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Kidneys – often forgotten yet so important

Microcirculation and Kidney Care

Each kidney contains more blood vessels than any other organ of the body. The blood vessels supply two different types of microcirculation in the cortex (glomerular) and in the medulla (peritubular), each with different functions. This microcirculation plays a major role in the oxygen supply to the kidney and ensures plasma filtration, electrolyte exchange and water reabsorption.1

The endothelium is the single layer of cells that line all blood vessels, and forms the interface between the circulating blood and underlying tissue.2 Abnormal functioning of the endothelium can lead to reduced renal function and eventually kidney disease.3 Many factors affect the microcirculation of the kidney. Good circulation is fundamental to the glomerular filtration rate and affects renal sodium handling in the tubules.1

The glomerular filtration rate is shown on regular blood tests as eGFR and the rate should ideally be >90 ml/min.  The glomerulus is a part of the kidney that contains the very fine tubules that filter the plasma (blood) removing waste for excretion but also balancing mineral levels and regulating blood pressure. Clinically, the glomerulus is considered to be the most important part of the kidney mainly because most of the disorders that affect the kidney involve the glomerulus.

Over time the kidney shows an age-associated reduction of function, such as a decline in glomerular filtration rate and renal blood flow, which is possibly driven by several factors. This can increase the susceptibility of the ageing kidney to injury.3 One in three Australians have an increased risk of kidney disease. There are many risk factors for developing kidney disease, including smoking, obesity, age (being 60 years or older), and dehydration but there are two groups of people who have a higher risk: people with diabetes and those with high blood pressure.5 

Supporting kidney health is an important preventative health goal, and ensuring good microcirculation facilitates this.

Supporting Microcirculation of the Kidney

As oxidation remains one of the main factors influencing microcirculation and kidney health, the importance of consuming sufficient fruit and vegetables daily is again highlighted. A cohort study of 948 elderly women conducted in Australia over five years found that increased consumption of dietary proanthocyanidins was associated with better renal function and substantially reduced renal disease-associated events. The mean total proanthocyanidin intake was 215 mg/day. Over 50% of total proanthocyanidin intake came from fruit (89 mg/day). Those who consumed at least 141 mg/day of proanthocyanidins, had lower cystatin C serum levels (which provides an early indication of renal dysfunction), compared to those with lower intakes. Participants consuming the highest amount of proanthocyanidins (at least 229 mg/day) were at 65% lower risk of experiencing a five-year renal event, compared to those with the lowest intake (less than 141 mg/day).6

Resveratrol improves microcirculation and also protects the kidney. For example, pretreatment with a modest oral dose of resveratrol protected against kidney injury caused by ischaemia/reperfusion in rats. There was a marked reduction in kidney dysfunction and tissue changes and the kidney antioxidant enzyme levels were restored. These effects were due to resveratrol increasing the release of nitric oxide, a natural dilator of blood vessels.7 The dose (5 mg/kg) corresponds to about 57 mg/day in a 70-kg human.

Other natural substances that improve microcirculation may also be of benefit. For example, Green Tea has been shown to significantly increase skin microcirculation, in an uncontrolled study involving 15 young and 15 older volunteers. Two cups of Green Tea were consumed daily, each made using a teabag containing 2.5 g of leaf, for 14 days.8 In vitro testing found EGCG, a major catechin in Green Tea, induced vasodilation in endothelial cells by rapid activation of eNOS, the endothelial isoform of nitric oxide synthase.9 In another study, Grape Seed Extract (150 mg/day extract, providing 136.5 mg/day of OPCs) administered to borderline hypertensive patients, significantly improved microcirculation measured in the foot, after 8 weeks.10

Diet rich in plant foods

A daily intake of 600 grams of non-starchy vegetables and fruit, preferably organically grown (but at least unsprayed) has been shown to provide optimal levels of antioxidants. The colourful plant foods are a rich source of polyphenols which  improved the formation of vasodilative NO, as measured by the increase in S-nitrosoglutathione in the plasma.11

Incorporating fresh herbs in your daily diet can also provide antioxidant support.  Some of these include turmeric, ginger,12,13 with parsley being particularly beneficial for kidney function.

