When we talk about eating too much sugar, the conversation usually revolves around excessive energy intake, empty calories, blood glucose and insulin spikes, or increased risk of chronic diseases (like diabetes, cancer, and heart disease). But, there’s actually another huge problem that gets less airtime in the sugar discussion: micronutrient deficiencies!
It turns out, a high intake of sugar can contribute to nutrient deficiencies in ways other than by displacing more nutritious foods. We’ve discovered a number of mechanisms by which sugar can actually deplete (or reduce the absorption) of certain vitamins and minerals. As a result, eating too much sugar can induce deficiencies, even when our overall micronutrient intake appears to be adequate.
So, which nutrients suffer on a high-sugar diet? Let’s take a look!
1. Vitamin D
It’s no secret that vitamin D deficiency is a big problem these days (especially for those living far from the equator), but lack of sun exposure isn’t the only cause. Excessive sugar intake (especially in the form of fructose) may actually exacerbate vitamin D deficiency!
How does it work? Researchers have discovered that a high intake of fructose can increase the expression of an enzyme responsible for degrading vitamin D (24-hydroxylase), while also decreasing the expression of an enzyme that helps synthesize vitamin D (1α-hydroxylase). As a result, fructose can enhance the breakdown of vitamin D in the kidneys while also impairing the body’s ability to synthesize it. The result is a reduction in vitamin D levels, and the potential for the harmful effects of deficiency to manifest (such as greater susceptibility to infection, higher risk of autoimmunity, increased rates of certain cancers, and overall lower immune function). No wonder 75% of people in Western countries are deficient in vitamin D!
And, it gets worse! Vitamin D deficiency and a high fructose intake can enter a vicious cycle, because low levels of vitamin D can actually exacerbate the inflammatory properties of fructose. Multiple studies have shown that vitamin D depletion increases non-alcoholic fatty liver disease (NAFLD) induced by fructose, and that vitamin D plays a crucial role in quelling the inflammation caused by high-fructose, Western-style diets. Historically, vitamin D levels would naturally be higher during sunny months when higher-fructose foods (like fruit) were in season. But, now that we have year-round access to nearly any food (and year-round roofs over our heads preventing sun exposure!), the potential for vitamin D and fructose to antagonize each other is greater than it’s ever been.
Calcium is famous for supporting skeletal health (including bones and teeth), as well as assisting in blood coagulation and acting as an electrolyte (helping nerves send signals and muscles contract). But, calcium is another nutrient negatively impacted by a high sugar intake!
Here’s how it works. Normally, vitamin D helps facilitate calcium absorption by regulating active calcium transport in the small intestine (a process that becomes even more important when calcium intake is on the low side, or when calcium requirements increase—such as during growth or lactation). Because the process is greatly dependent on blood levels of vitamin D3, the vitamin-D-lowering effects of fructose can have a ripple effect on calcium, causing our bodies to be unable to absorb as much as we need from dietary sources. That spells trouble during times when we need calcium the most, like during pregnancy or when we’re trying to heal broken bones.
And, along with fructose, a high intake of another form of sugar (glucose) has been shown to increase calcium excretion by the kidneys, through several proposed mechanisms (inhibiting tubular reabsorption of calcium, and possibly suppressing parathyroid hormone from the spiked blood sugar and insulin that comes after a high-sugar meal). Yikes!
Magnesium is a serious rock-star mineral that’s only started receiving the attention it deserves in recent years. Along with regulating muscle and nerve function, making protein, building bone, synthesizing DNA, and regulating blood sugar levels, magnesium is required by literally every organ in our bodies. In other words, it’s pretty important!
Both a high sugar intake and elevated insulin levels (which can result from a high intake of refined carbohydrates, including sugar) have been shown to increase the excretion of magnesium by the kidneys, by inhibiting tubular reabsorption (the same process that leads to calcium excretion) and by guzzling through the body’s magnesium reserves during sugar metabolism. That’s partly why people with diabetes or chronically high insulin tend to have higher magnesium requirements and more rapid magnesium depletion.
In fact, the interaction between sugar and magnesium is a two-way street: along with sugar depleting magnesium, magnesium plays a role in stabilizing blood sugar (by influencing cellular uptake of glucose and insulin secretion). So, when magnesium levels are too low, blood sugar regulation can also be impaired—setting the stage for even greater magnesium depletion due to the higher levels of glucose in the blood!
Chromium is a trace mineral involved in macronutrient metabolism and blood sugar control, and although we only need small amounts of it to be healthy, a high sugar intake can increase the likelihood of deficiency. Consuming excessive amounts of simple sugars causes more chromium to be excreted in the urine (in one study, eating a diet of 35% simple sugars increased chromium excretion from 10% at baseline to 300%). The effect has been pinpointed to the insulinogenic properties of refined sugars, and the impact of elevated insulin on chromium loss.
Like with magnesium, chromium and sugar have an interactive effect due to chromium’s role in blood sugar regulation. Just as a high sugar intake can contribute to chromium deficiency, chromium deficiency can contribute to poor glucose tolerance and higher blood sugar levels (since adequate chromium is needed for insulin binding, increasing the insulin receptor number, and insulin receptor phosphorylation).
5. Vitamin C
It shouldn’t come as a surprise that humans are pretty weird (hey, its true!), and one of our quirks involves vitamin C. Out of all the mammals in the world, only a handful (including humans) are unable to synthesize their own vitamin C. (The reason is due to a mutation in the GULO (gulonolactone oxidase) gene, which codes a protein needed for converting glucose into vitamin C.)
So, what does this have to do with high-sugar diets? Both glucose and vitamin C use the same transporters to enter cells, and research has shown that high levels of glucose (whether in the intestines or in the blood) can slow down or limit the absorption of vitamin C by our bodies. The Glucose Ascorbate Antagonism theory, proposed by Dr. John Ely in the 1970s, describes the competition between vitamin C and glucose—where elevated glucose restricts vitamin C from entering cells (ultimately leading to reduced immune function).
Fortunately, many higher-sugar whole foods (like fruit) are naturally high in vitamin C, helping offset these effects. But, the same protection isn’t there when it comes to excessive intakes of refined sweeteners like white sugar and high-fructose corn syrup!
So, Should We Avoid All Sugar?
As I’ve discussed previously, smaller and occasional intakes of sugar are unlikely to be harmful. It’s the chronically high intakes typical of the Standard American Diet—not the occasional sweet treat or sugar-containing recipe—that we start to damage our health and raise our risk of a variety of modern diseases.
But, the fact that sugar (glucose and fructose) can deplete our bodies of essential nutrients is a good one to keep in the back of our heads as we go about our days making decisions on what to eat! If you’re someone who find themselves reaching for a sweetened treat frequently, that could be doing your body some harm even if that treat falls under the Paleo umbrella.
Yet, the takeaway isn’t to avoid anything containing sugar, but to focus on whole foods whenever possible, and emphasize nutrient-dense sources of sugar like berries and blackstrap molasses when we do want something sweet!
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