9.1 Vitamins: Introduction & Vitamin A


– HELLO AND WELCOME
TO OUR SECTION ON VITAMINS. WE’RE GOING TO BE
COVERING WATER SOLUBLE AND FAT SOLUBLE VITAMINS THIS WEEK. BEFORE WE GET STARTED, I WANT TO POINT OUT
THAT A LOT OF THE INFORMATION IN YOUR TEXTBOOK IS GOING TO
COVER NUTRITIONAL DEFICIENCIES OR VITAMIN DEFICIENCIES. WE DON’T SEE THAT OFTEN
IN THE UNITED STATES. THEY’RE MOSTLY FOUND
IN DEVELOPING COUNTRIES. BUT EVEN IF YOU’RE NOT
DEFICIENT IN A VITAMIN, DON’T DEVELOP THE DISEASE
ASSOCIATED WITH DEFICIENCY, HAVING LOW LEVELS OF VITAMINS
CAN IMPACT YOUR HEALTH. SO LET’S GO AHEAD
AND GET STARTED. AND FIRST WE’LL
JUST INTRODUCE THE DIFFERENT CATEGORIES
OF VITAMINS. NOW REMEMBER MICRONUTRIENTS
ARE BOTH VITAMINS AND MINERALS. AND OUR VITAMINS COME IN BOTH A WATER SOLUBLE AND
FAT SOLUBLE GROUP. WATER SOLUBLE VITAMINS
ARE VITAMINS C AND B, WHEREAS THE FAT SOLUBLE
VITAMINS ARE A, D, E, AND K. NOW WHAT I’D LIKE
TO DO IS HAVE YOU TAKE A LOOK AT THIS PICTURE AND THIS
IS FROM THE BP OIL SPILL. AND IT’S TAKEN FROM NASA, BUT YOU CAN SEE HOW OIL IS
DIFFERENT FROM THE WATER. YOU CAN SEE THERE IS A
SEPARATION OF THE TWO. BECAUSE OIL DOES NOT
DISSOLVE IN WATER THEY’RE ALWAYS
GOING TO BE SEPARATE, AND THIS REALLY IMPACTS HOW
VITAMINS ARE ABSORBED AND THEN THEY’RE BIO AVAILABILITY OR
HOW THEY FUNCTION IN THE BODY, HOW THEY’RE TRANSPORTED,
HOW THEY’RE STORED IN THE BODY. SO THINK ABOUT THIS PICTURE
OR YOU CAN THINK ABOUT A DRESSING WHERE YOU
KNOW THAT THE WATER PART IS VERY SEPARATE
FROM THE OILY PART. THEY’RE ALWAYS
GOING TO BE SEPARATE. NOW, OF COURSE, WE LEARNED ABOUT
LIPIDS THAT ACT AS EMULSIFIERS, SUCH AS LESS AS THEM, THAT CAN HELP BIND AND
BRING THOSE INTO SOLUTION. BUT LET’S START WITH OUR
WATER SOLUBLE VITAMINS. VITAMIN C AND ALL THE
VITAMINS ARE WATER SOLUBLE. SO THIS MEANS THAT THEY ARE
GOING TO DISSOLVE IN THE WATER. SO THAT MEANS THEY’RE EASILY
ABSORBED AND TRANSPORTED. NOW WHY IS THAT? IT’S BECAUSE THE
DIGESTIVE JUICES ARE WATER BASED AND SO
IS THE BLOODSTREAM. SO IT’S VERY EASY FOR THEM
TO BE BOTH DIGESTED AND– EXCUSE ME, ABSORBED AND THEN
TRANSPORTED THROUGHOUT THE BODY. BUT BECAUSE THEY’RE
WATER SOLUBLE THEY’RE NOT GOING TO BE STORED IN
ANY SIGNIFICANT QUANTITIES. SO YOU’RE NOT GOING TO
SEE THEM BUILD UP AS MUCH AS THE FAT
SOLUBLE VITAMINS. AND THIS ALSO MEANS THAT
THEY’RE RARELY TOXIC. IF THEY’RE NOT
DEVELOPING OR BUILDING UP THEN THEY’RE NOT
GOING TO BE STORE, THEREFORE THEY’RE NOT
