Vitamins & Antioxidants

Calories measure how much you ate; vitamins measure how varied. Calk reads your meals for the nutrients that rarely make headlines — and shows where the coverage runs thin, not as a diagnosis, but as a map of your plate.

Coverage, not a diagnosis

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A first thing to be clear about: Calk reads food sources, not blood levels. A thin week is a reason to add variety, never a verdict on your health. The recurring idea across these nutrients is that they travel together — eggs, leafy greens, fatty fish, seeds and legumes each carry several at once, which is why a diverse plate quietly closes more gaps than any single food (World 2024). The reference intakes themselves are set with a deliberate margin, so a single low reading sits well inside normal variation; a pattern across weeks is the part worth noticing (Institute 2005).

Two practical levers

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Two levers come up again and again. First, a little fat helps: vitamins A, D, E and K, and the antioxidant carotenoids, absorb far better alongside olive oil, nuts or avocado — see fat-soluble absorption. Second, where animal foods are limited a few nutrients are worth checking deliberately, most clearly B12, since for those, food alone may not cover the gap. Everything here is a starting estimate that sharpens as your data grows — suggestions, not a prescription.

Vitamin A sources

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What Calk looks at. Calk follows vitamin A from its two food routes — preformed retinol in liver, dairy and eggs, and the beta-carotene in orange and dark-green vegetables that your body converts. Both count toward the day, and conversion of carotene to active vitamin A varies from person to person (NIH 2023).

What you could try. One medium sweet potato or a large carrot covers a day’s worth as beta-carotene; eggs and dairy are steady sources of the preformed form. Liver is the richest source of all and goes a long way in a single small serving.

Vitamin C sources

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What Calk looks at. Vitamin C is water-soluble and barely stored, and ordinary cooking destroys a real share of it, so Calk treats it as something to top up regularly from fresh fruit and vegetables rather than bank (NIH 2021).

What you could try. A bell pepper, a kiwi or a cup of strawberries each carries more than a full day. One raw fruit or vegetable serving most days keeps the reading steady without any effort to “hit a number.”

Vitamin D sources

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What Calk looks at. Vitamin D is one of the hardest nutrients to reach from food alone — the short list is fatty fish, egg yolks, fortified dairy, and UV-exposed mushrooms — so Calk checks whether any of those actually show up, while noting that food is only part of the picture next to sunlight (NIH 2023).

What you could try. Fatty fish such as salmon, sardines or mackerel a couple of times a week does most of the work; fortified milk and eggs add to it. For many people, especially in winter or at higher latitudes, food alone tends to fall short — worth a conversation with a clinician rather than a guess.

Vitamin E sources

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What Calk looks at. Vitamin E is a fat-soluble antioxidant that protects cell membranes, and its food sources are a tight set — nuts, seeds, plant oils and leafy greens. Calk simply watches whether those turn up often enough; dietary intake is the lens here, not the supplements that have disappointed in trials (NIH 2021).

What you could try. A 30 g handful of almonds or sunflower seeds covers roughly half a day. Hazelnuts and avocado help, and because it rides along with fat, it pairs naturally with the absorption note below.

Vitamin K balance

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What Calk looks at. Vitamin K comes in two forms — K1 from green vegetables and K2 from fermented foods and some animal products — and most people get plenty of K1 but very little K2, so Calk tracks both (NIH 2021).

What you could try. A cup of cooked spinach or kale covers several days of K1 on its own. For K2, the reach is shorter: hard cheeses, egg yolks, or fermented foods like natto and sauerkraut are the everyday options.

B12 sources

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What Calk looks at. Vitamin B12 occurs almost only in animal products, so Calk checks meat, fish, dairy and eggs — or fortified foods and supplements for a plant-based plate. This is the one nutrient where food alone can genuinely come up short without animal sources, and absorption also drifts down with age (NIH 2024).

What you could try. If you eat animal foods, most plates already clear it. If you eat plant-based, fortified plant milks, nutritional yeast and fortified cereals matter — and a supplement is a reasonable thing to discuss, since this is the clearest case where variety on its own may not reach.

Folate sources

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What Calk looks at. Folate (vitamin B9) underpins cell division and DNA work, and Calk follows it across leafy greens, legumes, citrus and fortified grains. Folate from whole food is absorbed a little less efficiently than the fortified form, which is part of why variety helps (NIH 2022).

What you could try. A cup of cooked lentils lands near a full day on its own; greens, asparagus, avocado and fortified cereals round it out. Since some folate is lost to cooking, spreading sources across the week beats leaning on one.

Choline sources

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What Calk looks at. Choline matters for liver fat handling and cell membranes, yet most people fall below the recommended intake and many have never heard of it — its reference value was only set in 1998. Calk checks the usual carriers: eggs, liver, fish, soybeans and cruciferous vegetables (NIH 2022).

What you could try. Eggs are the most reliable everyday source — two cover a large share of the day. If eggs aren’t on the menu, salmon, soybeans and beef liver are the strongest stand-ins.

Eye-health nutrients

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What Calk looks at. Calk follows lutein and zeaxanthin — the carotenoids that concentrate in the retina as macular pigment. Higher dietary intake of these, alongside other antioxidants, has been studied in the context of age-related eye health (Age-Related 2013); Calk reports the food coverage, not any outcome.

What you could try. Dark leafy greens, egg yolks, corn and orange peppers are the densest sources. They’re fat-soluble, so a little olive oil or avocado alongside helps them land — the same lever as the next section.

Fat-soluble absorption

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What Calk looks at. Vitamins A, D, E and K and the carotenoids need a little dietary fat to absorb well, so Calk notices when a meal carrying them arrives with essentially no fat — an undressed salad delivers far less than the same salad with oil (Brown 2004).

What you could try. Add a small fat source to vegetable-forward meals — a drizzle of olive oil, a few nuts, a slice of avocado. It needn’t be much; even a modest amount of fat meaningfully improves how these vitamins are taken up.

Micronutrient coverage

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A wider-angle read rather than a single nutrient: Calk summarises how many of the vitamins and minerals it tracks your food is covering, so you can see whether the plate is broad or has a few standing gaps. Deficiencies rarely arrive alone — when one is low, neighbours often are too, because they share the same foods — which is exactly why a diverse, nutrient-dense plate of eggs, greens, fish, seeds and legumes does so much at once (World 2024).

Rare plant sources

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A modest food-source note: wheat germ, aged cheese, mushrooms, soybeans, and legumes are uncommon but useful signals of variety. Calk simply notes whether foods like these show up in your week — a coverage signal, not a health claim or a reason to chase any single food.