Fasting Q&A with Dr Jason Fung: Iron Deficiency, High Histamine Levels, Dry Fasting, Mitophagy, Benefits of Vinegar, and More
Jan 28, 2025
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Dr. Jason Fung, an expert in intermittent fasting, tackles various community queries. He dives into the implications of iron deficiency during fasting and whether supplements should be taken. The conversation also covers high histamine levels and the potential benefits of longer fasting durations. He addresses unique sensations some experience during weight loss, including tingling, and shares insights on dry fasting. Plus, he clarifies ketone levels for safe fasting and discusses the effects of vinegar on blood sugar control. A wealth of practical advice awaits!
Fasting may influence iron levels, necessitating a careful evaluation of protein intake and how iron supplements are administered for optimal absorption.
The connection between fasting and histamine levels suggests potential symptom relief during prolonged fasting, but the exact underlying mechanisms are not fully understood.
Deep dives
Iron Deficiency and Fasting
Fasting can influence nutritional intake, leading to concerns such as iron deficiency, but it is not typically a direct cause. The individual discussed in the episode was surprised to discover she had early stage iron deficiency despite typically consuming meat and other iron-rich foods. Dr. Fung advised her to evaluate her protein intake, particularly noting that limiting protein could exacerbate the issue. Additionally, he emphasized the importance of supplementing iron correctly, such as taking it with vitamin C to enhance absorption while being mindful of foods that may inhibit iron uptake, like certain nuts.
Fasting and Histamine Reactions
There is an emerging interest in the relationship between fasting and histamine levels, with some individuals reporting reduced allergic reactions during extended fasts. Although Dr. Fung noted that the research on this topic is limited, anecdotal evidence suggests fasting may help alleviate symptoms related to high histamine levels. He speculated that fasting might help calm inflammation, a key factor in histamine sensitivity, and acknowledged that while the exact mechanisms aren't well understood, any positive effects experienced by individuals should be recognized as valid. Ultimately, if fasting seems beneficial for managing histamine reactions, it may be worthwhile to continue this practice.
The Sensation of Weight Loss
Many individuals report a unique sensation during weight loss, often described as a tingling feeling in areas like the thighs and glutes. This phenomenon is connected to the biochemical process of lipolysis, where fat cells break down and release fatty acids, causing changes in local blood flow and nerve signaling. Dr. Fung confirmed that this sensation is real and reflects physical changes within the body as it loses fat. While there isn't a specific medical term for this sensation, it represents the body's response to fat cell degradation and the accompanying hormonal fluctuations.
Dry Fasting Considerations
Dry fasting, which involves abstaining from both food and water, can be manageable for short periods but requires caution to avoid dehydration. Dr. Fung shared his personal experiences, noting that he found dry fasting easier than expected, with his body still maintaining urination during the process. He also pointed out that glycogen breakdown during fasting releases some water, which can sometimes make dry fasting feasible for a limited time. Nevertheless, he advised that it is generally safe to attempt dry fasting for up to 24 hours, especially in contexts like Ramadan, but longer durations should involve water intake to prevent health risks.
In this Fasting Q&A episode, hosted by Coach Lisa Chance, Dr. Jason Fung answers questions from the TFM Community:
I’ve been fasting for six months and was surprised to discover on my annual screening that I am in the early stages of iron deficiency. I am post-menopausal, typically eat red meat twice a week, and fast twice a week. I have been restricting my protein intake but have been taking iron supplements. Should I take iron supplements when I am fasting and are there other things I should consider with fasting as a way of life? [02:03]
I recently found out I have high histamine, either from diet and/or not being able to process it. I was wondering if longer fasts, say over 24 hours, would help to get rid of high histamine and settle my body down? [05:37]
I can physically feel when I am losing weight. I feel a mild tingling on the back of my thighs and glutes. It doesn’t really bother me and I look forward to the sensation as I know I am headed in the right direction. Is there a name for this sensation and is it a cellular, biochemical function? I like to think of it as fat cells dissolving! [09:41]
What are your thoughts on dry fasting? [12:58]
What is the allowable ketone level while fasting for two to three days (on a strict ketogenic/carnivore diet), and at what level should you break your fast? [15:36]
If you have a lot of weight to lose and a lot of extra skin, how much dietary protein do you *really* need to eat during your meals? Don’t you want your body to scavenge that extra protein? Does it make a difference to fast with water, salt, and magnesium only, as opposed to using fasting aids such as bone broth? [17:47]
How does fasting affect blood circulation? [20:16]
Please can you explain the difference between autophagy and chaperone autophagy? [21:30]
Can you please explain what is happening when you take vinegar to reduce the impact of blood sugar spikes after eating? [23:02]
I don’t seem to be able to get beyond 50 hours when doing longer fasts. Is there a reason for this or is it just that 50 hours is my sweet spot when it comes to fasting? [27:43]
Please note that you need to be a member of the TFM Community to submit questions to the Q&A webinars with Dr. Fung but you can submit questions to our regular Q&A episodes here: https://bit.ly/TFMPodcastQs
This podcast is for educational purposes only and is not a substitute for professional care by a doctor or other qualified medical professional. You should always speak with your physician or other healthcare professional before doing any fasting, changing your diet, taking or adjusting any medication or supplements, or adopting any treatment for a health problem. The use of any other products or services purchased by you as a result of this podcast does not create a healthcare provider-patient relationship between you and any of the experts affiliated with this podcast. Information and statements regarding dietary supplements have not been evaluated by the Food and Drug Administration and are not intended to diagnose, treat, cure, or prevent any disease.
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