Vitamina C e constipações?

Prevenção, talvez não:
https://observador.pt/2019/01/19/tomar-vitamina-c-para-prevenir-constipacoes-a-ciencia-diz-que-afinal-e-um-mito/

Citando:
"(...)

Afinal, não há provas científicas de que tomar mais vitamina C durante o inverno ajuda mesmo a prevenir constipações. Quando muito, pode diminuir a duração da constipação. Essa é a conclusão de um estudo da Universidade de Harvard publicado no ano passado e noticiado esta sexta-feira pelo El Confidencial. (...)

Esse mito vem de um livro publicado por Linus Pauling nos anos 70 chamado “Vitamin C and the Common Cold”, especifica a Universidade de Harvard. Nesse livro, o químico admite que “o mecanismo da eficácia da vitamina C contra infeções virais, como constipações, ainda não é conhecido” e que a hipótese de essa vitamina evitar constipações “ainda não foi testada em experiências”. “No entanto, formulei a hipótese de que a eficácia do ácido ascórbico [nome científico da vitamina C] em dar proteção contra doenças virais resulta da sua função na síntese e atividade do interferão [uma proteína] na prevenção da entrada de partículas de vírus dentro das células”. (...) Tanto quanto parece, é quem faz muito exercício físico que mais ganha com o consumo de vitamina C: “Tomar pelo menos 200 miligramas de vitamina C todos os dias parece diminuir para metade o risco de apanhar uma constipação”.  No entanto, mesmo quem é menos ativo pode ter vantagens em tomar vitamina C: nenhum estudo diz que consumi-la evita constipações, mas a Universidade de Harvard descobriu que pode diminuir a duração da doença em um dia. E mesmo assim, duzentos miligramas de ácido ascórbico diariamente diminuiu a duração dos sintomas de constipação em apenas 8% nos adultos e em 14% nas crianças."

Homeopatia ou não homeopatia?

Provavelmente não, ver a história:
https://www.economist.com/blogs/economist-explains/2014/04/economist-explains?fsrc=scn/fb/te/bl/ed/whyhomeopathyisnonsense

Citando:
"The history of homeopathy – literally, “similar suffering” – dates back to the late 18th century. Samuel Hahnemann, a German doctor, was unimpressed by contemporary medicine, with good reason. Doctors used leeches to let blood and hot plasters to bring on blisters, which were then drained. In 1790, Hahnemann developed a fever that transformed his career. After swallowing powder from the bark of a cinchona tree, he saw his body temperature rise. Cinchona bark contains quinine, which was already known to treat malaria. Hahnemann considered the facts: cinchona seemed to give him a fever; fever is a symptom of malaria; and cinchona treats malaria. He then made an acrobatic leap of logic: medicines bring on the same symptoms in healthy people as they cure in sick ones. Find a substance that induces a symptom and it might be used to treat that symptom in another."
(...)
"One common designation is “NC”, where C signifies that a substance is diluted by a ratio of 1:100 and N stands for the number of times the substance has been diluted. So a dilution of 200C would mean that one gram of a substance had been diluted within 100 grams of water, with the process repeated 200 times. At this dilution not a single molecule of the original substance remains when the water is used to make pills; most homeopathic pills thus consist entirely of sugar. However, the water and the pills are supposed to retain a “memory” of the original substance.

This is nonsense. Studying homeopathy is difficult, points out the world’s biggest funder of medical research, the US National Institutes of Health (NIH), because it is hard to examine the effects of a medicine when that medicine has little or no active ingredient. Researchers can neither confirm that the medicine contains what it claims to nor show the chemical effect of the diluted medicine within the body. "
(...)
"The most comprehensive review of homeopathy was published in 2005 in the renowned medical journal The Lancet. Researchers compared trials of homeopathic and conventional medicines. In the bigger, well-designed trials, there was “no convincing evidence” that homeopathy was more effective than a placebo, they found. "

Soja ou não soja?

Como é que estamos em termos de estudos sobre soja e como interpretar uma série destes estudos que dizem que previne o cancro ao passo que outros referem que o promove? Com links para uma série de artigos adicionais e a história da indústria da soja desde 1940:
http://edition.cnn.com/2017/03/07/health/soy-foods-history-cancer-where-do-we-stand-explainer/

Citando:
"There have been numerous conflicting studies on the health benefits of soyHere's a look at the history of soy in America and where experts now stand"Soy foods are good; soy foods are safe; soy foods prevent breast cancer," one expert says [estudo de 2017]"
(...)
""Twenty-five grams a day is a good estimate or a good guideline to follow in trying to incorporate it into what we are eating," she said.

Yet she added that while natural soy food products offer health benefits, processed soy foods provide a different story.

"I think soy milk is one that would be OK, and tofu and tempeh and edamame. Again, those being more on the natural side," Stangland said.

"As we go into a lot of vegan and vegetarian products, like when they use that soy to make a meat patty and it's not just soybeans that are in there but it's also additional soy product to make it into a meat patty, then that's where I would say it's more processed," she said. "Any of the bars and the powders out there that are manipulated are not even giving us the same benefits that we are finding in the research.""

Nota final: A soja na Ásia é maioritariamente consumida fermentada. O que é algo completamente diferente.

História da "Vitamina" D e necessidade ou não da suplementação

Depois das notícias (p.e. da Time) sobre como evitar constipações (R: Tomando vitamina D), algumas críticas à recomendação e um pouco de história:
https://www.theatlantic.com/health/archive/2017/02/definitive-vitamin-d/517302/

Citando:
"The scientific process behind the health claims was ethically fraught, too, in that it came from University of Wisconsin researchers who owned the patent on producing the compound that had recently been named “vitamin D.” The term started as a colloquialism for what chemists know as cholecalciferol and ergocalciferol, which are not structurally or functionally similar to the other compounds widely known as “vitamins.”

D is technically a pre-hormone involved in multiple metabolic processes but mainly known to affect the levels of calcium and phosphorus in our bodies. Though little was known in the 1930s about exactly how “vitamin D” worked to prevent people’s bones from warping, the biochemist who patented the process of synthesizing the compound said, “If the public should demand vitamin D in its beer, there is no reason why [we] should not provide it.”

The demanding people weren’t ready for vitamin beer, apparently, and Schlitz took it off the market two years later. Instead cow’s milk became the delivery vehicle for vitamin D supplements in the United States. A milk-fortification law was passed to combat the scourge of rickets. So arose the belief that drinking cow’s milk was necessary for strong bones. As the dairy industry made the case in government-sponsored advertising, vitamin D actually became a primary selling point for milk—the reason that many Americans believe drinking cow’s milk is necessary still today. (Even though adult cows don’t drink it.)"