For many people who monitor their blood pressure, taking a vitamin D supplement seems like a simple way to lower it. Studies show that vitamin D deficiency is associated with a higher risk of hypertension.
Known for its role in bone health and the proper functioning of the immune system, this vitamin is also intriguing for its effects on the heart and blood vessels. But one question often comes up: what is really happening on the blood pressure monitor?
The scientific data generally comes to the same conclusion. Vitamin D supplements only lower blood pressure to a limited extent.
A meta-analysis published in 2022 observed an average drop of approximately 0.7 mmHg for systolic pressure and 0.7 mmHg for diastolic pressure. For most people, such an effect remains almost imperceptible in everyday life.
Vitamin D and blood pressure: what the studies show
Studies show a link between low vitamin D levels and higher blood pressure.
On the other hand, when vitamin D is taken in supplement form, the results are much less marked. The 2022 meta-analysis found an average drop of less than 1 mmHg, an effect considered clinically very small.
The HAS emphasizes, however, that certain hypertensive or diabetic patients who received between 200 and 3,500 IU per day recorded a drop in systolic pressure of between 2.5 and 6.2 mmHg. However, the results vary greatly from one study to another.
Verywell Health summarizes this situation by reminding that the hypotensive effect is “not guaranteed”.
What happens in the body after taking a supplement?
After ingestion, vitamin D is absorbed in the intestine. It is then transformed by the liver and then by the kidneys into active forms. This mechanism does not act immediately.
It often takes several days or even weeks before the blood level stabilizes.
Once activated, vitamin D acts in particular on the renin-angiotensin-aldosterone system, which participates in the regulation of blood pressure. It also affects blood vessels and calcium metabolism. These effects could promote slight dilation of the vessels and improve the flexibility of the arteries. This can contribute to a slight drop in blood pressure.
In practice, the effects depend above all on the profile of each person. In people who already have good vitamin D levels and normal blood pressure, clinical trials generally show no noticeable changes.
Even in people who are hypertensive but not deficient, major scientific reviews do not demonstrate a clear benefit on blood pressure.
However, some studies suggest that elderly, overweight and vitamin D deficient people could observe a slight drop of a few millimeters of mercury after supplementation.
What doses of vitamin D and what precautions?
According to Verywell Health, recommended intakes for adults are generally between 600 and 800 IU per day, depending on age. Without medical advice, it is not recommended to exceed 4,000 IU per day.
Doses that are too high can cause hypercalcemia, that is, excess calcium in the blood. This can lead to significant fatigue, heart rhythm disturbances or even kidney problems.
The Cleveland Clinic also reminds that vitamin D should not be used as a treatment for high blood pressure.
Correcting a deficiency remains important for health. On the other hand, current data show that its direct effect on blood pressure is limited and varies between people.