Ascorbic acid is essential for collagen, carnitine and neurotransmitters biosynthesis. Most plants and animals synthesize ascorbic acid for their own requirement, butpes and humans can not synthesize it due to lack of an enzyme gulonolactone oxidase. 

Though ascorbic acid was discovered in 17th century, the exact role of this vitamin in human biology and health is still a mystery in view of many beneficial claims and controversies.

Many health benefits have been attributed to ascorbic acid such as antioxidant, anti-atherogenic, anti-carcinogenic, immunomodulator and prevents cold etc. However, lately the health benefits of ascorbic acid has been the subject of debate and controversies:

• The relation between ascorbic acid and cancer is still a debatable.
• There is compelling evidence for antioxidant protection of lipids by ascorbic acid both with and without iron co-supplementation.
• Current evidences suggest that ascorbic acid protects against atherogenesis by inhibiting LDL oxidation.
• The data on vitamin C and DNA damage are conflicting and inconsistent. 

Clinical trails with varying doses of ascorbic acid showed that ascorbic acid does not have significant prophylactic effect, but reduced the severity and duration of symptoms of cold during the period of infection.

Consumption of ascorbic acid as high as 1 g a day for several winter months, had no consistent beneficial effect on the incidence of common cold.

There was a consistent beneficial but generally modest therapeutic effect on duration of cold symptoms. 

In trials that tested vitamin C after cold symptoms occurred, there was some evidence of greater benefits with large dose than with lower doses.

Researchers in Denmark randomized 63 patients to high fruit or low fruit intake, and after 12 weeks, the 2 groups had similar drops in glycated hemoglobin (HbA1c) levels, weight, and girth. They enrolled patients with newly diagnosed type 2 diabetes who had been referred for nutritional counseling. The patients were an even mix of men and women, with a mean age of 58 years and a mean body mass index (BMI) of 32.  

Allan S. Christensen, the lead of the research group: 

We conclude that advice to restrict fruit intake as part of standard [medical nutrition therapy] in overweight adults with newly diagnosed type 2 diabetes mellitus does not improve glycemic control, body weight, or waist circumference.

The 32 subjects in the low-fruit-intake group were advised eat no more than 2 pieces of fruit a day, whereas the 31 subjects in the high-fruit-intake group were told to indulge in 2 or more pieces of fruit a day.

A piece of fruit was defined as the amount that contained about 10 g of carbohydrate - for example, an apple (100 g), half a banana (50 g), or an orange (125 g). The subjects were also instructed to eat whole fruit, skip dried fruit, and not drink fruit juice.

Over the 12 weeks, on average, fruit consumption rose from 194 g/day to 319 g/day in the high-intake group and decreased from 186 g/day to 135 g/day in the low-intake group.

Patients in the high-fruit-intake group had a significant drop in HbAIC levels, from 6.74% to 6.26%. They also lost about 2 kg (from 92 kg to 90 kg) and trimmed their waist by about 4 cm (from 103 to 99 cm). Similar results were obtained by patients in the low-fruit-intake group, and there were no significant between-group differences in these 3 outcomes.

Intestinal microbiota may contribute to the well-established link between high levels of red meat consumption and cardiovascular disease risk. 

The study tested the carnitine and trimethylamine-N-oxide (TMAO) levels - a metabolite the researchers previously linked in a 2011 study to the promotion of atherosclerosis in humans - of omnivores, vegans and vegetarians, and examined the clinical data of 2,595 patients undergoing elective cardiac evaluations. The research finds that a diet high in carnitine promotes the growth of the bacteria that metabolize carnitine, compounding the problem by producing even more of the artery-clogging TMAO. 

Stanley Hazen, M.D., Ph.D.:

Carnitine metabolism suggests a new way to help explain why a diet rich in red meat promotes atherosclerosis.

The bacteria living in our digestive tracts are dictated by our long-term dietary patterns. A diet high in carnitine actually shifts our gut microbe composition to those that like carnitine, making meat eaters even more susceptible to forming TMAO and its artery-clogging effects. Meanwhile, vegans and vegetarians have a significantly reduced capacity to synthesize TMAO from carnitine, which may explain the cardiovascular health benefits of these diets.

Carnitine is naturally occurring in red meats, including beef, venison, lamb, mutton, duck, and pork. It is also a dietary supplement available in pill form and a common ingredient in energy drinks. 

Dietary Reference Intakes (DRIs) are reference values that are quantitative estimates of nutrient intakes to be used for planning and assessing diets for healthy people. They include both recommended intakes and upper intake levels.

