However, new research suggests you don't have to be that strict to see results.
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A new study helped one Santa Monica woman make some changes that appeared to help her brain.
"I have always had a poor memory," study participant Carol Marlowe said.
Even as a young adult, the 75-year-old said she grappled with school work.
"I struggled in college to really perform properly," she said.
But when Marlowe's mom was diagnosed with Alzheimer's, she discovered she was genetically predisposed. A scan also showed amyloid plaque on her brain. Doctors could only offer bleak advice.
"Get your affairs in order. You know, there was nothing they could really do," Marlowe said.
That was until she met researchers at Providence Saint John's Health Center who told her this.
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"Keep your blood sugar under control," Marlowe recalled.
"Things that manage your cardiovascular health and your diabetic risk in general are thought now to really help manage your brain health," said neuroscientist Jennifer Bramen, with Providence Saint John's Pacific Neuroscience Institute.
She and her colleagues studied the impact of eating a low-carb diet on people with blood markers for Alzheimer's Disease. In a small study, they found eating a whole foods diet that included about 130 grams of daily carbs may have a positive effect on the brain.
"Their brains were in better health than if they ate fewer carbohydrates," she said.
Bramen said the average American eats about 300 grams of carbs a day, so start with cutting that in half and add balance.
"You wanna have some fat, have some fiber, have some protein, and a lot of that is just to slow digestion," she said.
Slowing down digestion prevents blood sugar spikes which is better for your brain long term. For the past seven years, Marlowe has been sticking with veggie omelets, oatmeal, whole grains, salads, lean meats, yogurt, nuts, berries and high fiber greens.
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"I have seen slight improvement, but I haven't gotten worse," Marlowe said.
"What's startling is how well she has managed to maintain that, and that is a real achievement," Bramen said.
Marlow said doing something proactive about her brain health has made her less anxious, so she can focus on the little things we all tend to forget.
"Staying calm, staying less distracted. It makes life easier," she said.
The next step for Bramen and her colleagues is to study a larger group of people to see how low-carb eating can affect cognition and brain health over a longer period of time.