Can supplements help you find your car keys? Some just might. Research shows that taking the right supplements, in combination with a healthy lifestyle, can preserve and improve brain function.

Renowned brain specialist Daniel G. Amen, MD, knows this firsthand. During his studies of single-photon emission computerized tomography (SPECT) imaging, he decided to have some scans done of his own brain. What he found was that years of unhealthy habits—drinking diet soda, eating fast food, not exercising—had caught up with him. He started a healthy brain program, which included brain-building supplements. Now his brain is healthier than it was 20 years earlier.

Here, the best supplements for your brain. Caution: Most people can safely take all of them daily, but always check with your health-care provider first, particularly if you have any health problems such as high blood pressure or if you are on any medications, including blood thinners.

MEMORY VITAMIN

Americans don’t get enough sun, and because of this, about two-thirds of adults don’t meet their vitamin D needs through sunshine exposure.

You probably know that vitamin D is essential for bone strength as well as for preventing some cancers, including breast cancer. What’s new: Vitamin D appears to help the immune system remove beta-amyloid, an abnormal protein, from the brain. This is important because beta-amyloid causes the “tangles” that are associated with Alzheimer’s disease.

Brain cells use vitamin D for learning, memory and other cognitive functions. It also is an antioxidant that protects neurons from cell-damaging inflammation. A Tufts University study found that elderly adults with optimal levels of vitamin D performed better on cognitive tests and had better brain-processing speeds than those with lower levels.

Recommended: 2,000 international units (IU) of vitamin D daily is a typical dose, but I advise patients to get their blood levels of vitamin D tested before taking supplements. Everyone synthesizes and absorbs vitamin D differently.

FISH OIL

There’s compelling evidence that the omega-3 fatty acids in fish-oil supplements can improve your mood as well as your memory and other cognitive functions. I take fish oil every day, and I advise everyone to do so.

A large portion of the brain consists of docosahexaenoic acid (DHA), one of the main omega-3s in fish oil. The brain uses DHA to form cell membranes. People who consume fish oil, either by taking supplements or eating fish, have better brain functions, including a faster transmission of nerve signals and improved cerebral blood flow.

When Danish researchers compared the diets of more than 5,000 older adults, they found that those who ate the most fish were less likely to get dementia and more likely to maintain robust memories.

Important: The American diet is high in omega-6 fatty acids—found in processed foods, red meats, cooking oils, etc. Even if you eat a lot of fish, you still will need supplements to achieve the recommended ratio of one part omega-3s to every three parts omega-6s.

Recommended: 1 to 2 grams daily. Look for a supplement that provides roughly equal amounts of DHA and eicosapentaenoic acid (EPA).

MULTIVITAMIN

Most Americans don’t eat the recommended five daily servings of fruits and vegetables. A multivitamin, particularly one that includes B vitamins, is good insurance and can help your brain. In a 2010 study, researchers tested the mental performance of 215 participants. The participants then were given either a daily multivitamin or a placebo. When they were retested a month later, those in the vitamin group showed better mental performance than they had in the beginning. There wasn’t a change in the control group.

B vitamins nourish the myelin layer that covers brain cells. Studies have shown that adults who don’t get enough of these nutrients, particularly vitamins B-6, B-12 and folic acid, tend to have the greatest declines in memory and other cognitive functions.

Recommended: Look for a product with all seven of the major B vitamins.

VINPOCETINE

This vasodilator comes from the periwinkle plant. Unlike many supplements, it’s able to cross the blood-brain barrier and improve brain circulation. Studies show that it significantly increases the oxygenation of brain tissue and improves memory, particularly when used in combination with other brain-boosting supplements.

Recommended: 5 milligrams (mg) to 10 mg daily.

GINKGO

When I examine blood flow and activity patterns with SPECT, the “prettiest” brains often are found in people who take ginkgo. This popular herb is among the best-studied supplements. It dilates blood vessels and reduces the “stickiness” of platelets, cell-like structures in blood that increase the risk for clots. Ginkgo contains flavonoids as well as terpenoids, potent antioxidants that prevent damage to brain cells.

There’s strong evidence that ginkgo improves memory. It is also thought to help reduce the risk for vascular dementias and, possibly, Alzheimer’s disease.

Recommended: 60 mg to 120 mg, twice daily.

ST. JOHN’S WORT

Anxiety, stress and depression cause serious impairments in mental functions. Chronic stress, for example, increases levels of hormones that can damage the hippocampus (the part of the brain involved in memory). People who are depressed tend to sleep poorly and don’t take care of themselves. These and other factors can interfere with clear thinking.

The herb St. John’s wort is one of the best treatments for depression. It also is used for treating anxiety and stress. It improves mental focus and helps stop your mind from “spinning.”

A review of 29 studies involving 5,489 patients, published by The Cochrane Collaboration (an organization that analyzes medical research), concluded that St. John’s wort was just as effective as prescription antidepressants, while causing fewer side effects.

Recommended: If you feel depressed or anxious, take 900 mg of St. John’s wort daily, divided into two doses. Caution: St. John’s wort rarely causes side effects, but it can interact with other medications. Talk to your doctor.