The Latest Developments in Nutrition Therapy For CKD Patients

Previous studies have shown that a low-protein diet (LPD) can delay renal disease progression in patients with chronic kidney disease (CKD). There are currently three representative LPD diets, which are lacto-ovo vegetarian, vegan, and omnivorous. However, all three diets have their advantages and disadvantages, and the results of previous studies have been inconsistent. Therefore, for CKD patients, which diet is safer, and at the same time, is it necessary to supplement dietary supplements to avoid malnutrition?

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On November 29, 2022, American experts published the latest research results in the Journal of Renal Nutrition. The study found that among the three LPD diets suitable for CKD patients, the omnivorous LPD diet could provide a greater variety of amino acids and essential nutrients, and thus had the least minimum protein intake. However, all three LPD diets require the supplementation of other essential nutrients.

Method

This is a theoretical 3-day diet study. According to the renal dietary guidelines released by the American Academy of Nutrition (EAA), the researchers formulated three-day ovo-lactovegetarian, vegan and omnivorous LPD diets to simulate different protein intakes. These recipes meet the following conditions: ①The protein intake level of all recipes is between 0.5-1.2g/kg/d; ②Easy to cook or buy; ③The content of sodium, potassium, and phosphorus is strictly limited; ④Every meal and person must be Eat 2 servings of unprocessed fruits, vegetables or grains (that is, at least 6 servings per day) and at least 1 serving of nuts per day; ⑤The body weight of the research subjects is assumed to be 70kg; ⑥The calorie intake is 30kcal/kg/d.

The main purpose of the study is to evaluate the safety of the diet and whether patients need to take other nutritional supplements, so the main endpoint is the intake of essential amino acids and micronutrients.

Result

There was no significant difference in animal protein content between omnivorous and lacto-ovo-vegetarian diets, ranging from 63% to 66%. When the dietary protein intake level is only 0.5g/kg/d, lacto-ovo vegetarian, vegan, and omnivorous LPD diets cannot meet the needs of CKD patients for histidine, leucine, lysine, and threonine. To meet the recommended intake of all essential amino acids, the protein intake of omnivorous diets should be ≥0.6g/kg/d; the protein intake of ovo-lactovegetarian diets should be ≥0.7g/kg/d; Protein intake should be ≥ 0.8g/kg/d.

When protein intake was consistent, omnivorous diets were lower in potassium, phosphorus, and calcium, while lacto-ovo vegetarian and vegan diets were higher in potassium, phosphorus, and lacto-ovo vegetarian had the highest calcium content. Also, it's worth noting that vegetarian recipes contain tofu, rice milk, and soy milk, which are all fortified with calcium, which is why vegetarian recipes are higher in calcium. Finally, in terms of sodium content, the lacto-ovo-vegetarian diet was higher except in the case of higher protein intake, whereas in the case of LPD there was no significant difference in sodium content among the three recipes.

When the protein intake was within the LPD range, the choline and vitamin B6 contents of the three diets were not up to standard, and correspondingly lacked various micronutrients:

Omnivorous LPD is deficient in folic acid, biotin (vitamin H), zinc, and magnesium;

Lacto-ovo-vegetarian LPD is deficient in vitamin B3, folic acid and magnesium;

Vegan LPD is deficient in vitamin B12 and selenium.

Additionally, lacto-ovo and vegans are deficient in eicosapentaenoic acid (EPA); vegans are also deficient in docosahexaenoic acid (DHA).

Discussion

The results of this study suggest that for CKD patients weighing 70 kg, optimal daily protein intake levels differ among omnivorous, lacto-ovo-vegetarian, and vegan diets. Compared with lacto-ovo vegetarians and vegans, omnivorous LPD had the lowest lower limit of protein intake. At the same time, the LPD diet will make CKD patients lack certain micronutrients, such as choline, vitamins, and trace elements.

In addition to the above deficiencies, previous studies have found that lower plasma levels of sulfur amino acids are associated with malnutrition and hypoalbuminemia in CKD patients. Consumption of a plant mixture with equal amounts of lysine and thionine was associated with a lower rate of muscle protein synthesis compared with consumption of animal protein. Finally, a very low-protein diet (VLPD) based on plant proteins can delay the decline in renal function in CKD patients, but increases the risk of loss of muscle mass. This suggests that LPD or VLPD may delay CKD progression, but may cause some other problems, related to protein and calorie restriction.

The content of sulfur amino acid, methionine, and cysteine in legume food is lower, and the content of lysine is higher; in cereal food, the content of lysine is lower, and the content of methionine is higher. A combination of legumes and grains can provide patients with a complete amino acid profile. However, when the intake of protein and calories is restricted, the intake of some amino acids is low, and it is difficult to fully meet the amino acid requirements of CKD patients. Compared with lacto-ovo vegetarian or vegan, omnivorous LPD has a wider range of protein intake, and it is easier to meet the essential amino acid requirements of patients.

It is worth noting that previous studies have found that if the diet uses common ingredients or cooking methods in southern China, the minimum protein intake of omnivorous LPD is 0.6g/kg/d, while that of ovo-lactovegetarian or vegan is 0.7g/kg/d. d. These findings are similar to those of this study.

Previous studies have suggested that omnivorous LPD patients have lower intakes of sodium, potassium, phosphorus, and calcium compared with vegan or lacto-ovo-vegetarian LPD and are associated with slower progression of CKD. Studies have also found that an omnivorous dietary pattern rich in plant foods is associated with a lower incidence of CKD and a longer lifespan. This is also similar to the findings of this study that omnivorous LPD has a wider coverage of amino acids and micronutrients, or is more beneficial to CKD patients.

It is worth noting that no matter what kind of LPD is used, CKD patients are deficient in some micronutrients, suggesting that corresponding dietary supplements should be supplemented. However, more research is needed on issues such as dosage, dosage form, and mode of administration of supplements.

Overall, the study found that vegan and lacto-vegetarian LPD were more likely to be deficient in multiple amino acids and other micronutrients than omnivorous LPD. Supplementing corresponding dietary supplements may benefit CKD patients.

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