Updated 23rd August 2023

5 interesting studies: Almonds, heart health, and more

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Welcome to the sixth ZOE Nutrition Research Roundup. In this series, we zero in on five interesting, recent nutrition science studies.

We explain what the scientists did, why they did it, what they found, and, most importantly, what it means for your health.

In this edition, we look at a couple of studies on diet and heart health, one on meat, and one on inflammation and brain health. But our first study of the day examines almonds. Delicious.

1. Almonds and oxidative stress

As your body’s cells go about their daily business, they produce free radicals, which are highly reactive molecules. 

Thankfully, your body has antioxidant systems that mop these up and help maintain balance. 

But sometimes, free radicals build up — this is called oxidative stress. When it happens, it can lead to inflammation and cell damage.

Experts think that oxidative stress plays a role in the development of many health conditions, including cardiovascular disease and neurodegenerative diseases, like dementia.

Many factors influence the control of free radicals in your body, and your diet is one of them. So, some scientists are focusing on the role of specific dietary components.

In today's first study, the team homed in on almonds.

What did they do?

The researchers performed a meta-analysis of previous studies — they analyzed seven randomized controlled trials, including data from 424 adults. 

These studies focused on two markers of oxidative stress: malondialdehyde (MDA) and oxidized low-density lipoprotein (Ox-LDL).

What did they find?

The researchers found that consuming almonds didn’t affect levels of Ox-LDL. But it did significantly reduce levels of MDA.

They review's authors conclude that almonds “might play a beneficial role in the reinforcement of the antioxidant defense system and amelioration of oxidative stress in adults.”

However, as only seven studies were included in their analysis, they call for more research. 

What should you do?

The evidence that almonds can reduce oxidative stress certainly isn’t watertight. But at ZOE, we appreciate the impressive nutritional load that nuts in general provide.

So, if you like nuts, and you’re not allergic to almonds, feel free to add them (or other nuts) to your shopping list.

Nuts are rich in healthy fats, fiber, magnesium, selenium, and other nutrients. They’re also high in polyphenols and vitamin E, which are both antioxidants.

ZOE has a fascinating podcast on nuts if you’d like to learn more.

2. Dairy and saturated fats

Saturated fats have been demonized for decades. As a result, most dietary guidelines suggest you limit your intake of them.

However, more recently, it's become clear that the source of saturated fat makes a difference to the health outcome.

In particular, scientists have zeroed in on the saturated fats in dairy.

The latest study looks at links between saturated fat from dairy and a range of health measures. 

What did they do?

The scientists took data from 2,391 participants in the Framingham Offspring study. In total, they had detailed information on the participants' dietary habits and a range of health measures.

What did they find?

The researchers concluded that a higher intake of saturated fat from dairy products was associated with a lower body fat percentage in women. 

Higher intakes were also linked with lower levels of inflammation and improved blood lipid profiles in men.

What should you do?

Scientists will continue to investigate the role of dairy in our health. It has a long, controversial history, and the debate is likely to continue.

However, this recent study’s results are in broad agreement with other recent reviews. The scientific tide is turning in dairy’s favor.

At ZOE, we score milk, cheese, and plain yogurt pretty high (but not butter). Dairy can certainly be part of a healthy diet. 

So, if you like these products, feel free to eat them. But as with most things in life, moderation is key.

If you’d like to dive deeper, we have a podcast on saturated fats, one on dairy, and an article on the different types of milk.

3. Mediterranean diet and heart health

The Mediterranean diet is rich in plant foods and healthy fats. And it's been linked to various health benefits over the years.

A recent meta-analysis had a specific question: Is following the Mediterranean diet associated with a reduced risk of cardiovascular disease and mortality in women?

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The study's authors note that much of the previous research into heart health and diet was either conducted solely in men or the researchers didn’t separate their data to look at males and females separately.

Also, current heart health guidelines don’t provide sex-specific diet recommendations.

What did they do?

The scientists behind the recent meta-analysis looked at 16 studies, including data from 722,495 women.

