The placebos can be the usual pills filled with olive oil. The Nature’s Answer fish oil is lemon-flavored; it may be worth mixing in some lemon juice. In Kiecolt-Glaser et al 2011, anxiety was measured via the Beck Anxiety scale; the placebo mean was 1.2 on a standard deviation of 0.075, and the experimental mean was 0.93 on a standard deviation of 0.076. (These are all log-transformed covariates or something; I don’t know what that means, but if I naively plug those numbers into Cohen’s d, I get a very large effect: \frac{1.2 - 0.93}{0.076}=3.55.)

Last April the scientific journal Nature published the results of an informal online poll asking whether readers attempted to sharpen "their focus, concentration, or memory" by taking drugs such as Ritalin and Provigil, a newer kind of stimulant, known generically as modafinil, which was developed to treat narcolepsy. One in five respondents said they did. A majority of the 1,400 readers who responded said that healthy adults should be permitted to take brain boosters for non-medical reasons, and 69% said that mild side-effects were an acceptable risk. Though a majority said that such drugs should not be made available to children who had no diagnosed medical condition, a third admitted that they would feel pressure to give "smart drugs" to their kids if they learned that other parents were doing so.

Results: Women with high caffeine intakes had significantly higher rates of bone loss at the spine than did those with low intakes (−1.90 ± 0.97% compared with 1.19 ± 1.08%; P = 0.038). When the data were analyzed according to VDR genotype and caffeine intake, women with the tt genotype had significantly (P = 0.054) higher rates of bone loss at the spine (−8.14 ± 2.62%) than did women with the TT genotype (−0.34 ± 1.42%) when their caffeine intake was >300 mg/d…In 1994, Morrison et al (22) first reported an association between vitamin D receptor gene (VDR) polymorphism and BMD of the spine and hip in adults. After this initial report, the relation between VDR polymorphism and BMD, bone turnover, and bone loss has been extensively evaluated. The results of some studies support an association between VDR polymorphism and BMD (23-,25), whereas other studies showed no evidence for this association (26,27)…At baseline, no significant differences existed in serum parathyroid hormone, serum 25-hydroxyvitamin D, serum osteocalcin, and urinary N-telopeptide between the low- and high-caffeine groups (Table 1⇑). In the longitudinal study, the percentage of change in serum parathyroid hormone concentrations was significantly lower in the high-caffeine group than in the low-caffeine group (Table 2⇑). However, no significant differences existed in the percentage of change in serum 25-hydroxyvitamin D

It’s basic economics: the price of a good must be greater than cost of producing said good, but only under perfect competition will price = cost. Otherwise, the price is simply whatever maximizes profit for the seller. (Bottled water doesn’t really cost $2 to produce.) This can lead to apparently counter-intuitive consequences involving price discrimination & market segmentation - such as damaged goods which are the premium product which has been deliberately degraded and sold for less (some Intel CPUs, some headphones etc.). The most famous examples were railroads; one notable passage by French engineer-economist Jules Dupuit describes the motivation for the conditions in 1849:

For starters, it’s one of the highest antioxidant-rich foods known to man, including vitamin C and vitamin K and fiber. Because of their high levels of gallic acid, blueberries are especially good at protecting our brains from degeneration and stress. Get your daily dose of brain berries in an Omega Blueberry Smoothie, Pumpkin Blueberry Pancakes or in a Healthy Blueberry Cobbler.
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Choosing to take smart drugs is not an effective or long term solution. Smart drugs may help you study faster or keep you awake longer, but they are not your best option. Most of the ADHD medications are based on an amphetamine structure and they are not healthy for your heart or your liver. Also, by taking smart drugs, you are putting yourself at considerable risk for addiction to these substances.
The most common front-line of treatment for ADHD is medication and cognitive behavioural therapy (CBT). Prescriptions for ADHD drugs such as Ritalin, have doubled to 922,000 a year in the last decade, and whilst it offers symptom management for many, it has also been found to have significant negative side effects such as weight loss, liver toxicity, and suicidal thoughts, and in the short term may suppress pubertal growth. The aetiology of ADHD is multifactorial, meaning that there are varying influencing factors that drive the symptoms. This is perhaps why this condition has been hard to study and find effective treatment for.

Freshly brewed tea. Two to three cups a day of freshly brewed tea -- hot or iced -- contains a modest amount of caffeine which, when used "judiciously," says Kulze -- can boost brain power by enhancing memory, focus, and mood. Tea also has potent antioxidants, especially the class known as catechines, which promotes healthy blood flow. Bottled or powdered teas don't do the trick, however, says Kulze. "It has to be freshly brewed." Tea bags do count, however.
Mercury, as well as other heavy metals such as lead, can accumulate in brain tissue, as well as in the spinal cord, as they are fat-soluble - meaning that they can hide itself in fat tissue, which is abundant in both the brain and the spine. Once there, they can displace important nutrients for brain health such as zinc and iron, which are needed for neurotransmitter production, as well as induce an inflammatory process called oxidative stress among other things.

Systematic reviews and meta-analyses of clinical human research using low doses of certain central nervous system stimulants found enhanced cognition in healthy people.[21][22][23] In particular, the classes of stimulants that demonstrate cognition-enhancing effects in humans act as direct agonists or indirect agonists of dopamine receptor D1, adrenoceptor A2, or both types of receptor in the prefrontal cortex.[21][22][24][25] Relatively high doses of stimulants cause cognitive deficits.[24][25]