Pregnancy, Healthy Eating, and CKD: “Eat Food, Not Too Much, Mainly Plants.”

“Eat food. Not too much. Mostly plants.”

Michael Pollan In Defense of Food.

Penguin Press, 2008.

To the Editor:

We read with great pleasure the guidelines of the Dutch Society of Nephrology on pregnancy in chronic kidney disease (CKD) patients.¹ As enthusiastic supporters of nutritional management in CKD pregnancy, we were even more pleased to see that nutritional management came first in the list of advocated interventions. Sparked by this enthusiasm, we would like to add 2 comments, hoping that they may integrate the proposed approach. The first comment regards supplementation. Indeed, the Italian experience cited by the authors reports on moderately protein-restricted plant-based diets in pregnancy, which mostly include a mixture of essential keto acids and amino acids (the alternative being no supplementation), that differs from amino acid supplementation, alternately mentioned in the guidelines (point 6 in “diet restrictions,” point 7 in “dialysis,” whereas amino acid and keto acid supplementation is cited in point 13 in the “hypertension” paragraph).^1,2

One advantage of keto acids is the possibility to “recycle” urea, employing it for the amination of keto acids into amino acids. Furthermore, adding keto acids to a plant-based diet should not elicit glomerular hyperfiltration, which is at difference with aminoacids. However, comparative studies in pregnancy are not available and most of the comparative studies outside of pregnancy are old.³

The second point regards food choice (Figure 1). Even if moderately-protein-restricted plant-based diets are usually synonymous to increasing the intake of “healthy” fruits and vegetables, a concern regarding the use of canned, preserved, processed, and even worse, ultraprocessed foods, such as plant-based hamburgers and dairies, should be highlighted. “Ultra processed” food is formulated to be palatable or hyperpalatable; maintain flavor, texture, attractive color, long shelf-life; and is obtained using sophisticated industrial processes, typically resulting in energy-dense products, with added sugar, unhealthy fats, and food additives (potassium, sodium, phosphate, and chemical substances) that can also trigger addictive eating behaviors. Data on the deleterious effects of additives and contaminants are accumulating for the overall population and it is reasonable to consider that they may be even more dangerous in CKD patients.^4,5 Therefore, we suggest that dietary advice in CKD pregnancy should also focus on avoiding (ultra)processed and preserved food, regardless of its plant-based or animal-based origin, thus exploiting the opportunity to improve long-term health through nutritional education in pregnancy.⁵

Figure 1.

Are these carrots? Processing food, minimally or “ultra,” changes food; overall, the more you add, the less the prepared food costs. (a) carrots and vegetables from the market (100% carrots, 400 g, approximately 2 Euros), (b) carrots and vegetables, added lemon and salt (from the gourmet store: 10 Euros), (c) canned baby carrots, added salt and sugar (120 g, approximately 1.5 Euros), (d) seasoned “bio” carrots, added over 10 substances, including salt, sugar, 2 types of vinegar, different flavors, thickening products (200 g, approximately 3.5 Euros), (e) seasoned carrots (industrial) added: all the above plus antioxidants, overall >15 ingredients (500 g, approximately 2.5 Euros).

Therefore, the mantra of the bestselling author Michael Pollan “Eat food. Not too much. Mostly plants” can be adapted for pregnant CKD patients as follows: eat food, underlining that what has been excessively processed is no longer “food”; not too much, to limit weight gain, a risk factor of adverse pregnancy outcomes; mostly plants, wisely, however, flexibly, preferring plant-based diets.