Abeytú Naturals food supplements · UK retailer Free UK mainland delivery on every order / No US customs fees

Customer information

Fasting and electrolytes

Fasting is one of the oldest health practices there is, and one of the most actively researched. Here is what the studies show, how to fast sensibly, and why electrolytes matter.

What the research says

The metabolic switch. Somewhere between about 12 and 36 hours without food, depending on the person and what they last ate, the body shifts from running mainly on glucose to burning fat and producing ketones (Anton et al., Obesity, 2018). A 2019 review in the New England Journal of Medicine by Rafael de Cabo and Mark Mattson of the US National Institute on Aging describes this switch and the research on intermittent fasting in animals and people (de Cabo and Mattson, New England Journal of Medicine, 2019).

Cellular recycling. Autophagy is the process cells use to break down and recycle their own worn-out components. Food restriction is a well-recognised trigger: in mice, short-term fasting markedly increased autophagy even in brain cells (Alirezaei et al., Autophagy, 2010). Measuring autophagy in living people is much harder, so the human picture is still emerging.

Longer fasts under supervision. In an observational study of 1,422 adults at a German fasting clinic, medically supervised Buchinger fasting of 4 to 21 days (200–250 kcal a day, alongside a moderate-intensity lifestyle programme) was well tolerated: adverse effects were reported by fewer than 1%, ketone levels rose and well-being scores improved (Wilhelmi de Toledo et al., PLoS One, 2019). Four of the five authors have, or had, a role at the clinic as director, employee or consultant.

A 2014 review in Cell Metabolism summarises the molecular mechanisms studied in model organisms and people (Longo and Mattson, Cell Metabolism, 2014).

Why electrolytes matter when you fast

Food is where most of us get our sodium, potassium and magnesium. Stop eating and that supply stops too, while the body keeps using and excreting these minerals. That is why careful fasting guidance includes mineral support rather than plain water alone. Common signs of running low are headaches, light-headedness when standing, muscle cramps and fatigue. Any of these is a signal to take electrolytes, eat, or seek advice.

Our partner brand Autophagy Labs makes Fasting Salts for exactly this: 1 g sodium, 500 mg potassium, 100 mg magnesium and 25 mg thiamine per serving, unsweetened and calorie-free. It is between production runs at the moment, and you can join Autophagy Labs’ notify list. Autophagy Labs’ free guide at autophagylabs.co.uk covers daily targets and refeeding in detail.

How to fast sensibly

  1. Start small. A 12- to 16-hour overnight fast (for example 8 pm to noon) is how most people begin. Lengthen it only once that feels easy.
  2. Drink well. Water, plain tea and black coffee keep you hydrated; add electrolytes on any fast longer than a day.
  3. Keep activity gentle. Walking and stretching suit a fasting day; save hard training for when you are eating.
  4. Break it gently. After a longer fast, return to food with small, easily digested meals (soup, eggs, cooked vegetables) before a large meal.
  5. Listen to your body. Stop and eat if you feel faint, confused, have palpitations or feel unwell.

Who should not fast without medical supervision

  • Anyone pregnant, breastfeeding or under 18.
  • Anyone with a history of an eating disorder or who is underweight.
  • Anyone with diabetes, or taking medicines that lower blood sugar or blood pressure, diuretics or other regular prescription medicines.
  • Anyone with kidney, heart or liver disease, gout, or who is frail or recovering from illness.

If any of these apply, or you plan to fast for longer than 24 hours, talk to your GP first.

Fasting and your supplements

Every ingredient in our Abeytú Naturals formulas, including capsule shells and carrier oils, is listed on each product page so you can check it against your own fasting routine. Several are labelled to be taken on an empty stomach, such as Novalytic and Lactoferrin. See our guide to building a daily supplement routine.

References

This guide is general information, not medical advice. Reviewed 19 October 2026. More studies in our research library.

Back to top