What did they find?

They found that following the Mediterranean diet more closely was associated with a lower incidence of cardiovascular disease.

This diet was also linked to lower rates of mortality and coronary heart disease, in which a fatty substance builds up on the walls of arteries, making them narrower. 

Specifically, the scientists found that the Mediterranean diet was linked to a 24% lower risk of cardiovascular disease and a 23% lower risk of total mortality.

The authors write, “This study supports a beneficial effect of the Mediterranean diet on primary prevention of [cardiovascular disease] and death in women, and is an important step in enabling sex-specific guidelines.”

What should you do?

Compared with the standard Western diet, the Mediterranean diet is better for your health. It contains generous amounts of plant foods and fewer processed and ultra-processed foods.

It might not be the best option for everyone — we’re all different — but if you switch from a Western to a Mediterranean diet, you’ll likely feel the benefits.

And it might protect your heart health, too.

4. Meat and cancer

Digestive tract cancer (DTC) is a term that encompasses esophageal, stomach, liver, biliary tract, pancreatic, and colorectal cancers.

In 2020, two of the five most common cancers were DTCs — colorectal and stomach cancer.

Scientists have identified risk factors for these cancers, including smoking, obesity, and alcohol consumption.

According to the authors of a new study, researchers have paid less attention to the role of diet.

The new study explores whether there are links between meat consumption and DTCs.  Although this isn’t a new question, previous studies have produced inconsistent results.

What did they do?

The scientists accessed genetic information from hundreds of thousands of participants in Finland and the United Kingdom. And they used an innovative approach called Mendelian randomization

To do this, the scientists identified specific gene variants associated with eating different types of meat.

With this information, they could calculate which meats were associated with increased DTC risk.

What did they find?

The team found that processed meat was associated with an increased risk of colorectal cancer, but not any other type of meat.

Also, they found no evidence that red or white meat is associated with DTCs.

What should you do?

Previous research had linked red and processed meat intake to colorectal cancer risk. And this latest study is further evidence that processed meat might be involved.

At ZOE, no food is off the table, but we believe that processed meats are best to enjoy just once in a while.

White meat, however, doesn’t seem to be associated with cancer. In fact, there’s some evidence that it might protect against certain cancers. So, eating moderate amounts seems unlikely to be an issue.

5. Inflammation, diet, and cognitive health

As we age, our risk of mild cognitive impairment increases. This includes memory loss and a general decrease in mental abilities.

Not everyone with mild cognitive impairment goes on to develop dementia, but dementia always starts with this impairment.

Some scientists think that inflammation plays a role in both mild cognitive impairment and dementia. And because your diet can influence levels of inflammation, scientists are keen to understand the relationship.

Studies to date have produced mixed results. So, a group of scientists recently carried out a meta-analysis to understand how diet, inflammation, and cognitive health are linked.

What did they do?

The team pooled data from 12 studies, including 24,823 adult participants. Each study assessed individuals' diets using the dietary inflammatory index (DII). 

A high DII score means that the person has a diet likely to increase inflammation. And a low score means that their diet is, overall, anti-inflammatory. 

What did they find?

The scientists found that participants with the highest DII scores had 33% higher odds of developing mild cognitive impairment.

Also, these participants had 34% higher chances of developing Alzheimer’s disease — the most common form of dementia.

What should you do?

This study can only prove association, rather than causation, so understanding the nature of the link will require more research.

With that said, other research has shown that high-DII diets are linked to a range of conditions. So, following a lower-DII diet might be a sensible choice.

At ZOE, we recommend eating a wide variety of plant foods, which are considered anti-inflammatory.

We also recommend reducing your intake of ultra-processed foods, which are associated with higher DII scores.

Because everyone’s body is different, we can have different inflammatory responses to food. But consuming more plants will likely improve your health, even if it doesn’t reduce your dementia risk.

We have a more detailed article on anti-inflammatory diets, if you’d like to learn more. 

