The first recorded nutritional experiment is recorded in the Book of Daniel in the Bible. Daniel was amoung the finest young men captured by the King of Babylon when the Babylonians conquered Isreal, and was to serve in the King's court. He was to be fed from the King's table of fine foods and wine. Daniel objected and preferred his own choices which included vegetables (pulses) and water. The chief steward was afraid for his head, but agreed to a trial. Daniel and his friends received his own diet for 10 days and then were compared to the King's men. As they appeared fitter and healthier, they were allowed to continue with their own foods, not defiling themselves with those of the King.
The Ancient Greeks were great thinkers and philosophers. However, they were a little short on experimental methods or scientific observation. Hippocrates conjectured that since people were the same, regardless what they ate (near the sea coast, versus inland diets, for example) there must be one nutrient that everything is made of. This one nutrient theory persisted for a very long time, until almost the modern era.
In the late 1700's a brilliant young French scientist, Antoine Lavoisier, became the "Father of Nutrition" from his brilliant work in chemistry. He put weight measures into chemistry, designed a calorimeter which measured the head produced by the body from work and consumption of varying amounts and types of foods, and is famous for the statement "Life is a chemical process" (in French). He was elected to the French Academy of Science at age 24, and would have gone on to even greater scientific accomplishments, but was from an aristocratic family at the time in France when it was unpopular to be. He was beheaded in the French Revolution in 1794.
Dr. James Lind, in 1753, published his Treatise on Scurvy, ten years after the birth of Lavoisier. Lind, Physician to the Fleet, relieved the British navy of scurvy by prescribing lemon juice, then called lime. Hence, the British Limeys were healthy when they went against their enemies after lengthy engagements at sea, and Lind's efforts (although not truly the first discovery of the effect of nutrition on scurvy) helped maintain Britain's dominance of the seas. Some credit him as much as Nelson as being responsible for breaking the power of Napolean.
An interesting story is that of Dr. William Beumont and Alexio St. Martin in the 19th century. Beaumont was an army doctor stationed at Fort Mackinac on Mackinac Island in northen Michigan. Alexio St. Martin was a French trapper, who was shot in the stomach at a trading post bar. Despite his best efforts, Beumont was unable to close the hole in his stomach and it healed with an opening to the outside. We call that a fistula. St. Martin allowed Beaumont to make observations, periodically disappearing and then coming back to allow further investigation. One can imagine that it must have been a delicate situation, with a rough and ready trapper allowing the good army doctor to fiddle around with his innards. Eventually St. Martin left, returning to Canada where he lived a long life (hole and all). In the mean time however, Beaumont conducted many experiments and discovered many new and interesting things, previously unobserved. For example:
The 20th century became the era of the Golden Age of Nutrition, when most of the discoveries of the nutrients took place. Dr. Stephen Babcock was instrumental in helping to open the age. Babcock, better known for the Babcock test for milk fat which bears his name, conveived the idea to feed dairy cattle feed from just one source, all corn plant or all wheat plant. He placed two heifers on such diets, but when one died, his animals were taken away and his attempts to conduct the experiment were denied by his Experiment Station Director; afterall, everyone knew that such diets were impractical and not productive and that cows needed more vaired diets than that to be productive.
Babcock's experiment was eventually conducted by his associates (Hart, Humphrey, McCollum, Steenbock). Four five-month-old heifers each were fed either only feed from the corn plant, the wheat plant, the oat plant or a mixture of all three. Weight gain was similar the first year, but the corn fed animals were sleeker and more vigorous than the wheat fed ones. When they were bred, each of the corn fed cows had normal calves, but the wheat-fed cows all had calves that were dead or died soon after birth. The wheat-fed cows gave only one-third the milk as those fed corn. It was clear to them that:
A flurry of discovery followed, in which something in the fat soluble portion of the corn was discovered to affect reproduction, and was labeled factor A. (The term Vitamin came from Funk, who erroneously thought all these new things being discovered contained amines, and combined 'vital' and 'amine' to coin the term Vitamin).
Therefore, Babcock's experiment was important for 2 reasons:
Water soluble substances with active properties were labeled B, and it soon was obvious that more than one thing was involved, hence B1, B2, B3, etc., some of which turned out not to be vitamins at all, some of which were the same as others, and so on.
Vitamin C was elucidated with the fortuitous use of the guinea pig, since only man, the guinea pig, subhuman primates, the red-throated bul-bul, and very few other animals (certain bats, birds and reptiles) require vitamin C, the rest forming their own in intermediatary metabolism.