4. A Closer Look at Key Nutrients

Your Diet Vs. Chronic Disease

It’s estimated that half of all U.S. adults—about 117 million people—suffer from preventable, diet-related chronic diseases. Shifting to healthier eating patterns that contain the nutrients your heart and brain require can help bring about lasting improvements in individual health, according to the 2015-2020 Dietary Guidelines for Americans.

 “By focusing on small shifts in what we eat and drink, eating healthy becomes more manageable,” said Secretary of Health and Human Services Sylvia M. Burwell in announcing the guidelines with Secretary of Agriculture Tom Vilsack. “The Dietary Guidelines provide science-based recommendations on food and nutrition so people can make decisions that may help keep their weight under control and prevent chronic conditions like type 2 diabetes, hypertension, and heart disease.”

Understanding Nutrition Studies

The science behind those “science-based recommendations” generally takes the form of either epidemiological (also called observational or population) studies or randomized clinical trials. In epidemiological studies, researchers compare the dietary habits of large groups of people and seek to identify patterns based on different health outcomes. If people who eat more fatty fish, such as the Inuit of Greenland, have substantially lower rates of heart disease than those consuming the typical American diet, maybe something in the fish helps protect against heart disease. (In fact, this was how omega-3 fatty acids were first identified as heart-healthy.) The drawback of such studies is that, by their design, they can’t prove cause and effect.

In randomized clinical trials (RCTs, also called randomized controlled trials), a dietary intervention is administered to one group while a second “control” group doesn’t change its diet or receives a placebo (an inert substance). RCTs are considered the “gold standard” of medical research because they can demonstrate causation. They are very effective for conditions that change fairly rapidly, such as cholesterol levels or blood pressure, but they can be challenging and expensive for studying complex, long-term conditions such as the development of Alzheimer’s disease.

By analyzing results from a combination of such studies, scientists have identified nutrients that are important to healthy heart and brain functioning, as well as foods that are rich in these nutrients. The remainder of this chapter provides information about specific nutrients and what research has shown about how they affect your heart and brain.

Nutrients You May Be Lacking

The latest Dietary Guidelines for Americans also offer some guidance on what the experts call “nutrients of concern”—vitamins and minerals many Americans may not be getting enough of. For the general population, these include vitamin A, vitamin D, vitamin E, folate, vitamin C, calcium, magnesium, and potassium. Many people also fall short in consuming dietary fiber. (On the other hand, sodium, added sugar, and saturated fat are overconsumed.)

Many of these nutrient shortfalls have direct consequences for the health of your heart and brain. A lack of B vitamins can lead to increased blood levels of homocysteine—an amino acid that has been associated with a higher risk for heart disease and stroke. Besides building bones, calcium plays key roles in nerve transmission, constriction and dilation of blood vessels, and muscle contraction. Low levels of vitamin D, also vital for healthy bones, have been associated with a wide range of chronic conditions. Potassium can help control blood pressure, an important risk factor for stroke. Dietary fiber that occurs naturally in foods may help reduce the risk of cardiovascular disease.

These and some of the other nutrients that are most critical to your heart and brain are discussed below.

B Vitamins

Several of the B vitamins are specifically linked to a healthy heart and brain, although all have important functions in your body.

Low levels of vitamin B12 have been linked to poorer scores on cognitive tests, including memory tests, and to smaller total brain volume. Even if you’re just a little low in vitamin B12, you might be at risk for cognitive decline, according to Tufts researchers. They analyzed data collected from 549 men and women, average age 75, who participated in the Framingham Heart Study. Declines in cognitive abilities over an eight-year period were greater in those with the lowest vitamin B12 levels than in those with higher B12 levels.

Folate (a B vitamin) and vitamins B6 and B12 each are known to lower the blood levels of homocysteine, an amino acid linked to both heart disease and various forms of dementia. It isn’t clear, however, if lowering homocysteine levels reduces the risk for these conditions.

British researchers found that supplements of these three B vitamins slowed the progress of mild cognitive impairment. Older individuals who took supplements containing folate and vitamins B6 and B12 also showed less brain shrinkage in MRI scans than those who received a placebo. The individuals with the highest homocysteine levels at the beginning of the study experienced the greatest benefit from the B vitamins.

Getting enough vitamin B12 can be a challenge for older adults because as you age, it becomes more difficult to absorb B12 from food. Older people produce less stomach acid and often take acid-reducing medications, and acid is needed to break vitamin B12 free from proteins in food. The form of vitamin B12 in supplements and fortified foods doesn’t require an acidic environment for absorption.

