Fasting and Kidney Health: Bright's Disease and Modern Kidney Research

Kidney disease is one of the most feared chronic conditions — and historically, one of the most poorly understood. In Upton Sinclair's 1911 book The Fasting Cure, kidney disease appeared in the list of conditions that fasting was reported to help. The term used at the time was "Bright's disease," a broad Victorian-era label that covered what we would now call nephritis, chronic kidney disease, and related conditions. Over a century later, modern research has begun examining whether fasting holds any benefit for kidney function — and the picture that emerges is both cautious and genuinely interesting.

Historical Context: What Was Bright's Disease?

Richard Bright was a British physician who first described the condition in 1827 — describing patients with protein in the urine, oedema (fluid retention), and kidney damage visible at autopsy. For the rest of the 19th century and into the early 20th century, "Bright's disease" was used loosely to describe any chronic kidney disorder that didn't have another obvious cause.

In Sinclair's 1911 survey of 277 fasting cases collected from readers, Bright's disease appeared among the conditions that fasters reported benefit from. Sinclair framed this within his theory of autointoxication: that fermentation and toxic waste products from overeating clogged the organs of elimination — including the kidneys — and that a complete fast allowed those organs to rest, clear accumulated waste, and begin repairing themselves.

Sinclair wrote: "The fasting cure is Nature's own remedy for all other diseases." He did not claim it cured kidney disease outright, but he documented cases where patients reported improvement in symptoms after fasting, including reduction in oedema and improved urine output.

What Sinclair Observed

From Sinclair's compilation of reader reports and from references in the broader physical culture movement of his era, several patterns emerged:

Fluid retention (dropsy) appeared to respond. Several cases in Sinclair's records involved patients with significant oedema — swollen legs, fluid in the abdomen — who reported marked improvement after extended fasts. Sinclair explained this as the kidneys and lymphatic system clearing accumulated fluid once the burden of digestion was removed.

Urine changes during fasting were noted. Fasters reported changes in urine colour, odour, and volume — particularly in the first few days. Sinclair interpreted this as evidence of the kidneys actively clearing waste products. This aligns with what we now understand as the excretion of metabolic by-products during ketosis.

Mental clarity and reduced symptoms. Patients with chronic conditions including kidney-related fatigue reported improved energy and alertness during fasts — consistent with what modern science would attribute to reduced inflammatory load and metabolic repair.

It is essential to note that Sinclair's evidence was entirely anecdotal, collected from self-reporting readers, with no clinical controls, no laboratory confirmation of kidney function, and no follow-up data. These are historical observations from 1911, not clinical trials.

Connection to Modern Research

Modern understanding of the kidneys and fasting is still developing. A few key findings from recent research are worth noting:

Fasting reduces inflammation. Chronic kidney disease is driven significantly by inflammation — and multiple studies have shown intermittent fasting reduces key inflammatory markers including CRP, TNF-α, and IL-6. Since inflammation is a primary driver of kidney damage, this is biologically relevant.

Fasting improves blood sugar and blood pressure control. High blood sugar (diabetes) and high blood pressure are the two leading causes of kidney disease worldwide. Clinical trials have shown intermittent fasting significantly reduces both — which, over time, reduces the metabolic stress placed on the kidneys. A 2020 study in Cell Metabolism found that 10-hour time-restricted eating significantly reduced blood pressure in patients with metabolic syndrome, which is directly relevant to kidney health.

Ketone bodies may protect kidney tissue. There is emerging laboratory evidence that ketones — produced during fasting — may have a protective effect on kidney cells by reducing oxidative stress and inflammation. This research is still largely preclinical, but the mechanistic basis is biologically plausible.

Autophagy and cellular repair. One of fasting's most studied mechanisms is autophagy — the cellular process of cleaning out damaged proteins and organelles. Kidney tubular cells have been shown in laboratory studies to benefit from autophagy activation. Whether fasting-induced autophagy benefits human kidneys clinically remains under investigation.

What This Means for People with Kidney Concerns

This is an area where caution is particularly important. Unlike many other conditions where fasting has a clear and well-studied benefit, kidney disease requires individual assessment:

• People with established chronic kidney disease (CKD) have specific restrictions on protein and electrolytes that must be managed carefully. Fasting affects all of these.
• Fasting causes changes in urine concentration, electrolyte balance, and creatinine clearance that can affect how kidney function is measured and managed.
• People on dialysis or with severe kidney impairment should not fast without close medical supervision.
• For people without existing kidney disease, the long-term metabolic benefits of fasting — reduced blood sugar, blood pressure, and inflammation — may well support kidney health over time.

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Frequently Asked Questions

Did fasting help Bright's disease according to historical records?

Upton Sinclair's 1911 survey documented self-reported improvements in patients with Bright's disease after fasting. These were anecdotal reports without clinical controls — but they are consistent with what we now understand about fasting's effects on inflammation and metabolic health.

Can intermittent fasting damage the kidneys?

In healthy people without pre-existing kidney conditions, there is no evidence that intermittent fasting damages the kidneys. For people with existing kidney disease, fasting requires careful medical oversight due to protein, electrolyte, and hydration concerns.

Why did early fasters report improved fluid retention?

Sinclair and others observed that extended fasting appeared to reduce oedema (fluid retention). Modern understanding suggests this is partly due to reduced insulin levels (insulin causes sodium and water retention), caloric restriction, and possible improvement in kidney filtration capacity.

Does fasting affect creatinine levels?

Fasting can temporarily alter serum creatinine levels, which are used to assess kidney function. This does not necessarily reflect kidney damage — it may simply reflect changes in muscle breakdown or hydration status. People with kidney disease should have their function monitored regularly if fasting.

Is it safe to fast if you have kidney stones?

Fasting increases urine concentration, which can raise the risk of stone formation in susceptible individuals. Staying very well hydrated during any fast is essential. People with a history of kidney stones should discuss fasting protocols with their doctor before starting.

Related Articles

• What is autophagy and when does it start during fasting?
• Can intermittent fasting improve gut health?
• Does intermittent fasting reduce inflammation?

This article draws on historical research from 1911 and is for informational purposes only — not medical advice. Always consult a qualified healthcare professional before making any dietary changes.

Sinclair, U. (1911). The Fasting Cure. Mitchell Kennerley.