Although the reference values are based on data, the data are often insufficient or drawn from studies that had limitations in addressing the question. Scientific judgment is required in setting the reference values. 

• EAR - Estimated Average Requirement - a nutrient intake value that is estimated to meet the requirement of half the healthy individuals in a group.
• RDA - Recommended Dietary Allowance - the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a group.
• AI - Adequate Intake: a value based on observed or experimentally determined approximations of nutrient intake by a group of healthy people.
  Used when an RDA cannot be determined.
• UL - Tolerable Upper Intake Level - the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As intake increases above the UL, the risk of adverse effects increases.

Blue African fruit of a plant plant Pollia condensata contains no blue pigment. The blue and its iridescent shine are caused by a Bragg reflection - intense peaks of light generated at certain wavelengths and angles - created by spirally stacked cellulose fibers that form multiple layers in the fruit's skin.

History of Plant Studies: 

In the centuries following the time of Aristotle and his students, who made the first philosophical attempts to understand plants in their complexity, interest in herb plants was limited mainly to their medical usage. This changed in the sixteenth century when the first biological attempts were done to understand the basic principles of structure and function of plants. At first, studies were largely devoted to plant distribution, taxonomy, and morphology. Later, taking the lead from medicine, anatomy and cytology of plants were added to the curriculum of plant sciences, as studied in the early universities.

In fact, the cellular nature of living organisms was first elaborated using plants (Hooke 1665). By the end of the 19th century, it was realised that plants were even more similar to animals than had been thought hitherto.

• For their reproduction, plants use identical sexual processes.
• Plants attacked by pathogens develop immunity, using the corresponding processes and mechanisms in animals.
• Both animals and plants use the same molecules and pathways to drive their circadian rhythms.

Critical mass of new data has been accumulated, culminating in the emergence of plant neurobiology.

Plants are intelligent organisms, which perform complex information processing. The word "neuron" was taken by animal neurobiologists from Greek where the original meaning of this word is vegetal fibre.

Auxin emerges as a plant-specific neurotransmitter. Roots are specialized not only for the uptake of nutrients, but also seem to support neuronal-like activities based on plant synapses. Vascular elements allow the rapid spread of hydraulic signals and action potentials, resembling nerves. Plants are capable of learning and make decisions about their future activities according to the actual environmental conditions. It is obvious that they possess a complex apparatus for the storage and processing of information.

There is no good evidence of any adverse medical effects associated with the consumption of water with fluoride naturally or artificially added at a concentration of 0.5 – 1.0 mg / litre other than the increase in dental fluorosis. US studies in areas with natural fluoride levels of up to 8 mg / litre found no clinical evidence of harm. However there is clear evidence from India and China that skeletal fluorosis and an increased risk of bone fractures occur as a result of long-term excessive exposure to fluoride (total intakes of 14 mg fluoride per day), and evidence suggestive of an increased risk of bone effects at total intakes above about 6 mg fluoride per day.

Gut microbial composition depends on different dietary habits just as health depends on microbial metabolism, but the association of microbiota with different diets in human populations has not yet been shown.

Significant differences were found in gut microbiota between European children (EU) and that of children from a rural African village of Burkina Faso, , where the diet is high in fiber content, and is similar to that of early human settlements at the time of the birth of agriculture.

Burkina Faso children showed a significant enrichment in Bacteroidetes and depletion in Firmicutes, and a unique abundance of bacteria from the genus Prevotella and Xylanibacter, completely lacking in the EU children. Enterobacteriaceae (Shigella and Escherichia) were significantly underrepresented in Burkina Faso children.

In addition, we found significantly more short-chain fatty acids in Burkina Faso children. 

Gut microbiota might have coevolved with the polysaccharide-rich diet, allowing to maximize energy intake from fibers while also protecting from inflammations and noninfectious colonic diseases. 

An enterotype is a classification of living organisms based on its bacteriological ecosystem in the gut microbiome. Humans can be roughly divided into three enterotypes depending on which genus of bacteria dominates their gut: Bacteroides, Ruminococcus, or Prevotella. 

• People who eat a lot of meat and saturated fat tended to have more Bacteroides in their flora. 
• Ruminococcus prevailed in people who consumed lots of alcohol and polyunsaturated fats. 
• Prevotella favored a diet rich in carbohydrates.

Long-term diet is strongly associated with the gut microbiome composition. If switching gut enterotype is possible, it may take a long-term dietary intervention. 

Chimpanzees have enterotypes that are compositionally analogous to those found in humans.