Another fat-soluble vitamin that directly affects steroidogenesis and muscle building, and the decrease of estrogen and prolactin while boosting your well-being and mood is vitamin A (retinol). It also helps with eyesight (clear sight), night blindness and is anti-dry eyes. It is also very important for brain function such as maintaining neuronal plasticity and cognitive function in adulthood, improving learning, memory forming, recalling and mental clarity.
Vitamin A deficiency affects iron mobilization and impairs hemoglobin synthesis, leading to a low red blood cell count.
Furthermore, it’s important in adult growth and development, maintenance of immunity (resistance to infection by forming protective membranes and mucous) and the maintenance of epithelial barriers.
Vitamin A from animal sources is directly absorbed, utilized and stored, whereas vitamin A from plants (beta-carotene), first needs to be converted to retinol by the liver. Our bodies aren’t very good with this conversion and the ratio is about 6:1 or even worse. Under conditions of stress and disease, that ratio is further increased or even completely hindered.
Retinol is stored in the body as retinyl esters, and the active form of retinol is retinoids – which act as a steroid hormone.
Retinyl ester is stored in the eyes, lungs, adipose tissue, testes, skin, and spleen where it exerts its functions.
Retinoic acid binds to RAR (retinoic acid receptor) and RXR (retinoic x receptor), which are receptors that belong to the super-family of thyroid and steroid receptors. Vitamin A has a direct impact on thyroid and steroid production. It also works in synergy with steroid hormone – vitamin D – to be fully enabled to exert powerful actions. As vitamin D levels increase, so does vitamin A requirements. Elevated vitamin D can deplete vitamin A, if inadequate vitamin A is consumed through the diet.
Retinol is found in adipose tissue, where it is shown to inhibit adipogenesis (the formation of fat cells).
Vitamin A (all-trans retinol) has been found to activate and multiply the UCP1 gene in adipose tissue (which increases thermogenesis), while inhibiting genes that promote adipogenesis (fat formation), such as PPARγ. (1)
Vitamin A also lowers cortisol, which significantly lowers bodyweight and visceral fat. (s)
Growth & anti-cortisol
A deficiency in vitamin A leads to lower immunity, slows wound healing as well as hindered muscle protein synthesis (2). Adequate levels will ensure that muscle protein synthesis signaling is optimal and that you recover faster after injuries and training.
RAR is also involved in retinoic acid-induced activation of signaling cascades mediated by tyrosine kinases known as phosphoinositide 3-kinase (PI3K) and leading to cell differentiation – muscle growth.
Vitamin A is very good against inflammations as well.
During stress, cortisol and cortisone is increased, which then blunts wound healing and causes inflammation. Retinoids counter cortisone and stimulate corticosteroid-impaired (transforming growth factor) TGF-beta and IGF-I release, increases collagen production and inhibits inflammation markers (IL-6) in synovial cells. (3) Vitamin A is also a very potent cortisol antagonist (reduces 11β-HSD1 activity) and decreases cortisol receptors (s). Although big doses, 20 000IU daily, was needed to significantly lower cortisol in people with Cushing’s disease (whose cortisol is very high), doses as high as 500 000IU is pretty save long-term (6 months+). Stress hormones and inflammation suppress muscle protein synthesis.
Eating more protein can assist in building muscles faster, but as protein increases, so does the need for vitamin A, as it’s involved in the transport thereof. A high protein diet can deplete vitamin A stores if the intake thereof isn’t sufficient.
Steroid vitamin – testosterone & growth hormone
Retinol is such a powerful testosterone and growth promoter, that when vitamin A and iron are given as a supplementation during puberty in short stature boy, they have the same growth results as when given testosterone oxandrolone (a steroid) after 12 months. (4)
A vitamin A deficiency, however, leads to significantly low testosterone and growth hormones, as if in a state of castration (5). Retinoids also play a role in the maintenance and regulation of Leydig cell function and are able to stimulate testosterone synthesis and also increase LH receptor density and sensitivity (6).
Adequate amounts of retinoic acid increases testosterone levels, transferrin (iron transporter), IGF–binding protein 4 (IGF transporter), androgen-binding protein (androgen transporter), transforming growth factor-beta (TGF-beta – which causes cell growth but suppresses cancer) and steroidogenic acute regulatory protein (StAR – which transports cholesterol into the gonads to be converted to testosterone). Testosterone increases the production of red blood cells, and requires more iron to do so. Iron supplementation alone in iron deficient men increased testosterone from 345ng/dl to 432ng/dl after 6 weeks (7). The rise in testosterone requires more iron for hemoglobin production, and is limited by an iron deficiency. Vitamin A and iron are intertwined in testosterone production.
