046
Cassava, raw	160	1.36	0.28	38.06	1.8	271	21	27	0.27	0.34	20.6	0.088
Soybeans, cooked	173	16.64	8.97	9.93	6.0	515	86	245	5.14	1.15	1.7	0.234
Potato, sweet, baked	90	2.01	0.15	20.71	3.3	475	27	54	0.69	0.32	19.6	0.286
Yam, cooked	116	1.49	0.14	27.48	3.9	670	18	49	0.52	0.20	12.1	0.228

¹Adapted from Reference 8.

The energy provided by baked potatoes is ∼20% of that provided by rice or pasta. The assumption that potatoes are an energy-dense food may be based on their high carbohydrate content, which makes up ∼75% of their dry weight and contributes to ∼90% of their total energy, and the addition of fat and other energy sources in many popular potato recipes (Table 2).

Table 2.

Fat calories in popular potato foods¹²

Food	Amount	Energy	Total fat	Fat calories
		kcal	g	%
Potato, baked, plain	3.8 oz	100	0	0
Potato, baked, with bacon and cheese	3.8 oz	244	11	41
Potato, baked, with butter and sour cream	3.8 oz	385	29	63
Potatoes, oven-crisped	1/2 cup	72	1	12
Potato chips	1.0 oz	150	10	60
French fries	10 oz	160	8	45
Potatoes, mashed, with nonfat milk	1/2 cup	50	0	0
Potatoes, mashed, with butter and whole milk	1/2 cup	120	6	45
Potato salad, with nonfat yogurt dressing	1/2 cup	60	0	0
Potato salad, with mayonnaise	1/2 cup	180	10	50
Potatoes, scalloped, with nonfat milk	1/2 cup	100	0	0
Potatoes, scalloped, with butter and whole milk	1/2 cup	150	5	30

¹Weights of household measures varies with the food density. For conversion to gram measurements, refer to the USDA National Nutrient Database (SR24), 2011 (8).

²Adapted from Reference 3 with permission.

In many widely consumed potato foods, more than half of the energy is provided by fat. Without the addition of fat during preparation, the lipid content of potatoes is very low—only 0.1% of fresh weight. Only approximately one third of the total fat in white potatoes is composed of SFAs, whereas the remaining is primarily composed of PUFAs. In addition, the lipid content of potatoes is less than that found in rice (0.2%) and pasta (0.9%).

The protein content of potatoes is also low, averaging 1–1.5% of fresh weight depending on the cultivar (2). Compared with the 3 other major staples (pasta, rice, and maize/corn), potatoes have the lowest concentration of protein, providing 2.1 g/100 g of potatoes baked with skin. Corn flour has the highest concentration at 8.7 g/100 g, with pasta and rice providing 5.8 and 2.4 g/100 g, respectively. However, the quality of the potato protein, which reflects its digestibility and amino acid content, is very good. The biological value of potato protein—the proportion retained for growth or maintenance divided by the amount absorbed—is high. Depending on the cultivar, the biological value of potato protein is between 90 and 100 and is very similar to the biological value of whole egg protein (100) and is higher than that of soybeans (84) and legumes (73) (2). In fact, the protein quality of potatoes is higher than that of any other heavily consumed plant protein (9).

The ability of potatoes to meet human protein requirements was vigorously debated in Eastern Europe during the early 1900s because potatoes (along with bread) were the bulk of the diet. To resolve this question, Kon and Klein (10) undertook a long-term (167 d) nitrogen balance study in 1925 to determine whether nitrogen balance and body weight could be sustained on a diet composed primarily of potatoes. The study participants were 2 adults—a 25-y-old man and a 28-y-old woman. The potato diet was supplemented with butter or pork fat and a few fruits (apples and pears), and tea and black coffee with sugar were consumed occasionally. The man consumed ∼6 g nitrogen (37.5 g protein)/d, and the woman consumed 3.5 g nitrogen (21.9 g protein)/d. Both individuals lost ∼2 kg of body weight during the course of the study. The digestibility [(diet N − fecal N/diet N) × 100] of the potato diet averaged 66% and 75% in the man and woman, respectively. This level of digestibility is comparable to that reported for beans, maize, and millet (11). Both individuals achieved nitrogen balance over the entire study. However, the woman took longer than the man to achieve nitrogen balance. The results substantiated previous claims that a potato-based diet can support nitrogen balance in adults, but the capacity of potato protein to support growth was still questioned despite these results.

