Dietary supplements have surged in popularity as tools to enhance training performance. Among these, pre-workout supplements, formulated with a blend of ingredients, are widely used to boost physical capabilities. Some components have been linked to potential cardiovascular health benefits. However, the existing scientific literature presents conflicting results regarding the overall effects of pre-workout supplements. This article aims to analyze the impact of multi-ingredient pre-workout supplements (MIPWs) on cardiovascular health, identify common adverse effects, and examine the roles of key ingredients. Additionally, it will explore the potential benefits and risks of using pre-workout supplements for weight loss.
What are Pre-Workout Supplements?
A dietary supplement is defined as a nutrient, food component, or non-food compound consumed to achieve specific performance and/or health benefits. Pre-workout supplements are typically consumed before physical exercise and contain a mix of ingredients like caffeine, creatine, and arginine, intended to increase energy, reduce fatigue, and enhance physical performance, endurance, strength, and muscle mass gain.
Potential Cardiovascular Effects
Pre-workout supplements often include compounds that can affect the cardiovascular system. Some studies suggest that MIPWs may offer physical and cardiovascular benefits, including increased energy, focus, endurance, and strength during exercise, as well as potential positive impacts on blood pressure and triglyceride, low-density lipoprotein (LDL), and homocysteine levels. However, other studies have reported adverse cardiovascular effects, such as increased systolic and diastolic blood pressure and heart rate. This discrepancy may be due to variations in dosages, populations studied (active vs. non-active participants, healthy participants vs. those with cardiovascular diseases), and other factors.
Methodology of Research
An integrative literature review was conducted, analyzing scientific studies investigating the use of pre-workout supplements and their relationship with the cardiovascular system. A systematic search was performed in the PubMed and Web of Science databases by independent researchers between January 2010 and August 2024. The search was broadened to include more recent articles and to extend the search locations.
Original clinical studies conducted in humans, reviews, systematic reviews, and meta-analyses were considered for inclusion. The PICOTS framework model was used to determine the inclusion and exclusion criteria:
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- Population: Clinical studies in humans, of any sex, age, or level of physical conditioning (athletes or non-athletes).
- Intervention: Studies that evaluated the effects of multi-ingredient pre-workout supplements (MIPWs) and possible adverse cardiovascular effects as the primary outcomes.
- Comparator: Studies that used a control drink or placebo were included.
- Outcome: Studies that included the effects of MIPWs (including drink or food supplements that are commonly marketed as products to be consumed before engaging in any form of training and are characterized by a mix of nutrients that can promote positive effects on exercise performance) on cardiovascular outcomes as the primary outcome and changes in physical performance as secondary outcomes.
- Time: Intervention studies with acute or chronic effects were included in this review.
The exclusion criteria included articles not published in English, studies without complete abstracts, unavailable studies, and pre-print studies that had not undergone double-blind review.
Findings from Studies
A total of 406 studies were found through electronic and manual searches. After removing duplicates and screening titles and abstracts, 24 articles were included in the final analysis. Among these, only 4 studied cardiovascular complications and hemodynamic changes, while the remaining 20 investigations on acute or chronic MIPW consumption did not find deleterious changes in cardiovascular parameters, such as systolic or diastolic blood pressure, arrhythmias, cardiac events, or adverse events.
Specific Study Results
- One study involving 30 recreationally active women found an increase in systolic and diastolic blood pressure and heart rate in the MIPW group (acute effect).
- Other studies involving well-trained men and women, recreationally trained men, and recreationally active women did not find significant effects on mechanical variables.
Only 4 of the 24 articles used an MIPW containing synephrine.
Common Ingredients and Their Effects
Caffeine
Caffeine is a common component of pre-workout supplements, with dosages ranging from 100 to 400 mg in the studies analyzed. Caffeine antagonizes adenosine receptors, leading to the release of catecholamines, which alter cardiovascular responses. Its effects are augmented when co-administered with isopropylnorsynephrine or other by-products.
Creatine and Beta-Alanine
Pre-workout supplements also commonly contain creatine and beta-alanine. Among the studies included:
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- 7 investigations used MIPWs with creatine or creatine monohydrate.
- 16 studies used MIPWs with the non-essential amino acid beta-alanine.
- 4 studies used MIPWs containing nitric oxide.
Some studies also added vitamin complexes from the B1 family to the MIPW, as well as other compounds.
Risk Factors and Population Characteristics
Some studies reported risk factors that may contribute to adverse cardiovascular outcomes, including smoking, alcohol consumption, a high body mass index, high blood pressure, and a family history of cardiovascular disease. In contrast, other case reports highlighted patients with no history of cardiovascular risks, but who were highly sensitive to caffeine. The majority of the investigated population in the 24 articles were young adults with an average age between 18 and 35 years.
Most articles used MIPWs with varying doses of the ingredients, with caffeine doses ranging between 100 and 300 mg. One article found that the amounts of beta-alanine and caffeine were below or at the lower limit of the recommended doses for efficacy. Beta-alanine doses varied between 1 and 3 g, creatine content was approximately 5 g, and synephrine doses ranged between 10 and 200 mg. The time between consuming the MIPW and engaging in exercise ranged between 30 and 40 min.
