What facilitates the absorption of vitamin D?

From the Guidelines

Vitamin D helps absorb calcium in the body, and adequate levels of vitamin D are essential for maintaining bone density and growth. According to the study published in the Annals of Internal Medicine 1, vitamin D controls calcium absorption in the small intestines and interacts with parathyroid hormone to help maintain calcium homeostasis between the blood and bones. The study also notes that insufficient amounts of vitamin D can lead to impaired dietary calcium absorption, which can weaken existing bones.

Some key points to consider for optimal calcium absorption include:

• Maintaining adequate levels of vitamin D through diet, sun exposure, or supplements
• Ensuring good gut health, as vitamin D is absorbed in the small intestine
• Consuming a balanced diet that includes calcium-rich foods, such as dairy products, leafy greens, and fortified foods
• Being aware of conditions that can impair calcium absorption, such as Crohn's disease, celiac disease, or other digestive disorders

It's also important to note that the Institute of Medicine and the World Health Organization have recommended standards for adequate daily intake of calcium and vitamin D as part of overall health 1. However, the specific recommendations for fracture prevention are still being studied and debated.

In terms of specific dietary recommendations, consuming dietary fats, such as those found in olive oil, avocados, nuts, or fatty fish, can help enhance vitamin D absorption, as vitamin D is fat-soluble and requires fat to be properly dissolved, absorbed, and transported through the bloodstream. Additionally, adequate magnesium levels are also important for vitamin D metabolism, as magnesium is needed for vitamin D to convert to its active form in the body.

From the Research

Factors that Enhance Vitamin D Absorption

• The presence of fat in a meal can significantly enhance the absorption of vitamin D-3 supplements, with a 32% increase in mean peak plasma vitamin D-3 levels compared to fat-free meals 2
• The type of fat, whether monounsaturated or polyunsaturated, does not appear to influence vitamin D-3 absorption 2

Dietary Sources of Vitamin D

• Vitamin D can be found in limited amounts in certain foods, including:
  • Fatty fish (5-25 μg/100 g) 3, 4
  • Mushrooms (21.1-58.7 μg/100 g) 3
  • Reindeer lichen (87 μg/100 g) 3
  • Fish liver oils (250 μg/100 g) 3
  • Egg yolk, and offal such as liver 4
  • Fortified foods like milk, yoghurt, fat spreads, orange juice, breakfast grains, and plant-based beverages 3, 4, 5

Supplementation and Fortification

• Dietary supplements of vitamin D are often recommended to achieve adequate intake, as it can be difficult to obtain sufficient amounts through diet alone 3, 4, 6
• Food fortification with vitamin D is a strategy to increase intake and improve vitamin D status in populations 4, 5