In 1981, Lopez de Romaña et al. (12) evaluated the capacity of potato-based diets to rehabilitate Peruvian infants and children with severe malnutrition. Diets supplying 50%, 75%, or 84% of total energy from potatoes were tested. The 50% potato diet was well accepted, but the children were unable to tolerate the 84% potato diet over a prolonged period of time. The diets providing 50–75% of total energy and 80% of nitrogen requirements from potatoes supported growth in the children while maintaining normal serum albumin concentrations. Thus, long-term consumption of potato protein is of sufficient quality to support growth in undernourished infants and children as well as to maintain nitrogen balance and body weight in adults.

The protein quality of a food is determined by its amino acid composition in addition to digestibility. Amino acid quality is estimated from the amino acid score of a food (i.e., amino acid composition of a food compared with human amino acid requirements) (11). Only 4 essential amino acids are likely to limit the protein quality of mixed diets consumed by humans—lysine, methionine, threonine, and tryptophan. Therefore, the amino acid score for potatoes can be determined by comparing the levels of these amino acids found in potatoes with the amino acid scoring pattern for individuals 1 y and older recommended by the Institute of Medicine (Table 3) (13).

Table 3.

Comparison of amino acid levels in potato and selected grains with recommended IOM amino acid pattern¹

Amino acid	IOM pattern	Potato	Pasta	White rice	Whole-grain cornmeal
	mg/g protein
Lysine	51	61	22.6	36.1	28.1
Methionine + cysteine	25	28.8	30.3	44.1	38.9
Threonine	27	36.3	35	35.7	37.6
Tryptophan	7	15.5	14	11.8	7

¹Adapted from References 8 and 13.

Potatoes exceed the recommended levels for all 4 of these essential amino acids, demonstrating that potato protein is of high quality. Compared with pasta, white rice, and whole-grain cornmeal, potatoes are the only staple food meeting the recommended lysine level. However, the sulfur-containing amino acids (methionine + cysteine) are lower in potatoes than in the other common staple foods. Scientists are currently developing transgenic forms of potatoes that have higher levels of the sulfur-containing amino acids (14). Using the amaranth gene (AmA1), the total protein and amino acid concentrations in these potatoes were increased by 35–60%. In addition, these transgenic potatoes had higher yields. In vitro and in vivo studies of the transgenic potato completed using experimental animals show that these potatoes are safe, and they are currently being grown in India.

Carbohydrates comprise >95% of the potato by weight. The 2 primary carbohydrates (i.e., “starches”) in potatoes are amylose and amylopectin, which occur in a 1:3 ratio, respectively (2). The branched structure of amylopectin, the predominant starch, allows greater digestibility than the linear chain structure of amylose, which is associated with a higher glycemic response. Amylose, a “resistant” starch, is generally resistant to amyloytic digestive enzymes. This resistance is decreased during cooking, which causes the starch to become gelatinized and increases its solubility. On cooling, amylose undergoes retrogradation. This process causes the starch to become more crystalline and increases its resistance to digestive enzymes and explains why the glycemic index of cold cooked potatoes is lower than that of hot cooked potatoes (15).

Dietary fiber is supplied by the cell walls of the potato, especially the thickened cell walls of the peel (2). Cooked potatoes without the skin provide 1.8 g fiber/100 g, whereas cooked potatoes with the skin provide 2.1 g fiber/100 g. Potatoes contain less fiber than whole-grain cornmeal (7.3 g/100 g), but more fiber than white rice (0.3 g/100 g) or whole-wheat cereal (1.6 g/100 g). The potato cannot be considered a high-fiber food, but it can be a significant source of fiber for individuals regularly eating potatoes. An analysis using data from the Continuing Survey of Food Intake by Individuals indicated that potatoes provided >11% of the total fiber intake of low-income women. Only intake from vegetables (23%) and bread (12%) provided these women with more total fiber (16). Higher income women tended to eat more fruits and vegetables and get less of their fiber from white potatoes.

Micronutrients

In addition to energy, high-quality protein, and dietary fiber, potatoes provide significant amounts of several vitamins, minerals, and phytochemicals (Table 4).

Table 4.

