Biol 135 Lecture: VI. Structure, Function and Source of Micronutrients

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Fat Soluble Vitamins

Biol 135 Lecture: VI. Structure, Function and Source of Micronutrients.

The Fat Soluble Vitamins

Vitamin A

Vitamin A is actually a family of fat soluble vitamins which need to be consumed with fat in order to be absorbed by the body properly.Like all vitamins, A is an essential nutrient and is required for vision, gene transcription, boosting immune function, and great skin health.

Beta-Carotene and itsRole

Carotenoids arepigments in plants that give an intense orange/yellow color to a variety of fruits and vegetables. The most accessible example is the color of carrots! Also, most of us will know that eating carrots is good for your eyes; it is the carotenoids that are beneficial. Beta-Carotene is a carotenoid and an exceptionally important one in human nutrition.

The human body has 2 functions for carotenes:

1)It turns it into Vitamin A*40% of carotenes

2)It turns it into an antioxidant. * 60% of carotenes

When we ingest foods with beta-carotene in them, itis either converted into vitamin A (retinol), or it acts as an antioxidant in our body. The typical proportion is 40/60, but sometimes as much as 50% of vitamin A in a typical diet is provided the carotenoids(especially by beta-carotene).

Your body will turn carotenes into Vitamin A only if your body needs it. The rest will circulate through your blood as antioxidants. This is helpful because there are some issues with Vitamin Aoverdose and toxicity. However, if you start with carotenesas the source in your diet you do not need to worry about that, as it will never make more vitamin A than you need!

A small number of carotenes, including beta-carotene, are often called "provitamin A" because they are a precursor to production of vitamin A in the body. The carotenes lycopene, lutein and zeaxanthin cannot be converted into vitamin A, though they provide other health benefits.

Deficienciesin vitamin A can lead to blindness and increased viral infection. Deficiency is not typically problem in most developed, but is the leading cause of blindness in children in some third world countries.

Overconsumption of vitamin A can lead to jaundice, nausea, loss of appetite, irritability, vomiting, and even hair loss. As always, like any other vitamin, the overconsumption of vitamin A is not possible from eating too much food that is rich in vitamin A – it is only possible from taking excessive amounts through dietary supplements!

Food Sources for Vitamin A:

Preformed vitamin A is found almost exclusively in animal products, such as human milk, glandular meats, liver and fish liver oils (especially), egg yolk, and whole milk and dairy products.

Top 10 Foods for Vitamin A (in 100g)

#1: Sweet Potato (Cooked) - 19218IU (384% DV)

#2: Carrots (Cooked) - 17033IU (341% DV)

#3: Dark Leafy Greens (Kale, Cooked) - 13621IU (272% DV)

#4: Squash (Butternut, Cooked) - 11155IU (223% DV)

#5: Cos or Romaine Lettuce - 8710IU (174% DV)

#6: Dried Apricots - 12669IU (253% DV)

#7:Cantaloupe Melon - 3382IU (68% DV)

#8: Sweet Red Peppers - 3131IU (63% DV)

#9: Tuna Fish (Bluefin, Cooked) - 2520IU (50% DV)

#10: Tropical Fruit (Mango) - 1082IU (22% DV)

The Benefits of Vitamin A

Vitamin A as an Antioxidant

One benefitof Vitamin A is that it acts as an antioxidant, but only carotenes (i.e. beta carotene, alpha carotene) which are the precursor of Vitamin A and are found in plant sources (i.e. carrots, sweet potatoes, pumpkin).

As we have seen, the human body has 2 functions for carotenes: Turns it into Vitamin A(40%) turns it into an antioxidant (60%).

There are many types of carotenes that act as antioxidants, such as:

• alpha carotene
• beta carotene
• lycopene

Carotenes specifically fight off the singlet oxygen free radical. Again, only the carotenes have antioxidant powers. The Vitamin A that comes from animal sources do not possess the same antioxidant powers as beta carotene.

Lycopene

Lycopene is a bright red pigmented carotene and phytochemical. A perfect example of a food source rich in lycopene are the tomato species. It is also found in other red fruits and vegetables, such as red carrots, watermelons and papayas and also in brown beans and parsley, even though not red. However, lycopene is not found in cherries, strawberries or red bell pepper. Unlike beta carotene, it cannot convert into vitamin A. Lycopene is a polyunsaturated hydrocarbon, insoluble in water.

Anti-Infection

One of the other main benefits of Vitamin A is their anti-infection powers. The frontline of your defense system is really your skin and other exposed parts of your various tissues and organs.

The epithelial tissue of your skin is called the epidermis. Immediately deep to this is the dermis and hypodermis. The hypodermis (or subcutaneous) tissue is mostly made of fat (adipose) tissue, and this is where Vitamin A is stored, since it is a fat-soluble vitamin it is rich in this tissue and it benefits these fatty tissues.

