Nutritional adequacy of very low- and high-carbohydrate, low saturated fat diets in adults with type 2 diabetes: A secondary analysis of a 2-year randomised controlled trial

Diabetes Res Clin Pract. 2020 Dec:170:108501. doi: 10.1016/j.diabres.2020.108501. Epub 2020 Oct 13.

Abstract

Background: Growing evidence supports use of very low-carbohydrate (LC) diets for glycaemic control in type 2 diabetes. However, limited data on the micronutrient adequacy of LC diets exist.

Objective: This study compared the long-term effects of a very low-carbohydrate, high unsaturated/low saturated fat (LC) diet to a high-carbohydrate, low-fat (HC) diet on micronutrient biomarkers in adults with obesity and type 2 diabetes.

Methods: 115 adults with type 2 diabetes (mean[SD]; BMI:34.6[4.3]kg/m2, age:58[7]yrs, HbA1c:7.3[1.1]%, 56[12]mmol/mol) were randomized to one of two planned, nutritionally-replete, energy-matched, hypocaloric diets (500-1000 kcal/day deficit): (1) LC:14% energy carbohydrate, 28%protein, 58%fat[<10% saturated fat]) or (2) HC:53%carbohydrate, 17%protein, 30%fat [<10%saturated fat]) for 2 years. Nutritional biomarkers- folate, β-carotene, vitamin B12, D, E, copper, zinc, selenium, calcium, magnesium, sodium, potassium, iron, ferritin, transferrin and transferrin saturation were measured in fasting blood at baseline, 24, 52 and 104 weeks.

Results: 61 participants completed the study with similar dropouts in each group (P = 0.40). For all biomarkers assessed, there were no differential response between groups overtime (P ≥ 0.17 time × diet interaction). Mean vitamin and mineral levels remained within normal (laboratory-specific) reference ranges without any reported cases of clinical deficiencies.

Conclusion: In free-living individuals with type 2 diabetes, nutrition biomarkers within normal ranges at baseline did not change significantly after 2 years on a prescribed LC or HC diet. These results demonstrate the feasibility of delivering a nutritionally replete LC diet and the importance of considering nutritional factors in planning LC diets that have strong public health relevance to the dietary management of type 2 diabetes.

Trial registration: http://www.anzctr.org.au/, ANZCTR No. ACTRN12612000369820.

Keywords: Diet; Low-carbohydrate; Nutritional adequacy; Type 2 diabetes; Weight loss.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Carbohydrates / adverse effects*
  • Diabetes Mellitus, Type 2 / diet therapy*
  • Diet, Carbohydrate-Restricted / methods*
  • Diet, Fat-Restricted / methods*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Nutrition Assessment*
  • Time Factors

Substances

  • Carbohydrates