Table 4 Lifestyle modification and impact on blood pressure

Salt intake

The evidence base for the benefit of salt restriction in type 1 diabetes without advanced CKD is not strong. Reduced blood pressure has been found in some but not all short-term studies, but an important long-term observational study recorded higher dietary sodium intake was associated with higher all-cause mortality and the development of ESKD [115, 116]. The KDIGO guidelines suggest lowering salt intake to < 90 mmol of sodium per day (< 2 g of sodium, which corresponds to 5 g of sodium chloride) [23]. High salt intake has a greater impact on blood pressure for people with diabetes, especially in those with CKD, due to their reduced ability to excrete salt load in their urine. Restricting salt intake lowers blood pressure by a moderate amount, as shown in a systemic review of seven trials where salt intake was restricted to 4–6 g (70–100 mmol), systolic blood pressure was reduced by 4.7 mmHg and diastolic blood pressure was reduced by 2.5 mmHg [117].

Given that salt restriction is inexpensive and it helps to lower blood pressure in the general population, despite a lack of availability of large-scale, long-term randomised controlled trials of salt restriction in people with CKD, there is no reason to believe that it would not be beneficial, although it would add to the dietary restrictions for managing diabetes. A low-salt diet has been shown to reduce blood pressure and albuminuria in the short term in people who are on angiotensin receptor blockers (ARBs) and it may be a consideration for those with high blood pressure who have had a poor response to ACEIs or ARBs [118, 119].

Weight and BMI

Although abdominal obesity has been associated with higher blood pressure and use of antihypertensive therapy in type 1 diabetes [120], there is a dearth of evidence that weight reduction in type 1 diabetes reduces blood pressure, although this would be expected intuitively [121]. There is evidence of weight gain accompanied by increases in blood pressure in type 1 diabetes as a consequence of improved blood glucose control. The KDIGO guidelines recommend achieving or maintaining a healthy weight (BMI 20–25) [23]. Some observational studies, but not randomised trials, suggest that weight loss is likely to improve blood pressure in people with CKD, but there is a lack of high-quality randomised controlled trials in this area.

Although obesity has been proposed to be a potential mediator of CKD progression, trials are conflicting and reliable data remain sparse. There is no role of weight loss diets in CKD either. Overall, achieving a healthy body weight will improve blood pressure levels and prognosis in CKD, particularly in the early stages (stages 1–2). Malnutrition needs to be avoided in more advanced stages of CKD [122].

Exercise programme

There is documentation that exercise training for 12 weeks or more reduces blood pressure in type 1 diabetes [123]. The KDIGO guidelines recommend undertaking an exercise programme that is compatible with cardiovascular health and tolerance, aiming for at least 30 min of exercise five times per week [23]. Increased physical exercise has a broad range of positive health outcomes in the general population. However, there are no randomised controlled trials in the CKD population: there are mostly observation studies. The benefits of exercise on blood pressure and on general health are likely to be similar in the CKD population as they are in the general population [124].

Alcohol intake

Evidence that alcohol intake affects blood pressure and reduction in intake helps blood pressure in type 1 diabetes is sparse. The KDIGO guidelines suggest limiting alcohol intake to no more than two standard drinks per day for men and no more than one standard drink per day for women [23]. Most of the effects of alcohol reduction are related to its effect on blood pressure; that is, suggesting that restricting alcohol intake would lower blood pressure. All the trial evidence is mostly related to the general population and there are no specific data on people with CKD, but the effects of alcohol intake on blood pressure are expected to be similar [125].