by Lisa Marshall

“Have you seen my keys?” “Now, why did I come in here?” “Her name is on the tip of my tongue.” If you catch yourself uttering such phrases, listen up:

“Memory generally starts to decline in our 30s, as the brain shrinks with age. One of the first and most prominent signs is that ‘tip of the tongue’ phenomenon,” advises neuroscientist Sandra Aamodt, Ph.D., co-author of Welcome to Your Brain.

Studies show that the adult brain can shrink as much as one-half to 1 percent annually in midlife, as neurons in the prefrontal cortex and hippocampus wither and the branches between them thin. Add hormonal changes, which can starve gray matter of nourishing estrogen and progesterone; less-than-stellar cardiovascular health, which tends to limit blood flow to the brain; and a gummy protein called amyloid plaque, which can hamper neuronal function; and cognitive decline may be exacerbated.

Already, one in five people older than 65 suffer from “mild cognitive impairment” (persistent memory problems severe enough to be noticeable by others). According to the Alzheimer’s Association, if we live to age 90, as many as half of us could ultimately be diagnosed with that disease.

The good news: Such fates are far from inevitable.

“People seem to expect that as soon as we start to need reading glasses, we should also expect some of these cognitive issues to arise, but it does not need to be that way,” says Naples, Florida-based Neurology Doctor David Perlmutter, co-author of Power up Your Brain. “You can absolutely do things early on in life and throughout your lifetime that work to maintain the bulk and function of the brain.”

Here’s how:

Stay lean. It may seem counterintuitive, but mounting evidence suggests that in order to grow a bigger brain, many of us should be eating less. “The key to the brain maintaining and even regenerating itself is the activation of a set of genes that code for a protein called brain derived neurotrophic factor (BDNF),” explains Perlmutter. “BDNF is significantly enhanced in people that simply cut down their calorie consumption.”

Several animal and human studies support this conclusion. One 2009 study, published in the Proceedings of the National Academy of Sciences, divided 50 men and women age 50 and older into three groups that slashed calorie intake by 20 percent, 30 percent and not at all. After three months, the groups that restricted their calories saw their verbal memory scores jump by more than 20 percent.

Perlmutter notes that just being overweight in the prime of life can promote excess inflammation and free radical production—two enemies of a healthy brain. A 2005 study of 10,000 men and women conducted by researchers at Kaiser Permanente found that people that were obese in their early 40s had a 74 percent increased risk of developing dementia later in life. “Just a 25 percent reduction in calories over one month’s time can have a profound effect on boosting memory,” Perlmutter notes.

Eat a brain-building diet. Aside from cutting calories, experts say it’s critical to load up on foods that boost neurogenesis (the development of new brain cells) and stall brain atrophy. Eating more fish (or omega-3 supplements), adding fruits and vegetables and cutting back on refined carbohydrates do just that, advises Dr. Christiane Northrup, obstetrician, gynecologist and author of Women’s Bodies Women’s Wisdom. “The brain is mostly made up of omega-3 fats, and many women, in particular, are lacking them in their diet,” she observes.

Perlmutter notes that supplementing one’s intake of omega-3 fatty acid DHA, present in fatty fish and marine algae, has been shown to switch on the genes that jumpstart BDNF production. DHA is also anti-inflammatory and promotes healthy blood flow to the brain. But people shouldn’t wait too long to load up on it.

One 2010 trial of 485 healthy adults with mild memory complaints found that those who took 900 milligrams per day of algae-based DHA supplements for six months made significantly fewer errors on memory tests than they had at the study’s onset. Another study by the National Institute on Aging, however, found that DHA supplementation had little impact on patients once severe dementia had set in. So, sooner is better.

Healthy fats aside, dark-colored fruits such as blackberries, blueberries and plums are all rich with antioxidants, substances known to scavenge cell-damaging free radicals in the brain. Also, cruciferous vegetables like broccoli and broccoli sprouts contain a powerful compound called sulforaphane, believed to boost the body’s own production of antioxidants.

