Vitamin D3 & K2: Die unterschätzte Kombination

Vitamin D3 & K2: The Underrated Combination

Energy & Cell Health · approx. 7 min. reading time

Vitamin D is probably the most discussed micronutrient in Germany – and for good reason: between October and March, solar radiation in this country is usually not sufficient to produce enough of it naturally. What is often overlooked in the discussion: with Vitamin D, it's not so much the sheer quantity that matters, but the correct intake.

What happens in the body

Most Vitamin D is formed in the skin under UV-B radiation, not through food. As a fat-soluble vitamin, it needs fat to be absorbed at all – a detail that explains why the form of intake is often more important than the dose on the label.

Timing and intake: the crucial point

Always take with a fatty meal – never on an empty stomach. This is the most important practical advice of all: Since Vitamin D is fat-soluble, it is absorbed significantly less well without fat in the meal. A breakfast with butter, avocado, nuts, or eggs is already sufficient. Anyone who takes Vitamin D drops on an empty stomach in the morning with a glass of water wastes part of the absorption.

  • Time of day: Unlike melatonin, the time of day itself plays hardly any role – the decisive factor is the combination with a fatty meal, whether in the morning or in the evening.
  • Regularity over exception: Since Vitamin D is stored in fatty tissue, a daily, consistent intake is more sensible than sporadically high single doses.

Why K2 belongs with it

Vitamin D increases the absorption of calcium from the intestine – that is undisputed. Vitamin K2 is needed to activate proteins that bring precisely this calcium to the right place: into the bones instead of the vessel walls. If you take a lot of Vitamin D without enough K2, this second building block in the same metabolic pathway is missing – which is why the combination makes more physiological sense than Vitamin D alone.

There is a relevant difference in the K2 form: MK-7 has a significantly longer half-life in the blood than the shorter-acting MK-4, which results in a more even level throughout the day instead of a short peak.

How to best absorb the combination

  • In an oily carrier form (e.g., MCT oil) instead of as a pure powder – this further supports absorption, as the vitamin is already present in a fat-based solution.
  • One drop, a fixed routine – e.g., always with breakfast coffee with milk or plant-based drink, instead of irregularly, sometimes in the morning, sometimes at noon.
  • Do not take concurrently with very high-dose calcium supplements if you already consume plenty of calcium through dairy products – normal diet is usually sufficient here.

What else supports the effect

  • Regularly get fresh air, even in winter – even diffuse daylight supports the rhythm, even if the UV-B radiation is often not sufficient for it.
  • Keep an eye on magnesium. Magnesium is needed as a cofactor to convert Vitamin D into its active form in the body at all – with a simultaneous magnesium deficiency, Vitamin D can unfold its effect less well.
  • Do not completely avoid fatty meals, especially when supplementing Vitamin D – a consistently very low-fat diet measurably slows down absorption.

For athletes: Muscle function and bone resilience

Vitamin D is needed for muscles to function normally – relevant for all forms of training, not just competitive sports. Especially in indoor sports and winter sports, where sun exposure is already low, Vitamin D deficiency is more common. A review of Vitamin D in athletes describes both the connection with muscle function and with bone resilience – a low Vitamin D level is associated with a higher risk of stress-related bone and muscle injuries (PubMed 34315203). For Vitamin K2, its role in calcium utilization in the bone is added – relevant for anyone who regularly stresses their bones.

For women during and after menopause

With a decreasing estrogen level, the decline in bone density also accelerates – one reason why calcium and Vitamin D supply are particularly in focus during this phase of life. This is exactly where the study on Vitamin K2 (MK-7) mentioned above comes in: It was specifically conducted on healthy postmenopausal women and found an improvement in arterial stiffness compared to placebo after several years of intake – a collective that is usually overlooked in marketing around Vitamin D, even though the evidence here is comparatively good.

How much is realistic?

The actually appropriate amount depends on the baseline value, body weight, skin tone, and sun exposure. Anyone who suspects a real deficiency should ideally have their 25-OH-Vitamin D level determined in the blood, instead of dosing high on a whim – consistently very high amounts over a longer period without medical supervision can lead to an increase in blood calcium levels.

Good to know

Anyone taking blood-thinning medications (Vitamin K antagonists) should definitely discuss additional Vitamin K intake with their treating physician beforehand.

Also suitable

medi Vitamin D3 & K2 Drops provides 25 µg (1,000 IU) of Vitamin D3 and 20 µg of Vitamin K2 as MK-7 per drop, dissolved in MCT oil – i.e., already in the fat-based carrier form described in the text.

Sources

  • Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women, Thrombosis and Haemostasis (2015). PubMed
  • Effects of One-Year Menaquinone-7 Supplementation on Vascular Stiffness and Blood Pressure in Post-Menopausal Women. PMC
  • Studies on the Synergistic Interplay of Vitamin D and K for Improving Bone and Cardiovascular Health, Current Research in Nutrition and Food Science Journal. foodandnutritionjournal.org
  • Vitamin D in athletes: focus on physical performance and musculoskeletal injuries. PubMed 34315203

This article is for general information purposes and does not replace individual medical advice. An actual deficiency should be medically clarified by a blood test.

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