This guide explains what bone broth contains, whether it breaks a fast, how it fits different fasting goals, and which popular health claims hold up. The short answer: bone broth contains calories and protein, so by a strict definition it breaks a fast. Many people still find a cup helpful for comfort and sodium during longer fasts. Whether it makes sense for you depends on why you are fasting.
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What Bone Broth Is
Bone broth is stock made by simmering animal bones (and often connective tissue, vegetables, and herbs) for a long time, typically 8-24 hours or more. A splash of vinegar is often added in the belief that it helps extract minerals. The longer cooking time pulls more gelatin from the bones than a quick stock, which is why good bone broth sets like jelly when chilled.
Calorie and Macro Content
Approximate values per cup (240 ml). These vary a lot by recipe and brand, so check the label on anything you buy:
- Calories: 30-80 (varies widely by recipe)
- Protein: 5-10 g (mostly collagen-derived)
- Fat: 0-5 g
- Sodium: anywhere from very little (unsalted homemade) to several hundred milligrams or more (many commercial products)
- Various minerals: calcium, magnesium, phosphorus in modest amounts
Marketing claims about exceptional nutrient density tend to be overstated. Bone broth contains some minerals, but generally in modest amounts. Its protein is mostly collagen/gelatin, which is rich in glycine and proline but low in some essential amino acids (it lacks tryptophan entirely), so it is not a complete protein source.
Does It Break a Fast?
Strictly: yes. Any calories break a fast by definition, and the protein in broth can cause a small insulin response and provides amino acids that act as a “fed” signal to the body.
Practically: how much it matters depends on what you’re fasting for.
- If your goal is to keep the fast as “clean” as possible (for example, for autophagy-related reasons): treat it as breaking the fast
- For weight management: a cup adds relatively few calories, so the practical impact is usually small
- For comfort during longer fasts: many people find the warmth and sodium worth the small number of calories
By Fasting Goal
Weight loss / metabolic health
One cup of broth during a fast adds roughly 30-80 kcal. For most people that has little effect on their overall weekly calorie balance. If it helps you stick with your schedule, it is a reasonable compromise.
Autophagy
Protein and amino acids are among the signals thought to dampen autophagy, although how much a single cup of broth affects it in humans has not been measured well. If autophagy is your reason for fasting, the conservative choice is to skip broth and use plain water, unsweetened tea or coffee, and calorie-free electrolytes. See autophagy and fasting for what is and isn’t known.
Extended water fasts (3+ days)
Broth is most often used here, mainly for sodium and comfort. Some people who do multi-day fasts have a cup once a day, accepting that it makes the fast less strict. Fasts longer than about 72 hours carry more risk and are best done with medical guidance, especially if you have any health conditions or take medication.
Religious fasting
This depends entirely on the tradition. Some fasting practices allow broth or other liquids, while others exclude all food and drink or specifically exclude animal products. Follow the guidance of your own tradition.
When It’s Most Helpful
- Cold weather - warm savoury liquid is comforting
- Multi-day fasts - sodium plus some comfort
- People who get headaches or feel light-headed on water-only fasts (low sodium is a common contributor)
- Adapting to longer fasts gradually
- As a light starter when breaking a longer fast
DIY vs Store-Bought
DIY bone broth
- Inexpensive (bones are often cheap from butchers, or saved from previous meals)
- Quality control over ingredients
- Long cooking time (8-24+ hours)
- Keeps in the fridge for about 3-5 days and in the freezer for a few months
Store-bought bone broth
- Convenient
- Usually considerably more expensive per cup than homemade
- Quality varies; some are essentially flavoured stock
- Check sodium content - varies widely
Health Claims Examined
Supports collagen production
Unclear. Collagen is broken down into amino acids and small peptides during digestion, and the body then uses amino acids from all protein sources to build its own collagen. Research on collagen supplements is mixed, and bone broth itself contains variable, often small, amounts. Any effect is likely modest.
Gut health (“leaky gut”)
There is little direct evidence in humans. Amino acids such as glycine and glutamine have been studied for gut barrier function, mostly in laboratory and animal research. Claims that broth “heals” the gut go well beyond the evidence.
Joint health
Evidence is limited and mixed. Some people report feeling better, but controlled studies of bone broth specifically are scarce.
Immunity
Warm soup when you are unwell provides fluid, salt, and comfort. Beyond that, evidence that broth meaningfully affects the immune system is weak.
Bone broth is a perfectly good food. Framing it as a superfood with special healing properties is not supported by current evidence.
Frequently Asked Questions
How much bone broth can I have during a fast?
People who allow broth during a fast (sometimes called “dirty fasting”) usually limit it to 1-2 cups a day. The more you have, the more calories and protein you add and the less the day resembles a fast.
Will bone broth kick me out of ketosis?
A cup is unlikely to have a large effect for most people. Larger amounts add more protein, and some of that can be converted to glucose, so ketone levels may drop somewhat. Individual responses vary.
Is bone broth better than electrolyte drinks for fasting?
They do different jobs. Calorie-free electrolytes (salt, potassium, magnesium in water) don’t break a fast; bone broth technically does. Broth offers warmth and flavour that plain electrolytes don’t. Choose based on how strict you want your fast to be.
Can vegans get the same benefits from vegetable broth?
Vegetable broth usually has fewer calories and little protein, which makes it closer to a strict fast. It contains no collagen, but as noted above, the benefits of collagen from broth are uncertain anyway. Salted vegetable broth provides sodium in the same way.
What about bone broth fasts (only broth)?
A “broth fast” is a modified fast, usually 24-72 hours of only broth, water, and tea. Many people find it easier than water-only fasting, but because it contains calories and protein, it is not metabolically the same as a water fast. The same safety cautions apply as for any extended fast.
Is the sodium in bone broth a concern?
During a fast, some sodium is often helpful because the body excretes more of it when not eating. However, if you have high blood pressure, heart failure, kidney disease, or have been told to limit salt, check with your doctor before adding salty broth or electrolytes.
The Bottom Line
Bone broth technically breaks a fast, but a cup adds relatively few calories and can make longer fasts more comfortable. If your goal is weight management, 1-2 cups on fasting days is a reasonable compromise for many people. If you want the strictest possible fast, stick to water, plain tea or coffee, and calorie-free electrolytes. The popular health claims are overstated: broth is a good food, not a remedy. Homemade is cheaper if you use it often; if you buy it, check the sodium content.