Nutritional composition of white potato and other white/starchy vegetables¹

Food	Energy	Protein	Fat	CHO	Dietary fiber	Potassium	Magnesium	Phosphorus	Iron	Zinc	Vitamin C	Vitamin B-6
100 g	kcal		g					mg
Potato, white, flesh and skin, baked	94	2.10	0.15	21.08	2.1	544	27	75	0.64	0.35	12.6	0.211
Other white vegetables
Cauliflower, boiled	23	1.84	0.45	4.11	2.3	142	9	32	0.32	0.17	44.3	0.173
Jicama, raw	38	0.72	0.09	8.82	4.9	150	12	18	0.60	0.16	20.2	0.042
Kohlrabi, boiled	29	1.80	0.11	6.69	1.1	340	19	45	0.40	0.31	54.0	0.154
Leek, cooked	31	0.81	0.20	7.62	1.0	87	14	17	1.10	0.06	4.2	0.113
Mushroom, boiled	28	2.17	0.47	5.29	2.2	356	12	87	1.74	0.87	4.0	0.095
Onion, boiled	44	1.36	0.19	10.15	1.4	166	11	35	0.24	0.21	5.2	0.129
Parsnip, boiled	71	1.32	0.30	17.01	3.6	367	29	69	0.58	0.26	13.0	0.093
Turnip, cooked	22	0.71	0.08	5.06	2.0	177	9	26	0.18	0.12	11.6	0.067
Other starchy vegetables
Cassava, raw	160	1.36	0.28	38.06	1.8	271	21	27	0.27	0.34	20.6	0.088
Corn, yellow, sweet, boiled	96	3.41	1.50	20.98	2.4	218	26	77	0.45	0.62	5.5	0.139
Peas, black-eyed, boiled	97	3.17	0.38	20.32	5.0	418	52	51	1.12	1.03	2.2	0.065
Peas, green, boiled	84	5.36	0.22	15.63	5.5	271	39	117	1.54	1.19	14.2	0.216
Beans, lima, boiled	126	8.04	0.38	23.31	7.7	401	53	127	2.40	1.03	0.0	0.078
Plantain, cooked	116	0.79	0.18	31.15	2.3	465	32	28	0.58	0.13	10.9	0.240
Parsnip, boiled	71	1.32	0.30	17.01	3.6	367	29	69	0.58	0.26	13.0	0.093
Squash, acorn, boiled	34	0.67	0.08	8.79	2.6	263	26	27	0.56	0.11	6.5	0.117
Potato, sweet, boiled	76	1.37	0.14	17.72	2.5	230	18	32	0.72	0.20	12.8	0.165
Taro, cooked	142	0.52	0.11	34.60	5.1	484	30	76	0.72	0.27	5.0	0.331

¹Adapted from Reference 8.

A cooked potato provides 544 mg potassium/100 g and 27 mg magnesium/100 g, representing 12% of the adequate intake of potassium recommended by the Institute of Medicine and 7% of the RDA for magnesium for adult males. According to the 2005 Dietary Guidelines Advisory Committee report, both minerals are shortfall nutrients in the American diet (17). Volpe (18) and Weaver (19) provide a more detailed discussion of the potential health benefits associated with the high magnesium and potassium content of potatoes, respectively. Potatoes also supply 75 g phosphorus/100 g, but unlike many other plants, relatively little of the phosphorus in potatoes is in the form of phytate. This lack of phytate makes the bioavailability of the iron and zinc in potatoes higher than that found in similar plant foods with high phytate levels (i.e., beans, wheat, and maize/corn) (2, 20). The ascorbic acid found in potatoes may further increase the bioavailability of iron. The amount of iron and zinc in potatoes is relatively low at ∼8% and 3% of the RDA for adult males, respectively, for every 100 g consumed. However, evaluations of potato cultivars for iron and zinc content show that the range is wider than previously thought. Selective breeding of potato cultivars could increase the levels of iron and zinc in future potato crops (2).