The frontline tissues also include the outer layer of your eyes, mouth, nose, throat, digestive tract and urinary tract. This frontline is your body’s first line of defense against disease, infection and free radicals. Vitamin A helps to strengthen the mucous membranes of your body, thus protecting your body against infection. The vitamin A fortified mucous membranes are also found in the eyes, nose, throat, lungs, digestive tract & urinary tract strong. This also helps fight off and protect you against infection.

Immunity Booster

Vitamin A can also have the effect of helping to boost your immune system. This is because it plays a role in the development of lymphocytes, the white blood cells (WBS’s) of your immune system that fight off bacteria and disease. It has been found useful in:

• Treating measles and respiratory infections – especially helpful for children.

• Viral infections

• Assisting anyone whose immune system is depressed by boosting immune cells (e.g., in AIDS).

Vitamin A and Your Eyesight

Vitamin A assists your eyes in3 major ways:

• Prevents Night Blindness
• Prevents Cataracts (like Vitamin C)
• Preserve Eyesight throughout life time

Night Blindness

Your retinas contains light-sensitive cells that have a large amount of Vitamin A stored in them, the two photo receptors for vision are Rods (for black and white vision) and Cones (for color vision).

Rods are specifically used for night vision. And they use the combination of a protein called opsin and a form of Vitamin A (called retinal) in order to function properly. Without the Vitamin A portion the rods cannot function properly and you won’t be able to see as well in dark or in dim lighting.

Cataracts

The lens of the eye is made of collagen and cataracts form when the lens becomes cloudy, either clumping of protein or deposits of yellow-brown pigmentin the lens. Cataracts reduce the transmission of light to the retina at the back of the eye making it very difficult to see. Cataracts used to be one of the leading causes of blindness. A phenomenal way to prevent this from happening is having a diet rich in carotenoid, especially beta carotene.

The antioxidant power ofbeta carotene wipes out the free radicals before they damage the lens.Vitamin C is also helpful in preventing cataracts. The combination of these two will definitely help to prevent cataracts.

There is the possibility of getting Age-Related Macular Degeneration (AMD) as you age.

The macula lutea is a structure on the retina inside the fovea centralis (central pit) where the highest density of cones cells reside! This is the spot where you focus your field of view in order to clearly see something. The moment you start losing the functions of cones due to damage you will lose your visual acuity, and may involve some vision loss. AMD is one of the leading causes of blindness in people older than 65. And about 31% of Americans 75 and older has it

One study suggests that eating just one serving of a food high in Vitamin A or beta carotene can reduce the chances of AMD by almost half! A few other carotenoids (i.e. Lutein and zeaxanthin) are also helpful in preserving your eyesight.

Other possible Benefits of Vitamin A

Vitamin A benefits pregnantand nursing mothers. The retinoic acid form aids in protein and growth hormone development for the developing fetus. They also help in forming the heart, eyes, limbs and ears. Note the warnings that excess vitamin A during pregnancyis to be avoided.

Vitamin A aids in red blood cell (RBC) formation and help to transport iron to your blood cells. This translates to more oxygen and oxygen is very beneficial for your body.

Vitamin A helps in the creation of important proteins used throughout your body. This is important because your muscles are made from proteins and proteins also affect your genes. It is advisable to get at least 10,000 to 15,000IU per day of Vitamin A and beta carotenein your diet. The best is the preformed version (from animal sources such as eggs, liver, poultry & dairy) and from carotenes (these come from plant sources). One large egg has around 320IU of preformed Vitamin A while 1 medium carrot has about 8,000IU of beta carotene.

Vitamin D

The Sunshine Vitamin: Vitamin D deficiency is a pandemic in the United States, but many Americans, including physicians, are not aware that they may be lacking this important nutrient. Despite its name, vitamin D is not a regular vitamin. It's actually a steroid hormone that you get primarily from either sun exposure or supplementation, and its ability to influence genetic expression that produces many of its wide-ranging health benefits. Researchers have pointed out that increasing levels of vitamin D3 among the general population could prevent chronic diseases that claim nearly one million lives throughout the world each year. Incidence of several types of cancer could also be slashed in half.

Vitamin D is a powerful defender of your body. It fights infections, including colds and the flu, as it regulates the expression of genes that influence your immune system to attack and destroy bacteria and viruses. In this interview, one of the leading vitamin D researchers, Dr. Michael Holick, expounds on these and many other health benefits of vitamin D. He's both an MD and a PhD, and wrote the book, The Vitamin D Solution.Since the early 2000s, scientific investigations into the effects of vitamin D have ballooned. By the end of 2012, there were nearly 34,000 of them. Dr. Holick is one of those who has really helped advance our understanding of the massive importance of vitamin D—far beyond its influence on bone metabolism.

"I've been doing vitamin D research for more than 40 years," he says. "As a graduate student for my master's degree, I was responsible for identifying the major circulating form of vitamin D, 25-hydroxyvitamin D that doctors typically measure now for vitamin D status in their patients."

Are You Vitamin D Deficient?

