Common spices can improve gut and brain health

Spices and herbs have been used around the world for centuries, mostly originating from the Mediterranean, the Middle East, or Asia. They were originally used to enhance the flavor of food, as preservatives, and for medicinal purposes. Herbs are derived from fresh leaves and flowers, while spices are derived from roots, seeds, bark, stems, berries, or buds, and are typically dried.

Many national dietary guidelines recommend using spices to reduce salt intake. For example, the DASH (Dietary Approaches to Stop Hypertension) diet, developed by the U.S. National Institutes of Health, suggests replacing salt with spices and herbs to lower blood pressure. Studies have shown that people who consume spicy foods tend to consume less salt and have lower blood pressure.

The polyphenolic compounds in spices help reduce oxidative stress caused by excess free radicals. Antioxidants, such as phenolic acids and flavonoids, neutralize free radicals and can protect against damage associated with chronic diseases.

Between 2010 and 2024, the UCLA Human Nutrition Center conducted eight clinical trials and 12 laboratory experiments with individual spices, herbs, and their blends. The researchers studied their effects on human health.

Two clinical trials showed that consuming cinnamon reduced insulin and glucagon levels after a meal in individuals with normal and overweight bodies. Additionally, cinnamon consumption was associated with lower average glucose levels and significant changes in the gut microbiome compared to placebo. At the same time, some participants experienced temporary increases in their glucose levels at certain times, which suggests that the metabolic effects of cinnamon are complex.

In addition to its effects on blood sugar levels, cinnamon may also provide protection against respiratory and gastrointestinal infections. It has anti-inflammatory, antioxidant, hepatoprotective, and neuroprotective properties. Cinnamaldehyde, the primary active compound in cinnamon, plays a crucial role in these effects. It modulates the expression of inflammatory genes, inhibits inflammatory enzymes, and affects cellular signaling related to metabolism, insulin sensitivity, and cell protection.

Capsaicin in chili peppers stimulates thermogenesis, but in effective doses, it can cause severe gastrointestinal side effects. Sweet red peppers contain capsinoids, such as dihydrocapsaicin (DCT), which provide similar metabolic effects without adverse reactions. DCT activates TRPV1 receptors in the gut, triggering the sympathetic nervous system and potentially increasing thermogenesis and fat metabolism.

A 2010 UCLA study found that all overweight participants who followed a low-calorie diet lost weight. However, only the group that received 9 mg of DCT showed a significant increase in energy expenditure after eating. Although later studies did not find a significant effect of DCT on energy expenditure or fat oxidation during exercise or at rest, a small thermal effect was still observed when the data from the groups was combined.

A 2014 study found that the combination of arctigenin, EGCG, and curcumin had a stronger anti-cancer effect in prostate and breast cancer cells compared to each compound alone. This led to increased cancer cell death and the inhibition of pathways that promote cancer development.

A separate 2018 study found that daily intake of a bioavailable form of curcumin for 18 months improved memory, attention, and mood in older adults. There were also changes in brain imaging that were potentially related to the accumulation of amyloid and tau protein.

Curcumin alleviated knee pain in patients with osteoarthritis and improved the cholesterol profile in individuals with metabolic syndrome, increasing high-density lipoprotein (HDL) levels and reducing low-density lipoprotein (LDL) levels. It acts as a powerful antioxidant, neutralizes free radicals, enhances the activity of the body’s antioxidant enzymes, suppresses key inflammatory pathways, and promotes the death of cancer cells through cell cycle arrest and apoptosis.

Laboratory and clinical studies have shown that spice blends (black pepper, cayenne pepper, cinnamon, ginger, oregano, rosemary, and turmeric) are rich in polyphenols. These polyphenols stimulate the growth of beneficial gut bacteria, such as lactobacilli and bifidobacteria, and inhibit the growth of certain potentially pathogenic bacteria.

UCLA research has confirmed that adding polyphenol-rich spices to meat before cooking significantly reduces markers of lipid oxidation. The polyphenols in spices also reduce markers of oxidative stress and improve endothelial function.

It is important to note that the antioxidant activity varies among different spices and depends on the cooking method. For example, oregano has the highest antioxidant capacity. Curcumin in turmeric retains its effectiveness after heat treatment, and when combined with black pepper, its effect against lipid peroxidation during cooking is enhanced — although piperine itself does not have antioxidant properties.

Although research has revealed many potential health benefits of spices and herbs, much remains to be learned about their effects in real-world dietary contexts. As natural and widely available ingredients, they offer promising opportunities for improving public health. However, additional well-designed studies are needed to clarify their role and inform future recommendations.

The review also highlights: Many laboratory studies use doses that are higher than those typically consumed in food. Cooking methods, digestion, metabolism, and interactions with other foods can affect the bioavailability and effectiveness of compounds found in spices.

In the future, a closer examination of spices and herbs in nutrition research could lead to practical strategies that help individuals make healthy food choices and maintain their long-term health.