Skin Nutrition
Skin products often contain nutrients with claims of benefits. While the skin
is the visible organ of the body that displays evidence of food-related
problems, malnutrition and advertises the presence of many diseases, nutrients
applied on the surface have little no value. Adding nutrients to shampoos is
probably the most absurd marketing practice, since hair is a non-living product
of skin that has no ability to utilize nutrients. Nutrients required by skin
cells should be delivered orally. The addition of nutrients to skin creams and
shampoos makes little biological sense except for the addition of vitamin C to
sun protective skin creams and the treatment of some skin conditions with creams
containing analogues of vitamins A and D that have drug-like activity.
The skin provides visible evidence of malnutrition and suffers many food
related diseases. The "three D's" of vitamin B3 deficiency, pellagra, are
diarrhea, dermatitis, and dementia. Scurvy is expressed as easy bruising. Scurvy
is perhaps the first vitamin deficiency to be recognized. British sailors would
die often of scurvy on long ocean voyages until limes were added to ships’
rations. Easy skin bruising and petechiae are the most obvious signs of scurvy.
Even in affluent patients vitamin C deficiency may occur in a concealed form. It
is common for patients to report easy bruising to MDs, but many blood
abnormalities are considered before nutrient deficiency. In a review of
easy bruisability, Valente and Abramson suggested: “Children who only eat a
limited diet (such as macaroni and cheese, chicken fingers and candy) can
develop nutritional deficiencies,[leading to a coagulopathy, vascular fragility
and/or bruising. If the patient is a thin teenage girl, she may be avoiding
certain food groups (such as meat or fat) because of an eating disorder that
would predispose her to bruising or bleeding. Middle-aged persons may also cut
out specific nutrients or food groups; fad diets such as Atkins have gained
popularity over the last few years and more people are eliminating fruits and
vegetables and adding meats and cheeses to their diets, again leading to
nutritional deficiencies over an extended period of time. An elderly person
living alone or in a nursing home can develop nutritional problems as well due
to poorly fitting or absent dentures, lack of access to certain foods or simply
a decreased appetite. Lastly, consider the oral habits that may contribute to
bleeding. Is the patient a heavy drinker, smoker or illicit drug user? Does the
patient's occupation expose him/her to oral or inhaled toxins?”
A deficiency of riboflavin is expressed as soreness of the tongue and lips,
painful cracks at the corners of the mouth, a red swollen tongue, and teary or
bloodshot eyes. Vitamin B6 deficiency causes skin lesions around the eyes, nose
and mouth, cheilosis (fissuring and scaling at the angle of the mouth),
glossitis (inflammation of the tongue), and stomatitis (inflammation of the oral
mucosa). Symptoms of biotin deficiency include hair loss and a scaly red rash
around the eyes, nose, mouth, and genital area.
Glycation End Products
The effects of sugar modified proteins are of great importance in aging of
all tissues. The effect is visible as skin aging. Sugar modification of protein
was identified as an important cause of multi-organ disease in diabetes. These
advanced glycation end products (AGEs) are formed by the random attachment of
glucose and fructose to proteins. Increased accumulation of AGEs in human tissue
is associated with end stage renal disease, chronic obstructive pulmonary
disease, and, recently, skin aging. Glycated hemoglobin (hemoglobin A1C) is now
used to measure glycemic control in diabetes. Nguyen and Katta provided a
comprehensive review of AGEs: “Characteristic findings of aging skin, including
decreased resistance to mechanical stress, impaired wound healing, and distorted
dermal vasculature, can be in part attributable to glycation. Glycation is
increased by sugar in the diet and the formation of AGEs through cooking.
Certain methods of food preparation (i.e., grilling, frying, and roasting)
produce much higher levels of AGEs than water-based cooking methods such as
boiling and steaming… AGEs accumulate in various tissues as a function, as well
as a marker, of chronological age. Proteins with slow turnover rates, such as
collagen, are especially susceptible to modification by glycation. Collagen in
the skin, in fact, has a half-life of approximately 15 years and thus can
undergo up to a 50% increase in glycation over an individual's lifetime. Other
cutaneous extracellular matrix proteins are functionally affected by glycation,
including elastin and fibronectin. This further compounds dermal dysfunction as
glycation crosslinked collagen, elastin, and fibronectin cannot be repaired like
their normal counterparts. general cellular function may be compromised in the
presence of high concentrations of AGEs. In vitro, human dermal fibroblasts
display higher rates of premature senescence and apoptosis, which likely
explains the decreased collagen and extracellular matrix protein synthesis
observed in both cell culture and aged skin biopsies. Similarly, keratinocytes
exposed to AGEs express increased levels of pro-inflammatory mediators, suffer
from decreased mobility, and also undergo premature senescence in the presence
of AGEs… Of interest, several culinary herbs and spices are believed to be
capable of inhibiting the endogenous production of AGEs (specifically
fructose-induced glycation). These include cinnamon, cloves, oregano, and
allspice.[42] Other dietary compounds that have been linked to inhibition of AGE
formation based on in vitro data and preliminary animal models include ginger,
garlic, α-lipoic acid, carnitine, taurine, carnosine, flavonoids (e.g., green
tea catechins), benfotiamine, α-tocopherol, niacinamide, pyridoxal, sodium
selenite, selenium yeast, riboflavin, zinc, and manganese. The cosmeceutical
industry has taken notice of this data, and several have recently released
topical products containing carnosine and α-lipoic acid, with claims related to
anti-AGE formation.”
