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Healthy adults living in temperate climates need 12 to 13 cups (men) and 9 cups (women) of water a day. Pregnant women need 10 cups each day and women who breastfeed should drink 13.

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You've probably heard that the right diet can stave off memory loss. Eating a combination of brain-friendly foods such as leafy greens, berries, fish, nuts and olive oil is thought to delay age-related thinking problems and guard against Alzheimer's disease.

Is it possible, though, to increase your short-term memory through good nutrition?

According to a new study from Britain, if you drink plenty of water, the answer is yes. It seems that being even just slightly dehydrated can impair attention and memory.

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For the study, published recently in the American Journal of Clinical Nutrition, researchers subjected 101 undergraduate students to a temperature of 30 C for four hours, over three occasions, during which they either did or did not drink 300 millilitres of water. All performed a battery of memory tests.

Participants' body temperatures and body weights were measured and urine samples were collected at the beginning and throughout the study.

After three hours into the experiment, a greater loss of body weight – as little as 0.72 per cent of total weight – was associated with poorer memory (tested by word-list recall) and attention.

Those who weren't allowed to drink water found the tests more difficult to perform than did those who hydrated during study.

You don't have to sweat it out in hot, humid weather to lose less than 1 per cent of your body weight.

Such a minor degree of dehydration can easily occur during a normal day – even a cool, fall day – if you don't drink water often enough.

Healthy adults living in temperate climates need 12 to 13 cups (men) and 9 cups (women) of water each day. Pregnant women need 10 cups of water each day and women who breastfeed should drink 13 cups. All beverages – excluding alcoholic drinks – count toward your daily water requirement.

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Keep in mind, though, that the study didn't distinguish between the role of mild dehydration and the response to heat on memory.

The researchers also didn't measure habitual water, caffeine and alcohol intake, factors that could have influenced participants' hydration status at the onset of the study.

Even so, previous research has shown that being mildly dehydrated impaired performance in tasks that require attention, memory and psychomotor skills (i.e. brain-muscle co-ordination). It even reduced mood, a consequence that can also affect memory.

Water accounts for 55 to 60 per cent of body mass; hydration status plays an important role in all body functions and in many chronic diseases.

It's not surprising, then, that drinking too little water may hinder optional brain function. In fact, a few studies have shown that cognitive performance in schoolchildren improves when they're given a drink.

Over all, however, the evidence that certain foods and nutrients can increase your memory power is limited. Much of it is observational, which doesn't prove cause and effect.

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Findings from randomized clinical trials, the scientific gold standard, have been inconsistent.

Different tests used to measure memory, different study populations and varying study durations may have contributed to conflicting results.

Even so, your brain needs a steady supply of nutrients to function properly. Many vitamins and minerals, for example, help the brain burn glucose for fuel.

Your brain also relies on certain nutrients to synthesize neurotransmitters, chemicals that send impulses to brain cells. Other nutrients allow the brain to transmit those impulses rapidly and efficiently. Still others protect the integrity of brain cells.

My advice: Eat a varied, nutrient-packed diet that focuses on plant foods. Doing so will fuel your brain today and, as mounting evidence suggests, help preserve your memory as you age.

Six foods to boost brain health

When it comes to boosting short-term memory through diet, the research is limited. The following foods, however, provide key nutrients needed to support cognitive function. Even better, many are part of the MIND Diet, a pattern of eating tied to a lower risk of Alzheimer's disease. (MIND stands for Mediterranean-DASH Intervention for Neurodegenerative Delay.)

Salmon

Fatty fish is loaded with DHA (docosahexaenoic acid), the dominant omega-3 fatty acid found in the brain. Here, this omega-3 fat keeps the lining of brain cells flexible so memory messages can pass easily between them.

DHA is also thought to prevent the build-up of beta amyloid, a protein that can impair brain-cell communication.

Eggs

One whole egg provides one-quarter (men) to one-third (women) of a day's worth of choline (found in the yolk), a nutrient that's a building block for acetylcholine, a neurotransmitter involved in memory.

Observational studies have associated higher dietary choline intakes to better memory performance in healthy adults.

Lentils

These pulses deliver a sustained release of glucose (e.g. they provide low glycemic carbohydrates) – the brain's preferential fuel – along with plenty of folate, a B vitamin that maintains the integrity of nerve fibres for proper nerve transmission.

Also, lentils are an outstanding source of iron, a nutrient that helps transport oxygen to the brain. Iron is also needed for healthy nerves and the production of memory neurotransmitters.

Avocado

One medium avocado (200 g) delivers 30 g of fat, two-thirds of it monounsaturated fat, the type that helps reduce inflammation and is thought to improve brain function.

A 2012 study published in the Annals of Neurology found that among 6,183 women aged 65 and older, those who consumed the most monounsaturated fat had better cognitive scores than women who consumed more of their fat as saturated fat (found in animal foods).

Spinach (frozen)

This leafy green is an excellent source of vitamin E, an antioxidant nutrient that plays a key role in protecting brain-cell membranes from free-radical damage.

You get twice as much vitamin E from frozen spinach as you do from fresh. That's because spinach is blanched before it's frozen to preserve freshness, making it denser than raw spinach. (It's a great addition to smoothies and protein shakes.)

One-half cup of frozen spinach delivers 3.6 milligrams of vitamin E, one-quarter of your daily requirement (15 mg).

Kiwifruit

This fruit is an exceptional source of vitamin C, an antioxidant that, like vitamin E, protects brain cells from free-radical damage. Vitamin C also regenerates the body's supply of vitamin E and is used to synthesize neurotransmitters.

Studies conducted in older adults have linked lower blood levels of vitamin C with poorer memory tests.

Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto

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