GOING TO BE TOXIC. NOW THE FAT SOLUBLE VITAMINS,
THAT’S A, D, E, AND K, THESE ARE NOT GOING TO
DISSOLVE IN WATER. THEY NEED FAT TO BE ABSORBED. SO IF YOU’RE CONSUMING
THESE VITAMINS, BUT YOU ARE NOT CONSUMING
ANY FAT WITH THEM, THE ABSORPTION IS GOING TO
BE MUCH LOWER THAN IT WOULD BE IF YOU WERE
CONSUMING THEM WITH FAT. AND THIS COMES MOSTLY WHEN YOU THINK ABOUT
FORTIFICATION OF FOODS. SO THEY NEED FAT TO BE ABSORBED. THEY ALSO ARE
STORED EXTENSIVELY. NOW BECAUSE OF THAT, BECAUSE THEY HAVE THE
CAPACITY TO BE STORED, WE DON’T NEED THEM
ON A DAILY BASIS LIKE WE DO THE WATER
SOLUBLE VITAMINS. IN FACT, YOU KNOW, VITAMIN D
YOU CAN GET ENOUGH THROUGH THE SUMMER MONTH AND WE’LL
TALK ABOUT THIS IN A LITTLE BIT, BUT THEN THAT WILL
HELP CARRY YOU THROUGH THE WINTER
MONTHS IN SOME CASES. AND THAT’S TRUE
FOR A LOT OF THESE DIFFERENT FAT SOLUBLE VITAMINS. IT’S NOT A DAILY
NEED BECAUSE THEY ARE STORED AND CAN BE UTILIZED. THE WATER SOLUBLE,
ON THE OTHER HAND, THEY’RE NOT BEING
STORED SO YOU NEED A MORE CONSISTENT DOSE
OF THESE VITAMINS. BUT WITH THE FAT SOLUBLE, AND I KNOW I’M JUMPING
BACK AND FORTH HERE, BUT WITH THE FAT
SOLUBLE THEY CAN REACH TOXIC LEVELS BECAUSE
THEY CAN BE STORED. AND WE’LL GO OVER THIS. THIS IS MOSTLY FROM
FORTIFICATION AND SUPPLEMENTS, RARELY FROM FOOD. OKAY, I’M GOING TO MENTION THE– START WITH THE FAT
SOLUBLE VITAMINS, AND THEN WHAT WE’RE
GOING TO DO IS TALK ABOUT VITAMIN A. SO VITAMIN A,
D, E, AND K ARE OUR FAT
SOLUBLE VITAMINS, AND WE’LL BE GOING
OVER ALL OF THEM, BUT I’M START WITH
VITAMIN K IN THIS SECTION. SO THE FUNCTIONS OF VITAMIN A
INCLUDE FUNCTIONING WITH VISION, WITH GROWTH AND MAINTENANCE. AND THAT BASICALLY MEANS
IT’S GOING TO HELP WITH REPLACING THE BODY LININGS,
SUCH AS THE SKIN. IT ASSISTS WITH THE GROWTH
OF BONES AND EVEN THE TEETH. AND IT DOES HELP WITH IMMUNITY. VITAMIN DEFICIENCY CAN
LEAD TO PROBLEMS WITH VISION, GROWTH AND MAINTENANCE,
CONDITIONS OF THE SKIN, SUCH AS KERATINIZATION
AND IMMUNITY, SO DECREASED IMMUNITY. I THINK MOST PEOPLE
ARE MOST FAMILIAR WITH THE CONNECTION BETWEEN
VITAMIN A AND VISION. THIS IS AN EYE, AND THIS
IS THE CORNEA OUT HERE. WHEN YOU THINK OF A PUPIL HERE,
THE CORNEA, AND THEN THIS IS THE
RETINA BACK HERE. WHEN UV LIGHT
COMES INTO THE EYE, PASSES THROUGH THE CORNEA,
AND THAT’S ONE OF THE FUNCTIONS OF VITAMIN A. IT
HELPS MAINTAIN THE CORNEA, THE SHEATHS OF THE CORNEA. AND IT ALSO HELPS
