Because of all the processed food now consumed in the US, getting the necessary nutrients from our diet has become increasingly difficult. Of course, we can turn to nutritional supplements, but research has consistently shown that fresh food-which has an abundance of healthful compounds that are believed to work synergistically-is usually our best source of valuable nutrients.

What most people don't realize: Choosing the right foods and food combinations allows you to consume these vital nutrients in a form that is most bioavailable, meaning the food components are efficiently digested, absorbed and assimilated.

What you must know to maximize the bioavailability of nutrients in your food...

Iron. This mineral is critical for brain function and helps your immune system operate normally by increasing your resistance to stress and disease. Iron can help you avoid symptoms of fatigue, weakness and irritability.

Plant foods are rarely a good source of iron. For example, although spinach is a good source of magnesium, bone-building vitamin K and other important nutrients, the fiber and plant chemicals in the spinach leaf bind to iron, inhibiting the mineral's bioavailability.

Helpful: When shopping for meat, look for dark meat products, such as liver, beef or dark meat turkey. They are the best sources of iron. Tofu and seafood (especially clams and shrimp) are also rich in iron.

Zinc. This mineral is essential for a healthy immune system. It is highly bioavailable in red meat, though some zinc is also found in nuts (almonds and walnuts). Poultry is another good source of zinc.

Helpful: Consider adding oysters to your diet. They are one of the richest sources of zinc.

Caution: Raw oysters are often contaminated with bacteria.

Magnesium. Up to 75% of Americans are deficient in this vital mineral, which is needed for heart health and strong bones as well as for blood sugar control.

Helpful: Vegetables are among the richest sources of magnesium. Eat raw or lightly steamed vegetables-highly processed or overcooked veggies lose their magnesium content. whole grains are also much richer sources of magnesium than refined grains.

Calcium. Many experts advocate the green, leafy vegetables for calcium, but these foods do not provide ample amounts of this mineral in a bioavailable form.

Sardines are an often-overlooked source of calcium, but they are not standard fare for many Americans.

Dairy foods remain the best regular source of calcium. Milk that has 1% or 2% fat is a good choice. Skim milk is not recommended because the bioavailability of fat-soluble vitamins, such as vitamin D, is diminished when you remove all the fat from milk.

Helpful: Avoid "fat-free half - and-half. " This product provides no nutritional value-it is usually filled with corn syrup and other sugars to give it the creamy feel of real half-and-half.

Selenium. The number-one source of this cancer-fighting mineral is the soil in which plants are grown. Soil in the Great Plains states contains adequate levels of selenium, so products from this area, such as whole-grain wheat, are generally good sources of selenium.

Helpful: If you are at an increased risk of cancer (due to family history, exposure to secondhand smoke or other carcinogens), consider taking a 50- to 2OO-microgram (mcg) selenium supplement.

Important: If you are currently undergoing treatment for cancer, talk to your doctor before taking selenium.

Chromium. This mineral, shown in dozens of studies to help control levels of blood sugar, is poorly absorbed by the body. Unless you eat organ meats, such as liver it is best consumed in supplement form.

Helpful: Everyone should consider taking a 200-mcg chromium supplement daily for general health. If you have diabetes, ask your doctor about taking 1,000 mcg of chromium daily.

Carotenoids. More than 600 nutritious plant compounds known as carotenoids can be found in vegetables and fruits.

Examples: Lycopene, found in tomatoes, watermelon and pink grapefruit, may help prevent prostate cancer. ..lutein and zeaxanthin, found in dark green, leafy vegetables and corn, may help prevent and treat macular degeneration, the leading cause of vision loss in people older than age 65.

Helpful: Because carotenoids are fat-soluble nutrients (that is, they require some amount of dietary fat for optimal absorption), consume carotenoid-rich foods along with olive oil or other healthful fat sources. Low-fat salad dressings can be used, but avoid no-fat versions.

Also helpful: Steam or lightly simmer vegetables. Raw fruits and vegetables contain valuable enzymes, and cooking breaks the cell walls, thus increasing the bioavailability of many valuable nutrients.

Examples: To maximize the amount of cancer-fighting lycopene you get from tomatoes, make them into a sauce.

Protein. On the bioavailability scale, meat, poultry, fish and eggs are among the best sources of protein. Although the protein found in lunch meats, such as ham and bologna, is bioavailable, these foods typically contain high levels of sodium and harmful fillers and preservatives known as nitrates.

Aim for 50 to 120 grams (g) of protein daily. One-half of a salmon fillet contains 42 of a chicken breast contains 27 g...three ounces of top sirloin contains 25 g.

Helpful: To maximize the bioavailability of the nutrients that are found in beef, prepare it medium-rare.

For a convenient protein source that lasts for several days, roast a turkey breast or chicken in an oven cooking bag, slice it up and use it during the week.

As an alternative to meat, consider using whey protein powder-an excellent source of protein derived from milk.

Look for cold filtered and ion exchanged on the label, which indicates that the processing has removed lactose (milk sugar) and casein (a highly allergenic protein found in milk). This process breaks down the whey, making it more absorbable.

Next Nutrition as well as Jarrow each make excellent whey products. Only approximately 2% of the people who have dairy allergies are allergic to whey protein.

Whey protein powder can be easily added to a smoothie.

What to do: Mix one scoop of protein powder (typically 20 g of protein) with 8 ounces of water, milk or juice and ice in a blender. Add frozen blueberries or other fruit, if desired.

If you are allergic to whey protein, consider soy powder-the protein in soy powder is more easily utilized than that in other soy foods. Soy powder can also be used in smoothies.

Important: If you eat a vegan diet (no animal products of any kind), take a multivitamin as nutritional insurance. Plant-based diets do not contain adequate amounts of all nutrients.

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