1. Average testosterone levels in men have declined by 25% over the past two decades.
This finding is straight out of a study published in the Journal of Clinical Endocrinology and Metabolism (3).
Researchers based their study on data from the Massachusetts Male Aging Study (MMAS), in which three separate blood samples were collected from 1,500 randomly selected men over a period of 17 years (1987-2004).
After analyzing the data, and accounting for factors such as age, obesity, and smoking, the researchers found that the subjects’ bio-available testosterone (i.e. total and free testosterone combined) decreased by an average of 1.3 percent per year.
It's a well researched fact that testosterone levels in men tend to decline with age, but what the researcher's found was an age-independent decline in T.
Now:
Assuming this trend has maintained its pace and not sped up (which is unlikely), the average man in 2017 has about 25% lower bio-available testosterone than the average man had just 20 years ago (1.3 x 20 = 26).
2. 1 in 4 men over the age of 30 have low testosterone levels.
This finding is also from a study published in the Journal of Clinical Endocrinology and Metabolism (4).
1475 men, between the ages of 30 and 79, were randomly selected from the Boston Area Community Health Survey.
After analyzing their blood work, researchers found that approximately 24% of the subjects had total testosterone levels less than 300 ng/dL. That's just about 1 in 4 men.
3. Every 10-year increase in age confers a 17% increase in risk of low T.
This figure is from a study published in the International Journal of Clinical Practice (5).
Researchers came to this conclusion after analyzing the blood samples of 2498 randomly selected men throughout the United States.
So yes, a correlation between aging and lower testosterone levels does exist, but this does not necessarily imply a causation.
In the words of researcher Dr. David Handelsman:
"By itself, age does not cause lower testosterone in older men. It's more likely that lowering of testosterone is a consequence of illnesses men acquire as they get older..."
Handelsman bases this statement off of the research (6) him and his team performed down in Australia.
They recruited 325 men (40-97 years old, average age = 60) who had self-reported excellent health and no symptoms to complain off. Nine separate blood samples were taken over a period of three months.
When they looked at the entire sample of 325 men, even with the large age range, T-levels did not significantly differ.
Now obviously this sample size does not represent the general population. But the lesson here is that it is possible to maintain optimal testosterone levels well into old age.
Signs and Symptoms of Low Testosterone
There isn't one facet of your physical, mental, and emotional health that's not affected by your testosterone levels.
Many men experience the following symptoms without even knowing that low testosterone may be at the root of what's causing them.
4. Low energy and fatigue
Fatigue and low energy levels are a trademark side-effect of low testosterone levels (7).
If you're tired all the time, despite getting enough sleep, or if you're finding it increasingly difficult to get some exercise, low T might be to blame.
5. Reduced bone density
Men with low testosterone levels are more susceptible to bone fractures, and in extreme cases, to developing osteoporosis (8).
This is because testosterone plays a key role in overall bone health (9).
More precisely, it is involved in stimulating bone mineralization and decreasing bone resorption (10).
6. Decreased muscle and strength
Testosterone is the primary hormonal driver of muscle growth.
When testosterone molecules enter the androgen receptors in muscle tissue, they trigger muscle growth by stimulating protein synthesis (11).
On the flip side, sub-optimal testosterone levels mean that protein synthesis, and therefore muscle growth, is slowed down.
Regardless of how many reps and sets you crank out in the gym, if you have low T, your muscles will not grow to their potential.
7. Low libido and sex drive
Testosterone plays a key role in regulating libido (sex drive) in both men and women (12).
A disinterest in sex is usually the first symptom experienced by men with low testosterone.
The research is clear on this:
Libido is directly correlated with the amount of testosterone running through your veins (13).
Low testosterone = low libido.
What the research isn't clear on is the relationship between T and erectile dysfunction (14).
Libido can be described as sexual appetite, whereas erectile dysfunction is the inability to perform the physical act of sex (due to the inability to develop or maintain an erection).
ED is not usually caused by a lowering of testosterone. But in cases where low T is accompanied by ED, then increasing T may positively affect ED as well.
8. Increased body fat
Testosterone plays a key role in the regulation of the key fat-loss hormones; namely, insulin and glucose (15).
As our T levels decrease, our body's ability to regulate fat metabolism also goes down, in turn leading to increased body fat.
This is why obese men tend to have significantly lower testosterone levels (16).
And to add fuel to the fire, increased body fat further contributes to the lowering of our T by increasing estrogen (17).
This has the potential of becoming a serious downward spiral, but it can be reversed if you start taking the steps to lower your body fat.
9. Depression
The extent of the relationship between T and depression is not yet fully understood, but researchers have found that men suffering from depression tend to have significantly lower testosterone levels compared to non-depressed men (18).
Research has also shown that men suffering from depression who received testosterone treatments, generally reported improvements in mood (19).
What's Causing Low Testosterone?
In our modern society, sub-optimal testosterone levels can largely be narrowed down to lifestyle factors.
10. Rising obesity epidemic
Since the early 1960s, the prevalence of obesity among adults has more than doubled, increasing from 13.4 to 35.7 percent in U.S. adults age 20 and older (20).
Excess body fat produces an enzyme called aromatase, which converts testosterone into the female sex hormone estrogen.
The more body fat you have the more testosterone is converted into estrogen leading to serious feminizing effects on the body.
Even being overweight can contribute to the lowering of your T, and according to the National Institute of Diabetes and Digestive and Kidney Diseases (as cited above), 2 in 3 adults are considered overweight.
11. Sleep deprivation
According to the Centre for Disease Control and Prevention, over 1 in 3 adults get less than the recommended 7 hours of sleep each night (21).
Given that the majority of our testosterone is produced while we sleep (22), a lack of sleep seriously inhibits it's production (23).
The screens we stare at (smartphones, laptops, televisions, etc) past dark, further disrupt our sleep by disrupting our natural circadian rhythms and hormone secretions.
12. Vitamin and mineral deficiencies
Large portions of the US population are deficient in vitamins A, C, D, and E (35, 31, 74, and 67% respectively), calcium (39%), and magnesium (46%) (24).
Vitamins and minerals are required by your body in trace amounts to maintain normal body development and growth. Getting adequate amounts of the required vitamins and minerals through your diet is important to ensure optimal body function.
With regards to testosterone production, vitamin D and magnesium are especially important, and as you can see from the stats above, their deficiencies are amongst the most prevalent.
Vitamin D is the "sunshine" vitamin, and as the time we spend outdoors goes down a global trend of vitamin D deficiency occurs. It is in fact the most common and drastic deficiency in first world countries.
Research has shown (25) that men with sufficient vitamin D levels tend to have significantly higher T compared to men who are deficient in it.
And it's the same with magnesium:
Research has shown (26) magnesium levels to be strongly and independently associated with testosterone.
13. Chronic stress
According to the American Psychological Association (27), 77% of Americans report feeling physical symptoms of stress.
When we're stressed, our body releases cortisol.
Cortisol is indirectly correlated with testosterone:
Higher cortisol = lower testosterone.
How to Fix Low Testosterone Naturally
Many men are unaware of the fact that it's even possible to increase T-levels naturally. So they opt for expensive and potentially dangerous treatments instead.
But this is merely addressing the symptoms and ignoring the root cause.
Since it's lifestyle factors that have led us down this path, it makes sense that optimizing these factors will have the opposite effect.
The following is some of the best and most actionable advice on how to naturally optimize your testosterone levels.
14. Lose your gut
