Question 1

What does bioavailability mean in nutrition?

Accepted Answer

The proportion of a nutrient that is **actually absorbed and available for use** — as distinct from the amount present in the food. It is why the number on a label can substantially overstate what you receive, and why some nutrients need more thought than a total suggests.

**Why absorption varies so much:**

**The chemical form.** **Haem iron** from meat is absorbed at a far higher rate than **non-haem iron** from plants, which is the single clearest example. Different forms of the same mineral in supplements also differ.

**What it is eaten with.** Some combinations help and some hinder:

**Vitamin C markedly increases non-haem iron absorption.**

**Fat is required** for vitamins A, D, E and K, so a salad eaten without any fat delivers less than it appears to.

**Phytates** in wholegrains and legumes and **oxalates** in spinach bind minerals and reduce absorption — which is why spinach is a poor calcium source despite the content.

**Tannins in tea and coffee** reduce iron absorption when drunk with a meal.

**Calcium and iron compete**, so large doses together reduce both.

**Processing and preparation.** Cooking, soaking, sprouting and fermenting all reduce anti-nutrients and raise availability. **Cooking increases lycopene availability from tomatoes** while reducing vitamin C — so there is no single "better" preparation.

**The body's own status.** Absorption is regulated: iron uptake rises when stores are low, and calcium absorption is more efficient when intake is low.

**Age and gut health**, both of which reduce absorption of several nutrients — B12 particularly, where stomach acid and intrinsic factor are required.

**What follows practically:**

**Plant-based diets need attention** to iron, zinc, B12, omega-3 and calcium — not because the diet is deficient by nature, but because availability differs.

**Pair strategically**, and separate competing nutrients.

**Be sceptical of supplement content claims** when the form is not stated.

General information, not dietary advice.

Question 2

What nutrients should I focus on when following a vegan diet?

Accepted Answer

Focusing on protein, vitamin B12, iron, calcium, omega-3 fatty acids, and vitamin D is crucial for a balanced vegan diet to prevent deficiencies.

Question 3

What is the difference between a vitamin and a mineral, and can you take too much?

Accepted Answer

Vitamins are organic compounds made by living things; minerals are chemical elements that come from soil and water. Both are needed in small amounts, and both can be harmful in excess — though not

Question 4

Why does vitamin D matter, and who actually needs a supplement?

Accepted Answer

Because it is required for calcium absorption and bone mineralisation, and because it is the one nutrient most people in northern latitudes genuinely cannot obtain adequately from food or, for much

Question 5

Why are some foods more filling than others?

Accepted Answer

Because satiety is driven by several mechanisms that have little to do with calories — and foods engineered to be easy to overeat are engineered to defeat each one of them. What actually produces

Question 6

Is a calorie on a label the same as a calorie your body gets?

Accepted Answer

No — the label is a reasonable estimate, not a measurement of what you absorb, and several factors mean the number on the packet and the energy your body extracts differ. How labels are calculated.

Question 7

What does the evidence say about ultra-processed food?

Accepted Answer

The association with poor health outcomes is reasonably consistent; why is much less settled, and that gap matters for what anyone should actually do. What the term means. It comes from the NOVA

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