Before the year 2000, very few doctors ever considered the possibility that you might be vitamin D deficient. But as the technology to measure vitamin D became inexpensive and widely available, more and more studies were done, and it became increasingly clear that vitamin D deficiency was absolutely rampant. For example:

• The Centers for Disease Control and Prevention (CDC) reported that 32% of children and adults throughout the US were vitamin D deficient.
• The National Health and Nutrition Examination Survey found that 50% of children aged one to five years old, and 70% of children between the ages of six to 11, are deficient or insufficient in vitamin D.
• Researchers estimate that 50% of the general population is at risk of vitamin D deficiency and insufficiency.

When it comes to vitamin D, you don't want to be in the "average" or "normal" range, you want to be in the "optimal" range. The reason for this is that as the years have gone by, researchers have progressively moved that range upward. At present, based on the evaluation of healthy populations that get plenty of natural sun exposure, the optimal range for general health appears to be somewhere between 50 and 70 ng/ml. For treatment of chronic disease such as cancer, recommendations go even a bit higher than that.

As Dr. Holick explains:

"The Institute of Medicine, including the Endocrine Society, recommends at least 20 for bone health. But there's this area between about 21 and 30 that we consider to be an insufficient level. Most experts agree that if you're above 30 nanograms per milliliter, this is a healthy level. Because of its variability in the assay, the recommendation from the Endocrine Society Clinical Practice Guidelines that looked at all the literature and made recommendations for prevention and treatment of vitamin D deficiency for doctors is 40 to 60 nanograms per milliliter... A study was done in Maasai warriors who are outside every day. That really gives us an insight where we should all be with our blood levels of 25-hydroxy D. They were found to be around 50 nanograms per milliliter."

Sunshine: The Best Way to Optimize Your Vitamin D Levels

I firmly believe that appropriate sun exposure is the best way to optimize your vitamin D levels. In fact, I personally have not taken a vitamin D supplement for three or four years, yet my levels are in the 70 ng/ml range. If you can't get enough sunshine, then a safe tanning bed would be your next best option. What makes for a safe tanning bed? Most tanning equipment use magnetic ballasts to generate light. These magnetic ballasts are well known sources of EMF fields that can contribute to cancer. If you hear a loud buzzing noise while in a tanning bed, it has a magnetic ballast system. I strongly recommend you avoid these types of beds and restrict your use of tanning beds to those that use electronic ballasts.

When you make vitamin D in your skin, it lasts two to three times longer in your body than getting it from foods or supplements! During the winter, if you live North of Atlanta, Georgia, you essentially cannot make any vitamin D in your skin from about November through March. Therefore people in these regions need to either take a supplement or use a tanning bed/UVB light to produce vitamin D. Let us not forget that getting sun exposure is also good for other reasons, one being that exposure of skin to sunlight generates beta-endorphins, an endogenous (made from within) opioid peptide that makes you feel really good! No wonder many people feel very happy from laying in the sun. Beta endorphins, by the way, are about 1,000 times more potent than heroin or opium – chemically they are all opioids which are natural analgesics (painkillers). What this means is that by safe exposure of your skin to the beautiful rays of the sun there are multiple benefits to your health – the high potency of endogenous beta-endorphins means that very low levels will have a powerful effect on your mood and pain tolerance. Beta endorphins are also released after strenuous physical activity and after a good cry! If we stop to analyze it, chances are you feel a lot better after gardening or exercise and also after letting go and crying your eyes out!

It is recommended that you protect your face when using a tanning bed, and to only go in for half the time recommended for tanning. Make sure the tanning bed you're using is putting out UVB radiation. There are some on the market that only put out UVA - as this is what creates a tan. UVA rays are also the ones responsible for skin damage, however, and they do NOT make your skin produce vitamin D. Beds tend to vary between three to 10% UVB, and the higher the percentage of UVB, the better. There are also beds that make UVB only. They're not as popular since they won't make you tan! However, if you're doing this solely for the health benefits, then a UVB tanning bed is certainly an option.

Want Safer Sun Exposure? There's an App for That!

Apparently there is an app called DMinder, available on Based on your local weather conditions (reported from the weather service) and other individual parameters such as your skin tone and age, it tells you how much UV radiation you're getting, and how many units of vitamin D you're making. It will also tell you when to get out of the sun, to protect yourself from sunburn.

Beware that you CANNOT make any vitamin D when you're exposed to sunlight through glass since glass filters out most of the UVB that stimulates vitamin D production. All you're mostly getting are UVA rays, which penetrate deeply into your skin, causing wrinkling, and increasing your risk of skin damage and skin cancer. Also beware that UVA radiation is harsher in the morning, and late afternoon. So, contrary to popular advice, which was more tailored to tanning than optimizing your vitamin D stores, you'll want to avoid early morning and afternoon sun. Essentially you cannot make vitamin D until about 10:00 in the morning until about 2:00 in the afternoon. With daylight savings time is can be confusing, so a good rule of thumb is that the best time to get safe sun exposure is 2 hours on either side of solar noon!

Dosing Recommendations if You Need to Take a Vitamin D Supplement