One famous 2005 study followed 13,388 women over several decades, and found that those that ate the most cruciferous vegetables and leafy greens stayed mentally sharp for far longer than those that ate the least. New research from Rush University, in Chicago, further suggests that a deficiency of B12, found in fish, liver, milk and eggs, may hasten brain shrinkage as previously functioning cells die off.

Overloading on refined carbohydrates like white flour, pasta and potatoes carries a similar result. “Elevated blood sugar can destroy the brain,” advises Perlmutter, pointing to a 2005 study in the journal Neurology, which linked accelerated brain shrinkage with elevated blood sugar.

Prevent hormonal havoc. Ebbing hormones can also have a measurable impact on our ability to recall words and follow through on tasks, says Hawaii naturopathic physician Laurie Steelsmith, author of Natural Choices for Women’s Health.

One 2009 University of California study of 2,362 women between the ages of 42 and 52 found that 60 percent suffered memory and mental-processing problems. “I hear about it almost every day from women in my practice,” comments Steelsmith. “They’re trying to find the word for, say, ‘garlic’ or ‘pen,’ and it just won’t come to them. It can be very frustrating.”

Steelsmith notes that estrogen plays a critical role in influencing verbal and spatial memory and fine motor skills and bolstering the blood-brain barrier to keep toxins out. Meanwhile, progesterone acts on the same brain receptors that Valium does, promoting calm and aiding sleep. In the days immediately prior to menstruation, when estrogen and progesterone levels are low, or once women begin to approach menopause and they stay low, the brain feels it.

In an ideal world, the adrenal glands kick in to pick up where the ovaries leave off—producing sex hormones. “But women that are stressed out or not nourishing themselves tend to experience adrenal fatigue, so their adrenals are not able to act as a secondary source of hormones,” says Steelsmith.

For ovulating women, she recommends taking 100 to 175 milligrams (mg) daily of the herb Rhodiola rosea during the second half of the menstrual cycle to support fatigued adrenal glands and ward off hormone-related brain fog. If the condition occurs only for a few days before a menstrual period, and is accompanied by tender breasts, lack of sleep and heavy monthly bleeding, the problem may be low progesterone. For that, try the herb chaste tree berry during the second half of the menstrual cycle, or consider a low dose, over-the-counter progesterone cream, says Northrup.

For post-menopausal women, she recommends taking up to 50 mg per day of pregnenolone, an adrenal hormone that the body naturally converts into estrogen and progesterone. (While pregnenolone is available over the counter, Steelsmith suggests that women have a naturopath first test their hormone levels in order to determine an appropriate dose.)

Or, older men and women experiencing age-related memory loss can try a soy-based nutritional supplement called phosphatidylserine (PS), which is believed to bolster cell-to-cell communication and levels of the memory-boosting neurotransmitter acetylcholine.

Exercise mind and body. Aamodt notes that a common cause of cognitive decline is the accumulation of clogged blood vessels in the brain that choke off blood and oxygen. Thus, “Regular exercise is the single most useful thing you can do to maintain your cognitive abilities later in life,” she says.

Recent studies by researchers at the University of Illinois and elsewhere have shown that as little as 45 minutes of aerobic exercise, three times per week, may not only stall age-related brain atrophy in the elderly, but even help regenerate parts of the brain that have withered. “There is no medication on the planet that can do that,” says Perlmutter.

Brain exercise is helpful, as well. Exposure to new experiences prompts the brain to literally lay down new neuronal networks, becoming stronger. A 2009 Mayo Clinic study found that of 1,300 people ages 70 to 89, those that had regularly engaged in mentally challenging activities in their 50s and 60s (such as playing games, quilting, building model airplanes, or learning a new language or instrument) were 40 percent less likely to suffer memory problems.

The key, advise the experts, is not to stick with the same crossword puzzle for years. Instead, try something new. As Steelsmith puts it: “Use it or lose it.”

Lisa Marshall is a freelance health writer headquartered near Boulder, CO. Connect at [email protected].