There is still debate about which vitamin D blood levels produce benefits. The very latest evidence suggests that circulating levels in excess of 50 nmol/L, or even 75 nmol/L, may be optimal for overall health. Those below 30 nmol/L, on the other hand, are associated with adverse effects on health.

Achieving a blood concentration of 75 nmol/L often requires supplementation with at least 2000IU a day. In the same vein, taking 3000IU a day for eight weeks has been shown to result in a concentration of more than 75 nmol/L of 25(OH)D (19-20).

In 2010, more than 40 international scientists called for greater awareness among doctors of the importance of vitamin D in preventing osteoporosis and cardiovascular disease. They recommended that the entire Western population (living at middle latitudes) should supplement with 1000-2000IU, especially from October to March.

What about dietary intake?

There are very few sources of vitamin D in the diet. They are mainly restricted to animal-sourced fats, particularly those from oily fish, and fortified foods such as dairy products, and some vegetable oils and plant-based drinks.

According to the French SUVIMAX study, the diet may only provide an average of 136IU of vitamin D a day. It is thus the body’s endogenous production from UV-B which is primarily responsible for circulating levels.

Magnesium passes between intestinal cells in the small intestine (8). Absorption begins around an hour after the supplement is ingested, and continues for almost six hours (9). Magnesium malate is a highly-bioavailable form of magnesium, though other factors can affect how well it is absorbed.

It’s best to take the supplement with a meal high in protein and fibre in order to optimise this phase of intestinal absorption. Food slows down transit which increases the amount of time the magnesium is exposed to intestinal cells. Protein increases its solubility and prevents the formation of calcium-magnesium complexes which impair absorption. And fibre helps to produce short-chain fatty acids and reduce intestinal acidity, two factors which improve magnesium’s transport to the bloodstream.

Conversely, there are three factors to avoid:

1. Taking another mineral supplement at the same time. Other minerals reduce magnesium’s absorption capacity (10-11).
2. Including spinach or cabbage in the meal. These vegetables contain oxalic acid, a chelator which reduces magnesium absorption.
3. Taking several capsules in one dose. The higher the amount of magnesium, the less well it’s absorbed (12). It’s therefore best to take a maximum of one tablet per meal.

These recommendations are important as intestinal absorption declines with age.

Follow the doses recommended: excess magnesium is associated with adverse side-effects in the gut. In addition, taking a magnesium supplement may reduce the absorption of antibiotics and some osteoporosis medications.
Those suffering from kidney disease should only take this supplement under medical supervision.

Vitamin D3 5000 UI is an exceptional supplement that you can choose to buy for at least three main advantages:

1. It contains vitamin D3, which is more effective than the vitamin D2 form found in plant-sourced products (23). The two forms were long thought to be equivalent but recent trials have shown this is not the case.
2. It offers a powerful dose of 5000IU per supplement. It is designed to be taken every day (in which case it’s best to check your 25-hydroxyvitamin D status), twice-weekly, or weekly. Several studies have confirmed supplementation with 1000-10,000IU a day to be effective (24-27).
3. It comes in the form of softgels and contains sunflower oil to maximise the absorption of the vitamin D. Comparative studies have shown that this form is better absorbed than the dry form and that it produced a more significant increase in 25(OH)D levels.