A couple of decades ago, a nutrition professor told me that one of the reasons she loves being a dietitian is because when people hear what she does for a living, they are interested and want to talk with her about the field. In contrast, most practicing dietitians I know dislike talking about their work, so much so that some of them purposely shade what they do, such as saying, “I work in healthcare,” or “I am a therapist,” in order to discourage follow-up questions. It’s not that these dietitians hate their jobs or anything; rather, they do not want to get sucked into irritating conversations during their free time.
Personally, I have found that quickly adding that I specialize in eating disorders tends to keep at bay the annoying questions and commentary that are more likely to arise when I simply say that I am a dietitian and leave it at that. My approach, while usually successful, still has its failures, as evidenced by an experience we had last month in a Puerto Rican swimming pool.
Joanne and I were on the island vacationing with our daughter, and we ended up in conversation with another couple who were also enjoying the hotel pool with their son. Upon hearing what we do for work, the father began talking about a favorite dietary approach of his: the potato diet.
Given that the potato diet is actually a real thing, let’s talk about this guy’s diet of choice. According to him, the potato diet consists of eating nothing but potatoes and supplementing with vitamin E because, according to him, potatoes – when eaten in abundance – contain sufficient amounts of all nutrients except for vitamin E. He also claimed that the diet “works” without ever defining what constitutes success in this context, although he did make mention of a celebrity who supposedly lost a significant amount of weight on the potato diet, thus suggesting that “works” means something along the lines of “will cause someone to lose weight.”
Okay. So, according the USDA’s nutrient database, a generic large russet potato, including its flesh and skin, is said to provide 292 calories. For a generic person who needs 2,000 calories per day (and many of us need more), that means eating nearly seven of these large potatoes a day. Putting aside the feasibility of that for the moment, would seven potatoes per day really contribute enough of each nutrient besides vitamin E? Let’s take a look.
The low end of the recommended carbohydrate range is 45% of total calories, so the person needing 2,000 calories per day would need at least 900 calories, or 225 grams, of carbohydrate from these seven potatoes. Because potatoes are densely packed with carbohydrates, they would easily exceed this minimum. Check mark.
What about protein? Estimated protein needs are based on body weight, activity level, and medical conditions, so let’s say that the person in question weighs 130 pounds, is generally sedentary, and has no medical conditions that would influence their protein needs. The low end of their protein range would be about 47 grams per day. Their seven potatoes would contribute 55 grams, so check mark again. If the person is heavier, more active, or has higher protein needs for any other reason, this check mark is probably replaced with a red X.
How about fat? The low end of the recommended fat range is 20% of total calories, so this person would need at least 400 calories from fat, or approximately 44 grams. Their seven potatoes only contribute a couple of grams total, so a huge red X here.
Unfortunately, the low fat content spells trouble for the fat-soluble vitamins. Russet potatoes do actually contain some vitamin A and K, but too bad the dieter’s body will be unable to absorb it due to the lack of dietary fat. The same would be true with vitamin D if the potatoes actually contained any, which they do not.
The seven potatoes do contain enough vitamin C to stave off scurvy, and the thiamin content is enough to prevent beriberi disease, but the lack of vitamin B12 would likely cause fatigue and, if sustained long enough, possibly anemia. We could go on, talking about other micronutrients, phytochemicals, and other nutrients, but you probably already realize that the potato diet is not a great idea if the goal is any semblance of health.
But what if the goal is not actually better health but rather, say, weight loss? (And remember, weight and health are not synonymous.) Personally, I imagine that the first couple of potatoes on day one would taste great, but by potatoes six and seven, I would already be sick of them. In subsequent days, I would probably be so tired of them that I am not sure I could continue to stomach all seven even if I was still hungry. Restricting variety to just one food carries the likely intended side effect of restricting one’s intake overall, and while restriction does not always lead to weight loss, sometimes it does, at least in the short term.
And isn’t that really what the potato diet is? Just another fad diet to bring about short-term weight loss that will likely be regained plus more? Instead of focusing on our daughter and having a good time, we had to spend a portion of our vacation talking with this guy about this nonsense. See, this is why so many dietitians hesitantly offer some version of, “Umm, I work in healthcare,” and then try to change the subject.