Glycine may modestly lower blood pressure, but the evidence is still early and limited. A small number of human studies suggest that glycine supplementation can reduce systolic blood pressure, particularly in people with metabolic syndrome. However, no major cardiology organization currently includes glycine in its hypertension treatment guidelines, and the research that does exist comes from small trials rather than the large, definitive studies that would change clinical practice.
What the Human Evidence Shows
The most direct evidence comes from a clinical trial in men with metabolic syndrome, a cluster of conditions that includes high blood pressure, elevated blood sugar, and excess abdominal fat. In that study, men who took glycine supplements experienced a statistically significant decrease in systolic blood pressure (the top number in a blood pressure reading) compared to those who did not. The study also found reductions in oxidative stress, a type of cellular damage that contributes to blood vessel stiffness and elevated blood pressure.
A 2022 review published in the Journal of Endocrinology Investigation examined the broader relationship between glycine and metabolic syndrome. It concluded that glycine supplementation improves several components of metabolic syndrome, including diabetes markers, obesity, abnormal cholesterol levels, and hypertension. The review also noted something interesting: people with metabolic syndrome tend to have lower circulating glycine levels than healthy individuals, and interventions that improve metabolic health (exercise, weight loss, certain medications) also raise glycine levels. This suggests glycine isn’t just a bystander but plays an active role in metabolic regulation.
How Glycine Might Affect Blood Vessels
Glycine is a simple amino acid, one of the building blocks your body uses to make proteins. But it also functions as a signaling molecule with effects on blood vessels and the nervous system. Glycine helps produce a compound that relaxes blood vessel walls, allowing them to widen and reducing resistance to blood flow. It also acts as an inhibitory signal in the nervous system, which can calm the “fight or flight” responses that raise heart rate and constrict blood vessels.
The oxidative stress connection matters too. When cells produce too many reactive oxygen molecules and not enough antioxidant defenses, blood vessel linings become damaged and inflamed. This makes arteries stiffer and less responsive, which drives blood pressure up over time. Glycine appears to reduce this oxidative burden, which could explain part of its blood pressure effect in clinical trials.
Who Might Benefit Most
The existing research points most clearly toward people who already have metabolic problems. If you have metabolic syndrome, prediabetes, or are carrying significant extra weight, your baseline glycine levels are likely lower than average. Supplementing in that context may address a genuine shortfall. For people with normal metabolic health and blood pressure already in a healthy range, there’s little reason to expect glycine would push numbers meaningfully lower.
This distinction is important. Many supplements show effects in people with an existing deficiency or disorder but do little for those who are already in good shape. Glycine follows that pattern based on the data available so far.
What We Don’t Know Yet
Several critical gaps remain. The human trials have been small, and the specific magnitude of blood pressure reduction (in exact mmHg) is not well established across multiple studies. We also lack clear data on how long you need to take glycine before seeing an effect, or whether the benefit persists over months or years. Most cardiovascular supplements that initially looked promising in small studies have gone on to disappoint in larger, longer trials. Glycine could follow the same path, or it could hold up. There simply isn’t enough data to say.
The doses used in metabolic syndrome studies have generally ranged from 5 to 15 grams per day, split across multiple doses. Glycine is considered safe at these levels for most people, as it’s a naturally occurring amino acid found in protein-rich foods like meat, fish, dairy, and legumes. Bone broth and collagen supplements are particularly high in glycine. But “safe” and “proven to lower blood pressure” are different claims, and only the first one is well supported.
Glycine vs. Proven Blood Pressure Strategies
For context, lifestyle changes with strong evidence behind them typically produce the following systolic blood pressure reductions:
- Reducing sodium intake to under 2,300 mg per day lowers systolic pressure by roughly 5 to 6 mmHg.
- Regular aerobic exercise (150 minutes per week) reduces it by about 5 to 8 mmHg.
- The DASH diet, rich in fruits, vegetables, and low-fat dairy, can lower systolic pressure by up to 11 mmHg.
- Losing 5% of body weight can reduce systolic pressure by 3 to 5 mmHg.
Glycine hasn’t been tested head-to-head against any of these interventions, and its effect size remains poorly defined. If you’re actively managing high blood pressure, the strategies above have decades of large-scale research behind them. Glycine is better understood as an area of scientific interest than a reliable tool for blood pressure control at this point.