MAINTAIN THE RETINA. BUT SPECIFICALLY AS LIGHT COMES
THROUGH AND HITS THE BACK OF THE RETINA IT’S ACTUALLY GOING TO
HIT A PIGMENT CALLED RHODOPSIN. AND RHODOPSIN IS RESPONSIBLE FOR SENSING THOSE LOW
LIGHT SITUATIONS. AND WHEN THE UV LIGHT
COMES THROUGH IT ACTUALLY, YOU KNOW, BREAKS
APART RHODOPSIN, AND VITAMIN A IS
PART OF RHODOPSIN. THAT FUNCTION, YOU KNOW,
KIND OF THAT BREAKING APART OF THAT MOLECULE SENDS
A SIGNAL TO THE BRAIN SO THE BRAIN PERCEIVES THE LIGHT
THAT IS COMING IN TO THE EYE. A LITTLE BIT OF VITAMIN A
IS LOST, AND IT’S RETINAL. IT’S THE ACTIVE
FORM OF VITAMIN A. AND THEN HAS TO BE REGENERATED. SO YOU NEED THAT VITAMIN A THERE
TO REGENERATE THIS RHODOPSIN, AND IT’S ESSENTIALLY GOING TO,
YOU KNOW, SIT OUT HERE IN THE RETINA. SO LET’S TAKE THE EXAMPLE OF
WALKING AROUND AT NIGHT AND YOUR EYES ARE SOMEWHAT
ADJUSTED TO THE DARK. AND YOU CAN SEE, BUT SOMEONE FLIPS ON A
LIGHT AND ALL OF SUDDEN IT’S JUST THIS BRIGHT WHITE,
BUT THEN EVERYTHING– IT TAKES YOU A MINUTE AND IT– YOU KNOW, A FEW SECONDS AND
THEN YOU CAN SEE AGAIN. YOUR EYES ADJUST
BACK TO THE DARK. WELL, THAT IS RHODOPSIN BEING
BLEACHED OUT BY THE LIGHT. THAT’S WHAT THEY
CALL BLEACHING OUT. BUT IT SENDS A
SIGNAL TO THE BRAIN. SO IT’S ALMOST OVERLOADED
WITH BLINDNESS, YOU KNOW, WHITE LIGHT, BUT THERE’S ENOUGH VITAMIN
A ACTIVE TO REGENERATE THAT RHODOPSIN AND THEN BRING
IN WHATEVER LITTLE LIGHT IS IN THE ROOM AND ALLOW YOU
TO RETURN TO YOUR VISION. IF YOU’RE VITAMIN A DEFICIENT, ONE OF THE FIRST SIGNS
IS NIGHT BLINDNESS. AND WHAT HAPPENS IS THERE
ENDS UP BEING A LAG TIME. SO LIGHT GOES IN AND HITS
THE BACK OF THE RETINA, IT HITS THE RHODOPSIN,
YOU HAVE THE BLEACHING, SO YOU SEE THE WHITE,
BUT IF THERE’S NOT ENOUGH VITAMIN A AVAILABLE
TO THAT RETINAL, WHICH IS WHAT WE NEED,
RETINAL, A-L, TO REGENERATE THE RHODOPSIN. THEN IT’S GOING TO TAKE A
LOT LONGER TO REGAIN VISION. SO THAT’S ONE OF
THE FIRST SIGNS. I JUST WANT TO MAKE A QUICK
MENTION OF KERATINIZATION. KERATIN IS A PROTEIN THAT
IS IN SKIN STRUCTURES, AND THIS IS A MICROSCOPIC
VIEW OF KERATIN. BUT WHEN THE SKIN LININGS
AREN’T CHANGING OVER– I MEAN MOST OF YOUR BODY
LININGS ARE CONSTANTLY BEING REBUILT AND
BROKEN DOWN ALL THE TIME, BUT WHEN YOU DON’T HAVE THAT
AVAILABLE BECAUSE VITAMIN IS IN PART OF THAT MAINTENANCE,
THAT TURNOVER, THEN THE KERATIN
TENDS TO BUILD UP, AND YOU CAN ACTUALLY GET
A REALLY, LUMPY, BUMPY, THICK SKIN THROUGHOUT
ALL OF THE SKIN, AND THAT’S ANOTHER SIGN