Vitamin A increases nocturnal growth hormone in vitamin A deficient boys via the cyclic AMP pathway, and the greatest spike was seen after a 100nM (10 000IU) retinoic acid dose (8). The fastest growth occurs during sleep and that’s where nocturnal growth hormone is so important (9).
Vitamin A deficiency interfered with the pituitary-thyroid axis by: 1) increasing the synthesis and secretion of thyroid-stimulating hormone (TSH) by the pituitary gland, 2) increasing the size of the thyroid gland, 3) reducing iodine uptake by the thyroid gland and 4) impairing the synthesis and iodination of thyroglobulin (precursor to thyroid hormones), thus leading to hypothyroidism.
Hypothyroidism is associated with elevated thyrotropin releasing hormone (TRH), which is released to stimulate the pituitary gland to release TSH to stimulate the thyroid to increase thyroid hormone production. Vitamin A inhibits TSH secretion via the down regulation of TSH-β gene expression, protecting against elevated TRH levels. Elevated TRH leads to hypothyroidism and also increases prolactin.
Vitamin A is positively associated with triiodothyronine (T3) and free T3 index (FT3I), which indicates better conversion from thyroxine (T4) to T3 (10)
Increased T3 will signal back to the hypothalamus to decrease TRH via a negative feedback loop. Vitamin A helps prevent hypothyroidism, keep prolactin low and helps it to keep the thyroids’ function optimally.
Vitamin A increases dopamine, and dopamine directly lowers TSH and prolactin and increases T4 to T3 conversion. (11) Dopamine increases goal orientation, general well-being and happiness and is also the hormone that antagonizes serotonin – which has the opposite effect. A good dose of about 100 000IU was used in this study to lower prolactin and increase dopamine. More on dopamine here…
Anti-estrogen & prolactin
Retinols are able to allow or inhibit the transcription of certain receptors such as thyroid, vitamin D, steroid receptors. Among these receptors are estrogen, prolactin and PPAR. Retinol down-regulates all these receptors. (12) Adipose tissue is associated with estrogen, and vitamin A is able to help reduce fat, thus indirectly lowering estrogen as well.
Not only is it able to reduce and inactivate estrogen and prolactin receptors, but also by increasing thyroid activity and dopamine, which both antagonize estrogen and prolactin.
High doses of vitamin A (200 000 – 250 000 IU) can be used to lower estrogen significantly in just one or two days if a dramatic reduction is wanted quickly (13).
Not only is vitamin A beneficial for your body on the inside, but also on the outside.
Tropical retinol treatment significantly increased skin thickness and collagen synthesis and formation, which prevents wrinkles, and are even able to reverse wrinkles. It does so by increasing glycosaminoglycan expression, which primary role is to maintain and support collagen, elastin and turgidity in the skin.
It also increases genes that increase collagen, such as collagen type 1 (COL1A1), and collagen type 3 (COL3A1) with corresponding increases in procollagen I and procollagen III protein expression. (14, 15). Retinol can also be absorbed transdermally to increase serum vitamin A levels in the body.
Vitamin A interacts with various other nutrients, so it would be wise to first look at your diet and your symptoms before deciding to start supplementing with vitamin A.
Vitamin A synergists: Iron, manganese, vitamin C, fats, CLA, zinc (dose dependent), vitamin E (dose dependent), vitamin D (dose dependent)
Vitamin A antagonists: Zinc, vitamin E, iron (dose dependent), vitamin D (dose dependent), alcohol
For e.g. if you have low levels of iron (anemia), you might benefit from taking vitamin A.
Vitamin A’s demands in the body increase when:
- Exercising intensely
- Eating more protein
- You want to increase testosterone production
- You want to improve certain health aspects, such as dandruff, vision, skin, etc…
- Vitamin D levels increase
Thus, you’ll need much more than just the recommended daily value, but requirements can go up to and even past +100 000 IU a day. Toxicity only happens with synthetic vitamin A. 300 000IU retinol acetate treatment for a few months is well tolerated (16). Adequate retinol would be ~10 000IU for an inactive individual.
Keep in mind, you need adequate amounts of zinc as well, as zinc is essential for transporting vitamin A through the blood, activating vitamin A to retinoic acid, and is also a component of the nuclear receptor that binds to retinoic acid and allows it to regulate gene expression.
Excellent sources of retinol include liver, cod liver oil, and animal fat including dairy and eggs.
Get your vitamin A extract from a natural source for maximal benefits.
Retinol palmitate or retinol acetate would be the best options, and take with a fatty meal to enhance the absorption thereof.
Great trustworthy supplements that I would advise include:
Retinil – 2400IU retinyl acetate/palmitate per serving, 340 serving per container (highly purified and excellent quality) – $19.99 (for external use only, which is for great absorption and requires smaller amounts for the same effect as when taken an oral supplement)
Vitamin A – 10 000IU per serving, 100 servings per container