8/17/2026

This is the fourth piece in my series about Eric Topol's book, Super Agers: An Evidence-Based Approach to Longevity.

There is so much to talk about in this book. In this chapter, Topol takes a close look at some of the most basic components of our diet: sweeteners, salt, carbohydrates, protein, and fat.

What I find particularly interesting is that he doesn't simply label one nutrient “good” and another “bad.” Again and again, he emphasizes that the amount matters, but so does the type and quality of what we consume.

Sweeteners

The evidence linking sugar-sweetened beverages to poor health outcomes is particularly consistent. Topol cites studies associating high consumption with higher all-cause mortality, cardiovascular mortality, cancer mortality, increased atrial fibrillation, and dental disease.

One reason is obvious: sugary drinks can deliver a large amount of rapidly absorbed sugar without making us feel particularly full.

Topol is much more cautious about artificial and non-nutritive sweeteners. The evidence is mixed. Some studies have found little compelling evidence of harm, while others suggest that certain sweeteners may affect glucose regulation or alter the gut microbiome.

His overall conclusion is that artificial sweeteners appear less concerning than large amounts of sugar, but they should not automatically be regarded as completely harmless.

For ordinary people, the practical advice is simple:

Best choices: water, unsweetened tea, unsweetened coffee, and whole fruit.

Occasionally having a sweetened drink is one thing, but don't make it a regular part of your life.

Perhaps the deeper lesson is to gradually train ourselves to need less sweetness altogether.

Salt

Topol's discussion of salt is more nuanced than simply saying, “The less, the better.”

1. Too much sodium is a problem.

The relationship between high sodium intake and hypertension is well established, although the size of the effect varies considerably from person to person.

2. Don't blindly pursue “the lower, the better.”

Different health organizations recommend somewhat different sodium limits, and the evidence doesn't support the idea that reducing sodium indefinitely will produce proportionally greater benefits.

Topol notes that moderate sodium intake is not necessarily a problem, while very high intake is much more clearly associated with cardiovascular risk.

3. Sodium may affect more than blood pressure.

Topol also discusses evidence that excessive sodium may impair blood flow to the brain through dysfunction of the blood-vessel lining, potentially affecting cognitive health.

4. Moderation is more realistic than a miserable diet.

His practical suggestions include:

• Don't routinely add salt to food.

• Pay attention to sodium on food labels.

• If you have hypertension, be particularly careful about sodium.

• If you don't have kidney disease, consider a potassium-chloride salt substitute.

• Don't turn healthy eating into an intolerable, flavorless diet.

In other words, the goal is sensible reduction, not eliminating salt from your life.

Carbohydrates

Topol introduces the term “carbotoxicity” to describe the potential harms associated with excessive carbohydrate consumption.

His message is both very low carbohydrate intake—less than about 40% of total calories—and very high intake—more than about 70%—have been associated with increased all-cause mortality.

The more important question is:

What kind of carbohydrates are you eating?

Good carbohydrates

Topol gives priority to:

• non-starchy vegetables

• legumes

• fruits

• whole grains

• resistant starch

• other high-fiber, minimally processed foods

He cites a large body of research involving 185 prospective studies and 58 randomized trials showing that consuming roughly 25–30 grams of dietary fiber per day was associated with substantially lower risks of cardiovascular disease, type 2 diabetes, colorectal cancer, and all-cause mortality.

Poor-quality carbohydrates

These include:

• added sugars

• refined grains

• rapidly digested starches

• highly processed potato products

• foods with a high glycemic load

These foods can cause rapid rises in blood glucose and insulin and are associated with weight gain and poorer cardiovascular outcomes.

So once again, the message:

“Eat better carbs.”

Protein

The standard protein RDA of 0.8 grams per kilogram of body weight per day may not adequately reflect the needs of seniors. Much of the evidence behind that recommendation came from relatively short-term studies involving younger adults.

Because sarcopenia—the age-related loss of muscle mass and strength—is one of the major threats to healthspan.

Topol argues that older adults probably need more protein than the basic RDA, although the optimal amount remains uncertain. He considers increasing intake to around 1.2 g/kg/day reasonable.

But he also warns against assuming that more protein is always better.

Very high protein intake—particularly above about 1.5 g/kg/day—has been associated in some research with potentially unfavorable effects, including changes in the gut microbiome and production of pro-inflammatory metabolites. He also discusses concerns about leucine-rich animal proteins and pathways related to atherosclerosis and cellular waste disposal.

However, this is an area where Topol acknowledges significant uncertainty.

We don't yet have the kind of long-term, large-scale randomized trials that could definitively tell us exactly how much protein older adults should consume to maximize healthspan and prevent sarcopenia.

There's another interesting limitation: food labels don't tell us how much of each essential amino acid a food contains. So consumers can't easily compare foods based on amino acids such as leucine, lysine, or methionine.

The practical message I take from this section is:

Older adults should pay attention to getting enough protein to preserve muscle, but don't assume that an extremely high-protein diet is automatically healthier.

Fat

Fat is another example of why nutrition isn't as simple as “avoid fat.”

Topol explains that fat activates a gut-brain reward pathway involving the vagus nerve. This pathway can work together with the brain's sugar-reward pathway to increase dopamine signaling and encourage overeating.

That helps explain why combinations of fat + sugar can be so difficult to resist.

These foods combine multiple powerful reward signals while packing a lot of calories into a relatively small amount of food:

• ice cream

• pastries

• donuts

• cookies

• chocolate

• many packaged desserts

Fat quality matters

Topol also emphasizes that the type of fat matters.

Replacing saturated fats with mono- and polyunsaturated fats, particularly plant-based unsaturated fats, has been associated with more favorable cardiovascular and metabolic outcomes.

This is another reason not to think simply in terms of “high-fat” versus “low-fat.”

A handful of nuts, olive oil, or avocado is very different from a highly processed food loaded with saturated fat.

What about the ketogenic diet?

Topol is skeptical of the popular ketogenic diet, which is extremely high in fat and very low in carbohydrates.

He cites research associating ketogenic diets with potential problems including:

• higher cholesterol

• cardiovascular risk

• “keto flu”

• brain fog

• fatty liver

He also discusses a randomized NIH study comparing a ketogenic diet with a plant-based, low-fat diet. Interestingly, participants on the ketogenic diet consumed about 700 more calories per day during the two-week study, and the low-fat group lost more weight.

That finding challenges the idea that simply lowering carbohydrates and insulin will necessarily reduce hunger and food intake.

So what is the big picture?

I think Topol's message can be summarized in one sentence:

On carbohydrates, protein, or fat; pay attention to their quality, their source, and the amount you consume.

All three macronutrients are necessary. They can also contribute to health problems when consumed in inappropriate forms or excessive amounts.

In summary:

Carbohydrates: choose fiber-rich, minimally processed sources.

Protein: get enough to preserve muscle as you age, but don't assume extremely high intake is better.

Fat: favor unsaturated fats and pay attention to the powerful combination of fat and sugar in highly palatable foods.

Sugar: particularly avoid making sugary beverages a regular habit.

Salt: reduce excessive intake without turning healthy eating into an unsustainable low-sodium diet.