OF VITAMIN A DEFICIENCY. NOW VITAMIN A TOXICITY, YOU DON’T SEE THAT OFTEN,
BUT IT ACTUALLY– VITAMIN A IS CONSIDERED THE
MOST TOXIC OF ALL THE VITAMINS. WE USED TO LUMP
A AND D TOGETHER, BUT WE FOUND OUT VITAMIN D
DEFICIENCY IS PRETTY RARE. I MEAN, SORRY, VITAMIN D
TOXICITY IS PRETTY RARE. VITAMIN A TOXICITY CAN
RESULT IN SKIN RASHES, HAIR LOSS, HEMORRHAGE,
FRACTURES, LIVER FAILURE, AND EVEN DEATH. AND WHAT HAPPENS WITH
VITAMIN A TOXICITY, IT’S NOT SO MUCH FROM FOOD, AND WE’LL GO OVER THE
FOOD SOURCES NEXT. BUT IT’S A COMBINATION OF SUPPLEMENTATION
AND FORTIFICATION. AND THAT’S GET PEOPLE
TO THE UPPER LIMIT. REMEMBER I SAY YOU
DON’T REALLY NEED TO GET VITAMIN A
EVERY SINGLE DAY. IT NEEDS TO BE AVERAGED OUT. YOUR INTAKE MAY BE OVER
A WEEKLY PERIOD OF TIME, BUT IF YOU’RE CONSTANTLY EATING
FORTIFIED FOODS WITH VITAMIN A AND THEN YOU’RE POPPING A
SUPPLEMENT ON TOP OF THAT, THEN YOU DO HAVE A CHANCE OF
HAVING A VITAMIN A TOXICITY. SO VITAMIN A,
EVEN THOUGH IT’S NOT COMMON, IT IS POTENTIALLY THE
MOST TOXIC VITAMIN. NOW BETA-CAROTENE IS A
PRECURSOR TO VITAMIN A. SO THAT MEANS IT IS CHANGED INTO VITAMIN ONCE IT
GETS INTO THE BODY. AND BETA-CAROTENE HAS A– IT’S LIKE A TWOFOLD EFFECT. BETA-CAROTENE ITSELF IS AN
ANTIOXIDANT, A PHYTONUTRIENT. WE DISCUSSED THIS
EARLY ON IN THE CLASS. AND AS THAT PIGMENT IMPLANTS
WE THINK OF CARROTS, WE THINK OF THAT ORANGE COLOR, BUT IT’S IN THE FAMILY
OF THOSE CAROTENOIDS. ONCE IT’S IN THE BODY IT CAN BE
CHANGED TO VITAMIN A. NOW ONE OF THE KEYS WITH BETA-CAROTENE IS
IT’S NOT ABSORBED AT A HIGH OF RATE AS VITAMIN A IS AND
THAT’S THE ANIMAL FORMS. AND BETA-CAROTENE
ONLY OCCURS IN PLANTS, WHEREAS VITAMIN A
SOURCES OCCUR IN ANIMALS. SO IT’S NOT AS STRONG,
I SHOULD SAY, ALTHOUGH IT HAS A
SEPARATE ACTION, THAT PHYTONUTRIENT ACTION IS
NOT GOING TO BE ABSORBED AND HAVE THE SAME ACTIVITY AS AN
ANIMAL SOURCE OF VITAMIN A. SO THINK OF BETA-CAROTENE AS
A PLANT SOURCE OF VITAMIN A, BUT A WEAKER SOURCE. AND THEN VITAMIN A FROM
ANIMAL FOODS AS A MORE POTENT SOURCE WOULD BE A BETTER
WAY OF THINKING ABOUT IT. SO YOU ACTUALLY WON’T FIND
ACTUAL VITAMIN A IN ANIMAL– I MEAN IN PLANT FOODS. THIS ONLY OCCURS
IN ANIMAL FOODS. NOW BECAUSE OF THIS,
YOU KNOW, BETA-CAROTENE IS JUST
ONE OF THE CAROTENOIDS, AND SOME OF THE OTHER
CARTENOIDS ARE GOING TO BE CONVERTED INTO VITAMIN A. THEY
FOUND OUT THAT THERE ARE MANY, I SHOULD SAY, CONVERSION RATES
THAT NOT ALL ARE EQUAL. FOR EXAMPLE, IF YOU HAD
