If you want to optimize and protect your brain health, know your important numbers …

Most people can tell you their age. Many can tell you their weight. Far fewer know the health measurements that may be influencing how well they think, focus, remember, make decisions, regulate their emotions, and age over time.

According to Daniel Amen, one of the most practical steps people can take to improve their brain health is to know their “important numbers.” Dr. Amen is a psychiatrist, internationally-renowned brain imaging researcher, founder of the Amen Clinics, and one of the leading advocates for taking a brain-focused approach to health and mental health. Throughout his work, he teaches that the brain does not operate independently from the rest of the body. The health of your heart, hormones, metabolism, immune system, and even your waistline can influence how well your brain functions.

That is why Dr. Amen encourages people to move beyond simply asking whether they feel healthy. Instead, he recommends understanding the measurable factors that can affect brain performance and long-term brain health. Many of these numbers can be checked through routine medical evaluations and laboratory testing. Knowing them can help identify potential problems before they become more serious and can provide valuable information for improving overall health.

Here are the ten “important numbers” Dr. Amen believes everyone should know:

Body mass index

Body Mass Index, commonly called BMI, compares your weight to your height. It is one of the simplest ways to assess whether your weight falls within a healthy range. Dr. Amen frequently discusses the relationship between excess body weight and brain health. Research has shown that obesity is associated with reduced blood flow to the brain, and reduced blood flow is one of the major predictors of poor brain function. Since the brain relies on a constant supply of oxygen and nutrients delivered through the bloodstream, anything that interferes with circulation can affect its performance.

BMI categories include:

• • Normal: 18.5 to 25.
  • Overweight: 25 to 30.
  • Obese: Greater than 30.

Although BMI is not a perfect measurement, it provides a useful starting point for understanding whether weight may be placing added stress on the body and brain.

Waist-to-height ratio
Dr. Amen often emphasizes that where you carry excess weight matters. A person may have a BMI that appears acceptable while still carrying unhealthy amounts of abdominal fat.

The waist-to-height ratio is calculated by dividing your waist measurement by your height, both measured in inches. The waist measurement should be taken at the level of your belly button rather than estimated from clothing size. Pants sizes vary widely among manufacturers, and many people underestimate their true waist measurement.

For women:

• • Less than .35: Underweight.
  • .35 to .42: Extremely slim.
  • .42 to .49: Healthy.
  • .49 to .54: Overweight.
  • .54 to .58: Seriously overweight.
  • Greater than .58: Highly obese.

For men:

• • Less than .35: Underweight.
  • .35 to .43: Extremely slim.
  • .43 to .53: Healthy.
  • .53 to .58: Overweight.
  • .58 to .63: Seriously overweight.
  • Greater than .63: Highly obese.

Abdominal fat is metabolically active tissue. It contributes to inflammation, insulin resistance, and other metabolic problems that can negatively affect the brain. For this reason, Dr. Amen considers waist measurements an important indicator of overall health risk.

Blood pressure
Blood pressure measures the force of blood pushing against the walls of the arteries. Because the brain is supplied by an extensive network of blood vessels, blood pressure has a direct impact on brain function. Dr. Amen teaches that high blood pressure is associated with lower overall brain function and can damage blood vessels over time.

Optimal blood pressure is:

• • Systolic: 90 to 120.
  • Diastolic: 60 to 80.

Stage 1 hypertension:

• • Systolic: 130 to 139.
  • Diastolic: 80 to 89.

Stage 2 hypertension:

• • Systolic: 140 or higher.
  • Diastolic: 90 or higher.

Hypotension, or blood pressure that is too low, can also create problems:

• • Systolic below 90.
  • Diastolic below 60.

Dr. Amen recommends taking elevated blood pressure seriously. Weight loss, regular exercise, fish oil supplementation, and medical treatment when necessary may help bring blood pressure into a healthier range.

Vitamin D level
Vitamin D is often called the sunshine vitamin because the body produces it when skin is exposed to sunlight. Yet many people have levels that are lower than optimal.

According to Dr. Amen, low vitamin D levels have been associated with obesity, depression, cognitive impairment, heart disease, and numerous other health concerns. Because vitamin D receptors are found throughout the brain and body, adequate levels appear to play an important role in overall health.

The test used to evaluate vitamin D status is the 25-hydroxy vitamin D level:

• • Low: Less than 30 ng/dL.
  • Optimal: 50 to 100 ng/dL.

When levels are low, Dr. Amen recommends discussing appropriate strategies with a healthcare provider, which may include increased sunlight exposure and vitamin D supplementation.

Thyroid function
The thyroid gland helps regulate metabolism and energy production throughout the body. When thyroid function is low, brain activity can also slow down. Dr. Amen teaches that low thyroid levels can impair thinking, judgment, self-control, and mental clarity. They can also make weight loss significantly more difficult.

Important thyroid measurements include TSH, Free T3, and Free T4. According to the American Association of Clinical Endocrinologists, a TSH level above 3.0 warrants further investigation.

Dr. Amen notes that there is no single symptom, laboratory value, or test result that perfectly diagnoses hypothyroidism. Physicians typically evaluate symptoms along with TSH, T3, and T4 results to determine whether thyroid dysfunction may be present.