A Few Sources of B Vitamins

• Folate: Garbanzo beans (chickpeas), lentils, asparagus, other types of beans (pinto, black, lima, navy, white, kidney) and peas (cowpeas, split peas), spinach, turnip greens, broccoli, whole grains, and fortified flours, cereals, and juices
• B6: Tuna, turkey, chicken, beef, salmon, halibut, sweet potatoes, white potatoes, sunflower seeds, spinach, bananas, nuts, fortified cereals, and soy products
• B12: Sardines, salmon, tuna, lamb, cod, scallops, dairy, eggs, fortified cereals, and soy products. Plant foods do not contain B12, so people who consume few or no animal foods need to take supplemental vitamin B12 or seek out fortified foods.

Vitamin D

Vitamin D has been the subject of much recent research and headlines.  Promising findings from epidemiological studies of vitamin D have frequently not been supported by randomized trials, however, leading some experts to view vitamin D as a subject of “hype.”

Nonetheless, vitamin D plays a key role in functions throughout the body, such as helping to maintain healthy bones, and may help protect your heart as well as your brain. Although extra vitamin D may not deliver the health benefits some scientists had hoped for, it’s clearly important to get enough. Vitamin D—called the “sunshine vitamin” because the body can naturally synthesize vitamin D when the skin is exposed to sunlight—can be difficult to obtain in adequate amounts from diet and sun exposure alone.

Low levels of vitamin D have been linked to cognitive decline and dementia. In a review of the evidence, researchers reported that in 18 out of 25 studies, individuals with low vitamin D levels did worse on tests of cognitive functioning or were more likely to develop dementia than individuals with higher levels of the vitamin. Similarly, in a Tufts study of nearly 1,100 seniors, those with higher levels of vitamin D performed better on tests of executive function, such as planning, organizing, paying attention to detail, forming concepts, and thinking abstractly.

Vitamin D and Calcium

As for your heart, supplements of vitamin D and calcium might modestly improve your cholesterol numbers, according to one study. Researchers randomly assigned study participants to take either 1,000 milligrams of calcium plus 400 IU of vitamin D supplements or a placebo. Supplementation was associated with an average 4.46 mg/dL decrease in unhealthy LDL cholesterol compared to the placebo group—a modest, but statistically significant, reduction. Triglycerides also decreased in the supplement group, while healthy HDL cholesterol levels increased.

A Few Sources of Vitamin D

• Fortified dairy products and orange juice, salmon, mackerel, sardines, halibut, flounder, rainbow trout, tuna, eggs, mushrooms (especially those exposed to ultraviolet light during growing)

Antioxidants

Another subject of recent media hype has been antioxidants—compounds that combat oxidative damage caused by molecules called free radicals. Here, too, some of the excitement has faded as research has failed to back up initial hopes. Many researchers now refer instead to “phytonutrients,” indicating that the health benefits of compounds found in coffee, tea, red wine, dark chocolate, and many other plant foods are more extensive than merely combating oxidation. Many familiar vitamins and minerals also act as antioxidants, including selenium, beta-carotene (a precursor to vitamin A), and vitamins C and E.

A diet with a high total antioxidant content, especially from fruits and vegetables, has been linked to a reduced risk of stroke, both in people known to have cardiovascular disease and those initially free of the disease. Results from one study suggest that eating a single additional serving of fruits or vegetables daily reduces the risk of dying from heart disease by four percent. Study participants who ate at least eight servings of fruits and vegetables daily were 22 percent less likely to die of heart disease than those who ate no more than two daily servings.

Vitamin C appears to protect the endothelium (a layer of cells that lines blood vessels, the heart, and lymph vessels), which may reduce the risk of both heart disease and dementia.

Diets rich in both vitamin E and the mineral selenium have been linked to a lower risk of age-related cognitive decline. In one study, researchers found that, among adults age 55 and older, those who consumed the most vitamin E from foods were the least likely to develop Alzheimer’s disease and other forms of dementia. Another study that measured the selenium levels of elderly people found that those with the highest levels scored 10 years younger on tests of cognitive function compared to those with the lowest levels.

None of these findings, however, should be interpreted to suggest that you need supplements of antioxidants. In fact, supplements of certain antioxidants have been found to be harmful to certain populations: Extra beta-carotene increased the risk of lung cancer in smokers, and vitamin E and selenium supplements were associated with higher prostate-cancer risks. By following a healthy dietary pattern, you can get all of the antioxidants you need.

