Posts

LCHF and kidney function

Except from MSc (Med) Physiology Dissertation (UCT), by Tamzyn Murphy (RD)

 

Safety concerns have been raised over low carbohydrate high fat (LCHF) diets’ relatively high protein content, for renal function [100]. While protein intake on LCHF diets may be higher than on conventional diets, it seldom exceeds 30 % total daily energy intake (TDEI) [10, 101]. Critics theorise that high protein intake (> 25% of TDEI or > 2 g. kg body weight (BW)-1 [102])  may chronically increase glomerular pressure and hyperfiltration, thereby damaging the kidneys [103] – particularly concerning in Type 2 Diabetes (T2D) with its high nephropathy risk. Indeed protein restriction helps preserve renal function in pre-existing kidney disease [104]. However, evidence doesn’t support the theory that high protein diets impair renal function in the absence of kidney disease [100, 102, 103, 105], even in obese individuals with T2D [106].  In fact, very low carbohydrate high fat (VLCHF) diets may improve renal function [107], as indicated by results showing reversal of diabetic nephropathy in rodents [108] and reduced creatinine concentrations in an intervention study in overweight and obese humans with and without T2D [109].

 

References

  1. Crowe, T., Safety of low‐carbohydrate diets. Obesity reviews, 2005. 6(3): p. 235-245.
  2. Adam‐Perrot, A., P. Clifton, and F. Brouns, Low‐carbohydrate diets: nutritional and physiological aspects. Obesity Reviews, 2006. 7(1): p. 49-58.
  3. Møller, G., et al., Higher Protein Intake Is Not Associated with Decreased Kidney Function in Pre-Diabetic Older Adults Following a One-Year Intervention—A Preview Sub-Study. Nutrients, 2018. 10(1): p. 54.
  4. Martin, W.F., L.E. Armstrong, and N.R. Rodriguez, Dietary protein intake and renal function. Nutrition & metabolism, 2005. 2(1): p. 25.
  5. Rhee, C.M., et al., Low‐protein diet for conservative management of chronic kidney disease: a systematic review and meta‐analysis of controlled trials. Journal of cachexia, sarcopenia and muscle, 2018. 9(2): p. 235-245.
  6. Brinkworth, G.D., et al., Renal function following long-term weight loss in individuals with abdominal obesity on a very-low-carbohydrate diet vs high-carbohydrate diet. Journal of the American Dietetic Association, 2010. 110(4): p. 633-638.
  7. Tay, J., et al., Long-term effects of a very low carbohydrate compared with a high carbohydrate diet on renal function in individuals with type 2 diabetes: a randomized trial. Medicine, 2015. 94(47).
  8. Azar, S., H. Beydoun, and M. Albadri, Benefits of ketogenic diet for management of type two diabetes: a review. J Obes Eat Disord, 2016. 2(2).
  9. Poplawski, M.M., et al., Reversal of diabetic nephropathy by a ketogenic diet. PLoS One, 2011. 6(4): p. e18604.
  10. Hussain, T.A., et al., Effect of low-calorie versus low-carbohydrate ketogenic diet in type 2 diabetes. Nutrition, 2012. 28(10): p. 1016-1021.

Diets that do and diets that don’t: Part 4 – The Dukan Diet

By Tamzyn Murphy

BSc Med(Hons) Human Nutrition and Dietetics, RD

 

Unlike the typical low carb diet, Dukan is high in protein (starting at 40% of calories) and low in fat (20% of calories). It’s big on rules and the restrictive phases are incredibly strict – any indiscretion is seen as a major failure. The idea is to replace much of your dietary carbs and fat with protein, which is filling, low in calories and takes time and work to digest. Studies on low carb, low fat, high protein diets show that you’ll naturally eat far fewer calories, feel full and you’ll likely experience metabolic benefits, including improved cholesterol, blood fat, glucose and insulin levels, thereby possibly reducing heart disease, diabetes and metabolic syndrome risk.[i], [ii] But weight loss benefits don’t appear to out-do other diets.

There are four phases. Phase one lasts about 5 days and consists almost exclusively of protein food – meat, seafood, poultry, eggs, vegetable-protein and fat-free dairy. No vegetables. Phase two allows non-starchy veg to be added to phase one’s protein foods, on every alternate day, and continues until you’ve lost the weight. The third phase last a few months and allows all the protein food and non-starchy veg you like, as well as limited fruit, whole grain bread and cheese. Phase three also allows two starch servings (e.g. pasta) and two anything-you-want meals each week. Phase four: eat what you like six days of the week, bearing in mind what you learnt during phase 3. On day seven you must eat like you did in phase one. A daily oat bran serving forms part of each phase, probably in an attempt to increase the fibre content of the diet.

Dukan’s excessive protein may increase your risk of gout[iii] and put strain on the kidneys[iv]. And a high protein and low fibre diet is bound to give you constipation. Cutting out entire food groups may put you at risk for nutritional deficiencies. So if you’re insistent on following this diet, it’s probably prudent to take a complete vitamin and mineral supplement, especially during the first two very restrictive phases. Phase four’s sudden dietary freedom may leave you directionless and reverting back to your old ways, resulting in rebound weight gain. And with all the expensive protein you’re guzzling, prepare for dent in your bank balance; as well as a conscience-prick at the number of animals that are being killed and the environmental impact of a carnivorous diet.

References

[i] Dumesnil JG, Turgeon J, et al. Effect of a low-glycaemic index–low-fat–high protein diet on the atherogenic metabolic risk profile of abdominally obese men. British Journal of Nutrition. Nov 2001;86(5):557-68 

[ii] Farnsworth E, Luscombe ND, et al. Effect of a high-protein, energy-restricted diet on body composition, glycemic control, and lipid concentrations in overweight and obese hyperinsulinemic men and women.

[iii] Torralba KD, De Jesus E, Rachabattula S. The interplay between diet, urate transporters and the risk for gout and hyperuricemia: current and future directions. Int J Rheum Dis. 2012 Dec;15(6):499-506 

[iv] Juraschek SP, Appel LJ, et al. Effect of a high-protein diet on kidney function in healthy adults: results from the OmniHeart trial. Am J Kidney Dis. 2013 Apr;61(4):547-54