Can Diet Protect Your Mind?

Which Diet Is Best?

Author: Dr. Stephen Chaney 

can diet prevent alzheimer'sAlzheimer’s is a scary disease. There is so much to look forward to in our golden years. We want to enjoy the fruits of our years of hard work. We want to enjoy our grandkids and perhaps even our great grandkids. More importantly, we want to be able to pass on our accumulated experiences and wisdom to future generations.

Alzheimer’s and other forms of dementia have the potential to rob us of everything that makes life worth living. What is the use of having a healthy body, family, and fortune if we can’t even recognize the people around us?

Alzheimer’s and other forms of dementia don’t happen overnight. The first symptoms of cognitive decline are things like forgetting names, where you left things, what you did last week. For most people it just keeps getting worse.

Can diet protect your mind? Recent studies have given us a ray of hope. For example, several meta-analyses have shown that adherence to the Mediterranean diet was associated with a 25-48% lower risk of cognitive decline and dementia.

However, there were several limitations to the studies included in these meta-analyses. For example:

  • For most of the studies the diet was assessed only at the beginning of the study. We have no idea whether the participants followed the same diet throughout the study. This means, we cannot answer questions like:
    • What is the effect of long-term adherence to a healthy diet?
    • Can you reduce your risk of cognitive decline if you switch from an unhealthy diet to a healthy diet?
  • These studies focused primarily on the Mediterranean diet. This leaves the question:
    • What about other healthy diets? Is there something unique about the Mediterranean diet, or do other healthy diets also reduce the risk of cognitive decline?

This study (C Yuan et al, American Journal of Clinical Nutrition, 115: 232-243, 2022) was designed to answer those questions.

How Was The Study Done?

clinical studyThe investigators utilized data from The Nurse’s Health Study. They followed 49,493 female nurses for 30 years from 1984 to 2014. The average age of the nurses in 1984 was 48 years, and none of them had symptoms of cognitive decline at the beginning of the study.

The nurse’s diets were analyzed in 1984, 1986, and every 4 years afterwards until 2006. Diets were not analyzed during the last 8 years of the study to eliminate something called “reverse causation”. Simply put, the investigators were trying to eliminate the possibility that participants in the study might change their diet because they were starting to notice symptoms of cognitive decline.

The data from the dietary analyses were used to calculate adherence to 3 different healthy diets:

  • The Mediterranean diet.
  • The DASH diet. The DASH diet was designed to reduce the risk of high blood pressure. But you can think of it as an Americanized version of the Mediterranean diet.
  • The diet recommended by the USDA. Adherence to this diet is evaluated by something called the Alternative Healthy Eating Index or AHEI.

Adherence to each diet was calculated by giving a positive score to foods that were recommended for the diet and a negative score for foods that were not recommended for the diet. For more details, read the article.

In 2012 and 2014 the nurses were asked to fill out questionnaires self-assessing the early stages of cognitive decline. They were asked if they had more trouble than usual:

  • Remembering recent events or remembering a short list of items like a grocery list (measuring memory).
  • Understanding things, following spoken instructions, following a group conversation, or following a plot in a TV program (measuring executive function).
  • Remembering things from one second to the next (measuring attention).
  • Finding ways around familiar streets (measuring visuospatial skills).

The extent of cognitive decline was calculated based on the number of yes answers to these questions.

Can Diet Protect Your Mind?

Vegan FoodsHere is what the investigators found when they analyzed the data:

At the beginning of the study in 1984 there were 49,493 female nurses with an average age of 48. None of them had symptoms of cognitive decline.

  • By 2012-2014 (average age = 76-78) 46.9% of them had cognitive decline and 12.3% of them had severe cognitive decline.

Using the data on dietary intake and the rating systems specific to each of the diets studied, the investigators divided the participants into thirds based on their adherence to each diet. The investigators then used these data to answer two important questions that no previous study had answered:

#1: What is the effect of long-term adherence to a healthy diet? To answer this question the investigators averaged the dietary data obtained every 4 years between 1984 and 2006 to obtain cumulative average scores for adherence to each diet. When the investigators compared participants with the highest adherence to various healthy diets for 30 years to participants with the lowest adherence to those diets, the risk of developing severe cognitive decline was decreased by:

  • 40% for the Mediterranean diet.
  • 32% for the DASH diet.
  • 20% for the USDA-recommended healthy diet (as measured by the AHEI score).