Potatoes contribute significant amounts of ascorbic acid to the diet by providing ∼13 mg/100 g, which is 14% of the RDA for ascorbic acid for adult men. However, the amount of ascorbic acid provided varies widely among the various potato cultivars and is greatly affected by the cooking method used (21). Baked and microwaved potatoes have approximately twice the amount of ascorbic acid than do potatoes that have been boiled or fried (21). Analysis of dietary data from nearly 12,000 US adults participating in the second NHANES from 1976 to1980 showed that potatoes and fried potatoes were the sixth and seventh contributors of total ascorbic acid in the diet, respectively, with each category providing ∼4% of total ascorbic acid in the diet (22). The 10-country European Prospective Investigation Into Cancer and Nutrition included >36,000 adults and found that potatoes contributed ∼5–12% of ascorbic acid intake. Higher amounts of ascorbic acid were obtained from potatoes in the Scandinavian countries, Germany, and the Netherlands compared with Greece, Spain, and Italy (23).

Potatoes are a rich source of vitamin B-6 and provide ∼0.2 mg/100 g or 15% of the RDA for adult males. Analysis of dietary data from NHANES 2003–2006 showed that white potatoes contributed between 14% and 18% of the total vitamin B-6 intake for US children and adolescents (24). The European Prospective Investigation Into Cancer and Nutrition also found that potatoes were a major contributor of vitamin B-6. The United Kingdom and the Netherlands consumed ∼17% of their vitamin B-6 from potatoes, whereas the estimate was 7% for Greece, Spain, and Italy (23). However, meats were the primary source of vitamin B-6 in all of these countries.

Potatoes are also a good source of phytochemicals, many of which function as antioxidants. The total phenolic antioxidant index for potatoes was estimated to be 124.5 mg vitamin C equivalents/150 g of fresh weight, 13% of which was derived from the ascorbic acid content with the balance derived from carotenoid and phenolic compounds (25). Phenolic acid and polyphenols from potatoes also play an important role in human health (26).

White potatoes and human health

Until the early 1900s, potatoes played an important role in preventing starvation and malnutrition worldwide. Although the importance of potatoes to food security has decreased in the United States and Europe, potatoes continue to be an essential component of the diet for millions of people in South America, Africa, and Asia (27). At present, more than half of the global potato production comes from developing countries. Potato and other root and tuber production is actively supported by the International Potato Center in Lima, Peru, as a means to achieve food security and improve the lives of poor people in the developing world. Potato production also provides farmers in the developing world with a source of income. Referring to the potato as a “hidden treasure,” the United Nations officially declared 2008 as the International Year of the Potato to raise awareness of the potato in developing nations experiencing severe food shortages (28).

In the United States, however, the potato is often maligned for contributing to obesity and diabetes. As American writer Jean Kerr once said, “If you have formed the habit of checking on every new diet that comes along, you will find that, mercifully, they all blur together, leaving you with only one definite piece of information: French-fried potatoes are out.” In fact, potatoes are shunned on weight-loss diets with little scientific evidence that they contribute to weight gain. Schulze et al. (29) reported in 2006 that a “Western” dietary pattern, characterized by high intakes of red and processed meats, refined grains, sweets and desserts, and potatoes, was associated with weight gain among women enrolled in the Nurses’ Health Study from 1991 to 1999. The researchers compared “Western” (i.e., energy dense) with “prudent” (i.e., energy poor) dietary patterns and included all potatoes and potato foods in the Western dietary pattern and all other vegetables in the prudent dietary pattern. However, because not all potatoes are fried, their relegation to the Western dietary pattern seems arbitrary and judgmental. Potatoes, along with all the other energy-dense foods included in the Western dietary pattern, were found to be linked to weight gain.

In 2011, Mozaffarian et al. (30) followed up on the Schulze et al. (29) study and evaluated weight gain in 4-y intervals between 1986 and 2006 in 3 separate prospective cohorts. On average, the participants gained 3.35 lb within each 4-y period. The weight change was strongly associated with an increase in the intake of potato chips (1.69 lb), fried potatoes (1.28 lb), sugar-sweetened beverages (1.00 lb), and unprocessed (0.95 lb) and processed (0.93 lb) meats. In a Letter to the Editor, Bistrian (31) noted that an association between potato consumption and weight gain does not imply causation. He also mentioned that approximately half of the calories in potato chips and French fries come from added fat, which is more likely to be the etiological factor for the weight gain. Bistrian concluded by stating that “[i]t would be unfortunate if potatoes were stigmatized and their consumption and production discouraged. The potato is too valuable to a world where population pressures, limited productive farmland, and high food costs are a present reality.” These 2 prospective cohort studies showing a relationship between potato consumption and weight gain did not separate the effect of potato consumption from the effect of the fat consumed with the potato. Furthermore, potatoes are frequently consumed with other energy-dense foods that can also contribute to weight gain. To date, no randomized, controlled trials evaluating the role of potatoes in a weight-loss program have been conducted.

