Your body's biological clock: when to take what

What is the circadian rhythm?

The circadian rhythm is the body’s internal clock that regulates nearly every physiological process according to the day–night cycle. It’s controlled by a small group of cells in the brain that receive light signals from the eyes and use them to synchronise the body.

Each organ also has its own “local” clock that runs alongside the central rhythm. The liver is more active in processing substances in the morning, the kidneys filter more efficiently in the afternoon, and the gut reaches its highest absorption capacity around midday.

Morning: activation and start‑up

In the morning, cortisol levels rise. This hormone activates the body and kick‑starts metabolism. Digestion begins to wake up, and the liver prepares for a day of processing.

Supplements that fit this start‑up phase:

• B‑Vitamins support energy metabolism and align well with the morning activation of metabolic processes.
• Vitamin C is water‑soluble and generally well tolerated with breakfast. It supports processes that are active during the day.
• Iron is absorbed more efficiently on an empty stomach in the morning; combining it with Vitamin C supports uptake.
• Adaptogens such as Ashwagandha or Rhodiola are sometimes taken in the morning because of their role in daily stress responses, although timing is less strict here.

Midday: peak digestion and absorption

Around midday, digestion reaches its daily peak. The production of digestive enzymes is highest, and the gut is most active in transporting nutrients into the bloodstream.

This peak is also the reason why, in theory, eating the main warm meal at midday makes more sense than in the evening, as is common in the Netherlands. The body can generally process a meal more efficiently at this time. For many people this isn’t practical due to work or school, but even a slightly more substantial lunch and a lighter evening meal already align better with this natural rhythm.

Midday is a suitable moment for:

• Fat‑soluble vitamins (A, D, E, K) because dietary fats from lunch support absorption.
• Calcium, which is better absorbed with a meal than on an empty stomach.
• Multivitamins, which benefit from increased enzymatic activity around midday.

Evening: recovery and preparation for sleep

In the evening, the body shifts toward recovery and repair. Cortisol levels drop, melatonin rises, and muscles and tissues prepare for regeneration during sleep.

Supplements that fit this recovery phase:

• Magnesium supports muscle relaxation and nervous‑system regulation. Taking it in the evening aligns with the body’s declining activity level.
• Zinc plays a role in cell renewal and repair processes that primarily occur at night.
• Vitamin D can intentionally be taken in the evening to avoid possible activating effects during the day.
• Probiotics, taken just before bed or with the evening meal, can be beneficial because gut bacteria can make use of the relatively quiet night‑time period.

What happens at night: liver activity and cell renewal

Night‑time is not a period of rest for the body. The liver actively processes stored substances and produces proteins. Growth hormones involved in muscle and tissue repair reach their daily peak in the first hours of sleep.

This explains why taking certain minerals and amino acids in the evening aligns logically with physiology: the active substances are available at the moment the body uses them most.

Quick overview: morning, midday or evening?

• Morning: B‑Vitamins, Vitamin C, Iron (on an empty stomach), adaptogens
• Midday (with a meal): fat‑soluble vitamins (A, D, E, K), Calcium, multivitamins
• Evening: Magnesium, Zinc, Probiotics, possibly Vitamin D

And when do you take botanicals?

Botanicals follow their own timing logic. Activating herbs such as Ginseng and Rhodiola are best taken early in the day. Calming botanicals such as Valerian and Passionflower belong in the evening routine. Adaptogens such as Ashwagandha can fit either moment, depending on the desired effect.

You don’t need to overhaul your routine to benefit from this. Small shifts — such as moving Magnesium to the evening and B‑Vitamins to the morning — already align more consciously with how your body works.

Do you exercise regularly? Your training time also influences supplement timing. Read more in Timing of sports supplements.

Want to build a supplement routine that fits your day? Get in touch with our specialists for personal advice. Phone: +31 318 64 89 89 · WhatsApp: +31 683 702 040 · Email: info@gezondheidaanhuis.nl