#2: Can you reduce your risk of cognitive decline if you switch from an unhealthy diet to a healthy diet? To answer this question, the investigators looked at participants who started with the lowest adherence to each diet and improved to the highest adherence by the end of the study. This study showed that improving from an unhealthy diet to a healthy diet over 30 years decreased the risk of developing severe cognitive decline by:

  • 20% for the Mediterranean diet.
  • 25% for the DASH diet.

There were a few other significant observations from this study.

  • The inverse association between healthy diets and risk of cognitive decline was greater for nurses who had high blood pressure.
    • This is an important finding because high blood pressure increases the risk of cognitive decline.
  • The inverse association between healthy diets and risk of cognitive decline was also greater for nurses who did not have the APOE-ɛ4 gene.
    • This illustrates the interaction of diet and genetics. The APOE-ɛ4 gene increases the risk of cognitive decline. Healthy diets reduced the risk of cognitive decline in nurse with the APOE-ɛ4 gene but not to the same extent as for nurses without the gene.

This study did not investigate the mechanism by which healthy diets reduced the risk of cognitive decline, but the investigators speculated it might be because these diets:

  • Were anti-inflammatory.
  • Supported the growth of healthy gut bacteria.

The investigators concluded, “Our findings support the beneficial roles of long-term adherence to the [Mediterranean, DASH, and USDA] dietary patterns for maintaining cognition in women…Further, among those with initially relatively low-quality diets, improvement in diet quality was associated with a lower likelihood of developing severe cognitive decline. These findings indicate that improvements in diet quality in midlife and later may have a role in maintenance of cognitive function among women.”

Which Diet Is Best?

Mediterranean Diet FoodsIn a sense this is a trick question. That’s because this study did not put the participants on different diets. It simply analyzed the diets the women were eating in different ways. And while the algorithms they were using were diet-specific, there was tremendous overlap between them. For more specifics on the algorithms used to estimate adherence to each diet, read the article.

That is why the investigators concluded that all three diets they analyzed reduced the risk of cognitive decline rather than highlighting a specific diet. However, based on this and numerous previous studies the evidence is strongest for the Mediterranean and DASH diets.

And I would be remiss if I didn’t also mention the MIND diet. While it was not included in this study, the MIND diet:

  • Was specifically designed to reduce cognitive decline.
  • Can be thought of as a combination of the Mediterranean and DASH diets.
  • Includes data from studies on the mind-benefits of individual foods. For example, it recommends berries rather than all fruits.

The MIND diet has not been as extensively studied as the Mediterranean and DASH diets, but there is some evidence that it may be more effective at reducing cognitive decline than either the Mediterranean or DASH diets alone.

Which Foods Are Best?

AwardThe authors of this study felt it was more important to focus on foods rather than diets. This is a better approach because we eat foods rather than diets. With that in mind they analyzed their data to identify the foods that prevented cognitive decline and the foods increased cognitive decline. This is what they found:

  • Fruits, fruit juices, vegetables, fish, nuts, legumes, low-fat dairy, and omega-3 fatty acids (fish oil) reduced the risk of cognitive decline.
  • Red and processed meats, omega-6 fatty acids (most vegetable oils), and trans fats increased the risk of cognitive decline.

While this study did not specifically look at the effect of processed foods on cognitive decline, diets high in the mind-healthy foods listed above are generally low in sodas, sweets, and highly processed foods.

What Does This Study Mean For You?

Question MarkThe question, “Can diet protect your mind”, is not a new one. Several previous studies have suggested that healthy diets reduce the risk of cognitive decline, but this study breaks new ground. It shows for the first time that:

  • Long-term adherence to a healthy diet can reduce your risk of cognitive decline by up to 40%.
    • This was a 30-year study, so we aren’t talking about “diet” in the traditional sense. We aren’t talking about short-term diets to drop a few pounds. We are talking about a life-long change in the foods we eat.
  • If you currently have a lousy diet, it’s not too late to change. You can reduce your risk of cognitive decline by switching to a healthier diet.
    • This is perhaps the best news to come out of this study.

