Don’t treat blood donation as a health habit: claims that it “detoxifies, lowers cholesterol, and prevents heart attacks” lack randomized trial support, while frequent donation truly causes iron deficiency

There is no monetary cost. A single donation — including registration, drawing blood, and post-donation observation — takes about an hour. Over the following weeks, the body works to replenish the lost iron.

The Kuopio study in Finland followed 2862 men aged 42–60 for nearly nine years. In the 24 months prior to tracking, 153 men donated blood; only one (0.7%) suffered an acute heart attack. Among the remaining 2529 non-donors, 316 (12.5%) experienced the same outcome (P<0.0001). After adjusting for age and other coronary risk factors, donors showed an 88% lower risk of heart attack; the relative risk was 0.12 (95% CI 0.02–0.86, P=0.035). However, this result came from an observational study without randomization. The Nordic SCANDAT database included 1182495 donors observed over 9526627 person-years; 15401 deaths occurred. After controlling for age and gender, each extra yearly donation lowered mortality by 18.6% (95% CI 16.8%–20.4%). Once the fact that only healthy individuals are allowed to donate was factored in, the benefit fell to 7.5% (95% CI 5.7%–9.4%). Researchers concluded this does not constitute solid proof of health benefits. The FeAST randomized trial enrolled 1277 patients with symptomatic peripheral artery disease; one group received regular blood removal every six months to reduce iron levels, while the other served as a control. Overall mortality rates were 125 out of 636 (20%) versus 148 out of 641 (23%). HR 0.85 (95% CI 0.67–1.08, P=0.17). Combined outcomes of death, heart attack, and stroke also showed no significant difference: 180 out of 205 (28% vs 32%) with HR 0.88 (95% CI 0.72–1.07, P=0.20). The INTERVAL trial involved 45263 whole-blood donors divided into three groups based on donation intervals: 12 weeks, 10 weeks, or 8 weeks for men; 16 weeks, 14 weeks, or 12 weeks for women. Shorter intervals indeed yielded more blood within two years (the 8-week group produced 1.69 extra units compared to the 12-week group, 95% CI 1.59–1.80). Yet no differences emerged in quality of life, physical activity, or cognitive function. However, more donors reported fatigue, shortness of breath, dizziness, lightheadedness, and restless legs — especially at night. Average hemoglobin and ferritin levels also dropped, and more donations were postponed due to low hemoglobin (all P<0.0001). Iron deficiency impairs heat production: ten women with iron-deficiency anemia, eight with depleted iron stores but no anemia, and twelve controls were immersed in 28°C water for 100 minutes. The anemia group’s rectal temperature averaged 36.0±0.2°C versus 36.2±0.1°C in controls (P=0.001); oxygen consumption was 5.28±0.26 versus 5.99±0.29 mL·min⁻¹·kg⁻¹ (P=0.04). Thyroid hormones thyroxine and triiodothyronine were also lower (P<0.002). This pattern occurs because donors are repeatedly screened for good health; the hypothesis that “removing iron protects the heart” has not been confirmed in randomized trials.

Salonen JT, Tuomainen TP, Salonen R, Lakka TA, Nyyssönen K (1998). Donation of blood is associated with reduced risk of myocardial infarction. The Kuopio Ischaemic Heart Disease Risk Factor Study. American Journal of Epidemiology, 148(5), 445-451. https://doi.org/10.1093/oxfordjournals.aje.a009669；Ullum H, Rostgaard K, Kamper-Jørgensen M, et al. (2015). Blood donation and blood donor mortality after adjustment for a healthy donor effect. Transfusion, 55(10), 2479-2485. https://doi.org/10.1111/trf.13205；Zacharski LR, Chow BK, Howes PS, et al. (2007). Reduction of iron stores and cardiovascular outcomes in patients with peripheral arterial disease: a randomized controlled trial. JAMA, 297(6), 603-610. https://doi.org/10.1001/jama.297.6.603；Di Angelantonio E, Thompson SG, Kaptoge S, et al. (2017). Efficiency and safety of varying the frequency of whole blood donation (INTERVAL): a randomised trial of 45 000 donors. Lancet, 390(10110), 2360-2371. https://doi.org/10.1016/S0140-6736(17)31928-1；Beard JL, Borel MJ, Derr J (1990). Impaired thermoregulation and thyroid function in iron-deficiency anemia. American Journal of Clinical Nutrition, 52(5), 813-819. https://doi.org/10.1093/ajcn/52.5.813；全国人大常委会 (1997). 中华人民共和国献血法（第二、九、十四条）. https://flk.npc.gov.cn/detail?id=2c909fdd678bf17901678bf5e71801f9；国家卫生健康委等 (2024-01-08). 关于进一步做好无偿献血者激励奖励工作的通知. https://www.gov.cn/zhengce/zhengceku/202401/content_6924875.htm

What to reject is “donate for your own body,” not donation itself. The blood is for others; by this book’s beneficiary tiers it sits in tier ④ (strangers). What can return to you is what the system provides. Article 14 of the Blood Donation Law says unpaid donors pay none of the collection, storage, separation, or testing fees when they use blood in hospital. Spouses and lineal relatives may be exempted or charged less under provincial rules. A January 2024 National Health Commission notice states that in 28 provinces unpaid donors and relatives already get those fees waived at discharge in provincial hospitals. Holders of the Voluntary Blood Donation Dedication Award may also, under local “three frees,” ride public transport free, enter government-run parks free, and skip ordinary outpatient consultation fees at public hospitals. Donate on the legal interval. Article 9 of the Blood Donation Law says each session is generally 200 mL, at most 400 mL. Intervals are no less than 6 months. The encouraged age is 18 to 55. Do not compress the interval to chase honors or group quotas. Women, people with low body weight, and people with heavy periods already run tight on iron; frequent donors may pay privately for one ferritin check. If after donating you stay weak, cold-sensitive, or at night must move restless legs, do not guess “vital energy was harmed” — get a blood count and ferritin. If iron deficiency is found, supplement as the doctor says and lengthen the donation interval. The cold-sensitivity human evidence is only 10 people; it explains why it can happen, not how many people it happens to.