Alzheimer's isn't inevitable. Many experts now believe you can prevent or at least delay dementia -- even if you have a genetic predisposition. Reducing Alzheimer's risk factors such as obesity, diabetes, smoking and low physical activity by just 25 percent could prevent up to half a million cases of the disease nationwide, according to a recent analysis from the University of California, San Francisco.

Here are 10 ways to boost your brain health now.

1. Get moving. "If you do only one thing to keep your brain young, exercise," said Art Kramer, professor of psychology and neuroscience at the University of Illinois.

Higher exercise levels can reduce dementia risk by 30 to 40 percent compared with low activity levels, and physically active people tend to maintain better cognition and memory than inactive people. How you work up a sweat is up to you, but most experts recommend 150 minutes a week of moderate activity.

2. Pump iron. Older women who participated in a yearlong weight-training program at the University of British Columbia at Vancouver did 13 percent better on tests of cognitive function than a group of women who did balance and toning exercises. "Resistance training may increase the levels of growth factors in the brain such as IGF1, which nourish and protect nerve cells," said Teresa Liu-Ambrose, head of the university's Aging, Mobility and Cognitive Neuroscience Laboratory.

3. Seek new skills. Learning spurs the growth of new brain cells. "When you challenge the brain, you increase the number of brain cells and the number of connections between those cells," said Keith Black, chairman of neurosurgery at Cedars-Sinai Medical Center in Los Angeles. "But it's not enough to do the things you routinely do -- like the daily crossword. You have to learn new things, like sudoku or a new form of bridge."

4. Say, "Om." Chronic stress floods your brain with cortisol, which leads to impaired memory. To better understand if easing tension changes your brain, Harvard researchers studied men and women trained in a technique called mindfulness-based stress reduction (MBSR). This form of meditation has been shown to reduce harmful stress hormones. After eight weeks, researchers took MRI scans of participants' brains that showed the density of gray matter in the hippocampus rose significantly in the MBSR group, compared with a control group.

5. Eat like a Greek. A heart-friendly Mediterranean diet -- fish, vegetables, fruit, nuts and beans -- reduced Alzheimer's risk by 34 to 48 percent in studies conducted by Columbia University. Data from several large studies suggest that older people who eat the most fruits and vegetables, especially the leafy-green variety, may experience a slower rate of cognitive decline and a lower risk for dementia than meat lovers.

6. Spice it up. Your brain enjoys spices as much as your taste buds do. Herbs and spices such as black pepper, cinnamon, oregano, basil, parsley, ginger and vanilla are high in antioxidants, which might help build brainpower. Scientists are particularly intrigued by curcumin, the active ingredient in turmeric, common in Indian curries. "Indians have lower incidence of Alzheimer's, and one theory is it's the curcumin," Black said.

7. Find your purpose. Discovering your mission in life can help you stay sharp, according to a Rush University Medical Center study of more than 950 older adults. Participants who approached life with clear intentions and goals at the start of the study were less likely to develop Alzheimer's disease over the following seven years, researchers found.

8. Get a (social) life. Who needs friends? You do! Having social networks helps lower dementia risk, a 15-year study of older people from Sweden's Karolinska Institute shows. A rich social life might protect against dementia by providing emotional and mental stimulation, said Laura Fratiglioni, director of the institute's Aging Research Center.

9. Reduce your risks. Chronic health conditions such as diabetes, obesity and hypertension are often associated with dementia. Diabetes, for example, roughly doubles the risk for Alzheimer's and other forms of dementia. Controlling these risk factors can slow the tide.

10. Check vitamin deficiencies. Older adults don't always get all the nutrients they need from foods, because of declines in digestive acids or because their medications interfere with absorption. That vitamin deficit -- particularly vitamin B12 -- can also affect brain vitality, research from Rush University Medical Center shows. Older adults at risk of vitamin B12 deficiencies had smaller brains and scored lowest on tests measuring thinking, reasoning and memory, researchers found.