Other prospective cohort studies have evaluated the association between potato consumption and the risk of type 2 diabetes. Using data from the Nurses’ Health Study, Halton et al. (32) found that substituting 1 serving of potatoes per day for 1 serving of whole grains per day increased the risk of type 2 diabetes by 30%. However, the association was primarily seen in obese women (BMI ⩾30) at the highest quintile of potato consumption, with a 22% increased risk of type 2 diabetes. An increase in risk was not found for nonobese women (BMI <30). Liese et al. (33) found that high intakes of several energy-dense food groups, including fried potatoes, were associated with higher levels of plasminogen activator inhibitor-1 and fibrinogen, 2 biomarkers of inflammation and hemostasis. An increase in the intake of energy-dense foods was also associated with an increased risk of type 2 diabetes. The authors recognized that interventions should be directed to reduce consumption of energy-dense foods rather than focusing only on fried potatoes.

In contrast to Halton et al. (32) and Liese et al. (33), Villegas et al. (34) found that the intake of tubers was associated with a lower risk of type 2 diabetes in the Shanghai Women’s Health Study, whereas rice increased the risk. The divergent results of these studies may be due to the lower amounts of fat added to potatoes in the cooking process by Chinese versus American women. Three additional studies also found no association between potato intake and type 2 diabetes (35–37). To date, all of the studies of potato intake and diabetes focused on a potential positive association. However, given the substantial amount of fiber, polyphenols, and antioxidants in potatoes, a study investigating the association between potato consumption and diabetes, metabolic syndrome, and cardiovascular disease, while controlling for fat intake, is needed. Some evidence shows that potato protein, resistant starches, and phosphorylated starches have cholesterol-lowering properties in experimental animals and cell lines (2). In vitro studies also suggest that anthocyanins, glycoalkaloids, and lectins from potatoes are antitumor agents.

Dietary guidance and white potatoes

Food groupings and dietary guidance

The USDA has provided dietary guidance to the American public since 1894. W.O. Atwater, the first USDA Director of the Office of Experiment Stations, stated in 1902, “Unless care is exercised in selecting food, a diet may result which is one-sided or badly balanced—that is, one in which either protein or fuel ingredients (carbohydrate and fat) are provided in excess…. The evils of overeating may not be felt at once, but sooner or later they are sure to appear—perhaps in an excessive amount of fatty tissue, perhaps in general debility, perhaps in actual disease” (38).

Although Atwater understood the need to have a balanced diet, his advice failed to provide a way to translate nutritional recommendations into food intake. Thus, nutritionists at the USDA began combining foods sharing similar nutritional properties or biological characteristics into food groups. Published in 1917, the first USDA food guide placed foods into 5 groups: milk and meat, cereals, vegetables and fruit, fats and fatty foods, and sugars and sugary foods. In 1933, 12 major food groups were recommended: milk and milk products, lean meat/poultry/fish, dry mature beans/peas/nuts, eggs, bread/flour/cereals, leafy green/yellow vegetables, potatoes/sweet potatoes, tomatoes/citrus, other fruits/vegetables, butter, other fats, and sugars. Since 1943, the USDA has released 4 different food guides: Basic Seven (1940s), Basic Four (1950s–1970s), Food Pyramid/MyPyramid (1980s–2010), and MyPlate (2011) (38, 39). All of these food guides include a milk/milk products group, a meat/poultry/fish/eggs/dried beans/peas/nuts group, and a breads/cereals/rice/pasta group. The major differences among the 4 guides are whether the fats/oils/sweets group was included and how vegetables and fruits were categorized. The fats/oils/sweets group was not included in the Basic Four and MyPlate. The Food Pyramid/MyPyramid and MyPlate separated vegetables and fruits into 2 groups, whereas the 2 earlier guides either combined them into 1 group (Basic Four) or divided them by color or botanical characteristics (Basic Seven).

