Growth and aging are thought to be processes that are mirror images of each other. When development has stopped and maturity reached, cellular and biochemical processes that promote growth in the earlier part of life then promote aging. Strength is part of growth, but in my opinion, strength and longevity are compatible.
There’s good evidence for the relation between growth and aging, and for an overview I recommend the paper by Mikhail Blagosklonny, who has written extensively on this, Aging is not programmed: Genetic pseudo-program is a shadow of developmental growth.(1)
According to Blagosklonny, aging is a “quasi-program”, the continuation of the growth program. Among the most important systems that promote both growth and aging is the cellular nutrient sensor mTOR.
Without getting bogged down in the theoretical reasons why this may be true, the immediate question that comes to mind is, do interventions that promote growth also promote aging?
If they do, then we may want to avoid them in order to slow aging.
For example, milk and other dairy products increase the activity of mTOR.(2) This makes sense: mammals use milk to promote the growth of their offspring.
Iron deficiency down-regulates mTOR.(3) If iron acts this way in a linear fashion with no threshold, as it does in other aspects of physiology, then increased iron activates mTOR, thus promoting both growth and aging. This also makes sense, as growing animals require large amounts of iron; after maturity, not much iron is required, and excess amounts promote aging through mTOR activation.
Is this the whole story? Do we all want to become vegans in order to slow aging?
Probably not, because the growth program is needed in aging as well. The key, I believe, is balance.
Consider that levels of IGF-1, a growth hormone, were positively correlated with scores on an exam designed to test cognitive function.(4) Furthermore, the lower the IGF-1, the greater the thickness of carotid arteries.
Patients with AD [Alzheimer’s disease] and VaD [vascular dementia] had significantly lower IGF-1 concentrations and greater mean IMT [carotid artery intima-media thickness] than nondemented controls.
Low levels of IGF-1 are also seen in osteoporosis.(5)
Low levels of growth hormone and IGF-1 may be involved in the development of sarcopenia (muscle wasting) in the elderly.(6)
With this evidence we see that lower levels of growth factors could lead to frailty and cognitive decline in aging.
In aging, the ideal is to slow it or fight it as much as possible while remaining strong and vigorous. If you’re going to be confined to a wheelchair or be unable to read in your old age, that’s not going to be much fun.
How do we find balance in aging between slowing the aging process and maintaining strength and energy and a sharp intellect?
Adequate protein is necessary for strong bones, muscles, and brain. Too much, however, conduces to aging.
Trained bodybuilders need only about 1.1 grams of protein per kilogram of body weight to maintain muscle mass. Adding muscle may require somewhat more.
So, to promote strength but to slow aging as much as possible, don’t eat more protein than this.
The study cited above discussed how milk and dairy products activate mTOR and thus promote growth. One of the mechanisms through which dairy products do this is through their relatively large fraction of branched-chain amino acids (BCAAs).
Here’s the thing though: BCAAs increase lifespan in mice and enhanced physical endurance (exercise capacity).
So don’t forgo the dairy, would be my advice.
As we’ve discussed ad infinitum on these pages, excess iron promotes aging. Here, the link between growth and aging is less strong, since in the developed world, it’s difficult to get too little iron. In almost all stages of life, iron levels will be more than adequate enough to support strength in older age; it’s the excess we need to be worried about, and there are a number of things you can do about it.
To my mind, the best way to balance strength and energy with fighting aging is through emphasizing the natural cycles of buildup and breakdown, anabolism vs catabolism, that the body normally does on its own but the amplitude of which declines with age. Both catabolism (autophagy) and anabolism (synthesis of muscle and bone) are equally necessary for health.
I wrote up my program for this in my book Stop the Clock: The Optimal Anti-Aging Program.
Cycles of feasting and fasting, of building strength through weight training, and of hormetic challenges through dietary phytochemicals and other methods like cold showers should be a powerful program for both maintaining strength and health and fighting aging.
It’s simplistic to conclude that because certain interventions or factors cause growth, that we ought to discard them fully in order to counteract aging.
This leads to the conclusion of veganism, and that can conduce to frailty and dementia in older age.
Instead, the best way to be both strong and energetic, and to fight aging, is to challenge the body cyclically through exercise and fasting, and then with rest, protein, and anabolism.
It might be the way to have the best of both worlds: strength and a long life.