Optimizing your brain function is not only about getting the right nutrients. It's also important to minimize the nutrients that can pollute the brain and potentially damage and age it.
Here are five 'anti-nutrients' for the memory that you should avoid.
The dry matter of the brain is made up of 60 per cent fat, and therefore the kind of fat you eat alters the kind of fat in your brain. The worst fats you can eat are called 'trans' fats, which are damaged fats found in deep fried food and foods containing hydrogenated vegetable oils. Therefore avoid these fats by limiting your intake of fried food, and don't buy foods containing hydrogenated fats.
Why are trans fats so bad for you?
Trans fats are one of the main factors that introduce oxidants into the body, other factors are smoking and pollution. These fats are taken directly into the brain after being eaten, and cause a chain reaction of damage to the essential fats attached to phospholipids in nerve cell membranes. They also block the conversion of essential fats into vital brain fats. As the brain is more than half made up of fat, there is a danger of these fats becoming oxidized or going rancid.
The good news is that Vitamin E can protect your brain from these damaging effects. Vitamin E is a fat-based antioxidant and many studies have shown that it is consistently associated with better memory performance. [1,2]
Vitamin E is properly called 'd-alpha tocopherol', and is present in foods like seeds, cold-pressed seed oils and fish.
Eating lots of sugary foods and refined carbohydrates makes it difficult to maintain even blood sugar levels.
Another reason sugar is bad for you is that it uses up your body's stores of vitamins and minerals and provides next to none in return.
Conclusive evidence has shown that high sugar consumption is linked to poor mental health. Researchers have found that the higher the intake of refined carbohydrates, the lower the IQ. 
Sugar has also been implicated in depression , learning difficulties , aggressive behavior  and anxiety .
So the message is clear, if you want to optimize your mental performance, cut back on sugar and refined carbohydrates.
Blood sugar problems can also be affected by excessive intake of stimulants. When blood sugar levels dips, one way to raise them is to eat more glucose; the other is to raise your levels of the stress hormones adrenalin and cortisol. Consuming a stimulant like tea, coffee or chocolate is one way to do this.
Studies have shown that coffee is not only addictive, it also worsens mental performance. One study showed that moderate and high consumers of coffee (more than 1 cup a day) had higher levels of depression, anxiety, and other medical problems, as well as lower academic performance, than abstainers. 
Caffeine blocks receptor to the brain whose job it is to stop the release of the neurotransmitters dopamine and adrenalin. This causes the levels of these hormones to increase, as do alertness and motivation. The more caffeine is consumed, the more the body and brain become insensitive to their own natural stimulants, dopamine and adrenalin, and therefore need more of these to feel normal, pushing the body to produce more and more, eventually causing adrenal exhaustion.
If you want to stay in top mental health, restrict your intake of stimulants, including coffee, tea, cola, energy drinks and chocolate. The occasional cup of tea or coffee is unlikely to cause a problem and may even be beneficial due to the high polyphenol content, which acts as an antioxidant.
Stress increases levels of the hormone cortisol, and cortisol damages the brain. According to research conducted at Stanford University, two weeks of raised cortisol levels caused by stress causes the connections between brain cells to shrivel up. 
Numerous other studies have shown that elevated cortisol levels are linked to impaired memory function . However, another study found that that high levels of another stress hormone, DHEA, contributed to improved memory. 
This adrenal hormone, dehydroepiandrosterone, or DHEA, not only helps to control stress, it also maintains proper mineral balance and builds lean body mass while reducing fat tissue. Levels of this hormone can be boosted with stress management through diet, exercise and lifestyle changes, as well as supplementation.
Prolonged stress also disturbs blood sugar balance, which can affect memory and alertness, as well as potentially damaging the brain, as explained earlier.
Potentially harmful chemicals are used everywhere, from the food we eat, to in our homes. Much of our fresh food is sprayed with pesticides and herbicides, and chemicals have made their way into our homes through cookware, fumes, our water supply and many other ways. These chemicals are sometimes classified as anti-nutrients- substances that interfere with either our ability to absorb essential nutrients, or promote the loss of nutrients from the body.
The full effects of toxic minerals on our mental health is not yet known, but studies have shown that high intakes of lead, aluminium, mercury, certain food colorings and other chemicals can have a disastrous effect on intellectual performance and behavior.
The good news is that certain substances, called chelators, can latch onto these toxic minerals when they have been absorbed by the body, and try to take them out. Vitamin C is especially effective at removing heavy metals in the blood.  Other useful vitamins are zinc, calcium and selenium. 
There are also some foods that can help to clear the brain of toxicity. Sulfur-containing amino-acids as found in garlic, onions and eggs can protect against mercury, cadmium and lead toxicity. The pectin from apples, carrots and citrus fruits can also help chelate and remove heavy metals.
-  A.J. Perkins et al., 'Association of antioxidants with memory in a multiethnic elderly sample using the Third National health and nutrition Examination Survey', Am J Epidemiol, Vol 150(1), 1999, pp. 37-44
 J. Perrig et al., 'The relation between antioxidants and memory performance in the old and very old', JAm Geriatr Soc, Vol 45(6), 1997, pp. 718-24
-  A.G. Shauss, 'Nutrition and behavior', Journal of Applied nutrition, Vol 35(1), 198 pp. 30-35 and MIT Conference Proceedings on Research Strategies for Assessing the Behavioural Effects of Foods and Nutrients, 1982
-  L. Christensen, 'Psychological distress and diet - effects of sucrose and caffeine', J Appl Nutr, Vol 40(1), 1988, pp. 44-50
-  M. Colgan and L. Colgan, 'Do nutrient supplements and dietary changes affect lean and emotional reactions of children with learning difficulties? A controlled series cases', Nutr health, Vol 3, 1984, pp. 69-77
-  D. Benton et al., 'Mild hypoglycaemia and questionnaire measures of aggression', Biol Psychol, Vol 14(1-2), 1982, pp. 129-35
-  M. Bruce and M. Lader, 'Caffeine abstention and the management of anxiety disorders', Psychol Med, Vol 19, 1989, pp. 211-14
-  K. Gilliland and D. Andress, 'Ad lib caffeine consumption, symptoms of caffeinism, and academic performance', American Journal of Psychiatry, Vol 138(4), 1981, pp. 512-4
-  R.M. Sapolsky, 'Why stress is bad for your brain', Science, Vol 273(5276), 1996, pp. 749-50
-  C. Kirschbaum et al., 'Stress- and treatment-induced elevations of cortisol levels associated with impaired declarative memory in healthy adults', Life Sci, Vol 58(17), 1996, pp. 147583
-  LE Carlson et al., 'Relationships between dehydroepiandrosterone sulfate (DHEAS) and cortisol (CRT) plasma levels and everyday memory in Alzheimer's disease patients compared to healthy controls', Horm Behav 35(3), 1999, pp. 254-63
-  R. Goyer and M.G. Cherian, 'Ascorbic acid and EDTA treatment of lead toxicity in rats', Life Sci, Vol 24(5), 1979, pp. 433-8
-  E.J. O'Flaherty, 'Modeling normal aging bone loss, with consideration of bone loss in osteoporosis', Toxicol Sci, Vol 55(1), 2000, pp. 171-88