Vegetables have historically had a prominent place in dietary guidance because of their high concentrations of vitamins (especially vitamins C and A) and minerals, including electrolytes. More recently, vegetables have been recognized for their contributions of phytochemicals, dietary fiber, and resistant starch to the diet. In fact, most countries have dietary recommendations that acknowledge the importance of vegetables. A comparison of the recommendations concerning vegetable intake in the national food guides for the United Kingdom and the United States is shown in Table 5 (40–42).

Table 5.

Comparison of United Kingdom and United States National Food Guide Recommendations concerning vegetable intake¹²

Comparison Category	United Kingdom	United States
Food guide	Eatwell Plate	MyPlate
Government agency	National Health Service	USDA
Number of food categories	5	6
Key messages	Try to eat plenty of fruits and vegetables	Make half your plate fruits and vegetables
		Eat a variety of vegetables, especially dark green and red-orange vegetables and beans and peas
Intake units	Portions (1 portion = 80 g)	Cups: The following can be considered as 1 cup from the vegetable group:
		1 cup of raw or cooked vegetables
		1 cup of or vegetable juice
		2 cups of raw leafy greens
Recommended vegetable intakes	Fruits + vegetables:	Vegetables only:
	5 portions/day (400 g/d)	2–3 cups/d (age and sex dependent)
Vegetable amounts	A portion is	A serving is
	3 heaping tbsp of vegetables (raw, cooked, frozen, or tinned)	1 cup green salad
	3 heaping tbsp of beans and pulses (maximum 1 portion/day)	1 baked potato
	A dessert bowl of salad	1/2 cup cooked broccoli
		1/2 cup serving of other vegetable
		1/2 cup tomato juice
Vegetable categories	—	Dark green
		Red/orange
		Beans/peas
		Starchy
		Other
Potatoes included?	No (considered starchy food)	Yes
Legumes included?	Beans and pulses can only be counted as 1 vegetable portion/day regardless of amount consumed	Beans and peas can be counted toward vegetable servings only after suggested intake from protein foods group has been met

¹Weights of household measures varies with the food density. For conversion to gram measurements, refer to the USDA National Nutrient Database (SR24), 2011 (8).

²Adapted from References 40–42.

A variety of strategies have been used to separate vegetables into subgroups. The most common approach is to divide vegetables by color, which typically reflects the presence of pigmented phytochemicals. MyPlate separates vegetables into 5 subgroups (Table 6).

Table 6.

Subgroups within the vegetable food group¹

Subgroup	Examples
Dark green	All fresh, cooked, frozen, and canned dark green leafy vegetables (e.g., spinach, romaine lettuce, collard greens, kale, bok choy) and broccoli.
Red and orange	All fresh, cooked, frozen, and canned red and orange vegetables (e.g., tomatoes, red peppers, carrots, sweet potatoes, winter squash) and tomato juice.
Beans and peas	All cooked, frozen, and canned beans and peas (e.g., kidney beans, lentils, chickpeas, pinto beans, black-eyed peas). Does not include green beans, lima beans, or green peas.
Starchy	All fresh, cooked, frozen, and canned starchy vegetables (e.g., white potatoes, corn, green peas, lima beans, cassava).
Other	All fresh, cooked, frozen, and canned vegetables not included in other subgroup (e.g., iceberg lettuce, green beans, onions, mushrooms, beets).

¹Adapted from Reference 42.

Red/orange vegetables are rich sources of lycopene and β-carotene. However, many dark green vegetables (i.e., spinach, broccoli) also contain these phytochemicals. Dark green vegetables are most likely placed in a separate subgroup because they are rich sources of magnesium, calcium, and folate. Blue/purple vegetables are beginning to be recognized as another subgroup due to the presence of anthocyanins. Anthocyanins are antioxidants that may reduce inflammation, lower cholesterol, and support retinal health. Based on the association between fruit and vegetable color and nutrient content, some suggest that color should be used to translate the science of phytochemicals into dietary guidance. In fact, 2 leading nutritionists have published consumer-directed dietary guidance that emphasize the role of colorful fruits and vegetables in a healthy diet (43, 44).

