Oxidative stress can disrupt the regulation of blood vessels and thereby contribute to the development and consequences of high blood pressure. The vasodilator nitric oxide, or NO for short, plays a key role in this process.
What are free radicals?
Many normal metabolic processes produce reactive oxygen species. Some of these are known as free radicals. In small amounts, they are by no means solely harmful: the body uses them, among other things, as signaling molecules and to defend against pathogens.
At the same time, the body has various protective systems that keep these reactive compounds under control. However, if more of them are continuously produced than the body can compensate for, this balance is disrupted. This is known as oxidative stress.
Why is nitric oxide so important for blood vessels?
The inner lining of the blood vessels, known as the endothelium, plays a crucial role. It produces nitric oxide – NO for short. This signaling molecule causes the muscles in the vessel wall to relax. This allows the vessel to widen, blood to flow through it more easily, and blood pressure to be regulated more effectively.
Certain reactive oxygen compounds can scavenge NO or impair its formation. This means that less of it is available. The blood vessels lose some of their ability to relax, and resistance in the vascular system may increase.
Oxidative stress can also:
- promote inflammatory processes,
- alter the structure of blood vessel walls,
- affect the kidneys and their salt balance, and
- intensify hormone systems that increase blood pressure.
This can create a harmful cycle: oxidative stress can contribute to high blood pressure. At the same time, persistently high blood pressure strains the blood vessels and can thereby promote further oxidative stress.
What do the studies say?
In cell and animal studies, the link between reactive oxygen species and high blood pressure is well established. In humans, the relationship is more difficult to assess. Studies often find signs of increased oxidative stress in people with high blood pressure. However, such observations do not clearly show which came first.
According to current research, both are probably true: Oxidative stress can contribute to the development and consequences of high blood pressure, while high blood pressure can in turn increase oxidative stress.
Oxidative stress is therefore not the single cause of hypertension. Rather, it is one part of a complex process. Age, genetic predisposition, obesity, lack of exercise, high salt intake, smoking, kidney disease and other factors also affect blood pressure.
Can antioxidants help?
The biological rationale initially seems plausible: If oxidative stress is involved, antioxidant substances might help. However, clinical studies have not yet provided a reliable basis for treatment.
Small reductions in blood pressure were observed in some cases with vitamin C and vitamin E. However, the results are inconsistent. Many studies were small or lasted only a short time; they also differed in dosage, participants, and study design. For example, a meta-analysis of vitamin E found a small average reduction in systolic blood pressure, but no convincing effect on diastolic blood pressure.
Dietary supplements are therefore not considered an established treatment for high blood pressure. They should not replace prescribed medication or effective lifestyle changes. As high-dose supplements can cause side effects and interact with medications, their use should be discussed with a doctor or pharmacist.
What can you do yourself for your blood vessels?
The most effective measures will come as no surprise: regular exercise, not smoking, a balanced diet, less salt, and good blood pressure control. This is not a particularly new or exciting message. However, maintaining these habits in everyday life is often more difficult than it first appears.
Particularly helpful are:
- regular physical activity that can be easily incorporated into everyday life,
- plenty of vegetables, fruit, legumes and wholegrain foods,
- less salt and fewer highly processed foods,
- as little alcohol as possible,
- gradual weight loss if you are overweight,
- not smoking,
- regular blood pressure checks, and
- taking prescribed medication reliably.
A plant-rich diet also provides substances with antioxidant effects. Its health benefits probably result from the interaction of many nutrients and other beneficial effects – not from a single “miracle vitamin”.
Conclusion
Free radicals are not inherently harmful. However, if their production becomes unbalanced, oxidative stress can develop. This can reduce the availability of nitric oxide, impair the relaxation of blood vessels, and thus contribute to the development and consequences of high blood pressure.
In humans, cause and effect cannot yet be fully distinguished. There is much to suggest that they reinforce each other: Oxidative stress can promote high blood pressure – and high blood pressure can increase oxidative stress. To date, antioxidant supplements have not proven to be a reliable treatment.
Sources and further reading
- Touyz RM et al. Reactive oxygen species in hypertension.Hypertension. 2024. PubMed
- Griendling KK et al. Oxidative Stress and Hypertension.Circulation Research. 2021. Article from the American Heart Association
- Ward NC et al. Oxidative stress in human hypertension: association with antihypertensive treatment, gender, nutrition, and lifestyle. Free Radical Biology and Medicine. 2004. PubMed
- Emami MR et al. Effect of vitamin E supplementation on blood pressure: a systematic review and meta-analysis. Journal of Human Hypertension. 2019. PubMed
- Juraschek SP et al. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials.American Journal of Clinical Nutrition. 2012. PubMed
- McEvoy JW et al. 2024 ESC Guidelines for the management of elevated blood pressure and hypertension. European Heart Journal. 2024. Guideline of the European Society of Cardiology
Note: This article is for general information purposes and is not a substitute for individual medical advice.