Vitamin A and Analogues
Vitamin A is a set of biological activities produced by a family of
molecules. Several substances contribute to the Vitamin A effect, including the
fat soluble retinol group (pre-formed) and the water soluble carotene group
(provitamin A). The fat-soluble group is strictly a product of animal
metabolism, and must be obtained from animal-source foods. Fish-liver oils have
been the standard Vitamin A supplements.
Retinol is the principal Vitamin A, and fills all the nutrient roles that
Vitamin A plays metabolically. The activity of other members of the Vitamin A
group is referred to retinol activity as an index of their biological potency
(retinol equivalents). A cousin of retinol, retinal, is the substrate for the
production of the visual pigment, rhodopsin. Deficiency of rhodopsin leads to
night blindness, the best recognized symptom of vitamin A deficiency. Another
cousin, retinoic acid, and its derivatives have become important drug-like
Vitamin A used in the treatment of the skin conditions, cystic acne and
psoriasis. Many Vitamin A effects are hormone-like, influencing the growth and
differential of cells. Vitamin A may also be considered a biological response
modifier. This effect is most noticeable in the skin where Vitamin A activity
reduces the tendency of surface cells to pile up, producing thickened scaly
skin. This "hyperkeritinizing" effect is characteristic of skin diseases such as
psoriasis, acne, lichen planus, and dry-scaly skin (ichthyosis).
Naturally occurring, fat soluble Vitamin A (retinols) are toxic in overdose.
The source is usually an animal product such as mammalian or fish liver or
supplements such as cod liver oil. A single megadose of 1,500,000 IU
produces brain swelling with headache, drowsiness, and vomiting. Sustained
Vitamin A (retinol) doses over 50,000 IU may be toxic. In children, overdose
results in loss of appetite, itching, irritability, swelling and tenderness of
bones, and failure to gain weight. In adults other effects include sore mouth,
brittle nails, increased blood calcium, liver enlargement, low-grade fever and
headache. Clearly, Vitamin A intake should fit into an optimal range to achieve
all its benefits, without its toxicity.
High doses of betacarotene from food sources have no known toxicity, although
high dose supplements (10,000 IU or greater per day) of beta carotene are not
required and are not supported by existing research. Beta carotene and related
carotenoids are ingested in fruits and vegetables.
Over 1500 Synthetic Vitamin A analogues or retinoids have been developed.
Isoretinoin (13-cis-retinoic acid) was marketed as "Accutane" for the
treatment of severe acne ( discontinued in 2008). While this vitamin-drug is
effective, it is so biologically potent that a pregnant woman taking Accutane is
assured of a malformed fetus. A woman suffering severe acne can only take the
drug if she takes adequate precautions to avoid pregnancy. Etretinate is
similarly effective in the treatment of psoriasis and has benefits in the
treatment of skin cancers. The toxicity of these compounds limits their use.
Tretinoin or Vitamin A acid has been marketed as a skin cream or gel for the
treatment of acne. Observations suggest that Tretinoin reduces sun damage to
skin, and reduces facial skin wrinkling. Topical application of Tretinoin in
concentrations of 0.01 to 0.05% may produce redness and peeling of the skin;
reduced concentration and frequency of application limit the side effects of
this cream. Tretinoin may be the first effective anti-skin-aging substance.
Changes in the growth patterns of cells are characteristic of cancer, and
Vitamin A activity seems to protect against cancer development. Each Vitamin A
component may have different abilities as anti-cancer agents. The water-soluble
plant pigment, beta-carotene is receiving the most intense study in this role.
Many years ago W. Bollag in a review of Vitamin A activity stated:
“The finding that retinoids may divert a cell from proliferation to
differentiation may be a clue to a new approach for the prevention and treatment
of cancer... Very many chemically or virally induced tumors are influenced by
retinoids. It is possible to prevent or retard the development of tumors of
various organ sites (e.g., skin, oral cavity, stomach, intestine, colon,
pancreas, trachea, bronchus, urinary bladder, cervix, and breast) and induced by
many different carcinogens. Some of the tumors even regress under treatment with
retinoids."
