New research reveals a clear link between green tea consumption and fewer brain lesions, shedding light on its potential to safeguard cognitive health in aging populations.

Study: Green tea consumption and cerebral white matter lesions in community-dwelling older adults without dementia. Image Credit: New Africa / Shutterstock.com

A recent study published in the Nature Portfolio Journal Science of Food reveals that higher green tea consumption is associated with fewer lesions in the cerebral white matter, a characteristic feature of dementia.

The impact of tea and coffee on cognition

Tea and coffee, the most popular beverages worldwide, contain numerous compounds with neuroprotective properties, including caffeine, polyphenols, and vitamins. Green tea, black tea, and coffee also contain epigallocatechin gallate, theaflavins, chlorogenic acid, and caffeic acid, all of which exhibit antioxidant and anti-inflammatory properties.

Several epidemiological studies have reported that tea or coffee consumption reduces the risk of age-related cognitive decline. Dementia, a neurodegenerative disease that causes cognitive decline, is associated with a wide range of brain structural changes, including brain atrophy, hippocampal atrophy, and an increase in cerebral white matter lesions.

Previous studies have reported that green tea consumption is associated with reduced annual hippocampal atrophy, whereas regular coffee consumption can increase the thickness of brain cortices. To further explore these associations, the current study’s researchers investigate the associations between green tea and coffee consumption with cerebral white matter lesions, hippocampal volume, and total brain volume in an older Japanese population without dementia.

Study design

The current study included 8,766 community-dwelling individuals from the Japan Prospective Studies Collaboration for Aging and Dementia (JPSC-AD) who were recruited between 2016 and 2018. The JPSC-AD is an ongoing community-based observational study of dementia conducted in eight regions throughout Japan.

Study participants underwent brain magnetic resonance imaging (MRI) to assess cerebral white matter lesions, hippocampal volume, and total brain volume. Additionally, all study participants completed a Food Frequency Questionnaire to provide information on their daily frequency of green tea and coffee intake.

Approximately 91% and 82% of the study population reported drinking green tea and coffee, respectively. Study participants with higher daily green tea intake reported significantly higher levels of regular exercise and cognitive functions, as well as lower levels of smoking and alcohol drinking habits and depression. However, individuals with higher daily coffee intake reported significantly higher frequencies of diabetes, smoking habits, and cardiac abnormalities.

Association between green tea or coffee intake and brain changes

Potential confounding factors adjusted for in the analysis include age, sex, research site, educational level, apolipoprotein E (ApoE) ε4 carrier status, hypertension, body mass index (BMI), serum low- and high-density lipoprotein cholesterol levels, regular exercise, and smoking and drinking habits. The study revealed a dose-dependent association, with individuals consuming 600–1500 ml of green tea daily experiencing significantly fewer cerebral white matter lesions compared to those with lower consumption levels.

After adjusting for these factors, higher daily green tea intake was significantly associated with fewer lesions in the cerebral white matter. However, no significant associations were observed between green tea intake and hippocampal or total brain volumes.

Considering daily coffee intake, no significant associations were observed with cerebral white matter lesions, hippocampal volume, and total brain volume. This contrasts with some prior studies, which have reported positive effects of coffee on brain health in different populations.

Sensitivity analysis

The associations between green tea or coffee intake and brain changes in the sensitivity analysis were similar to those observed for the entire study population, including participants with normal cognitive functions and mild cognitive impairment.

Notably, strong negative associations were observed between green tea intake and cerebral white matter lesions in study participants without depression but not in participants with depression. Similarly, significant negative associations were reported in participants without the ApoE ε4 allele but not in those with the allele, suggesting these factors may mediate green tea’s protective effects.

Conclusions

A higher daily intake of green tea can significantly reduce the risk of cerebral white matter lesions in older adults without dementia; however, these benefits were not present in individuals who consumed coffee daily.

Cerebral white matter lesions are considered an independent risk factor for cognitive decline and are associated with vascular dementia and Alzheimer’s disease. Larger white matter lesions typically arise with severe brain atrophy in patients with Alzheimer’s disease.

The most significant risk factor for white matter lesions is hypertension or increased blood pressure. The beneficial impact of green tea on white matter lesions might be attributed to its antihypertensive effects, as several studies have reported that regular green tea intake may reduce both systolic and diastolic blood pressure levels.

The beneficial effects of green tea intake were restricted to participants without depression and the ApoE ε4 allele. This may indicate that green tea is less effective in individuals with these risk factors for dementia, possibly due to residual confounding or smaller sample sizes in these subgroups. Since depression and the presence of ApoE ε4 are substantial risk factors for dementia, green tea may not effectively reduce white matter lesions in individuals at higher risk of developing dementia, necessitating additional studies in these patient populations.