However, grouping vegetables by color would eliminate white vegetables, such as cauliflower, jicama, kohlrabi, onions, parsnips, shallots, turnips, and white potatoes. Although the white potato is a vegetable common to all ethnic groups and food cultures, only the white potato was arbitrarily eliminated from the white vegetable and fruit group in a study of fruit and vegetable consumption by color and incidence of stroke (45). Apples and pears made up 55% of the white fruit and vegetables consumed, and others included bananas, cauliflower, cucumbers, mushrooms, garlic, leeks, and onions. Oude Griep et al. (45) found that each 25-g/d increase in white fruit and vegetable consumption was associated with a 9% lower risk of stroke over a 10-y period. Green, orange/yellow, and red/purple fruits and vegetables were not associated with a lower risk of stroke. In addition, a recent meta-analysis showed that potassium intake is associated with reduced risk of stroke. For every 1000-mg increase in dietary potassium, the risk of stroke declined by 11% (46). White potatoes are one of the highest sources of potassium in the American diet, with 1 small baked potato providing ∼740 mg of potassium (19). Including white potatoes in the white fruit and vegetable group may have further reduced the risk of stroke associated with this group in the Oude Griep et al. (45) study.

Although dividing vegetables into subgroups based on color is a good tool for increasing phytonutrient intakes, this technique fails to clearly delineate the role that vegetables play in meeting nutrient requirements. Red peppers and tomatoes are rich sources of vitamin C, but so are green peppers, cabbage, spinach, and white potatoes. The subgroup of green leafy vegetables eliminates a number of nutrient-dense green vegetables (e.g., broccoli, Brussels sprouts, asparagus, green beans, cabbage). Furthermore, some yellow vegetables are excluded from the red/orange group simply because they have high complex carbohydrate content even though many of these vegetables are good sources of β-carotene (e.g., acorn squash, carrots, pumpkin, sweet potatoes). Therefore, 2 other vegetable subgroups are often used in food guides to accommodate these “outliers”: “starchy” and “other.” Although these subgroups ensure that all vegetables are included in the food guide, they tend to place the “starchy” and “other” vegetables in a less favorable position within the food guide than that of the colored vegetables. “Other” can be interpreted as not being important, and “starchy” may imply consumption limitations due to high caloric content.

Positioning white potatoes in food guides

White potatoes are a good source of several critical nutrients: potassium, magnesium, dietary fiber, and vitamin B-6 (7, 17). When the first USDA food guide was published by Dr. Hazel Stiebeling in 1933 (38), the problem of how to classify potatoes was avoided by giving white and sweet potatoes their own food group. Since then, potatoes have always been a subgroup within the vegetable food group, either as a “starchy” or “other” vegetable. Potatoes fall within the definition of a vegetable as a plant cultivated for its edible parts, such as the roots of the beet, the leaves of spinach, and the flower buds of broccoli (47). However, the “vegetable” label may also be applied to the fruit (e.g., squash, peppers, tomatoes) or seeds (e.g., corn, lima beans, green peas) of certain plant species (47). Many European immigrant households in the United States at the turn of the 20th century consumed potatoes as a staple food, with potatoes providing a major proportion of their energy and nutrient needs (48). Some populations still consume potatoes in sufficient quantities for the potato to be considered a staple food (48), but potatoes must increasingly compete with pasta and rice for the dominant position on the plate.

Given that white potatoes are a good source of energy as well as several vitamins, minerals, and phytochemicals, properly placing them within a food guide is a challenge. Although technically a root vegetable, their high carbohydrate content also allows populations to use them as a staple food. Their versatility also allows potatoes to be consumed as a main dish, side dish, or snack. Classifying potatoes as a “starchy,” “other,” or “white” vegetable does not fully define their nutritional role, nor does including them in the grains/cereals food group. Dr. Steibling may have had the best solution in 1933 when she placed potatoes and sweet potatoes in a group of their own (38).

Conclusions

White potatoes have historically been a staple food for many cultures and continue to be an inexpensive nutrient source around the world. Unfortunately, the white potato has been labeled as a “food to avoid” because of inconsistent epidemiologic research showing that a “Western” dietary pattern, which included all white potatoes regardless of preparation method, was linked to weight gain and increased risk of type 2 diabetes. Consequently, the role of white potatoes in providing a low-cost source of critical nutrients, high-quality protein, and a satiating carbohydrate is ignored. White potatoes are typically grouped with “other” or “starchy” vegetables in food guides, but these subgroups do not adequately describe the energy, vitamin, mineral, and phytochemical contributions that white potatoes make to the diet. Dietary guidance should continue to stress the need to moderate consumption of high-fat foods, and white potatoes prepared in a healthy way have an important role in a nutritious diet.