Role of Key Ingredients
MIPWs typically contain ingredients such as synephrine, caffeine, creatine, beta-alanine, taurine, and nitric oxide boosters.
Creatine
Creatine increases creatine phosphate reserves in muscle tissue, enhancing energy reserves for short-term tasks and creating maximum and explosive strength. Creatine monohydrate is used to maintain high-energy phosphate levels during exercise. Creatine in safe doses (up to 5 g/day) has been shown to have considerable beneficial effects for the cardiovascular system. It plays a crucial role in the production and storage of adenosine triphosphate (ATP), indirectly contributing to the maintenance of optimal cardiac function. Studies suggest that creatine supplementation may have a protective effect on cardiac muscle tissue due to its antioxidant properties.
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Beta-Alanine
Beta-alanine is used as a pre-workout supplement due to its role in carnosine synthesis. Carnosine acts as an intracellular pH buffer, regulating the acid-base balance in muscle cells during exercise, thus improving endurance and allowing for athletes to sustain more intense workloads for prolonged periods. Carnosine also has anti-inflammatory and antioxidant properties, potentially contributing to cardiovascular system health. Studies in animals have shown that beta-alanine supplementation can reduce infarct size after coronary artery occlusion.
Caffeine
Caffeine is a widely used stimulant known to increase energy, focus, and endurance, thereby improving physical performance.
Pre-Workout Supplements and Weight Loss
While pre-workout supplements are primarily designed to enhance exercise performance, some ingredients can indirectly support weight loss.
Caffeine and Thermogenesis
Caffeine is a stimulant that can increase thermogenesis, the process by which your body burns calories to produce heat. This can lead to a slight increase in metabolic rate, which may contribute to weight loss over time.
Increased Energy and Workout Intensity
By providing an energy boost, pre-workout supplements can help individuals push harder during their workouts. This increased intensity can result in more calories burned and greater fat loss.
Appetite Suppression
Some ingredients in pre-workout supplements, such as caffeine, may have appetite-suppressing effects. This can help reduce overall calorie intake, which is essential for weight loss.
Ingredients with Potential Weight Loss Benefits
- Green Tea Extract: Contains compounds that may promote fat burning and boost metabolism.
- L-Carnitine: Helps transport fatty acids into the mitochondria, where they can be burned for energy.
- Yohimbine: May promote fat loss by blocking alpha-2 adrenergic receptors.
Risks and Side Effects
Despite the potential benefits, pre-workout supplements carry several risks and side effects that users should be aware of.
High Caffeine Content
Many pre-workout supplements contain high levels of caffeine, which can lead to:
- Jitteriness
- Insomnia
- Nausea
- Increased heart rate
- Headaches
- Anxiety
- Restlessness
- High blood pressure
Other Side Effects
- Beta-Alanine: May cause paresthesia, a harmless tingling sensation in the hands and feet.
- Niacin: In high doses, can cause niacin flush, resulting in red patches on the skin.
- Digestive Issues: Ingredients like sodium bicarbonate and magnesium can cause nausea, headache, increased urination, and diarrhea.
- Headaches: Citrulline, which increases blood flow, may lead to headaches and migraines due to blood pressure changes in the brain.
Cardiovascular Risks
Pre-workout supplements containing synephrine have been linked with chest pain, heart palpitations, arrhythmias, and even heart disease.
Lack of Regulation
The dietary supplement industry is largely unregulated, meaning that pre-workout supplements may contain ingredients with unknown or inadequate safety data. There is also a risk of mislabeling, contamination, and the presence of banned substances.
Precautions and Recommendations
- Consult a Healthcare Professional: Before taking pre-workout supplements, especially if you have any underlying health conditions or are taking medications.
- Read Labels Carefully: Pay attention to the ingredient list and dosages, and avoid products with proprietary blends.
- Start with a Low Dose: Assess your tolerance to the supplement and gradually increase the dosage if needed.
- Avoid Excessive Caffeine Intake: Limit your overall caffeine intake to avoid negative side effects.
- Stay Hydrated: Drink plenty of water to minimize the risk of dehydration and digestive issues.
- Choose Third-Party Tested Products: Look for a stamp from an independent lab (e.g., Informed Sport, the Banned Substances Control Group (BSCG) and NSF) to ensure quality and safety.
- Be Aware of Potential Interactions: The varied ingredients in pre-workout supplements may interact differently in individuals, potentially causing allergic reactions or adverse side effects.
Alternatives to Pre-Workout Supplements
Many of the benefits associated with pre-workout supplements can be achieved through natural means.
Balanced Diet
A healthy diet rich in vitamins and nutrients can provide sustained energy for workouts.
Caffeine from Natural Sources
Coffee, tea, and other natural sources of caffeine can provide an energy boost without the added ingredients found in pre-workout supplements.
Creatine and Beta-Alanine from Food
Creatine can be obtained from animal-based foods, while beta-alanine is found in poultry and fish.
Nitrate-Rich Foods
Beets, spinach, and other nitrate-rich foods can enhance blood flow and improve exercise performance.