Based on current evidence, the best diets for protecting against cognitive decline appear to be the Mediterranean, DASH, and MIND diets.

And if you don’t like restrictive diets, my advice is to:

  • Eat more fruits, fruit juices, vegetables, fish, nuts, legumes, low-fat dairy, and omega-3 fatty acids (fish oil).
  • Eat less red and processed meats, omega-6 fatty acids (most vegetable oils), and trans fats.
  • Eat more plant foods and less animal foods.
  • Eat more whole foods and less sodas, sweets, and processed foods.

And, of course, a holistic approach is always best. Other lifestyle factors that help reduce your risk of cognitive decline include:

  • Regular exercise.
  • Weight control.
  • Socialization.
  • Memory training (mental exercises).

The Bottom Line 

Alzheimer’s is a scary disease. What is the use of having a healthy body, family, and fortune if we can’t even recognize the people around us?

A recent study looked at the effect of diet on cognitive decline in women. The study started with middle-aged women (average age = 48) and followed them for 30 years. The investigators then used these data to answer two important questions that no previous study had answered:

#1: What is the effect of long-term adherence to a healthy diet? When the investigators compared participants with the highest adherence to various healthy diets for 30 years to participants with the lowest adherence to those diets, the risk of developing severe cognitive decline was decreased by:

  • 40% for the Mediterranean diet.
  • 32% for the DASH diet.
  • 20% for the USDA recommendations for a healthy diet.

#2: Can you reduce your risk of cognitive decline if you switch from an unhealthy diet to a healthy diet? This study showed that improving from an unhealthy diet to a healthy diet over 30 years decreased the risk of developing severe cognitive decline by:

  • 20% for the Mediterranean diet.
  • 25% for the DASH diet.

The investigators concluded, “Our findings support the beneficial roles of long-term adherence to the [Mediterranean, DASH, and USDA] dietary patterns for maintaining cognition in women…Further, among those with initially relatively low-quality diets, improvement in diet quality was associated with a lower likelihood of developing severe cognitive decline. These findings indicate that improvements in diet quality in midlife and later may have a role in maintenance of cognitive function among women.”

For more details on the study, which diets, and which foods are best for protecting your mind, and what this study means for you, read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease.

Diet And Mental Health In Teens

Is Your Teen Crazy Because Of What They Eat?

Author: Dr. Stephen Chaney

 

diet mental health teensIf you have teenagers or have had teenagers in the past, you know they can be a little crazy at times. Sometimes they are a lot crazy. It’s easy to dismiss the occasional weird behavior by attributing it to raging hormones. I wouldn’t want to dismiss the difficulty teens experience adjusting to all these new hormones running around inside their body.

However, if you have a teenager, you also know their diet often isn’t the best. Many of them live on sodas, fast foods, snack foods and sweets. Could there be a correlation between what they eat and their mental health? In fact, several recent studies have suggested there is a correlation between poor diet and mental health issues in teens.

What is the connection between diet and mental health in teens?

This study (WH Oddy et al, Brain, Behavior, and Immunity, doi.org/10.1016/j.bbi.2018.01.002) breaks new ground.

  • The scientists in charge of the study asked whether the effect of diet on mental health was direct or indirect. Specifically, they asked whether diet influenced obesity and inflammation which, in turn, influenced mental health.
  • They also investigated a reverse hypothesis model. Specifically, they asked whether poor mental health led to poor diet rather than the other way around.

How Was This Study Done?

diet mental health teens doctorsThis study has a very interesting history. It grew out of a major pregnancy study (The Raine study) initiated in Western Australia in 1989. The Raine study was designed to determine how events during pregnancy and childhood influence health later in life. Diet and many other variables were measured during pregnancy, at birth, and at 1, 2, 3, 5, 8, 10, 14, 17, 18, 20, and 22 years of age for the offspring. This particular study followed 843 teenagers who were assessed at ages 14 and 17.