A Few Sources of Antioxidant Nutrients

• Selenium: Brazil nuts, tuna, sunflower seeds, whole-grain breads and cereals, wheat germ
• Beta-carotene: Sweet potatoes, carrots, spinach, leafy greens, tomatoes, broccoli, cantaloupe, winter squash, peaches, mangos, apricots
• Vitamin C: Kiwi, watermelon, oranges, grapefruit, bell peppers, tomatoes, broccoli, strawberries, papaya, pineapple, cabbage
• Vitamin E: Sunflower, safflower and other liquid vegetable oils, almonds and other nuts, avocados, shrimp, fortified breakfast cereals

Your Blood Pressure and Your Diet

We’ve already seen that the DASH eating plan is effective at controlling high blood pressure, which is in turn a risk factor for stroke and some types of dementia. Sticking to such an overall healthy eating pattern is your best strategy for combating hypertension. But it’s also true that certain nutrients may play a particular role in blood pressure. Observational studies consistently show that diets with an abundance of foods rich in potassium and magnesium are associated with lower blood pressure, and research also suggests that calcium may play a role in controlling blood pressure and reducing stroke risk (see Box 4-1, “Lower Stroke Risk With Higher Magnesium and Potassium”).

Other research has shown that postmenopausal women who consume the most potassium are at lower risk of suffering a stroke. Researchers who analyzed data on 90,137 women, ages 50 to 79, found that women who consumed the most potassium were 12 percent less likely to suffer a stroke of any kind than those in the lowest-potassium group. In participants free of hypertension, women consuming the most potassium had a 27 percent lower risk of ischemic stroke than women consuming the least potassium.

Most American adults fall far short of meeting the recommended daily potassium intake of 4,700 milligrams. Similarly, it’s estimated that 70 to 80 percent of U.S. adults fail to get the recommended intake of magnesium (for adults ages 31 and older, 420 milligrams for men and 320 milligrams for women). Another benefit of magnesium: Tufts researchers have linked higher magnesium intake to reduced calcification in the coronary arteries.

Potassium and magnesium may be especially effective in countering the blood-pressure-boosting effects of excess sodium. In addition to getting these minerals from dietary sources, you can decrease your salt intake by switching to a salt substitute that contains these minerals.

One meta-analysis calculated that study participants who used salt substitutes for six months to two years had systolic blood pressure that was 4.9 mmHg lower than those who used sodium chloride (table salt).

A Few Sources of Blood Pressure Nutrients

• Potassium: Pumpkin, apricots, bananas, artichokes, avocados, beets, Brussels sprouts, tomatoes/tomato juice, sweet potatoes, cantaloupe, nectarines, oranges/orange juice, parsnips, potatoes, prunes/prune juice, spinach.
• Magnesium: Quinoa, pumpkin and sesame seeds, nuts, Swiss chard, spinach, beans, bananas, acorn squash, green peas.
• Calcium: Milk, yogurt and other dairy products, beans, canned salmon and sardines (with bones), collard and turnip greens, spinach, soybeans, kale, and fortified cereals, fruit juices, and non-dairy milks.

Fiber

Even though your body doesn’t digest fiber—it’s the part of plant foods that your gastrointestinal system is unable to break down—the fiber in your foods may help reduce your risk of cardiovascular disease, obesity, and type 2 diabetes. Most of us don’t get enough fiber, however. Typical dietary fiber intake in the U.S. is only about 15 grams per day, far below the recommended 25 grams daily for women (21 grams for women over 50) and 38 grams for men (30 grams for men over 50). Most of the fiber in American diets comes from breads, rolls, buns, and pizza crust made with refined flour, which is low in fiber and other nutrients. To boost fiber intake, Americans need to increase their consumption of beans and peas, vegetables, fruits, whole grains, and whole-grain products, including cereals, pastas, and breads (see Box 4-2, “Fiber Content of Selected Foods”).

Don’t simply seek out highly processed foods that contain added fiber or take fiber supplements. Many of fiber’s health benefits, maybe most, exist because of the mix of nutrients naturally present in fiber-rich fruits, vegetables, beans, and whole grains.

In addition to the numerous health benefits already associated with fiber, research supports a role for fiber in defending against strokes. The latest comes from an analysis of data on almost 70,000 participants in two long-running Swedish studies. The study participants who consumed the most total fiber were 10 percent less likely to suffer a stroke than those with the lowest intake.

Other research has found that, for every additional seven grams of daily dietary fiber consumed, the risk of stroke dropped by seven percent.

