High blood pressure and dietary supplements

Dietary supplements are literally everywhere at least that's what the advertising wants us to believe. We're constantly told we need product X, Y, or Z to stay or become healthy, energetic, young, attractive, or whatever else.

Often, effects on specific illnesses are suggested more implicitly than openly. Even though supplements come in forms that look like medicines capsules, drops, (effervescent) tablets, etc. they are legally classified as foods and must not be marketed as treatments or cures for diseases. Of course, they must also not have harmful effects on health.

Still, advertising copy and product descriptions often imply such effects. But how much truth is there to that? Given our specialty in blood pressure, we've looked into the topic of dietary supplements more closely.

First, ask yourself whether you actually need the supplement. Except for certain risk groups, it's usually unnecessary to add supplements. It's far more important to eat a balanced diet. Trying to make up for an unbalanced diet with supplements is rarely effective.

The risk groups mentioned above can include pregnant women or people with intestinal diseases who have an increased need for certain nutrients or problems absorbing them from food. In those cases, supplementation i.e., targeted addition of nutrients should always be done in consultation with the treating doctor.

Of course there are some supplements that are better researched than others. In general, however, it's noticeable that the effects that can actually be proven almost always fall far short of the marketing promises. This is especially true for new, hyped products that promise a broad range of effects basically anything from hair loss to athlete's foot.

CBD products

As an example, CBD oil (cannabidiol oil) is often mentioned. Although there are now studies, many do not support the advertising claims. Our detailed article on this can be found here:
Does CBD or hemp oil help with high blood pressure?

Ashwagandha

Ashwagandha is another currently popular example. The herb known from Ayurveda, often called the "sleep berry," is said to have strong effects.

If you look more closely, you'll find various studies examining one effect or another. The best-studied areas are sleep and a general stress-reducing effect although even that wording is not very specific.

Looking more closely at individual studies, a critical reader quickly notices their limitations. The studies usually ran over only a short period, and the participants when human subjects were used rather than animals or test tubes were often young and/or healthy.

Often you'll find limiting phrases listed under "limitations," such as "should be studied further." If you look a bit more, you'll also find mentions of possible side effects.

For example, people with cardiovascular disease and those taking blood-thinning medications should consult their doctor before taking ashwagandha.

Potassium

There are a few supplements that are relatively well researched, including their effects on blood pressure. However, desired effects almost always come with unwanted (side) effects. Potassium is an example: it's often promoted as an alternative to regular salt for people with high blood pressure, but it is not suitable for people with kidney disease.

Zinc

Another example is zinc, which is used not only as an ointment for wounds but also as a dietary supplement in connection with blood pressure. There are hints that a zinc deficiency may promote high blood pressure, but the current state of research is not sufficient to recommend zinc as a supplement.

So far, studies have been done in mice and rats and on human vascular tissue samples. They aim to investigate the mechanism of action of zinc to determine whether it could be a target for future vascular-directed medications.

Zinc is usually obtained in sufficient amounts through a balanced diet. On the other hand, overdosing on zinc which is classed among heavy metals can cause poisoning and can impair the body's absorption of copper. Copper deficiency, in turn, can lead to neurological problems and anemia.

Magnesium

The situation is similar with magnesium. There are indications that a deficiency can promote high blood pressure, but this needs to be demonstrated individually. Studies showed an effect of magnesium on blood pressure mainly in people who had an existing magnesium deficiency.

And here, too, there is a risk of overdose with potentially serious consequences. Too much magnesium can lead to paralysis that can affect the breathing muscles and to heart rhythm disturbances up to cardiac arrest.

Therefore, taking supplements should always be discussed with your treating doctor, especially if you are taking any medications. These medications don't have to be prescribed for the same condition interactions can occur with other drugs. That's why it's important, when asked about medication use, to mention not only prescribed medicines but also over-the-counter products and any supplements you take voluntarily.

Supplements as effervescent tablets

You should be particularly careful with supplements that come as effervescent (fizzy) tablets. Because of their often high sodium content they can negatively affect blood pressure. Researchers at the Saarland University Medical Center found this. They looked at both over-the-counter and pharmacy-only effervescent supplement tablets and found that on average they contained 283.9 mg of sodium. The top example was a vitamin C effervescent tablet containing 564.7 mg of sodium which equals 28% of the recommended daily maximum sodium intake. And that's in a single effervescent tablet. People with high blood pressure should therefore include any effervescent tablets they take in their daily salt intake.

Overall, most people can get all the substances they need from food. Overdoses of individual substances are almost impossible with a balanced diet. This contrasts with dietary supplements, where a reference value for an individual's actual need is often missing and the amount of active ingredient listed is as inconsistent as the dosage recommendations.

That makes overdosing easy. People often say the excess will simply be excreted. But that mainly applies to healthy (!) people. People with pre-existing conditions can develop metabolic problems, among other issues. Also, making an already damaged kidney handle the excretion of excess substances puts an additional burden on it and can worsen existing kidney disease. People with high blood pressure should be especially careful here.

Talk to your doctor about whether adding a particular nutrient makes sense and is advisable for you. At best you'll simply waste money; at worst you could harm your health.

This article comes from BloodPressureDB – the leading app since 2011 that helps hundreds of thousands of people monitor their blood pressure every day. Our content is based on carefully researched, evidence-based information and is continuously updated (as of 01/2026).

Author Sabine Croci is a certified medical assistant with many years of experience in internal medicine and cardiology practices as well as in outpatient care. Since 2015 she has led the editorial team at BloodPressureDB. With additional qualifications as a paramedic, first responder, and training in various therapy and emergency areas, she provides well-founded, practical, and reliably reviewed information.