Everything in middle age is easy - especially losing hair! Part of the reason that's it is so easy to lose hair is that there are so many factors that damage hair and hair follicles, leaving you looking a little less fuzzy and fluffy. And most of the factors are largely unknown by the great majority of men leaving them vulnerable to the onslaught of time and aging.
Futhermore, there are many kinds of hair loss, which only multiplies the ways your scalp line can expand. Of course, the most common is Male Pattern Baldness or androgenic alopecia (AA). Below we'll cover all the major factors that can cause you to lose hair, whether they lead to Male Pattern Baldness or a more general form of hair loss. Realize that some of these factors can lead to thinning and damaged hair as well.
NOTE: Read my link on Hair Loss and Male Pattern Baldness for other natural solutions (and a warning on the significant dangers of Rogaine/minoxidil and Propecia/Proscar/finasteride).
Here are just a few of the issues that can reinforce or sabotage your mountaintop warriors:
1. Protein. High protein diets were found (in one older study) to inhibit 5-alpha-reductase, the enzyme that converts testosterone to DHT.  Of course, this is just one study, but it does show that dietary factors can significantly affect DHT formulation. Interestingly enough, there are a couple of studies that show that high protein
2. Thyroid Dysfunction. Any malfunction of the thyroid, hypothyroidism or hyperthyroidism, can lead to hair loss.  One of the reasons is that the thyroid plays an important role in the regulation of new to dormant hair phases and any disruption can send your follicles on vacation.
3. Iron Deficiency. Women can quite frequently experience some hair loss that experts feel may be related to iron deficiency.  What about in men? Although this has not been directly verified, one of the fairly common symptoms of hypergonadal men is anemia and thus this could potentially be a factor in hair thinning or loss.
4. High Stress. Almost any major physical stress even, including "surgical trauma, high fever, chronic systemic illness, and hemorrhage," can cause "telogen effluvium" hair loss.  Telogen effluvium refers to a disruption in the normal cycle of hair growth and resting that normally occurs. It is likely that severe psychological stressors may cause some hair loss as well. Note that Cushing's Syndrome, which results in high cortisol, can also trigger hair loss.
5. Beta-sitosterol. One small study showed that this natural plant sterol (found in various nuts and seeds, rice, avocado, etc.) inhibited DHT when applied to the scalp. 
6. Green Tea. Green tea is a 5-alpha reductase inhibitor  and one study on mice showed that an extract actually regrew hair on mice. 
7. Hemp Protein and GLA (Gamma Linolenic Acid). GLA is a natural inhibitor of DHT and is abundant in certain plant fats, including hemp seed. Hemp proteins, a nice addition for bodybuilding by many accounts, usually have an ample supply. GLA can also play a role in fighting inflammation - see Chilton's Inflammation Nation for details.
8. Selenium. Selenium is a very important mineral, of course, for health. However, it is possible to consume to much and this can result in hair loss. For example, those with non toxic dosages of selenium and selenium shampoos (for medical purposes) have ended up with hair loss.  NOTE: Selenium is an alpha-reductase inhibitor  and so normal amounts are good for hair.
9. Vitamins D and E. Both of these are 5aR inhibitors  and thus should be part of your arsenal for hair maintenance. I would not recommend megadosing on Vitamin E, especially without mixed tocopherols, but a little in your diet might just help the wear and tear on your hair. Vitamin D deficiencies have been associated with hair loss as well. (See my link on Vitamin D and Testosterone for more details.
10. Lysine. A deficiency in L-Lysine, one of the essential amino acids that must be obtained through diet can lead to general hair loss. Some vegetarians might be careful to consume enough protein and make sure that their protein sources are not low in lysine. (Many plants have low ratio of lysine in proportion to the other aminos.) However, many men who supplement with L-Arginine - see my link on The Pros and Cons of Arginine - need to realize that L-Arginine competes with L-Lysine and, therefore, over consumption of L-Arginine will lead to decreased levels of L-Lysine and potentially a deficiency.
CAUTION: Coconut Oil and Soy. I am not a big fan of either of these, but I must admit they are probably both good for your hair. Soy is a natural 5-alpha reductase inhibitor  and lauric acid, about half of coconut oil, has been shown in a couple of studies to do the same.  In fact, lauric acid actually inhibits both forms of 5aR (types I and II). (Of course, I am very cautious about all saturated fats, including coconut when it comes to heart health and erectile strength. See my link on The Potential Dangers of Saturated Fat for more information.)
1) Proc Natl Acad Sci U S A, 1983 Dec, 80(24):7646â€“7649, "Nutrition-endocrine interactions: induction of reciprocal changes in the delta 4-5 alpha-reduction of testosterone and the cytochrome P-450-dependent oxidation of estradiol by dietary macronutrients in man"
2) The Journal of Steroid Biochemistry and Molecular Biology, Oct 2002, 82(2-3):233-239, "Inhibition of type 1 and type 2 5?-reductase activity by free fatty acids, active ingredients of Permixon"
3) Journal of the American Academy of Dermatology, May 2006, 54(5):824-844, "The diagnosis and treatment of iron deficiency and its potential relationship to hair loss"
4) Cleveland Clinic Journal of Medicine, Jun 2009, 76(6):361-367
5) Lancet 345 (8964): 1529â€“1532, " Â Randomised, placebo-controlled, double-blind clinical trial of beta-sitosterol in patients with benign prostatic Â hyperplasia. Beta-sitosterol Study Group."
7) J Natl Med Assoc, 2005 Jun, 97(6):816â€“818, "The effects of tea polyphenolic compounds on hair loss among rodents"
8) JAMA, 1956, 160(16):1397-1398, "DIFFUSE HAIR LOSS ASSOCIATED WITH SELENIUM (SELSUN) SULFIDE SHAMPOO"
9) Annals of Clinical and Laboratory Science, 26(2):99-113, "Metabolism of subtoxic levels of selenium in animals and humans"10) Int J Oncol, 2003 Jan, 22(1):5-13, "Chemoprevention of prostate cancer by diet-derived antioxidant agents and hormonal manipulation (Review)"
11) Arch Dermatol, 1972, 106(3):349-352, "Hair Growth and Alopecia in Hypothyroidism"