The take-home

So, what have we learned in this edition of the ZOE Nutrition Research Roundup? Here are your key takeaways:

  1. Almonds might reduce oxidative stress. And if they don’t, they’re a good addition to your diet, as are all nuts.

  2. Saturated fats from dairy might improve cardiovascular risk factors. And if they don’t, consuming a moderate amount of cheese, yogurt, or milk will likely benefit your health.

  3. Following the Mediterranean diet may protect women’s heart health. And if it doesn’t, it’s still a healthier option than the standard Western diet.

  4. Processed meat might increase the risk of DTCs. And overall, there’s a good amount of evidence that you should only eat these products once in a while.

  5. Following a more anti-inflammatory diet might protect your brain health as you age. And if it doesn’t, an anti-inflammatory diet is rich in plants and low in ultra-processed foods. So, it’s likely to benefit your overall health more than a Western diet.

Sources

Dietary inflammatory index and health outcomes: An umbrella review of systematic review and meta-analyses of observational studies. Frontiers in Nutrition. (2021). https://www.frontiersin.org/articles/10.3389/fnut.2021.647122/full 

Effects of almond intake on oxidative stress parameters: A systematic review and meta-analysis of clinical trials. Complementary Therapies in Medicine. (2023). https://www.sciencedirect.com/science/article/pii/S0965229923000225 

Framingham Heart Study (FHS) Offspring (OS) and OMNI 1 cohorts. (2023). https://biolincc.nhlbi.nih.gov/studies/framoffspring/ 

Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA: A Cancer Journal for Clinicians. (2021). https://pubmed.ncbi.nlm.nih.gov/33538338/ 

Meat consumption and cancer risk: A critical review of published meta-analyses. Critical Reviews in Oncology/Hemotology. (2016). https://www.sciencedirect.com/science/article/pii/S1040842815300780 

Meta-analysis of the association between dietary inflammatory index and cognitive health. Frontiers in Nutrition. (2023). https://www.frontiersin.org/articles/10.3389/fnut.2023.1104255/full 

Milk and dairy product consumption and cardiovascular diseases: An overview of systematic reviews and meta-analyses. Advances in Nutrition. (2019). https://www.sciencedirect.com/science/article/pii/S2161831322002083 

Oxidative stress in cardiovascular diseases. Antioxidants. (2020). https://pubmed.ncbi.nlm.nih.gov/32937950/ 

Oxidative stress, inflammation, and disease. Oxidative Stress & Biomolecules. (2016). https://www.sciencedirect.com/science/article/pii/B9780128032695000024 

Oxidative stress in vascular dementia and Alzheimer's disease: A common pathology. Journal of Alzheimer’s Disease. (2009). https://pubmed.ncbi.nlm.nih.gov/19221412/ 

Primary prevention of cardiovascular disease in women with a Mediterranean diet: Systematic review and meta-analysis. Heart. (2023). https://heart.bmj.com/content/early/2023/02/14/heartjnl-2022-321930 

Processed meat, red meat, white meat, and digestive tract cancers: A two-sample Mendelian randomization study. Frontiers in Nutrition. (2023). https://www.frontiersin.org/articles/10.3389/fnut.2023.1078963/full 

Red meat, diseases, and healthy alternatives: A critical review. Critical Reviews in Food Science and Nutrition. (2018). https://www.tandfonline.com/doi/abs/10.1080/10408398.2016.1158148 

Saturated fat from dairy sources is associated with lower cardiometabolic risk in the Framingham Offspring Study. The American Journal of Clinical Nutrition. (2022). https://academic.oup.com/ajcn/article-abstract/116/6/1682/6779726 

The impact of red and processed meat consumption on cancer and other health outcomes: Epidemiological evidences. Food & Chemical Toxicology. (2016). https://www.sciencedirect.com/science/article/pii/S0278691516301144

What is Mendelian randomization and how can it be used as a tool for medicine and public health? Opportunities and challenges. (2018). https://www.cdc.gov/genomics/events/precision_med_pop.htm 

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