While many polyphenols have been tested in vitro (in the laboratory) their protective action in the body is limited.  The highest protection and support for kidney health can be achieved by:

  • ensuring that you drink enough purified water daily – recommended total fluid intake is 40ml/kg body weight.
  • avoid or limit caffeine – coffee, tea (non herbal), energy drinks
  • avoid soft drinks
  • avoid smoking
  • limit alcohol intake
  • avoid refined and processed foods, especially those high in sugar – cakes, sweets, pastries
  • maintain healthy body weight

Consult a qualified Naturopath for assessment of your needs and quality supplements, herbal and/or homeopathic remedies.  It is important to keep your kidneys functioning optimally as once that function is compromised, it can be very difficult (and sometimes not possible) to repair.

References

  1. Guerci P, Ergin B, Ince C. The macro- and microcirculation of the kidney. Best Pract Res Clin Anaesthesiol. 2017 Sep;31(3):315-29.
  2. Aird WC. Spatial and temporal dynamics of the endothelium. J Thromb Haemost. 2005 Jul;3(7):1392-406.
  3. Chade AR. Small vessels, big role: renal microcirculation and progression of renal injury. Hypertension. 2017 Apr;69(4):551-63.
  4. Di Pietro N, Baldassarre MP, Cichelli A, Pandolfi A, Formoso G, Pipino C. Role of polyphenols and carotenoids in endothelial dysfunction: an overview from classic to innovative biomarkers. Oxi Med Cell Longev. 2020 Oct 19;2020:6381380.
  5. Kidney Health Australia [Internet]. South Melbourne; [cited 2023 Mar 29]. Available from: https://kidney.org.au/your-kidneys/know-your-kidneys/know-the-risk-factors
  6. Ivey KL, Lewis JR, Lim WH, Lim EM, Hodgson JM, Prince RL. Associations of proanthocyanidin intake with renal function and clinical outcomes in elderly women. PloS one. 2013 Aug 5;8(8):e71166.
  7. Chander V, Chopra K. Protective effect of nitric oxide pathway in resveratrol renal ischemia-reperfusion injury in rats. Arch Med Res. 2006 Jan;37(1):19-26.
  8. Wasilewski R, Ubara EO, Klonizakis M. Assessing the effects of a short-term green tea intervention in skin microvascular function and oxygen tension in older and younger adults. Microvasc Res. 2016 Sep 1;107:65-71.
  9. Lorenz M, Wessler S, Follmann E, Michaelis W, Düsterhöft T, Baumann G, et al. A constituent of green tea, epigallocatechin-3-gallate, activates endothelial nitric oxide synthase by a phosphatidylinositol-3-OH-kinase-, cAMP-dependent protein kinase-, and Akt-dependent pathway and leads to endothelial-dependent vasorelaxation. J Biol Chem. 2004 Feb 13;279(7):6190-5.
  10. Belcaro G, Ledda A, Hu S, Cesarone MR, Feragalli B, Dugall M. Grape seed procyanidins in pre-and mild hypertension: a registry study. Evid Based Complement Alternat Med. 2013;2013:313142.
  11. Taubert D, Roesen R, Lehmann C, Jung N, Schömig E. Effects of low habitual cocoa intake on blood pressure and bioactive nitric oxide: a randomized controlled trial. Jama. 2007 Jul 4;298(1):49-60.
  12. Boonla O, Kukongviriyapan U, Pakdeechote P, Kukongviriyapan V, Pannangpetch P, Prachaney P, et al. Curcumin improves endothelial dysfunction and vascular remodeling in 2K-1C hypertensive rats by raising nitric oxide availability and reducing oxidative stress. Nitric Oxide. 2014 Nov 15;42:44-53.
  13. Kukongviriyapan U, Pannangpetch P, Kukongviriyapan V, Donpunha W, Sompamit K, Surawattanawan P. Curcumin protects against cadmium-induced vascular dysfunction, hypertension and tissue cadmium accumulation in mice. Nutrients. 2014 Mar 21;6(3):1194-208.
  14. Edirisinghe I, Burton-Freeman B, Tissa Kappagoda C. Mechanism of the endothelium-dependent relaxation evoked by a grape seed extract. Clin Sci. 2008 Feb 1;114(4):331-7.
  15. Xia N, Förstermann U, Li H. Resveratrol and endothelial nitric oxide. Molecules. 2014 Oct 9;19(10):16102-21