ONE MICROGRAM OF RETINAL, THAT IS EQUIVALENT TO ABOUT TWO MICROGRAMS OF
BETA-CAROTENE IN OIL. BECAUSE BETA-CAROTENE IS FAT SOLUBLE SO IT NEEDS
FAT TO BE ABSORBED, BUT IT COMES IN A LOT OF FOODS,
SUCH AS A CARROT, WHICH DOESN’T HAVE
THAT MUCH OIL. SO IF YOU CONSUME IT WITH A,
SAY, JUST A DIETARY
BETA-CAROTENE IN CARROT, IT’S A 1 TO 12 RATE, SO IT’S 1/12 OF THE ACTUAL
DOSE COMPARED TO A RETINAL. AND IT’S BECAUSE IT’S
NOT ABSORBED WELL, AND IT DOESN’T HAVE AS HIGH OF
BIO AVAILABILITY IN THE BODY. NOW THERE ARE OTHER DIETARY– WE CALL THEM PRO
VITAMIN A CAROTENOIDS. I JUST WANT YOU TO THINK OF THEM
AS LESS ABSORBED, LESS ACTIVE. YOU DON’T NEED TO KNOW
THE CONVERSION RATES, THE 1 TO 2 OR 1 TO 12. BUT I DO WANT YOU TO KNOW,
ESPECIALLY WHEN YOU LOOK AT THE RETINAL ACTIVITY UNITS
EQUIVALENTS IS BECAUSE THE ANIMAL SOURCES ARE GOING TO GIVE
A MORE POTENT FORM OF VITAMIN A THAN THE PLANT SOURCES OR THE
PRO VITAMIN A CAROTENOIDS, WHICH ARE ESSENTIALLY
PRECURSORS IN THE BODY TO VITAMIN A BECAUSE
THEY ARE ABSORBED– LESS OF IT IS ABSORBED AND
IT’S LESS ACTIVE IN THE BODY. SO YOU’LL SEE INTERNATIONAL
UNITS SOMETIMES, AND THIS USED TO MAKE
EVERYTHING EQUAL. IT DIDN’T MATTER IF YOU WERE
GETTING VITAMIN A FROM, SAY, A BEEF LIVER OR YOU WERE GETTING
BETA-CAROTENE FROM CARROT. THEY CONSIDERED
EVERYTHING TO BE EQUAL, AND THEY FOUND OUT THAT’S
ACTUALLY NOT THE CASE. THE INTERNATIONAL UNITS
ARE NOT AS ACCURATE. SO WHERE ARE THESE SOURCES,
YOU KNOW, COMING FROM? WELL, RETINAL IS,
YOU KNOW, THIS YELLOW, FAT,
SOLUBLE SUBSTANCE. WE THINK OF IT COMING FROM
THINGS LIKE BEEF LIVER, WHEREAS THE PRO VITAMIN A CAROTENOIDS ARE
FROM PLANT SOURCES. YOU KNOW, EVERYTHING
THAT’S ORANGE OR, YOU KNOW, EVEN AN ORANGE
OR RED IS GOING TO BE– YOU RED BELL PEPPER,
YOUR CANTALOUPE, WHEN WE THINK OF SWEET POTATOES. NOW CAROTENOIDS, REMEMBER
THEY ARE PLANT PIGMENTS. THEY’RE ALSO PHYTONUTRIENTS,
AND THIS IS NOT A FOOD PICTURE. THIS HAPPENS TO BE
THE GRAND PRISMATIC SPRING FROM THE
NATIONAL PARKS SERVICE. I MEAN THIS IS– IS THIS JUST AN AMAZING
PICTURE OR WHAT? BUT LOOK AT THIS BRILLIANT RED,
THESE RED COLORS IN HERE. THESE ARE CAROTENOIDS. THIS IS HOW STRONG
THAT PIGMENT IS, HOW BRIGHT AND BRILLIANT IT IS. I JUST WANTED TO DEMONSTRATE HOW
POWERFUL THE PIGMENT WAS AND, OF COURSE, I JUST
LIKE THIS PICTURE. SO THIS IS THE END OF
OUR SECTION ON VITAMIN A.  

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