Nutrition & Deficiencies

Vitamin and mineral deficiencies, and what a healthy diet actually involves.

Written by HealthDiseases Research Team

Educational hub

Articles on nutrition & deficiencies are in preparation. Each passes editorial review and fact-checking before publication, and this hub will be opened to search engines once it holds a full introduction and several completed guides. Browse the conditions index for topics already covered.

Conditions

High cholesterol Cholesterol is where settled science meets loud folklore. The panel takes five minutes to understand, the LDL-causes-plaque case is as proven as biology gets, and the tools that move it have published numbers.
Peripheral neuropathy Neuropathy is not one disease but a pattern of nerve damage with more than a hundred causes. Finding the cause is what makes it treatable.

Symptoms

Bloating Most bloating is ordinary physiology amplified — fermentation, swallowed air, a reflex that relaxes the belly wall — and it sorts by pattern. The skill is matching fix to cause, and knowing the short list that means testing instead.
Brittle nails Most brittle nails are weathered, not sick — split by thousands of wet-dry cycles — and the famous vitamin sold for them has less evidence than its sales and one genuine downside nobody advertises.
Constipation Constipation is the symptom people treat hardest and diagnose least — usually a plumbing problem of fiber, fluid and habit with a proven fix sequence, occasionally a message worth hearing, and never improved by folklore about daily obligations.
Tingling in hands and feet Everyone knows the pins and needles of a leg that has gone to sleep. Tingling that arrives without a reason, keeps returning, or spreads is a different matter, and the pattern usually points to the cause.

Health guides

How to read a supplement label Every graded ingredient on this site comes with trial doses — which turns any label into a pass/fail test. This guide is the test: seven checks, ninety seconds, no chemistry degree required.
What 82 supplement reviews taught us We verified and reviewed 82 direct-to-consumer supplements across 17 categories — every label we could find, every guarantee as written, every claim against its trial. The products blurred together. The patterns did not. This is the field report.
Fibre and blood sugar Fibre is the part of plant food the body cannot digest — and that is precisely why it steadies blood glucose. Most adults eat about half the amount recommended.
Foods that affect blood sugar The glucose response to a meal depends less on any single "good" or "bad" food than on carbohydrate amount, how processed it is, and what it is eaten with. Here is how the pieces fit.
Protein and weight loss Protein is the one macronutrient with three separate jobs in weight loss — fullness, muscle protection and a higher cost of digestion — which is why it anchors every diet that works, whatever the diet calls itself.
Vitamin B12 deficiency B12 deficiency damages nerves before it shows in a blood count, and the damage can become permanent. It is common, easily missed, and one of the most rewarding things to find.

Ingredients

What the evidence says about ingredients commonly used in this area.

Beta-sitosterol Beta-sitosterol has better prostate-symptom trial results than saw palmetto — from a handful of studies in the 1990s that were never repeated at scale. Its cholesterol effect is on much firmer ground.
Chromium Chromium is one of the most common ingredients in blood sugar supplements and one of the most contested. Trials disagree, and the reasons why matter more than the headline.
Cinnamon Cinnamon is the household spice most often claimed to lower blood sugar. Dozens of small trials have tested it, and they do not agree — partly because "cinnamon" is not one thing.
Lutein and zeaxanthin Lutein and zeaxanthin are genuinely special — the only carotenoids the retina stockpiles, sitting exactly where AMD strikes. What the trials support is narrower than what the vitamin aisle sells on their name.
Magnesium Magnesium is involved in hundreds of enzyme reactions, and low levels are common in people with type 2 diabetes. That is why it helps some people and not others — the benefit depends on where you start.
Turmeric / curcumin Turmeric is the joint aisle's best performer — small trials repeatedly favor it for knee arthritis — attached to the aisle's classic asterisks: tiny studies, absorption chemistry doing marketing's work, and a safety file that recently acquired a liver page.
Vitamin C Vitamin C is the most-tested supplement in history against the most-common illness in history, and the answer has been stable for decades — smaller and more specific than Linus Pauling promised, and not quite nothing.
Xylitol Xylitol is the rare functional ingredient whose mechanism is genuinely elegant — decay bacteria swallow it and stall. The trial record is good-not-miraculous, the gut sets the dose, and one household warning outranks everything: it kills dogs.

Questions people ask

Should I take a multivitamin? Half of adults take one, mostly as insurance — and the trials priced that policy years ago: no protection against the outcomes people buy it for, a short list of groups with real needs, and a recent memory finding worth exactly its size.