C-reactive protein
C-reactive protein, commonly called CRP, is a marker of inflammation. Inflammation is one of the recurring themes in Dr. Amen’s work because chronic inflammation has been linked to a wide range of physical and neurological problems. Elevated inflammation can affect brain health, mood, cognitive function, and overall wellness. The healthy range is 0.0 to 1.0 mg/dL.

A high CRP level does not identify the exact source of inflammation. However, Dr. Amen notes that the most common cause is metabolic syndrome or insulin resistance. The second most common cause is some type of food reaction, including food sensitivities, true allergies, or autoimmune reactions such as those associated with gluten. Elevated CRP levels can also indicate hidden infections that deserve further medical evaluation.

Hemoglobin A1C
Hemoglobin A1C, often abbreviated HbA1C, provides an estimate of average blood sugar levels during the previous two to three months.

Dr. Amen frequently refers to diabetes as “type 3 diabetes” when discussing its relationship to Alzheimer’s disease because of the growing evidence connecting blood sugar problems with brain decline. For that reason, he considers blood sugar control one of the most important aspects of brain health.

HbA1C ranges include:

• • Normal for someone without diabetes: 4.0% to 5.6%.
  • Optimal: Below 5.3%.
  • Pre-diabetes: 5.7% to 6.4%.

Higher levels suggest that blood sugar has been elevated for extended periods, increasing the risk of metabolic problems that may affect both body and brain.

Lipid panel
A lipid panel evaluates several important blood fats and cholesterol measurements. According to Dr. Amen, healthy cholesterol and triglyceride levels support cardiovascular health, which in turn supports healthy blood flow to the brain.

Key measurements include:

• • Total cholesterol: 135 to 200 mg/dL.
  • HDL cholesterol: 60 mg/dL or higher.
  • LDL cholesterol: Less than 100 mg/dL.
  • Triglycerides: Less than 100 mg/dL.

Dr. Amen points out an often-overlooked finding in the research. Total cholesterol levels below 160 mg/dL have been associated with depression, suicide, homicide, and increased mortality from all causes. For that reason, he considers a total cholesterol range of 160 to 200 mg/dL optimal.

He also emphasizes the importance of LDL particle size. Larger LDL particles tend to be less harmful than smaller LDL particles, which are considered more toxic.

When lipid levels are abnormal, Dr. Amen recommends improving diet quality, exercising regularly, using a high-quality fish oil supplement when appropriate, and working with a healthcare provider.

Testosterone
Many people think of testosterone only as a sex hormone, but it influences far more than reproductive health. Dr. Amen teaches that low testosterone levels in both men and women are associated with low energy, obesity, depression, heart disease, and Alzheimer’s disease.

For adult males:

• • Total testosterone: 280 to 800 ng/dL.
  • Optimal total testosterone: 500 to 800 ng/dL.
  • Free testosterone: 7.2 to 24 pg/mL.
  • Optimal free testosterone: 12 to 24 pg/mL.

For adult females:

• • Total testosterone: 6 to 82 ng/dL.
  • Optimal total testosterone: 40 to 82 ng/dL.
  • Free testosterone: 0.0 to 2.2 pg/mL.
  • Optimal free testosterone: 1.0 to 2.2 pg/mL.

Because hormones influence mood, motivation, energy, cognition, and overall vitality, Dr. Amen considers testosterone an important marker to monitor as part of a comprehensive brain-health strategy.

Ferritin
Ferritin measures the body’s iron stores. Iron is necessary for producing energy and transporting oxygen throughout the body. However, both excessively low and excessively high ferritin levels can create concerns.

Dr. Amen recommends an optimal ferritin range of 30 to 100 ng/mL. Low ferritin levels have been associated with anemia, restless leg syndrome, attention problems, low motivation, and low energy. Women often have lower iron stores than men because of menstruation.

Ferritin can also increase in response to inflammation and insulin resistance. When ferritin levels become excessively high, some clinicians believe blood donation may be helpful in appropriate individuals.

The laboratory tests Dr. Amen recommends
To gain a broader picture of overall health and brain function, Dr. Amen recommends discussing a comprehensive laboratory panel with a healthcare provider. His suggested panel includes:

Complete Blood Count (CBC) for blood flow.

• • Lipid Panel for blood flow.
  • Ferritin for retirement and aging.
  • Homocysteine for retirement and aging.
  • C-Reactive Protein for inflammation.
  • Omega-3 Index for inflammation.
  • Comprehensive Metabolic Panel for toxins and liver and kidney function.
  • Vitamin D level for immunity.
  • DHEA-S for neurohormones.
  • TSH, Free T3, and Free T4 for neurohormones.
  • Total and Free Testosterone for neurohormones.
  • Fasting Insulin for neurohormones and diabetes-related risk.
  • Hemoglobin A1C for diabetes-related risk.

One of the central ideas in Dr. Amen’s teaching is that brain health is not something that happens by accident. The brain responds to the condition of the body that supports it. Learning these numbers does not require becoming a medical expert. It simply means becoming informed enough to recognize potential concerns, ask better questions, and work with qualified healthcare professionals to make decisions that support both physical health and the organ that drives every thought, decision, memory, and relationship in your life.

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