It is important to note that this study focused on an older Japanese population, and cultural dietary practices may limit the generalizability of these findings to other ethnicities and regions. Further research is needed to confirm these associations in more diverse populations.

The global dietary supplements market, valued at $178.8 billion in 2023, is rapidly growing. Exercise physiologist Keith Baar specializes in sports medicine and studies the effects of collagen, whey and omega-3 supplements on bone and tendon health. In this Q&A, Baar, who is a professor in the Departments of Neurobiology, Physiology and Behavior and Physiology and Membrane Biology, shares the findings from his studies of these supplements.

Why is collagen important for the body?

Collagen is the most abundant protein in our body. All our musculoskeletal tissues are built on a foundation of collagen. Collagen makes up our tendons, ligaments and bones. For this musculoskeletal system to work well, we need to have a good collagen turnover that replaces older collagen with new ones.

What foods are rich in collagen?

Collagen is a meat-based protein. Animal tissues are the only natural source of collagen. There are a few vegetables that are high in the amino acid glycine (key ingredient in collagen), but they are not as readily absorbed.

People who already eat a lot of meat or have bone broth don’t see as big of an effect of collagen supplementation. This is true for those who eat whole cuts of meat with some marbling in the connective tissues – not only the tender filet mignons. Those individuals are going to have good amounts of collagen in their diet. Vegetarians and vegans will need a good source of the right amino acids for their bodies to build collagen.

You have been studying collagen for many years. What does your research on collagen tell us?

What we eat both positively and negatively affects how much collagen we make. Making more collagen not only affects the skin, hair and nails, but also has musculoskeletal effects. So basically, the choices that we make at the dinner table directly affect how our skin looks and body works.

Does caffeine impede the body’s ability to make collagen?

If it’s a lot of caffeine, like 5-6 cups of coffee, it does. We have done a mouse study that showed that both muscle size and tendon adaptations to exercise seem to be slightly impaired by high caffeine intake. When we did lab experiments, we could see a direct effect of caffeine on decreasing both muscle and connective tissue protein synthesis, but it takes a lot of caffeine to do that in people.

There is a huge market for collagen supplements. Are they good for the bones?

Our studies have shown that when taking a collagen supplement, there is an increase in a circulating marker (known as procollagen N-Terminal peptide) of collagen synthesis. So, we know that hydrolyzed collagen supplements can be good. This is especially true in older individuals. One of the places where we have good evidence is in osteoarthritis. Individuals who supplement with collagen show a decrease in osteoarthritis symptoms, such as knee pain or restricted movement.

Are there side effects to taking collagen supplements?

There is no downside to taking high quality collagen supplements, i.e. those from animal skins. Collagen made from bones can have high amounts of heavy metals. However, more collagen largely means more protein with specific amino acids needed to make collagen in our bodies. In many cases, there seems to be a nice upside. How much of an upside depends on the individual: What their normal diet is, whether they are eating a high-fat diet or drinking too much caffeine.

Do collagen supplements help the body make more collagen, or are they ready-made collagen that gets absorbed?

So, any supplement you take is digested and absorbed down to very small peptides or amino acids, and then you rebuild something with those basic materials (amino acids). To build collagen, we need a lot of glycine and proline amino acids. If there isn’t enough glycine or proline, then we can’t make as much collagen as we want.

What is whey, and why is it important?

Whey is the acid-soluble component of milk. Cheesemakers used to throw the whey onto their fields because they thought it was a waste product.

But, since whey has all the amino acids and is a complete protein, unlike collagen, it is a high quality protein. Whey has a lot of leucine, a key amino acid for protein synthesis, and proline. However, it is not as rich in glycine, a building block of collagen.

Why is it recommended to take collagen supplements or food rich with collagen in addition to whey?

Together with our research collaborators at Maastricht University, we found that when people are fed milk protein like whey, their glycine levels in blood would go down. They wondered if that happened because the body was using the glycine to make more collagen. So, we tested that.

Our study showed that we can make more connective tissue in our muscles by taking a whey protein and collagen blend. The whey protein has all the amino acids and a lot of leucine, and the hydrolyzed collagen has a lot of glycine. Now, we have a protein that will support building both the connective tissue and muscle.

This study was the first time we have demonstrated, using a direct measure of collagen synthesis, that we can nutritionally change how much collagen we make in our muscles.

You also studied the effects of fish oil and omega-3 fatty acids on bone and joint health. What did your studies show?

Musculoskeletal health and inflammation are connected. If you have more inflammation, you will get more tendon and musculoskeletal injuries. Fish oils could have an effect by decreasing inflammation and that would potentially improve collagen turnover. Our studies have shown that, without inflammation, fish oil or omega-3 do not seem to directly affect our tendons and ligaments.