Do not pity the lowly white potato, for it has friends in high places. Late last year, Congress decided to add white potatoes to the list of foods that can be purchased with government-subsidized vouchers used by participants in WIC — the Special Supplemental Nutrition Program for Women, Infants and Children. The addition was part of the behemoth 1,600-page “cromnibus,” and it was a shocking example of Congress defying science and writing its own menu. White potatoes already figure heavily in the diets of low-income families, because potatoes are relatively inexpensive and usually come already prepared — albeit in the most unhealthy way imaginable. Since it was created more than 40 years ago, the WIC program has been one of this country’s most successful anti-poverty, pro-health programs. WIC gives federal grants to states for food, nutrition education and health care referrals for low-income mothers and children younger than age 5.