Alzheimer's

• What’s behind the study: Dementia cases are rising worldwide, and with no cure available, researchers are looking closely at everyday lifestyle factors—like diet—that might lower risk. Dairy foods have produced mixed results in past research, especially when it comes to fat content.

• What the researchers wanted to know: Does eating high-fat dairy (like full-fat cheese or cream) affect dementia risk differently than low-fat dairy?

• How the study was done: Swedish researchers tracked nearly 28,000 adults for about 25 years, comparing detailed dairy intake at midlife with later diagnoses of dementia, Alzheimer’s disease, and vascular dementia.

Spreads of high-fat cheeses are favorites at holiday parties, but as long as you keep calories under control, indulging in a bit of brie on a cracker may support your cognitive health.

For years, nutrition advice has tended to favor low-fat dairy products, especially for heart health. But a large new study from Sweden suggests that when it comes to brain health, some high-fat dairy foods may deserve a second look.

Researchers analyzing data from the long-running Malmö Diet and Cancer cohort found that people who regularly ate high-fat cheese and high-fat cream had a lower risk of developing dementia over the next two decades compared with those who ate little or none.

The study followed 27,670 adults, mostly in their late 50s at the start, for a median of 25 years. During that time, more than 3,200 participants developed dementia, allowing researchers to compare long-term outcomes across different eating habits.

The standout findings

Two dairy products stood out:

• High-fat cheese: People who ate at least 50 grams a day (about two slices) had a 13% lower risk of dementia overall. The reduction was even stronger – nearly 30% lower risk –  for vascular dementia, which is linked to blood vessel problems in the brain.

• High-fat cream: Those who consumed at least 20 grams per day had a 16% lower risk of dementia, with lower risks seen for both Alzheimer’s disease and vascular dementia.

By contrast, low-fat cheese, low-fat cream, milk, yogurt, and butter showed no clear link to dementia risk, positive or negative.

Genetics may matter

The researchers also looked at APOE ε4, a genetic variant that raises the risk of Alzheimer’s disease. Interestingly, the protective link between high-fat cheese and Alzheimer’s disease was seen only in people who did not carry this gene variant. That suggests genetics may influence how diet affects brain health.

The study didn’t test mechanisms directly, but scientists have some theories. Cheese and cream contain fat-soluble vitamins, bioactive peptides, and fermented compounds that may support brain health or reduce inflammation. The “food matrix” – how nutrients interact within whole foods – may matter more than fat content alone.

Despite the intriguing results, experts urge caution:

• This was an observational study, meaning it can show associations but cannot prove cause and effect.

• Eating more high-fat dairy doesn’t guarantee protection from dementia.

• Other lifestyle factors—such as physical activity, education, smoking, and overall diet—still play major roles in brain health.

The takeaway for consumers

If you enjoy cheese or a splash of cream in your coffee, this study offers some reassurance that moderate intake of certain high-fat dairy foods is not linked to higher dementia risk, and may even be protective. However, it’s not a green light to overhaul dietary guidelines just yet.

For now, experts recommend focusing on a balanced, varied diet, paying attention to overall eating patterns rather than single “superfoods.” As researchers continue to untangle how diet and genetics interact, studies like this help refine, rather than replace, nutrition advice.

• Even light drinking (under seven drinks a week) showed no protective effect in the largest combined study to date.

• Genetic analyses suggest the more alcohol you’re predisposed to consume, the higher your dementia risk.

• The drop in drinking before diagnosis hints that earlier studies showing benefits may have been misled by reverse causation.

If you’ve ever heard that a glass of wine a day is good for your brain, recent research suggests it’s time to pause and reconsider. 

A new large-scale study combining observational data and genetic methods argues that any amount of alcohol might increase the risk of dementia. What looked like a protective effect of light or moderate drinking in past studies could, in fact, be a misleading artifact. 

The findings challenge a long-held assumption: that low levels of alcohol are harmless — or even beneficial — for cognitive health.

“Our study findings support a detrimental effect of all types of alcohol consumption on dementia risk, with no evidence supporting the previously suggested protective effect of moderate drinking,” the researchers wrote. 

The study

To tackle this question, researchers used two main strategies:

1. Observational data. They drew from two major biobank projects — the U.S. Million Veteran Program and the U.K. Biobank — to examine real-world drinking habits and incidence of dementia. Participants between 56 and 72 years old were followed over time until they developed dementia, died, or reached the end of follow-up (2019 for MVP, 2022 for UKB). Alcohol intake was self-reported (frequency, volume) and supplemented with the AUDIT-C screening tool for risky drinking behaviors (like binge drinking). In total, 559,559 people entered the observational analyses, and 14,540 developed dementia during the follow-up.

2. Mendelian randomization (genetic analysis). This method treats genetic variants associated with alcohol consumption as proxies (or “instruments”) for long-term drinking behavior. In this study, they considered three different genetic measures: predisposition toward average weekly drinks, risky drinking, and alcohol dependence. The goal: to minimize confounding (other factors influencing both drinking and dementia) and test whether a causal link might exist. For the genetic analyses, they drew on genome-wide association study (GWAS) data covering millions of people.
   

By combining both approaches, the researchers hoped to triangulate evidence: observations can show patterns, and genetics can help clarify whether those patterns suggest causation.

The results

In the observational analyses, the relationship between alcohol and dementia looked U-shaped. This means that both low and high levels of something are linked to worse outcomes, while moderate levels are linked to the best outcomes.

For this study, that looked like: both abstainers and heavy drinkers (40+ drinks/week) had about a 41% higher risk of dementia, compared with light drinkers (less than seven drinks per week). That figure climbed to 51% higher for those with alcohol dependence. That pattern might look like light drinking is protective — but observational data alone can be misleading.

The genetic (Mendelian randomisation) analyses told a different story: there was no protective effect at low levels. Instead, dementia risk rose steadily with greater genetically predicted alcohol intake across all categories. For example, each additional one to three drinks per week (by genetic risk) was linked to a 15% higher dementia risk. Doubling the genetic propensity for alcohol dependence was tied to a 16% increased risk. In short, more drinking (genetically indicated) = more risk, in a roughly linear fashion.

One particularly telling insight: many individuals who were later diagnosed with dementia had gradually reduced their alcohol consumption in the years before diagnosis. That suggests that early (preclinical) brain changes might lead people to cut back — a phenomenon called reverse causation. If so, earlier observational studies that found benefits from light drinking may have been capturing that effect, rather than a true benefit of alcohol.

The authors do note limitations: the strongest associations came from those of European ancestry (because of sample sizes), and Mendelian randomization depends on certain assumptions that can’t be fully tested. Nonetheless, they conclude that their findings oppose the idea of a “safe” or beneficial low dose of alcohol for brain health and argue that reducing alcohol intake could be a meaningful strategy for dementia prevention.

“Our findings highlight the importance of considering reverse causation and residual confounding in studies of alcohol and dementia, and they suggest that reducing alcohol consumption may be an important strategy for dementia prevention,” the team wrote.