A Few Sources of Fiber

• Grains: Bran cereal, whole wheat, barley, popcorn, oats, bulgur, rye, buckwheat, brown rice
• Vegetables: Beans (black, kidney, navy, lima, white, pinto), nuts, peas, artichokes, broccoli, kale, sweet potatoes, carrots
• Fruits: Raspberries, pears (with skin), apples (with skin), blackberries, strawberries, bananas, figs

The Macronutrients

Proteins, carbohydrates, and fats are called “macronutrients” because they are the nutrients needed in the largest amounts by the human body. The macronutrients provide your body with energy in the form of calories. (Micronutrients, such as vitamins and minerals, are needed in smaller amounts, and are not assigned calorie values.)

While there is some debate about how much of each macronutrient should be included in a healthy dietary pattern, most nutrition experts agree that each macronutrient plays an essential role in your health.

Protein

How much protein do you need for a healthy heart and brain? Despite the recent proliferation of products touting their protein content, most Americans actually get plenty of protein. Some evidence does suggest, however, that older people may need more protein, not only to prevent frailty but also to protect against high blood pressure.

In one study, scientists followed 1,361 healthy, middle-aged (30 to 54 years old) men and women for an average of 11.3 years. Study participants who had the highest protein intake were 40 percent less likely to develop high blood pressure than those consuming the least protein. The high-protein group averaged 102 grams of protein a day (more than double the Daily Value of 50 grams for a 2,000-calorie-per-day diet). Higher protein intake also was associated with lower average systolic and diastolic blood pressure. Because this was an observational study, however, the data doesn’t prove a cause-and-effect connection.

Amino Acids for Heart and Brain

Amino acids are small molecules that bond together in long chains to form protein. Your heart needs amino acids to build cardiac muscle, which is essential for keeping the heart pumping. Other amino acids from proteins make hemoglobin, the component of red blood cells that carries oxygen throughout the body.

Your brain also relies on amino acids for a number of important processes. Amino acids are necessary to produce myelin, the protective sheath that covers nerve cells and helps speed messages through them. Amino acids are also used in the production and regulation of chemical messengers called neurotransmitters, such as dopamine, norepinephrine, and serotonin, which carry critical information from one nerve cell to another.

A Few Sources of Protein

• Animal sources: Meat, poultry, seafood, yogurt and other dairy products, eggs
• Plant sources: Soy products, beans, lentils, peas, nuts, seeds, whole grains. Among plant sources, only soy products and quinoa provide all the essential amino acids your body needs, making them “complete” proteins; to get all of the amino acids you need from plant foods with “incomplete proteins,” you’ll need to eat a variety of these foods, such as rice and beans, though not necessarily at the same meal.

Carbohydrates

Your body requires a constant supply of glucose (a type of sugar), which it breaks down from carbohydrates in foods such as fruits, vegetables, grains, and dairy.  Carbs include starches, sugars, and fiber (fiber is the only type of carb that is not broken down into glucose).

Your hard-working heart requires glucose to provide the energy it needs to keep pumping. Your brain also relies on glucose as its primary energy source—and it demands a disproportionately large share. Glucose is among the few substances able to pass unhindered through the blood-brain barrier. Because brain cells can’t store glucose like cells in other areas of your body, they need to be fed a steady stream of glucose throughout the day. Areas of the brain that control thinking are sensitive to drops in glucose, which is why your mind might feel fuzzy if it’s been several hours since your last meal.

The Recommended Dietary Allowance (RDA) for carbohydrates is based on the brain’s glucose requirement; it is 130 grams daily—the equivalent of 520 calories of carbohydrate—for adults of all ages. The Institute of Medicine (IOM) also set an Acceptable Macronutrient Distribution Range (AMDR) for carbohydrate of 45 to 65 percent of total calories. At the low end of this range, however, it is very difficult to meet the recommendations for fiber intake, and at the high end of the range, overconsumption of carbohydrates may result in high blood triglyceride values.

The key to consuming carbs is to ensure that they are good sources of important nutrients. Avoid foods and beverages that are high in carbs from added sugar and/or refined flour, such as soft drinks, white bread, and desserts, which are high in calories but have minimal nutritional value.

Carb Cautions

The current dietary guidelines stress the importance of limiting carbs in the form of added sugars, and research has also spotlighted starches as a culprit in weight gain and diabetes, both of which contribute to your risk for cardiovascular disease.

A 2015 study, for example, reported that high intakes of starchy vegetables such as corn, peas, and potatoes were associated with weight gain. In the same study, diets higher in fruits and non-starchy vegetables, including cauliflower, were linked with weight loss.