Based on food frequency questionnaires administered at both ages, the participants’ diets were given a score ranging from a “Healthy” at one extreme to “Western” at the other extreme.

  • The “Westerndiet was characterized by fast foods, convenience foods, red and processed meats, full-fat dairy, French fries, refined grains, sweets, soft drinks, chips, sauces, and dressings. (Does that sound like your teen?)
  • The “Healthydiet was characterized by whole grains, fruits, vegetables, legumes, and fish. (It’s nice to know that some teens eat that way.)

In addition to diet, the scientists measured BMI (a measure of obesity) and mental health in the 14-year-old group. When those same teens reached 17, the measurements were repeated, and blood markers of inflammation were also measured.

Two assessments of mental health were used.

  • The first assessment measured depression.
  • The second assessment measured “Internalizing Behaviors” (withdrawal, depression, and anxiety) and “Externalizing Behaviors” (aggression, delinquency, and attention disorders). High scores on this test indicate a higher level of emotional and behavioral problems.

 

Diet And Mental Health In Teens

diet mental health teens choicesHere are the results of the study:

  • Adherence to a “Western” diet was associated with greater caloric intake and obesity at age 14.
  • By the time the teens reached 17, adherence to a “Western” diet was associated with:
    • Obesity and inflammation
    • Depression and other mental health issues
  • A “Healthy” diet was protective against obesity, inflammation and mental health issues.
  • Obesity and inflammation were independently associated with depression and mental health issues in the 17-year-olds.

So what was the correlation between diet and mental health in teens?

On this basis, the investigators speculated that the effect of poor diet on mental health outcomes in teens was mediated by obesity and inflammation. (That is a fancy way of saying poor diet leads to obesity and inflammation, and obesity and inflammation lead to poor mental health.) However, the authors acknowledged they could not exclude a direct effect of diet on mental health.

  • Depression at age 14 did not correlate with poor dietary patterns at age 14. Simply put, if you started with everyone who had poor dietary habits at age 14, it correlated well with depression. However, if you went in the reverse direction – if you started with everyone who was depressed at age 14, it did not correlate well with poor diet.

On this basis, the investigators concluded that the reverse model hypothesis was unlikely. In short, they concluded that a model in which poor diet leads to depression and other mental health issues in teens is much more likely than a model in which mental health issues lead to a poor diet.

 

What Does This Mean For You?

diet mental health teens vegetablesWhen you put this in the context of previous studies, it is clear that what we eat matters. More importantly, what we eat matters at every stage of life. For example:

These studies are just the tip of the iceberg. There are dozens of recent studies that come to the same conclusion. In short, a good diet can make you happier as well as healthier. Whether you are 9 months or 90 years, a good diet is just as important for your mental health as for your physical health.

As for those crazy teens of yours, you might want to encourage them to eat healthier. It may be a hard sell at first, but once they start feeling happier and calmer they may just be converts to a healthy eating plan.

Remember, there is a connection between diet and mental health in teens.

The Bottom Line:

 

A recent study followed a group of teens in Western Australia from ages 14 to 17. They compared the effect of a “Western diet” (characterized by fast foods, convenience foods, red and processed meats, full-fat dairy, French fries, refined grains, sweets, soft drinks, chips, sauces, and dressings) with a “Healthy diet” (characterized by whole grains, fruits, vegetables, legumes, and fish) on obesity, inflammation, depression, and mental health. The study found:

  • Adherence to a “Western” diet was associated with greater caloric intake and obesity at age 14.
  • By the time the teens reached 17, adherence to a “Western” diet was associated with:
    • Obesity and inflammation
    • Depression and other mental health issues
  • A “Healthy” diet was protective against obesity, inflammation and mental health issues.

This study was consistent with dozens of other studies showing that diet affects mental health at every age. These studies show a good diet can make you happier as well as healthier. Whether you are 9 months or 90 years, a good diet is just as important for your mental health as for your physical health.

As for those crazy teens of yours, you might want to encourage them to eat healthier. It may be a hard sell at first, but once they start feeling happier and calmer they may just be converts to the healthy eating plan.

For more details, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

Health Tips From The Professor