Why I Go Upstream
By Valerie Robitaille, PhDWhen I choose a supplement, I am not always looking for the substance I ultimately want the body to have. Quite often, I prefer to go one step upstream. Instead of immediately supplying the finished compound, I look at what the body naturally uses to make that compound and ask a different question:
Can I give the body the building block, precursor, cofactor, or signal it needs to make it itself?
This is one of the principles that guides how I approach nutritional and functional support, and the reason is simple: the human body is a dynamic biochemical system that is constantly making, converting, recycling, regulating, and responding. When appropriate, I would rather support that system than bypass it, and I do that by “going upstream.”
The difference between supplying and supporting
Imagine that the body needs a particular molecule. There are two general approaches: give the molecule directly or provide something upstream that the body can convert into that molecule through its own metabolic pathways.
In the second approach, the body retains some control over the process. The precursor enters a pathway, enzymes act on it and cofactors participate. Cellular signals influence the rate of production and the resulting compound can then be used where it’s needed.
That’s very different from simply putting a finished molecule into the system, but it doesn’t necessarily mean that precursors are always better. Biology is more complicated than that. A person may have impaired conversion, inadequate cofactors, enzyme limitations, nutritional deficiencies, or other factors that affect the pathway.
But when the pathway is functional, supporting it can be a powerful way to work with physiology.
Example #1: Glucoraphanin → Sulforaphane
Broccoli contains glucoraphanin, a precursor to sulforaphane. When glucoraphanin encounters a specific enzyme it can be converted into sulforaphane. (PubMed Central (PMC))
Sulforaphane is a powerful activator of the Nrf2 pathway, which helps regulate the body’s cellular defense and antioxidant systems. It can influence enzymes involved in the body’s response to oxidative stress and the processing of certain environmental chemicals, e.g., microplastics.
So rather than automatically thinking: “I want sulforaphane, therefore I should take sulforaphane,” I think “What does the body need to produce sulforaphane from food?”
And this is where food preparation becomes fascinating. In a randomized crossover study, people who ate cooked broccoli with powdered brown mustard seed had more than four times the urinary sulforaphane metabolite compared with eating the cooked broccoli alone. (PubMed)
Even more recently, a 2026 randomized crossover study found that adding mustard seed to a broccoli preparation approximately doubled sulforaphane bioavailability. (PubMed)
That is a beautiful example of supporting a biochemical pathway rather than simply delivering the endpoint.
Example #2: NAC → Cysteine → Glutathione
Glutathione the body’s major antioxidant, and it plays an important role in cellular defense and detoxification. (PubMed Central (PMC))
N-acetylcysteine, or NAC, can serve as a precursor to cysteine and therefore support glutathione synthesis. (ScienceDirect)
So again, I think upstream:
NAC → cysteine → glutathione
That doesn’t mean supplemental glutathione has no place. It can, but NAC gives us an opportunity to support one of the body’s own routes for producing it.
When I look at a biochemical pathway, I want to know where the system is constrained.
Is the precursor missing?
Is an enzyme dependent on a particular nutrient?
Is a cofactor inadequate?
Is the pathway being overwhelmed?
Is the cell capable of making the downstream compound?
The body regulates its biochemical processes for a reason.
Production of many compounds is influenced by substrate availability, enzyme activity, cellular demand, feedback mechanisms, redox state, and signaling pathways. Providing an upstream substrate does not guarantee that the body will produce more of the downstream compound. The pathway still has to work.
Upstream supplementation is a way we can give the body the raw material and the conditions necessary to perform a job it is already designed to perform.
When the machinery is functioning, I prefer to support the machinery. I’m interested in the pathway, not just the product at the end of the pathway.
The important caveat: upstream isn’t automatically better
I don’t use the precursor approach as an ideology. There are situations where supplying the downstream compound makes more sense. If a someone’s ability to convert the precursor is impaired, simply providing more precursor may not solve the problem. The point isn’t: “always take the precursor or supplement.” The point is:“before I supply the endpoint, I want to understand the pathway.”
That is the difference. My approach: work with the system whenever possible. If the body has the machinery to produce something important, I consider whether we can support that machinery.
If a pathway requires a precursor, I want to consider the precursor. I want to ask whether I can give the body what it needs to make its own.
Want to Get More Sulforaphane from Your Diet?
If you want to take the broccoli–sulforaphane pathway a step further, SulforaXym® provides a concentrated source of broccoli sprout compounds along with myrosinase—the enzyme needed to convert glucoraphanin into sulforaphane.
This is what makes the formula especially interesting. Rather than relying solely on the naturally occurring enzyme activity in your food, SulforaXym® combines broccoli sprout extract with a stabilized source of myrosinase to support sulforaphane formation.
It’s a simple way to incorporate this powerful plant compound into a daily detox-support routine.
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