Another study published in 2015 linked higher starch consumption to a greater risk of type 2 diabetes in women, but higher intakes of total fiber, cereal fiber, and fruit fiber were all associated with lower diabetes risk, emphasizing the importance of choosing your carbs carefully.

A Few Healthy Sources of Carbohydrates

• Fruits and vegetables: Beans, winter squash, apples, pears, berries, bananas, grapes, melon
• Grains: Whole-grain breads, pasta, and cereals
• Dairy: Milk, yogurt, and cheeses, including cottage cheese

Fats

Remember when everyone was trying to avoid fats of all kinds? In place of fats, food producers pushed products high in added sugars and refined carbs (mostly in the form of white flour), which experts now argue contributed to America’s obesity epidemic. Now, nutritionists advise smart fat selection—substituting heart-healthy polyunsaturated and monounsaturated fats for saturated fats—instead of fat avoidance.

Some fats are actually essential for your body, particularly for your heart and brain. You must obtain these essential fatty acids from your diet because your body cannot produce them.

When your body digests fats, it breaks them down into fatty acid molecules. The membranes that make up neurons—the brain cells that communicate with one another—are made up of these fatty acids. Fats (along with amino acids) are also used to create myelin, the protective sheath that covers neurons.

There are two types of essential fatty acids, omega-3 fatty acids and omega-6 fatty acids. Both are subclasses of polyunsaturated fatty acids.

Omega-3 Fatty Acids

You’ve probably heard of “omega-3s” and may have even purchased fish-oil supplements to try to get more. But what exactly are they? The “omega-3” name refers to their molecular structure: These fatty acids have a double bond (carbon to carbon) at the third carbon atom from the end (“omega”) of the chain that makes up these organic compounds.

Omega-3 fatty acids include alpha-linolenic acid (ALA), found in plants, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found in fatty fish. The body converts a small portion of ALA to brain-active, heart-healthy DHA and EPA. Fish and fish oil are the best sources of EPA and DHA, although it’s important to get ALA from plant foods as well.

Research has found that both fish and walnuts have beneficial effects on cholesterol levels, which are closely associated with heart health. People who consumed 1.5 ounces of walnuts six days per week reduced their total cholesterol by five percent and LDL (bad) cholesterol by nine percent, and people who ate fish twice a week had a five percent increase in HDL (good) cholesterol and an 11 percent decrease in triglycerides.

In the brain, DHA is the most plentiful fatty acid, especially in the neurons and the gray matter—the area responsible for language, memory, and thought. DHA is essential for the proper growth and function of brain tissue, including the production of neurons and the transmission of nerve impulses across neurons. In studies, high blood levels of DHA have been linked to a reduced risk of dementia and Alzheimer’s disease (see Box 4-3, “More Omega-3s Associated With Lower Cognitive Risks”).

EPA and DHA also reduce insulin resistance and inflammation. Both problems have been associated with Alzheimer’s disease, heart disease, and cancer. The American Heart Association recommends eating two servings of EPA- and DHA-rich fatty fish each week for the prevention of heart disease.

Omega-6 Fatty Acids

Linoleic acid (LA) is the essential omega-6 fatty acid, which is most plentiful in vegetable oils. LA is necessary for normal growth, development, and brain function.

Substituting polyunsaturated fat for saturated fat remains the best healthy-fat advice for fighting heart disease, according to a recent meta-analysis. Researchers found that swapping five percent of calories consumed from saturated fat sources, such as red meat and butter, with foods containing linoleic acid—the main polyunsaturated fat found in vegetable oils, nuts, and seeds—was associated with a nine percent lower risk of coronary heart disease events. Switching from saturated fat to linoleic acid also was associated with a 13 percent lower coronary heart disease mortality risk. Study participants who consumed the most dietary linoleic acid had a 15 percent lower risk of heart-disease events and a 21 percent lower risk of coronary deaths than those who consumed the least linoleic acid. Substituting linoleic acid for five percent of calories from carbohydrates was associated with similar reductions in risks of heart disease.

A Few Sources of Essential Fatty Acids

• ALA: Flaxseed, walnuts, other nuts and seeds
• DHA and EPA: Salmon, sardines, tuna, mackerel
• LA: Liquid vegetable oils (sunflower, safflower, soybean, canola, grapeseed, olive, corn, peanut), nuts and seeds

Now that we’ve explored the basics of a dietary pattern that supports heart and brain health, as well as the foods and nutrients that are the key ingredients in that pattern, it’s time to put all the pieces together in our sample meal plans and recipes, which you will find in the next two chapters.

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